Annual Meeting

Annual Meeting 2009

October 9-12, 2009
THEhotel at Mandalay Bay & the MERIN Laboratory
Las Vegas, NV

The 2009 SMISS Board of Directors would like to whole heartedly thank all the attendees for their time and contributions that made SMISS 2009 the success it was. We look forward to seeing you at SMISS 2010!

The SMISS 2009 Annual Meeting was held at THEhotel at Mandalay Bay & the MERIN Laboratory in Las Vegas, Nevada. This "can't miss" meeting featured hands-on cadaver labs showing the latest MISS procedures, two full days of CME-accredited didactic sessions, including lectures from MISS leaders, in-depth case discussions, oral abstracts and e-Posters on the newest research. New technique forums, supported by MISS companies, featured detailed presentations, videos, and hands-on display of the most cutting-edge MISS technology. In addition, the meeting featured over 30 technical exhibits and ample time to network and enjoy the attraction of Las Vegas.

Save the Date! We hope that you can join us for the 2010 SMISS meeting held November 5-6 at the Loews Miami Beach Hotel in Miami, FL. Please check back frequently for updating meeting information.

Index of 2009 Presentations

The 2009 annual meeting of the Society for Minimally Invasive Spine Surgery featured the following presentations:

• 3-D Image-Based Computer Navigation Reduces Needle Malposition Rates in Balloon Kyphoplasty
  Presenting author: Jonathan Sembrano, MD
  Additional authors: Charles Ledonio, MD, Edward Santos, MD, David Nuckley, MD, MPH, David Polly, Jr., MD
  
  Presentation Summary

  Summary:
  This study demonstrated that 3-D image-based navigation decreased needle malposition rates in balloon kyphoplasty when compared with conventional 2-D fluoroscopy.

  Introduction:
  Balloon kyphoplasty, conventionally performed using 2-D fluoroscopy, is gaining wide acceptance as treatment for osteoporotic and pathologic compression fractures. Advantages include minimal tissue disruption, quick recovery and reliable pain relief. The benefit of image-based navigation in kyphoplasty has not been established.

  Methods:
  This is a retrospective comparison of navigated vs. non-navigated needle placement in 31 balloon kyphoplasty procedures (48 levels). Intraoperative 3-D image-based navigation (O-arm + Stealth) was used for needle placement in 22 cases (37 levels); conventional 2-D fluoroscopy was used in the other 9 cases (11 levels). In all cases, intraoperative CT scans performed post-needle placement and post-cement filling were used as reference standard. Navigated and non-navigated groups were compared for rates of needle malposition and cement leakage, as well as operative and radiation exposure times.

  Results:
  Three of 11 (27%) non-navigated cases were complicated by a malpositioned needle, two of which had to be repositioned. The navigated group had a significantly lower malposition rate (2/37, 5%; p=0.04). The rates of cement leakage into the disk space, spinal canal and paravertebral tissues were similar in the navigated and non-navigated groups (p=0.35, 0.35 and 0.70, respectively). Overall rate of cement leakage was also similar in both groups (p=0.18). Mean operative time was significantly greater in the navigated group (103 minutes vs. 57 minutes, p=0.003). Total radiation exposure time was similar in both groups (navigated 95 seconds per level, non-navigated 125 seconds; p=0.217).

  Conclusion:
  Navigation provides added safety to balloon kyphoplasty procedures by reducing needle malposition rates, thus obviating the need for needle repositioning. Furthermore, navigation did not lead to increased radiation exposure time despite obtaining an intraoperative 3-D scan for image registration.

• A clinical evaluation of two-level lumbar fusion using a combination of the AXIALIF and XLIF
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  38 patients underwent a combination of the XLIF and AxiaLIF minimally invasive approaches for fusion at L4-5 and L5-S1. Clinical and radiographic outcomes are reported and compared with traditional open approaches. The MIS combination results are comparable to – and the associated complications markedly less than – traditional open techniques.

  Introduction:
  Minimally invasive surgical fusion of the lumbar spine for multilevel disease presents special challenges at the lumbosacral junction. The combination of XLIF and AxiaLIF provides access to both L45 and L5S1. To our knowledge, no one has presented the results of this combination of procedures in comparison to traditional open fusion.

  Methods:
  Thirty-eight patients with a mean age of 59.6 years and a mean BMI of 30.4 received two-level fusions with an AxiaLIF at L5-S1 and XLIF at L4-L5 . The VAS scores, disc heights, and radiographic evaluations are presented at 3, 6, and 12 months post-operatively.

  Results:
  The mean VAS score in these patients pre-operatively was 8.6 and reached 2.8 at 12 months post-operatively, demonstrating a 5.8 point drop (67% reduction) in the VAS score. OR time averaged 150 minutes. There were no infections to date. Complications included a graft herniation requiring laminotomy at 3 mos, 1 wound problem requiring VAC, 1 urinary retention, 1 CHF requiring care in a rehab facility, and 1 postoperative transfusion. One patient required a laminectomy at 4 wks. We compared a similar group of 109 2-level open PLIF surgeries, in the MIS group the mean hemoglobin change of 2.08g; while hemoglobin change in PLIF patients averaged 3.1 (and 20% of PLIF patients were transfused). Hospital stay averaged 1.0 days for XLIFs and 3.2 days for PLIFs. In the PLIF group, there were 3 infections and 1 dural tear. While two MIS combination patients have required revision or reoperation (5%), there was a 10% reoperation rate in the PLIF cohort.

  Conclusion:
  Multilevel fusion at the lumbosacral junction can be achieved using a combination of XLIF and AxiaLIF procedures. The results are comparable to – and the associated complications markedly less than – traditional open techniques.

• A less invasive technique using interspinous process decompression implants with bone dowel fusion for moderate to severe stenosis
  Presenting author: Stewart Eidelson, MD
  Additional authors: Hildegarde Geisse, MD, Sarah Eidelson, Zach Ingwer
  
  Presentation Summary

  Summary:
  N/A

  Introduction:
  This study seeks to demonstrate a new technique using less invasive methods for treatment of patients w/ significant comorbidities suffering from severe spinal stenosis.

  Methods:
  Patients undergoing multilevel spinal decompression, foraminotomy w/ bone dowel fusions were assessed after insertion of interspinous process implants. 25 were studied and assessed for op time & blood loss.. Clinical measures, analogue pain scale & Oswestry Index reviewed. Specific attention is placed on comorbidities as function of outcome & post surgical complications.

  Results:
  Of the 25 patients, 70% completed preop & and postop questionnaires. 14 female & 11 males age range of 65 - 90. Patients decrease in Visual Analogue Pain was 35%.

  Conclusion:
  Study suggests less invasive use of spinal implants in treatment of moderate/severe stenosis can lead to substantial reduction in postop back pain & increased function. A larger time period is needed w/ randomized clinical studies to determine whether spinal decompression using interspinous process implants is reasonable alternative to more complex surgeries w/ pedicle fixation.

• Biomechanical Analysis of a Novel Technique for Dural Repairs in Minimally Invasive Spine Surgery
  Presenting author: John Mccormick, MD
  Additional authors: Michael MacMilian, MD, Bryan Conrad PhD
  
  Presentation Summary

  Summary:
  Dural repairs performed in minimally invasive spine surgery can be challenging to tie knots. We developed a knotless technique for dural repairs, which uses small hemoclips (Weck Hemoclip, Kenosha Wisconsin) as end fasteners. A hemoclip is applied to the end of the suture and the suture is passed through the dura. Tension is applied and a second hemoclip is placed. A biomechanical analysis was performed to compare the standard technique of tying knots vs hemoclips.

  Introduction:
  Dural tears during minimally invasive surgery present a greater challenge due to the lack of access for repair. Although benign neglect of dural tears during minimally invasive spinal surgery has been advocated, a simplified method of repairing dura may be helpful.

  Methods:
  Human spinal cords were harvested from an outside source (RTI Biologics, Alachua, FL) from donated tissue. Once received, the spinal cords were sectioned in 2 cm increments and the dura was harvested. Fifty two samples were collected and divided into 4 experimental groups. Group 1 consisted of samples sutured with a 4-0 silk in running style fashion with a knot at each end. Group 2 consisted of samples that were sutured with a 4-0 silk running style fashion using a small hemoclip (Weck Hemoclip, Kenosha Wisconsin) used at each end to secure the stitch. The groups were then compared to 4-0 proline running stitch with a knot at each end and 4-0 proline with hemoclips as end fasteners. The sutured dura was then tested to failure using a material testing machine (MTS MiniBionix, Eden Prairie, MN).

  Results:
  The average maximal load to failure for a running silk suture was 7.99 +/- 3.33N. The average maximal load to failure for a proline suture was 8.16 +/- 4.53N. Suture techniques using knots vs. hemoclips as end fasteners were then compared. The average maximal load to failure for knots was 8.19 +/- 3.26N. The average load to failure for the hemoclip samples was 7.93 +/- 4.55N. Of the 52 samples tested, 49 of the 52 samples failed within the dura away from the suture. One hemoclip sample within the silk group, one running silk suture with knots, and one running proline suture with knots failed within the suture. No statistical difference was seen when comparing a proline stitch vs. a silk stitch (p=0.567). No statistical significance was seen when comparing a hemoclip as end fasteners of the suture vs. a knot (p=0.291).

  Conclusion:
  The use of hemoclips with standard suture is an effective way to repair dural tears. The method can be employed through a minimally invasive portal without additional exposure and can be implemented in less time than tying knots in the suture.

• Biomechanical Comparison of an Interspinous Distraction Device with a Novel Interlaminar Dynamic Stabilization System in the Lumbar Spine
  Presenting author: Michael Macmillan, MD
  Additional authors: James Rice, MD, Bryan Conrad
  
  Presentation Summary

  Summary:
  This is a biomechanical study to test the stability provided by a novel interspinous distraction device. The device consists of opposite-facing laminar hooks placed on adjacent lamina, and connected by PEEK rods. Thirteen cadaveric lumbar spines were prepared and tested in flexion-extension and lateral bending. The hook-rod construct was tested against an intact specimen, x-stop, and a specimen after laminectomies. Testing showed that the PEEK hook-rod construct provided more stability than the other three groups.

  Introduction:
  We investigated a novel form of dynamic stabilization based on laminar hook fixation. Although the performance of hook fixation has been well characterized in rigid implants, this application has two new design aspects: the hooks were applied between adjacent lamina, and PEEK (poly ether-ether ketone) rod fixation was used. The stability afforded by the interlaminar dynamic stabilization system will be compared with an interspinous distraction device, the X-stop®. This is an appropriate comparison because both systems are applied to the posterior elements, anchored through ligamentous distraction, and have a similar surgical approach.

  Methods:
  Thirteen fresh frozen cadaveric lumbar spine motion segments were obtained for investigation (6 L2/L3, 7 L4/L5). The cranial and caudal vertebrae of each specimen were potted in polyester resin and aligned with the disc horizontal. Non-destructive flexion/extension and lateral bending flexibility testing was performed on a material test machine (MTS Systems, MN). Each specimen was sequentially tested in four conditions: intact, X-Stop, laminectomy, and laminectomy plus PEEK rod/hook construct.

  Results:
  Following the laminectomy, there were decreases in bending stiffness for flexion, extension, left and right lateral bending (-12%, -26%, -22%, -18%, respectively). For extension, the PEEK rod/hook group was significantly more rigid than the laminectomy group (p=0.045). For flexion, the PEEK rod/hook group was significantly stiffer than the Intact (p=0.005), Laminectomy (p=0.001) and X-Stop (p=0.014) groups. For Left lateral bending, the PEEK rod/hook group was significantly more rigid than the Laminectomy (p=0.005). For right lateral bending there were no statistically significant differnces.

  Conclusion:
  Interlaminar PEEK rods/hooks provided increased stability in all tested motion planes when compared to the other three groups. This device is a novel technique in the expanding area of dynamic stabilization. It combines the ability to decompress the interlaminar space while enhancing stability. This device can be applied through a single midline minimally-invasive incision, and has the potential to offer a significant benefit to patients with degenerative spondylolisthesis or spinal stenosis.

• Cervical Arthroplasty in Elderly: Prospective 6 year follow up
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Etevaldo Coutinho, MD, Luis Marchi, MSc Leonardo Oliveira, MD
  
  Presentation Summary

  Summary:
  Total disc replacement has been reported to restore motion in the cervical spine, but almost always indicated for the young population. Here we show our clinical and radiological experience in cervical disc replacement with PCM artificial disc in the elderly segment of the society.

  Introduction:
  Many surgical options are available to treatment the cervical spine disease. Traditional treatment of cervical spondylosis and cervical herniated disc disease with neurological compression is anterior spinal decompression followed by fusion. This leads to spinal immobility with increasing rate of adjacent level disease. Total disc replacement has been reported to restore motion in the cervical spine, but indicated for the young population. The purpose was to evaluate pain relief and radiographics outcomes of the cervical disc replacement utilizing the PCM artificial disc in the elderly segment.

  Methods:
  We report the results of 6 year follow-up for total disc replacement in a consecutive series of 14 patients, mean age 65.4 y/o (60 - 80) with a total of 24 Porous Coated Motion total cervical disc replacement from C3-4 to C6-C7 for the treatment of cervical degenerative disease with radiculopathy and/or myelopathy. The neural decompression was performed in standard Smith-Robinson technique. Radiographic (AP, lateral and dynamics images) and clinical outcomes were collected preoperatively and postoperatively after 1 week, 1, 3, 6 months and annually. The NDI, VAS and TIGT questionnaires were used to assess pain and functional outcomes.

  Results:
  At 72 months follow-up, there were no deaths, no infections, and no cases of iatrogenic neurologic progression. 8 patients had a single level PCM, 3 had two level arthroplasty, 2 with three levels and one patient had four levels PCM. The mean VAS and NDI improved significantly in all periods when compared to preoperative follow-up. One patient (4.2%) presented facet degeneration grade III in Pimenta’s scale1. Two prosthesis (8.3%) presented bone formation with no movement of the disc, and other two patients presented bone formation with decreasing of the range of motion, but with no worsening in their clinical outcomes.

  Conclusion:
  Following cervical arthroplasty with PCM prosthesis, radiographic and clinical outcome measurements were encouraging when compared to historical data of ACDF in elderly. Considering the aging population, cervical disc arthroplasty is a good treatment option for degenerative disc disease and a viable alternative to fusion in the elderly segment of the society.

• Changes in Coronal and Sagittal Plane Alignment after XLIF procedure in the treatment of Degenerative Scoliosis
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Etevaldo Coutinho, MD, Luis Marchi, MSc Leonardo Oliveira, MD
  
  Presentation Summary

  Summary:
  The traditional treatments to degenerative scoliosis consist in open surgeries, with high incidence of morbidity. Here we present a lateral retroperitoneal minimally invasive approach for the treatment of adult scoliosis.

  Introduction:
  Symptomatic adult scoliosis deformity presents as a difficult problem to solve. Traditional treatments include anterior and posterior open approaches. The purpose of this paper is to present a lateral retroperitoneal minimally invasive approach (eXtreme Lateral Interbody Fusion – XLIF) for the treatment of adult scoliosis requiring more than four levels of arthrodesis without the morbidity of an open procedure.

  Methods:
  A prospective, non-randomized, single center study with 14 patients, mean age 69.64 (51-87 years) with two year follow up. Lateral, A-P, flexion-extension X-rays, neurological examination and clinical outcome assessments using Oswestry and VAS scores were performed at the preoperative, 1, 6 week, 3, 6, 12 and 24 months postoperative intervals. The extreme lateral approach was done through the retroperitoneal space and through psoas muscle avoiding vascular lesions. A partial discectomy was done and the end-plate cleaned preserving ALL, keeping the spine more stable than the traditional anterior surgery. The operated levels ranged from four to seven levels, including T10-T11 to L4-L5.

  Results:
  The procedures were performed without complication in an average 121 minutes and with less than 50cc blood loss. Ten patients had four levels of fusion; two patients had five levels and two patients with seven levels of arthrodesis. VAS pain scores improved from an average 8.33 at pre-op to 3.16 at 2 years, standard deviation 1.49 and 1.06 respectively. Oswestry scores improved from an average 51.2 at pre-op to 27.33 at 2 years with standard deviation of 13.42 and 13.09 respectively. Coronal and sagittal alignments improved from average Cobb angles of 16.4 degrees at pre-op and 7.8 degrees at 2 years, and average lordosis angles of 17.1 degrees at pre-op to 37.4 degrees at 2 years.

  Conclusion:
  Using the XLIF approach we were able to treat long thoracolumbar deformities in a minimally invasive way targeting the pain improvement after surgery without the risks and morbidity associated with big corrections. Our intent was pain improvement and stabilization. We found reasonable coronal and sagittal correction in addition to successful clinical improvements in pain and function in long thoracolumbar reconstructions.

• Clinical Outcome of a Minimally Invasive Trans-Sacral Approach to L5-S1 Interbody Fusion
  Presenting author: William Bradley, MD
  Additional authors: Michael Hisey, MD, Donna Ohnmeiss, MD
  
  Presentation Summary

  Summary:
  Results of the study found that the trans-sacral approach to the L5-1 disc space can be performed with acceptable operating time and low blood loss. Using this minimally invasive approach combined with percutaneous pedicle screw placement, most patients had only a one night hospital stay. Mean VAS scores separately assessing back and leg pain both improved significantly as did Oswestry scores. This study supports that the trans-sacral approach is a viable technique for L5-1 interbody fusion.

  Introduction:
  Lumbar interbody fusion has long been used for treating painful degenerative spinal conditions. Access to the interbody space has traditionally been gained through a direct anterior or posterior approach. A trans-sacral technique was developed to allow access to the L5-1 disc space. The purpose of this study was to report clinical outcome of trans-sacral interbody fusion.

  Methods:
  Data were collected retrospectively for the consecutive series, beginning with the first case, of 47 patients undergoing interbody fusion performed using the trans-sacral approach (AxiaLIF; TranS1, Inc.). This report includes 40 patients with at least 6 month follow-up (mean 21.4 months, range 6 - 41 mo). Patients were treated for symptomatic disc degeneration at L5-1 unresponsive to non-operative care. In the majority of cases, posterior instrumentation was implanted using minimally invasive techniques. Clinical outcome measures were visual analog scales (VAS) assessing back and leg pain, and the Oswestry Disability Index (ODI).

  Results:
  Mean blood loss for the trans-sacral approach was 27.2 cc. The mean operative time for the interbody fusion and posterior instrumentation was 134.2 minutes and mean length of hospital stay was 1.3 days. VAS scores assessing back and leg pain improved significantly (p<0.01; Figure 1). Mean Oswestry score improved significantly from 45.2 to 28.4 (p<0.01). Two patients with pseudoarthrosis underwent a second fusion involving anterior supplementation of the trans-sacral interbody fusion and revised posterior fusion. Two patients underwent posterior instrumentation removal due to pain. One patient underwent debridement and removal of the trans-sacral cage and an anterior fusion two days after the index surgery due to a rectal tear.

  Figure 1. The mean VAS scores assessing back and leg pain improved significantly (p<0.01).

  Conclusion:
  The trans-sacral approach to L5-1 can be performed with acceptable operating time and low blood loss. Although the majority of procedures were combined anterior/posterior fusions, by using minimally invasive methods for both, most patients had only a one night hospital stay. Patients had significantly improved pain and function scores.

• Combined plasma-mediated radiofrequency ablation and cement augmentation for spine tumors diagnosed as Multiple Myeloma, Lymphoma, and Plasmacytoma
  Presenting author: Bassem Georgy, MD
  
  Presentation Summary

  Summary:
  Cavity creation with plasma mediated radiofrequency ablation before cement deposition in advanced myeloma cases allows better control of cement deposition and help stabilize vertebral column with surgery.

  Introduction:
  Vertebral body compression fractures secondary to advanced lesions of multiple myeloma (MM), lymphoma, or plasmacytoma of the spine can be complicated by cortical destruction and/or epidural extension are considered relative contraindications to conventional vertebroplasty and kyphoplasty. To evaluate whether the placement of bone cement in the anterior two-thirds of the vertebral body to stabilize the spine could be achieved using this new treatment, enabling stabilization in a patient set which is difficult to treat by conventional means.

  Methods:
  The 12 patients prospectively included in our study had painful secondary to advanced lesions of MM (n=6), plasmacytoma (n=4), or lymphoma (n=2) in the vertebral body (16 levels). All cases were accompanied by cortical destruction and/or epidural extension. Computed Tomography (CT) imaging was performed immediately before and after the procedure. Pain alleviation was measured using visual analogue scale (VAS) scores both pre-operatively and at follow-up 2-4 weeks post-procedure. A void was created in the anterior portion of the tumor-infiltrated vertebral body by using a bipolar plasma radiofrequency-based wand (ArthroCare Corporation, Austin, TX) Bone cement was then injected into the ablated cavity under fluoroscopic guidance.

  Results:
  75% of the cement was deposited in the anterior 2/3 of the vertebral body in all but 2 levels. Five levels showed no leakage. Minimal clinically insignificant extravasation was noted in 11 levels (venous: 8, cortical: 2, discal and epidural: 1). VAS pain scores were available for 9 patients; 5 (plasmacytoma: 3, MM: 2) showed significant improvement (VAS reduction >= 4), 2 (both lymphoma) showed moderate improvement (VAS reduction >= 2), and 2

  Conclusion:
  Combining two minimally-invasive procedures, plasma-mediated radiofrequency ablation and bone cement augmentation, enables treatment of advanced metastatic spine lesions with epidural extension and/or cortical destruction. Most of these patients are not candidates for open surgery, and so this less-invasive technique allows pain relief by stabilizing the anterior part of the vertebral body with a predictable and safe cement

• CT fusion assesment in XLIF patients at 1 year
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  67 XLIF patients of a single surgeon undergo a voluntary CT scan at 1 year postop; high fusion rates by CT criteria are reported.

  Introduction:
  XLIF has been shown to result in good short-term outcomes with minimal morbidity. Long-term outcomes have been assumed to mimic those of other interbody fusion procedures. However, no reports to date have focused specifically on fusion rates associated with XLIF.

  Methods:
  From our prospective, nonrandomized single-site consecutive series of 660 XLIF patients, patients reaching 1 year follow-up were asked to undergo a voluntary lumbar spine CT scan. CT scans from 67 patients with 1 year follow-up have been obtained to date, which were reviewed to evaluate fusion, and compared with clinical results and patient satisfaction.

  Results:
  Patient age ranged from 34-87yrs (average 62yrs). 89 levels were treated: 51 1-levels, 10 2-levels, and 6 3-levels; 16 at L2-3, 32 at L3-4, and 37 at L4-5. Grafting materials included a composite of DBM, local bone graft, and bone marrow aspirate. Twelve surgeries included supplemental unilateral pedicle screw fixation performed in the same surgical position. Average disk height improved from 6.2mm to 9.3mm at one-year follow-up. Signs of fusion by Lenke scores of 1or 2 were 97% at 6 months and 99% at 12 months. Fusion by CT criteria of >50% area fused was achieved in all but 3 levels (96.8%). Average VAS pain scores decreased from 8.6 at pre-op to 1.7 at 12months. At 1yr, 89% of patients were satisfied or very satisfied with their outcomes. The surgeon-reported clinical assessment was good or excellent in 84%.

  Conclusion:
  XLIF has proven to be a safe and effective procedure. This is the first report specifically highlighting fusion rates of XLIF by CT assessment. High rates of fusion can be reasonably expected using this minimally invasive interbody fusion procedure.

• Direct Economic Impact of Posterior Minimally Invasive Compared to Conventional Open Fusion Procedures for Lumbar Spondylolisthesis.
  Presenting author: Randolph Gray, MD
  Additional authors: Michael Fehlings, MD, Stephen Lewis, MD, Eric Massicotte, MD, MSc, Y. Raja Rampersaud, MD
  
  Presentation Summary

  Summary:
  In this cohort study, direct cost of 1-2 level MIS fusions were 28% lower than open fusions.

  Introduction:
  The utility of Minimally Invasive Fusion (MIS) remains controversial. Although reports of acute benefits exist, comparable controls are lacking and the impact of cost has not been assessed. The objective of this study was to compare the peri-operative morbidity and direct economic impact of one or two level primary decompression and fusions for degenerative or isthmic spondylolisthesis using a minimally invasive surgical (MIS) vs. conventional open techniques.

  Methods:
  A retrospective cohort study was performed using prospective data from 79 consecutive patients (n= 37 [MIS -one surgeon] / n=41 [open - three surgeons]) between 2005 and 2008 in a single institution from a completely socialized health care system. All 4 surgeons had at least 5 years of experience with the fusion techniques studied. Independent review was performed. In-hospital micro-costing data (OR, nursing, imaging, labs, pharmacy and allied health cost) was utilized.

  Results:
  The groups were comparable in age, sex, pre-operative hemoglobin (Hb), ASA, Charlson co-morbidity index, BMI and levels fused. All MIS patients had an inter-body cage(s) compared to only 14 in open group. Blood loss (206 vs. 798mls), transfusions (0 vs. 17%) and length of stay (5.9 vs. 8.6 days) were significantly (p<0.01) lower in the MIS group. Complications were also less in the MIS group (MIS: durotomy(1), UTI(3) / Open: durotomy (3), UTI(8), neurodeficit(1)). Average cost of an open fusion was 1.28 times greater then cost of a MIS fusion (p=0.001). There was a significant positive correlation between the length of stay and cost of surgery (Open p= 0.001, MIS p=0.01). Patient age, BMI or instrumentation did not have a significant influence on the cost.

  Conclusion:
  This matched cohort study demonstrates reduced acute postoperative morbidity and a 28% reduction in direct institutional cost associated with MIS lumbar fusion compared to open.

  Significance::
  This study refutes the common perception of high costs associated with minimally invasive fusion.

• Evaluation of the complication rate after 500 minimally invasive spinal (MIS) procedures: a European multicenter prospective study
  Presenting author: Alphonse Lubansu, MD
  Additional authors: Kanna Gnanalingham, MD, Paulo Pereira, M.D, Cornelius Wimmer, MD
  
  Presentation Summary

  Summary:
  The safety and effectiveness of MIS techniques has already been demonstrated. However, few information is available about the risk of complication associated with those techniques. In this prospective multicenter study, we evaluated the type and rate of complications associated to MIS procedures in a series of 500 MIS intervention, and the relation between those complications and the baseline variables and clinical outcome.

  Introduction:
  The reported complication rates after ??oeclassical? open surgical techniques used for instrumented lumbar fusion or stabilisation varies within wide ranges (12 to 40%). More recently, MIS techniques that associate percutaneous posterior fixation (PF) and minimal access techniques (TLIF or ALIF) have gained in popularity. The safety and effectiveness of those MIS techniques has already been demonstrated and encouraging clinical results have been reported (less operative blood loss, postoperative pain, ...). However, few information is available about the risk of complication associated with MIS techniques. In this series of 500 MIS procedures, we evaluated, prospectively, the risk of complication and its relation with baseline variables and clinical outcome.

  Methods:
  A prospective multicenter study was conducted, 500 patients (mean age: 49 yrs (12-82 years)) underwent lumbar fusion and/or stabilization using MIS techniques (TLIF + PF (n=296); ALIF + PF (n=95), PF alone (n=109)). Indications were osteochondrosis (n=232); spondylolisthesis (n=168); fracture (n=27); tumor (n=4), FBSS (n=69). Postoperative CT scans was performed to assess screw position. Instrument failures were monitored.

  Results:
  A mean follow-up of 20 months was available in our series. The total complication rate was 6.1%. Early complications: 3.6% (wound infection (n=5); dural leak (n=12), postoperative hematoma (n=4)); Late complications: 3.5% (pseudoarthrosis (n=13); hardware failure (n=5)). One major complication (dead after massive pulmonary emboli) was observed. A total of 2476 screws were placed. A misplacement rate of 1.2% (31/2476) was noted. Only 5 screws were symptomatic and need to be revised (0.6 %). No association between complications and sociodemographic characteristics, and technical variables (surgical technique, levels fused) was observed. There was no association between clinical outcome and complications. The reintervention rate was 4.6% (screw repositioning (n= 9); screw fracture (n=3), pseudoarthrosis (n=3), adjacent discopathy (n=5), hardware failure (n=2)).

  Conclusion:
  This large prospective series shows that MIS procedures can be performed with a low complication rate. Pre-existing comorbidities factors seem to have a low influence on this result.

• eXtreme Lateral Interbody Fusion (XLIF) for the treatment of Degenerative Spondylolisthesis
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Etevaldo Coutinho, MD, Luis Marchi, MSc Leonardo Oliveira, MD
  
  Presentation Summary

  Summary:
  The optimal surgical treatment for lumbar spondylolisthesis remains unclear. This work shows our clinical and radiological experience in treating degenerative spondylolisthesis in a lateral minimal invasive way.

  Introduction:
  Satisfactory clinical outcomes for the treatment of degenerative spondylolisthesis have been reported, but its optimal surgical treatment still remains unclear. The purpose of this paper is to present the extreme lateral interbody fusion (XLIF) minimally invasive for the treatment of degenerative spondylolisthesis, to stabilize, and improve the sagittal balance, foramen height and indirect decompression.

  Methods:
  27 patients, 9 males and 18 females, mean age 62.2 (39-85 years) up to two year follow up with a diagnosis of degenerative spondylolisthesis at L3-L4 or L4-L5. Lateral, A-P, and flexion-extension X-rays, neurological examination, and clinical outcome assessment using Oswestry and VAS scores were performed at the preoperative, 1, 6 week, 3, 6, 12 and 24 months postoperative intervals. The extreme lateral approach was done through the retroperitoneal space and through psoas muscle avoiding neurological and vascular lesions. A discectomy was done and the end-plate cleaned, a cage settled with graft and the ALL and PLL were preserved, adding more stability, thus the ligamentotaxis. In 16 patients the cage was left stand alone and 11 used pedicle screws for posterior supplementation.

  Results:
  The procedures were performed without complication in an average 121 minutes and with less than 50cc blood loss. VAS pain scores improved from the average 8.84 at pre-op to 3.2 at 2 years, standard deviation 1.75 and 1.16 respectively. Oswestry scores improved from an average 58.44 at pre-op to 20.75 at 2 years with standard deviation of 12.79 and 9.32 respectively. In the two groups, stand alone or supplemented with pedicle screws, occurred fusion, with no difference of consolidation time.

  Conclusion:
  Using the XLIF technique we were able to treat the deformity, decreasing pain, providing stabilization and fusion, with a quicker and better postoperative period. The XLIF technique has shown to be a safe and reproducible technique to treat spondylolisthesis deformity thought a minimally invasive way.

• Extreme laterla access to the L4-5 disk space
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  a single surgeon's series of 660 XLIF patients. XLIF is found to be a satisfactory method of accessing L4-5.

  Introduction:
  Access is limited to lumbar levels above L5-S1 due to the impediment of the iliac crest laterally. Results of XLIF procedures performed at the L4-5 level are reported to demonstrate the feasibility, safety, and effectiveness of the approach at this level.

  Methods:
  In our single-site consecutive series of 660 XLIF patients, 394 (60%) included the L4-5 level. 8 of these were lumbarized sacral levels (L5-6). Clinical and radiographic data were prospectively collected and reviewed to assess the feasibility and success of the XLIF procedure at the L4-5 level.

  Results:
  Ages ranged from 24-88 years (average 61 years). Diagnoses included stenosis(44%), spondylolisthesis(23%), HNP(9%), DDD(12%), scoliosis(7%), and post-laminectomy instability(4%). 76% had one or more comorbidities. 30% had prior lumbar surgery. 203 (52%) were obese, 58 of those morbidly obese. All procedures were successfully accessible using a breakable radiolucent table, significantly bent at the patient’s greater trochanter. Hospital stay averaged 1.2 days. Complications included 5 transient lower leg weaknesses (4 quads, 1 anterior tibialis, only one persisting longer than 6 wks); 1 endplate fracture (at L3, which resolved without intervention); 1 postoperative fracture of vertebral osteophytes which required reoperation, 2 broken cages on insertion (replaced at time of surgery without incident), 2 later-term hardware failures (1 broken rod @ 6 mos, 1 broken screw @ 12 mos), 3 respiratory complaints, 2 atrial fibrillation, 1 ileus, 1 iatrogenic HNP (laminectomy @ 4 wks), 2 compression fractures at adjacent levels (vertebroplasty at 6 and 9 mos), 1 hnp above fusion (required discectomy), 1 wound problem (subcutaneous hematoma drained POD0), and one transfusion. Average VAS pain scores improved from 8.9 pre-op to 2.4 at 12 mos. Disk height improved from 6.5 to 9.4mm; slip from 5.0 to 1.3mm. Lenke fusion scores of 1-2 were present in 89% of patients at 3 mos, 97% at 6 mos, and 99% at 12 mos.

  Conclusion:
  With adequate patient positioning, L4-5 can be accessed from the lateral approach with the same minimal morbidity advantages in other XLIF patients, no more complication, and comparable mid-term outcomes.

• Failed indirect decompression following ALIF and percutaenous pedicle screw fixation
  Presenting author: Gene Cheh, MD
  
  Presentation Summary

  Summary:
  Indirect decompression through ALIF and percutaneous pedicle screw fixation was attempted in 136 degenerative spine. The incidence, risk factors and management of failed indirect decompression were investigated.

  Introduction:
  Interbody fusion is gaining wide acceptance in lumbar spine because it has advantage of achieving lumbar lordosis and higher fusion rate. Some form of spinal stenosis, especially foraminal stenosis from disc space loss, can be decompressed by restoring disc height. But, the result of indirect decompression through realignment of anterior disc height has been inconsistent. The purpose of this study was to investigate the incidence, risk factors and management of failed indirect decompression following ALIF and percutaneous pedicle screw fixation.

  Methods:
  From 2006.6 to 2008.12 136 patients had underwent paramedian ALIF and percutaenous pedicle screw fixation. The disease entity included are described in table 1. Eight patients who had no stenosis preoperatively and 15 patients who had underwent direct decompressive laminectomy(ies) at the initial surgery were excluded from analysis. Postoperative relief of buttock and leg pain was investigated on this remaining 113 patients.

  Results:
  One hundred and sixty seven levels of ALIF were performed in 113 patients. (table2) Twenty-six out of 113 patients had residual buttock and/or leg pain that necessitated further treatment. Seven patients underwent additional decompressive laminectomy. Nerve root block and medication was tried for the remaining 19 patient resulting in temporary relief. The most frequent site of failed decompression was at L5-S1 (n=24), followed by L4-5(n=2). Posteroinferior traction spur, retrolisthesis, foraminal disc, hypertrophied superior articular process and thickend ligamentum flavum at the foramen was the causative pathology. During revision surgery, rod has to be temporarily removed to reach the foramen in five of the patients

  Conclusion:
  Twenty two percent of patients resulted in failed indirect decompression following ALIF and percutaneous pedicle screw fixation. Additional direct decompressive laminectomy relieved residual buttock and leg pain. The possibility of further direct decompressive laminectomy should be discussed with the patients when indirect decompression through ALIF is attempted.

• Feasability of Minimally Invasive Transforaminal Lumbar Interbody Fusions On a 23 Hour Stay Basis Using a Multimodal Pain Management Approach
  Presenting author: Raymond Gardocki, MD
  
  Presentation Summary

  Summary:
  Report of 11 patients undergoing MITLIF on a 23 hour or same day surgery basis using an 18-20mm fixed tubular retractor and an aggressive multimodal pain management approach.

  Introduction:
  The purpose of minimally invasive transforaminal lumbar interbody fusion (MITLIF) is to spare normal tissue function and allow for quicker recovery due to diminished post operative pain and recovery time. We have developed a MITLIF technique using an 18-20mm fixed tubular retractor (MetRx) which requires little more soft tissue disruption than a standard microscopic lumbar discectomy. This technique, combined with a multimodal pain management approach allows for MITLIF to be performed on a 23 hour stay basis.

  Methods:
  Between September 2008 and May 2009 we performed 11 MITLIF procedures in an outpatient surgical setting with 23 hour stay capabilities. We used a multimodal pain management approach including a pre-operative supplemental translaminar epidural and a combination of long acting and short acting oral narcotics post operatively. Indications for surgery included degenerative disc disease, degenerative spondylolisthesis, spondylolytic spondylolisthesis and recurrent disc herniation. Data was collected by retrospective chart review.

  Results:
  Average operative time was 126 minutes and average EBL was 124cc. Pain scores decreased from a pre-operative average of 8 on a 0-10 100mm Visual Analogue Pain Scale (VAS) to 1.73 at time of discharge. On average, patients were discharged 11.3 hours post operatively (median=7, range 3-21, SD= 7.3). Patients received an average of 20mg IV MSO4 equivalents in addition to the routine pain regimen on the day of surgery (median = 0, range = 0-14, Std Dev = 3.2). One intraoperative dural tear was encountered and closed with fibrin glue and there was one case of post operative urinary retention treated with outpatient catheterization. Post operative nausea was managed with IV Zofran and no hospital admissions were required.

  Conclusion:
  Using a minimally invasive tissue sparing technique and an aggressive pain management approach, MITLIF can be safely performed on a 23 hour stay basis. With refinement of surgical techniques and pain management approaches, MITLIF may one day be performed on an outpatient basis.

• Graft Extrusion in AxiaLIF
  Presenting author: William Smith, MD
  Additional authors: William Blake Rodgers, MD, Kyle Malone, Jamie Patterson
  
  Presentation Summary

  Summary:
  Examples of a rare AxiaLIF complication. The AxiaLIF® system for L5-S1 fusion works in a presacral corridor to access the L5-S1 disc space from the inferior aspect of the superior sacral segment. The graft aids in distracting the segment to restore disc height and spur bone growth after insertion of the rod. Compromises in the annulous, possibly exacerbated by the inflammatory response of BMP, could lead to graft extrusion as this system uses graft as a disc distracting agent.

  Introduction:
  The AxiaLIF® L5-S1 fusion is performed while leaving the annulous and ligamentous structures intact. When the annulous has been compromised, graft extrusion from the disc space is possible.

  Methods:
  Retrospective review of a combination of 447 AxiaLIF® cases by 2 surgeons.

  Results:
  5 patients (1.1%) experienced graft extrusion, 4 of which were revised.

  Case 1:
  A 64 year-old female with a transitional anatomy at L4-5 was scheduled to undergo an L4-5 XLIF® and L5-S1 AxiaLIF®. During the approach for the L4-5 XLIF®, due to her sacralized lumbar L4-5, a lateral corridor for approach could not be accessed. The XLIF® was aborted and the patient underwent a two-level L4-S1 AxiaLIF®. Shortly after surgery the patient developed a deep wound infection in the aborted XLIF® incision site and after cleaning, a CT was taken and revealed that graft material had extruded anteriorly from the L4-5 disc space (Figure 1). The patient was asymptomatic and did not require revision.

  Case 2:
  A 30 year-old female with DDD underwent an AxiaLIF®. The patient readmitted to the hospital POD4 complaining of pain and neurological deficits in the back and legs. A CT revealed graft extrusion posteriorly into the intradural space, and an immediate 4 hour operation was performed to remove the dura (Figure 2).

  Case 3, 4, and 5:
  A 53 year-old female with DDD and instability at L5-S1, a 62 year-old female with several degenerative spine conditions, and a 37 year old woman with a disk herniation at L5-S1, all underwent an AxiaLIF trans-sacral fusion with instrumentation. All 3 patients had prior annular tears, and all 3 patients experienced a recurrence of symptoms at 6 weeks postop AxiaLIF. MRIs revealed graft material herniations through prior annular tears (Figure 3), and all three patients underwent laminotomy and removal of graft material. All 3 report residual symptoms. One was revised at 12 months for pseudarthrosis.

  Conclusion:
  Compromises in the annulous, possibly exacerbated by the inflammatory response of BMP, could lead to graft extrusion as this system uses graft as a disc distracting agent, thus greatly increasing intra-annular pressure. This complication is rare in this series and we are unaware of any other similar cases.

• Incidence, Distrivution, and Surgical Relevance of Abnormal Pedicles in Normal and Deformed Spines: A CT Based Study of 6354 Pedicles
  Presenting author: Vishal Sarwahi, MD
  Additional authors: Adam Wollowick, MD, Terry Amaral, MD, Beverly Thornhill, MD, John Czerwein, MD, Melanie Gambassi, PNP
  
  Presentation Summary

  Summary:
  A CT based classification system of pedicle morphology was applied to patients with and without spinal deformity. Abnormal pedicles are more commonly seen in deformed spines than in normal spines. Spinal deformity also causes higher degrees of pedicle dysmorphism. Dysmorphic pedicles are more commonly found in the periapical region and are significantly more prone to screw malposition.

  Introduction:
  Pedicle screws are commonly used in spinal deformity surgery. Pedicle screw malpositioning can injure vital structures and can cause significant morbidity. An understanding of vertebral morphology is critical for accurate screw placement.

  Methods:
  96 patients who had whole body CT scans for non-spinal pathology and 97 pediatric spinal deformity patients with preand post-operative CT scans were reviewed. Pedicle morphology was recorded using the CT-based classification system. Pedicle morphology was classified as: Type A: >4mm cancellous channel, Type B: 2-4mm channel, Type C: cortical channel, and Type D: non-existent pedicle. The incidence of pedicle dysmorphism, the location within the periapical region, and the incidence of screw malpositioning were recorded.

  Results:
  The incidence of pedicle dysmorphism in non-deformity subjects was 9.8% compared to 22% in pediatric deformity patients (p<.001). Of the 300 abnormal pedicles in non-deformity patients, 77% were Type B, 22% were Type C, and 1% was Type D. Dysmorphism was more common in the periapical region than in non-apical vertebrae (32.6% vs. 19.7%, p<.001). The incidence of screw malpositioning was significantly higher in dysmorphic pedicles than in normal pedicles (17% vs. 6.7%, p<.001).

  Conclusion:
  Pediatric patients with spinal deformity have a higher incidence of abnormal pedicle morphology than non-deformity patients. The degree of pedicle dysmorphism was also higher in spinal deformity patients with significantly more Type C and D pedicles than control subjects. Abnormal pedicles are more commonly found in the periapical region and are more prone to screw malpositioning.

• Innovative vertebral augmentation technique maximizes fracture reduction compared to vertebroplasty and balloon kyphoplasty.
  Presenting author: Kent Remley, MD
  
  Presentation Summary

  Summary:
  Vertical reduction of spinal compression fractures with the StaXx? FX Structural Kyphoplasty System achieves greater fracture reduction when compared to standard percutaneous vertebral augmentation techniques. Assessment of fracture reduction was performed comparing preoperative and postoperative standing lateral radiographs. There was 83% height restoration of the vertebral body anteriorly and 86% height restoration centrally. This fracture reduction technique provides excellent structural support, preventing, intraoperative and postoperative loss of height restoration, when compared to other augmentation techniques.

  Introduction:
  One goal of vertebral augmentation is restoration of vertebral height. Mild to moderate height restoration has been reported for both vertebroplasty and balloon kyphoplasty. The StaXx® FX Structural Kyphoplasty System represents a technological advancement in vertebral augmentation, providing direct vertical fracture reduction, with fracture reduction in 1 mm increments. The PEEK implant is secured by placement of adjacent bone cement. The purpose of this study is to determine the percentage of fracture reduction achieved with the StaXx® FX system during vertebral augmentation.

  Methods:
  Retrospective review of the radiographs of 34 subjects undergoing vertebral augmentation with the StaXx® FX system was performed to evaluate for change pre- and postoperative vertebral body height. Using standing lateral radiographs, measurement points are marked on the superior and inferior endplates of each fractured ver¬tebra and the nearest non-fractured vertebra (reference vertebra). Vertebral height is measured at anterior, central, and posterior points. Digitized films are measured by an independent source using validated software. Vertebral body height is reported as a percentage of the reference height. The change between pre-operative and 2 week post-operative radiographs is then calculated.

  Results:
  Pre-operative and post-operative films sets were available for 24 levels in 21 patients. No device related neurological or pulmonary complications occurred. Pre-operatively, all fractures demonstrated at least 15% initial height loss, with a mean loss of 52%. Mean height restorations were statistically significant. Anteriorly, 83% (p<0.001) of the lost height was restored. Centrally, 86% (p<0.003) of the lost height was restored. Posteriorly, 79% (p<0.005) of the lost height was restored.

  Conclusion:
  Percutaneous vertebral augmentation, using the StaXx® FX System demonstrates superior height restoration when compared with vertebroplasty (3-48%) or balloon kyphoplasty (3-49%) techniques. The technique of vertical fracture reduction with implanted PEEK wafers minimizes intraoperative loss of correction, allowing the device to be more effective at retaining the positional and procedure reduction.

• Interspinous Indirect Decompression using the DIAM device for Focal Lumbar Spinal Stenosis (FLSS)
  Presenting author: Y. Raja Rampersaud, MD
  Additional authors: Oma Persaud, MSc
  
  Presentation Summary

  Summary:
  Comparable short-term outcomes where achieved using a interspinous device comapred to decompression.

  Introduction:
  Symptomatic FLSS is most commonly treated by direct decompression, however neural complications can occur. The primary objective of this study was to assess patient reported outcomes (PRO) following implantation of a composite viscoelastic interspinous device (indirect decompression) for FLSS.

  Methods:
  A prospecitve cohort pilot study with a priori protocols of a consecutive series of indirect decompression (ID) for FLSS was conducted. The primary clinical outcome measure was ODI, secondary measures were pain scores and SF-36 PCS/MCS. The device was inserted using a modifed minimally invasive unilateral technique. No direct neural decompression was performed. Outcomes were also compared to a consecutive series of direct MIS decompression (DD) for FLSS. Indications for surgery were similar in both groups.

  Results:
  Mean age was 62 years (ID:n=9; n=3-2level; n=3 -spondylisthesis) and 67 years (DD:n=134). As shown in table 1, significant improvements (statistical and clincial) was seen for all PRO measures in both groups. PRO between groups where not statitically significant (p>0.01). Both groups were performed as day surgery, however the operative time was 50% (ID=55.5 vs. DD 109.4 minutes; p<0.0001) less for the ID group. One complication occurred in the ID group (early post-operative spinous process fracture that required decompression and fusion). The prospective acute complication rate for the DD group was 12% (majority = dural tear) and included 1 epidural hematoma (cauda equina syndrome) and 1 nerve root injury.

  Conclusion:
  In the short-term, the outcome of ID using the DIAM device for FLSS compared to minimally invasive DD seem to be comparable. ID enabled significantly shorter operative time and reduces the risk of epidural or neural complications compared to DD. FLSS is one of the most common reasons for back surgery in people over the age of 50 in Canada and the United States. ID is completely reversible and can be considered as a less invasive intermediate approach along the continuum of care for FLSS. Furthermore it does not compromise any therapeutic alternatives, including traditional laminectomy (with or with out fusion) or less invasive –direct microsurgical decompressive procedures.

• Interspinous Lumbar Instrumented Fusion (ILIF) in a Sheep Model
  Presenting author: Hyun Bae, MD
  Additional authors: L.e.a. Kanim, MS
  
  Presentation Summary

  Summary:
  Interspinous process translaminar fusion occurs when treated with the ILIF procedure. ILIF with decompression is no more intrusive than a standard laminotomy and is an option when treating lumbar spinal stenosis (LSS).

  Introduction:
  Surgeons continue to debate whether the proper treatment for LSS is decompression alone or decompression with fusion. Posterior lateral fusion with instrumentation imposes significant morbidity. Thus, surgeons and patients are seeking safer, more efficient, and less-disruptive fixation and fusion methods to augment the decompression. The ILIF technique is a minimally disruptive procedure for segmental posterior instrumented fusion and decompression surgery. ILIF consists of a precision-machined allograft spacer that seats onto the lamina at the base of the spinous processes, and a spinous process plate system for posterior fixation of adjacent spinous processes.

  Methods:
  An interspinous process translaminar fusion procedure was performed using an allograft spacer (from sheep tibia) in the lumbar spine of 8 sheep at levels L2-3 and L4-5, with L3-4 level remaining intact. Posterior instrumentation (NuVasive® Affix™ plate) was also implanted in 50% of the operative levels. Treatments of allograft spacer, plate, and rhBMP2 were assigned and balanced across levels in two groups of sheep. Sheep were sacrificed at 6 or 12 months. CT scans and histology were completed as well.

  Results:
  Each specimen at the operative level at 6 months and 12 months showed a solid fusion (no motion) with supporting CT and histological data on all but one. The specimen from the spacer only treatment condition was manually stiff yet with slightly less continuous remodeling.

  Conclusion:
  Interspinous process translaminar fusion readily occurs when treated with the ILIF procedure. ILIF with decompression is no more intrusive than a standard laminotomy and may be an option when treating lumbar spinal stenosis (LSS).

• Interspinous Lumbar Instrumented Fusion (ILIF) in a Sheep Model
  Presenting author: Hyun Bae, MD
  Additional authors: L.e.a. Kanim, M.S.
  
  Presentation Summary

  Summary:
  ILIF with decompression is no more intrusive than standard laminotomy and maybe an option for treating lumbar spinal stenosis. ILIF using an allograft spacer (sheep tibia), plate, and rhBMP2 were compared across levels in the lumbar spines of sheep. Solid fusions were observed at 6 and 12 months. Interspinous process translaminar fusion occurs with the ILIF procedure. ILIF with decompression is no more intrusive than a standard laminotomy and is an option when treating lumbar spinal stenosis.

  Introduction:
  Surgeons continue to debate whether the proper treatment for LSS is decompression alone or decompression with fusion. Posterior lateral fusion with instrumentation imposes significant morbidity. Thus, surgeons and patients are seeking safer, more efficient, and less-disruptive fixation and fusion methods to augment the decompression. The ILIF technique is a minimally disruptive procedure for segmental posterior instrumented fusion and decompression surgery. ILIF consists of a precision-machined allograft spacer that seats onto the lamina at the base of the spinous processes, and a spinous process plate system for posterior fixation of adjacent spinous processes.

  Methods:
  An interspinous process translaminar fusion procedure was performed using an allograft spacer (from sheep tibia) in the lumbar spine of 8 sheep at levels L2-3 and L4-5, with L3-4 level remaining intact. Posterior instrumentation (NuVasive® Affix™ plate) was also implanted in 50% of the operative levels. Treatments of allograft spacer, plate, and rhBMP2 were assigned and balanced across levels in two groups of sheep. Sheep were sacrificed at 6 or 12 months. CT scans and histology were completed.

  Results:
  Each specimen at the operative level at 6 months and 12 months showed a solid fusion (no motion) with supporting CT and histological data on all but one. The specimen from the spacer only treatment condition was manually stiff yet with slightly less continuous remodeling.

  Conclusion:
  Interspinous process translaminar fusion readily occurs when treated with the ILIF procedure. ILIF with decompression is no more intrusive than a standard laminotomy and may be an option when treating lumbar spinal stenosis (LSS).

• Lateral Interbody Fusion without Neuromonitoring: A Novel Lateral Approach to the Lumbar Spine
  Presenting author: Mitchell Hardenbrook, MD
  
  Presentation Summary

  Summary:
  Current lateral approach systems require neuromonitoring to reduce risk of nerve injury. A novel technique has been developed which obviates the need for neuromonitoring. A technical report and patient outcomes are presented.

  Introduction:
  Eighty-two patients with a diagnosis of degenerative disc disease, or spondylolisthesis underwent minimally anterior retroperitoneal approach with interbody fusion using Peek spacers with Infuse (60% of cases) and FRA Infuse in 40% of the cases. The fusion level was stabilized with MIS pedicle screw fixation.

  Methods:
  The patients were followed from 2002 to 2008 (12-72 m; 40 m av). Thirty-two patients (41 levels) had FRA + BMP; fifty patients (72 levels) had Peek + BMP.

  Results:
  We looked at EBL, complications, length of hospital stay, rate of union and clinical outcome difference between the two groups. In the FRA group, 6 patients (18.5%) developed a nonunion. In the Peek group, one patient developed a nonunion (2%). Pre-op disc height in both groups was 8 mm; immediate post op was 12mm. At final follow-up, disc height was 8.5mm in FRA and 10.5mm in the Peek group. Surgical time and EBL were similar in both groups. Length of hospital stay was similar (24-36 hr).

  Conclusion:
  Mini-open ALIF with posterior MIS pedicular screw fixation is a useful technique for the treatment of lumbar disc disease. The rate of fusion with the Peek spacer is close to 100%. Disc height restoration and lordosis preservation is achievable. We do not recommend the use of FRA with BMP for anterior fusion.

• Lumbar Extracavitary Interbody Fusion (LEC LIF, Lé LIF): Optimizing Modern Minimally Invasive Spinal Surgery and Biomechanical Concepts
  Presenting author: Donald Dietze, MD
  
  Presentation Summary

  Summary:
  A novel minimally invasive extracavitary lumbar interbody fusion technique is presented along with a retrospective case series. Data collected from 15 cases with a postoperative follow up average of 14 months and median follow up of 10 months. 73% had a good result for back pain and 92% had a good result for leg pain. There was one pseudarthrosis and one spinal fluid leakage as complications. Outcomes cannot be determined from this retrospective study but the gestalt is promising.

  Introduction:
  There are two modern trends in lumbar interbody fusion for painful degenerative disc disease: 1) Oblique cages used with posterior approaches (TLIF) and 2) Lateral approaches (XLIF) using larger cages docked on the apophyseal ring. The oblique cage technique simplifies placement of interbody implant but may increase settling and loss of alignment. Lateral approaches provide reliable alignment restoration but requires repositioning for decompression and posterior spinal instrumentation. TLIF remains preferred when decompression is paramount, and XLIF is becoming preferred for deformity correction.

  We present a non-randomized retrospective study of a novel technique for lumbar interbody fusion that approaches the lateral disc outside of the spinal canal and retroperitoneal space called an extracavitary lumbar interbody fusion (LEC LIF, Lé LIF). With the patient in a prone position, a minimally invasive spinal approach is used to place a lateral implant onto the apophyseal ring. The Lé LIF bridges the advantages of the TLIF and XLIF by allowing decompression and reliable alignment restoration.

  Methods:
  Between October 2003 to April 2007, 69 patients with symptomatic lumbar disc disease underwent the Lé LIF procedure as part of their surgery. 15 of these cases involved one or two level Lé LIF surgery only and the results will be determined from their data for consistency. All patients had received a minimum of 6 months of conservative treatment. Postoperative follow-up averaged 14 months with a median follow-up of 10 months.

  Results:
  Using Visual Analog Scale for pain level (VAS), 73% had a good outcome for back pain and 92% had a good outcome for radicular pain. In only one case did a computed tomography scan suggest pseudarthrosis with unusual endplate and centrum lucency that was felt to be clinical symptomatic. No patient had new neurologic deficits postoperative including radiculitis. Complications included a cerebrospinal fluid leak in 1 patient. There were no wound complications. There were no cases of cage migration or settling. There were no spinal instrumentation complications.

  Conclusion:
  This small series shows the potential for the Lé LIF to be performed using a minimally invasive technique.

• Lumbar Plexus Palsy After XLIF: An Avoidable Complication?
  Presenting author: Jeffrey Coe, MD
  Additional authors: Steven Meyer, MD
  
  Presentation Summary

  Summary:
  The incidence of lumbar plexus injury in a series of 100 XLIF consecutive patients is 3.0%. If the L4-5 level is included, the incidence is 3.8%. The risk of injury to the lumbar plexus can be minimized by avoiding excessive table flexion (stretch) and excessive posterior retraction (compression). Despite significant short term impairment requiring the use of assistive devices, the prognosis for recovery by 6 month is excellent.

  Introduction:
  XLIF has gained wide acceptance in the last 3 to 5 years as an alternative to ALIF, PLIF and TLIF for interbody fusion of the lumbar spine above L5-S1. Continuous and evoked EMG monitoring ostensibly allows safe navigation through the mid to anterior psoas muscle by detecting proximity and thereby avoiding injury to the lumbar plexus. Despite the use of monitoring, however, the authors have noted several cases of lumbar plexus injury with XLIF. The purpose of this paper is to evaluate the anatomic and technical factors leading to lumbar plexus injury.

  Methods:
  The first 100 consecutive cases of XLIF performed by the authors with a minimum of 6 months follow-up formed the cohort for analysis in this study. All patients were observed for quadriceps weakness and subsequent recovery. The factors leading to quadriceps weakness were assessed.

  Results:
  The authors performed 100 consecutive XLIF cases with a mean follow-up of 16.6 months. The mean number of operated levels was 1.8. Three of the 100 total patients (3.0%) were noted to have significant quadriceps weakness lasting longer than 6 weeks that required the use of assistive devices for greater than two weeks. In all three the L4-5 level was included in the fusion, representing 3.8% of the 78 patients that included L4-5 as an operated level. In each of these patients, the L4-5 level was noted to be anatomically challenging, requiring aggressive table flexion to access the disc. Also, each of these patients had EMG stimulation thresholds < 5 Ma, mandating anterior transpsoas penetration and thus posterior retraction of the bulk of the psoas muscle to access the disc. All three patients experienced sufficient recovery by 6 months such that assistive devices were no longer required for ambulation.

  Conclusion:
  XLIF carries a risk of lumbar plexus injury that is reduced, but not eliminated, by the use of EMG monitoring; with L4-5 being the most susceptible level. The authors hypothesize that the risk of lumbar injury is associated with a combination of compression of the lumbar plexus (resulting from posterior retraction) and lumbar plexus stretch from aggressive table flexion. Fortunately, the prognosis for recovery from this injury is excellent.

• Mini open ALIF plus MIS pedicular screw fixation for treatment of lumbar disc disease
  Presenting author: Mohammad Majd, MD
  Additional authors: Richard Holt, MD
  
  Presentation Summary

  Summary:
  Mini-open ALIF with posterior MIS pedicular screw fixation is a useful technique for the treatment of lumbar disc disease. The rate of fusion with the Peek spacer is close to 100%. Disc height restoration and lordosis preservation is achievable. We do not recommend the use of FRA with BMP for anterior fusion.

  Introduction:
  Eighty-two patients with a diagnosis of degenerative disc disease, or spondylolisthesis underwent minimally anterior retroperitoneal approach with interbody fusion using Peek spacers with Infuse (60% of cases) and FRA Infuse in 40% of the cases. The fusion level was stabilized with MIS pedicle screw fixation.

  Methods:
  The patients were followed from 2002 to 2008 (12-72 m; 40 m av). Thirty-two patients (41 levels) had FRA + BMP; fifty patients (72 levels) had Peek + BMP.

  Results:
  We looked at EBL, complications, length of hospital stay, rate of union and clinical outcome difference between the two groups. In the FRA group, 6 patients (18.5%) developed a nonunion. In the Peek group, one patient developed a nonunion (2%). Pre-op disc height in both groups was 8 mm; immediate post op was 12mm. At final follow-up, disc height was 8.5mm in FRA and 10.5mm in the Peek group. Surgical time and EBL were similar in both groups. Length of hospital stay was similar (24-36 hr).

  Conclusion:
  Mini-open ALIF with posterior MIS pedicular screw fixation is a useful technique for the treatment of lumbar disc disease. The rate of fusion with the Peek spacer is close to 100%. Disc height restoration and lordosis preservation is achievable. We do not recommend the use of FRA with BMP for anterior fusion.

• Minimally Invasive Pedicle Screw Instrumentation For Pediatric Spinal Deformity: Safety And Feasibility In First 30 cases.
  Presenting author: Rasesh Desai, MD
  Additional authors: Vivek Sharma, MD, Atiq Durrani, MD, Alvin Crawford, MD
  
  Presentation Summary

  Summary:
  Early results in 30 cases with scoliosis/kyphosis treated by minimally invasive corrective surgery using pedicle screws and rods.

  Introduction:
  The aim of the study is to evaluate the feasibility of a new technique of minimally-invasive corrective surgery for scoliosis/kyphosis using pedicle screws and rods and to investigate its safety, corrective potential , complications and perioperative morbidity.

  Methods:
  A retrospective chart review of 30 patients treated by minimally invasive percutaneous posterior spinal instrumentation for either scoliosis or kyphosis from 11/01/07 through 12/31/08 was carried out after IRB approval. Patient demographics and perioperative data were reviewed. Preoperative and postoperative cobb angles were compared.

  Results:
  There were 23 females and 7 males with a mean age of 16.6 years. There were 25 scoliosis and 5 Kyphosis patients. Three (2 kyphosis, 1 scoliosis) had an additional video assisted thoracoscopic release at the same stage. The mean preoperative and postoperative cobb angle for scoliosis were 48.6 and 18.3 respectively.The mean preoperative and postoperative cobb angle for kyphosis were 64.7 and 36.2 respectively. Average no. of instrumented levels and screws per patient were 11 and 16 respectively. The average duration of surgery was 4 hrs 57 minutes. The mean estimated blood loss was 261.5 ml. Only 3 patients needed blood transfusion. The mean hospital stay was 3.4 days. Four patients had intraoperative spinal cord monitoring changes, 3 returned to baseline before the end of surgery. One patient had postoperative left leg weakness which resolved completely in two days. There were no postoperative complications.

  Conclusion:
  To our knowledge, this is the first study identifying safety and feasibility of using minimally invasive surgical techniques in treating spinal deformities in children and adolescents. Short term data suggests a trend towards decreased morbidity and feasibility of minimally invasive percutaneous pedicle screw instrumentation for scoliosis as well as kyphosis.

• Minimally Invasive Scoliosis Surgery in AIS Patients: A Technique and Feasibility Study
  Presenting author: Vishal Sarwahi, MD
  Additional authors: Terry Amaral, MD, Adam Wollowick, MD, Laury Cuddihy, MD, Melanie Gambassi,PNP
  
  Presentation Summary

  Summary:
  Minimally invasive scoliosis surgery is technically challenging but feasible in adolescent idiopathic scoliosis patients. At present, experience is limited to curves less than 70 degrees and curves that are flexible to more than 50 percent. If needed, osteotomies can be performed. The present instrumentation is limited in its capacity to enable various corrective maneuvers. However, reasonably good correction can be obtained with less blood loss and shorter hospital stay.

  Introduction:
  With minimally invasive spine surgery becoming fairly routine, the next logical step is to assess the feasibility in AIS patients.

  Methods:
  Five AIS patients underwent minimally invasive scoliosis surgery. Posterior spinal fusion and instrumentation was carried out over multiple levels. Three midline skin incisions were utilized; stab incisions in the fascia were made four screw incisions. Three vertebral levels (six screws) were instrumented per incision. Free hand pedicle screw placement technique was utilized and a mix of reduction screws and standard screws with open-ended MIS connector were utilized. The inferior facet was osteotomized with a quarter inch osteotome and BMP with local autograph was utilized for fusion purposes. Rod derotation, rod translation, and DVR maneuvers were utilized for correction. Use of reduction screws facilitated rod placement and curve correction.

  Results:
  There were five female patients with a mean age of 15.2 years, mean COBB angle of 42.1 degrees and mean preoperative kyphosis of 28.2 degrees. The average levels fused were 9.8 with an average EBL of 440cc, and average operative time of 7h 50min. There were no complications. The average length of stay was 6.6 days. Mean VAS was 3.23. The average postoperative Cobb angle was 7.3. The average postoperative kyphosis was 26.8.

  Conclusion:
  This study demonstrates that it is technically feasible to treat AIS patients utilizing the MIS techniques. Possible short-term benefits include less blood loss, lower pain scores, and shorter length of hospital stay. At present, flexible curves less than 70 degrees can be treated in this manner. Good correction in coronal and sagittal planes can be obtained. Pedicle screws can be placed in the standard freehand manner, thereby, decreasing the radiation exposure.

• Minimally Invasive Transforaminal Lumbar Interbody Fusions on a 23 Hour Stay Basis: Preliminary Results Out to 3 Month Follow Up
  Presenting author: Raymond Gardocki, MD
  
  Presentation Summary

  Summary:
  Preliminary results out to 3 months of 11 patients who underwent MITLIF using Infuse in a 23 hour setting. Results include VAS, ODI, SF-36 and narcotics use.

  Introduction:
  The purpose of minimally invasive transforaminal lumbar interbody fusion (MITLIF) is to spare normal tissue function and allow for quicker recovery due to diminished post operative pain and recovery time. We have developed a MITLIF technique using an 18-20mm fixed tubular retractor (MetRx) which requires little more soft tissue disruption than a standard microscopic lumbar discectomy. This technique, combined with a multimodal pain management approach allows for MITLIF to be performed on a 23 hour stay basis with quick recovery and excellent results.

  Methods:
  Between September 2008 and May 2009 11 MITLIF procedures were performed by a single surgeon with BMP (Infuse) in an outpatient surgical setting with 23 hour stay capabilities. Indications for surgery included degenerative disc disease, degenerative spondylolisthesis, spondylolytic spondylolisthesis and recurrent disc herniation. Data was collected by retrospective chart review and includes the VAS, ODI, SF-36 and narcotic use out to 3 months of follow up.

  Results:
  Average operative time was 126 minutes and average EBL was 124cc. Pain scores decreased from a pre-operative average of 8.05 on a 0-10 100mm Visual Analogue Pain Scale (VAS) to 2.33 (p<0.01) at 3 month follow up for a 71% average improvement in VAS. Oswestry disability index (ODI) scores decreased from a pre-operative average of 54 to 17.25 at three months. Pre-operative physical component (PCS) and mental component (MCS) scores from the SF-36 were 29 and 64 respectively. Both PCS and MCS improved to 79 and 66 at three months post-operative. Narcotics use decreased from 64% of patients pre-operatively to 38% at three months.

  Conclusion:
  Using a minimally invasive tissue sparing technique and an aggressive pain management approach, MITLIF can be safely performed on a 23 hour stay basis with good initial results. We believe that MITLIF will replace open TLIF as the standard of care for conditions like degenerative spondylolisthesis.

• Minimally invasive treatment of adjacent segment degeneration via XLIF
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  Clinical and radiographic outcomes of patients treated by XLIF for ASD are reported.

  Introduction:
  The XLIF approach provides a minimally disruptive alternative to anterior column access that allows for large graft placement, disk height restoration, and indirect decompression, while avoiding posterior scar tissue from the previous procedure. Results of ASD treated minimally invasively using XLIF are presented.

  Methods:
  Of our single-site consecutive series of 660 XLIF patients, 166 were treated for ASD. Clinical and radiographic measures were prospectively collected and evaluated to assess comorbidities, surgical details, hospital stay, complications, pain scores, changes in disk height and alignment, and fusion.

  Results:
  Age ranged from 29-87 years (ave 61.8 years). Comorbidities included smoking (35%), chronic steroid use (10%), diabetes (26%), CAD (48%), and COPD (8%). 89 patients (54%) were obese (BMI>30), 28 of those morbidly obese (BMI>38). All but one case included supplemental fixation: 45% unilateral pedicle screws, 2% bilateral pedicle screws, 19% lateral embroidered plate, and 36% laterally tabbed interbody implant. In 15 cases with prior posterior instrumentation, the pre-existing rods were removed unilaterally and revised on that side; in all other cases with prior instrumentation, adjunctive lateral fixation was used. Hospital stay averaged 1.09 days, with no blood transfusions or wound infections. Complications included intraoperative hardware failure (2, revised during same procedure with no incident), postop hardware failure (1, revised), ileus (2), urinary retention (1), peritoneal catheter occlusion (1), atrial fibrillation (3), MI at 6 weeks post-op (1), pulmonary embolism (1), compression fracture at adjacent level (5), sacral fracture (1), HNP at adjacent level (1), subcutaneous hematoma (1), and postoperative quadriceps weakness (1, resolved within 4 weeks of surgery). Average pain scores (VAS) improved by 5.4 points from pre-op to 12 months. Ave. disk height improved from 6.7 to 10.5 at post-op, settling to 8.6 at 12 mos; slip from 3.3 to 0.4mm. Definitive signs of fusion (Lenke 1-2) were present in 80% at 3 months, 91% at 6 months, and 100%.

  Conclusion:
  Our experience using XLIF for ASD has shown that clinical and radiographic indicators improve commensurately and the overall outcome is encouraging.

• Minimally invasive treatment of post-laminectomy syndrome via XLIF
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  Results of post-laminectomy syndrome treated minimally invasively using XLIF are presented of a single surgeon's series of 660 XLIFs.

  Introduction:
  The XLIF approach provides a minimally disruptive alternative to anterior column access that allows for large graft placement, excellent disk height restoration, and indirect decompression, while avoiding posterior scar tissue from the previous procedure. Results of post-laminectomy syndrome treated minimally invasively using XLIF are presented.

  Methods:
  Of our single-site consecutive series of 660 XLIF patients, 97 had prior decompressive surgery. Clinical and radiographic measures were prospectively collected and evaluated to assess surgical details, hospital stay, complications, pain scores, changes in disk height and alignment, and fusion.

  Results:
  Ages ranged from 30-89 years (average 62.8years). Comorbidities included CAD (49%), smoking (33%), diabetes (23%), and COPD (7%). 44 patients (45%) were obese (BMI>30), 14 of those morbidly obese (BMI>38). 130 levels were treated: 72 1-level, 17 2-level, and 8 3-level; 73.2% of cases included the L4-5 level. All cases included supplemental fixation: 87% unilateral pedicle screws, 2% transfacet screws. There were no blood transfusions or wound infections. Hospital stay averaged 1.4 days. Complications included 2 cases of pneumonia; 2 cases of neural trauma with transient lower limb weakness, both resolving within 6-12 weeks; one postop transfusion, and one infection. Average VAS pain scores improved from 8.6 at pre-op to 2.6 at 12 months follow-up. Average disk height improved from 5.7 to 9.5mm; slip from 5.1 to 0.9mm. At 3 months, Lenke fusion scores averaged 1.87; at 6 months, 1.33; and at 12 months, 1.10. 93% of patients with 12 month follow-up have a Lenke score of 1.

  Conclusion:
  Our results show that patients with prior posterior decompressive surgery who require additional surgery to stabilize the anterior column benefit from the XLIF procedure. Complications are few, and improvements in clinical and radiographic outcomes are encouraging. XLIF is an alternative surgical approach that avoids the prior approach scar in patients with post-laminectomy syndrome who require stabilizing surgery.

• Minimally Invasive Treatment of Thoracolumbar Spine Fractures
  Presenting author: Terrence Julien, MD
  Additional authors: Cara Sedney, MD, James Mills, MD, Brenton Coger, MD
  
  Presentation Summary

  Summary:
  Minimally invasive spinal fusion techniques are promising and growing in popularity. The purpose of this research is to analyze the use of MIS techniques in the field of thoracolumbar trauma.

  Introduction:
  Thoracolumbar spinal injuries are common, especially in blunt trauma such as motor vehicle accidents and falls. These injuries often necessitate operative interventions to restore stability to the spinal column. While more traditional methods of spinal fusion are successful for these injuries, newer minimally invasive techniques have been developed and show promise in the setting of traumatic injury.

  Methods
  All surgical cases from the senior author over a period of 15 months were reviewed. Cases of minimally invasive fusions done for thoracolumbar trauma were identified. Laminectomies and kyphoplasty/vertebroplasty were omitted. These cases were assessed for operative time, length of hospital stay, and estimated blood loss. The exact procedure and number of levels fused were also recorded.

  Results:
  Of the 210 cases done over a one year period by the senior author, 12 of these were minimally invasive fusions for thoracolumbar spinal trauma. The average number of levels fused was 5. Average estimated blood loss was 250 ml. Average operative time was 4 hours. Average hospital stay was 8.3 days.

  Conclusion:
  Minimally invasive spinal fusion techniques are promising and growing in popularity. Minimally invasive techniques in general have been shown to reduce length of stay, post-operative pain, and blood loss. There may be a particular utility for minimally invasive techniques in spinal trauma for these same reasons. A direct comparison of minimally invasive techniques with more traditional methods of spinal fusion for trauma is warranted to assess these topics.

• MIS 2 Level Fusion v. Open 2 Level Fusion: The Significance of a Surgeon's Efficiency
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  A surgeon examines data and finds that his transition to minimally invasive spine surgery from traditional open platform increases his clinical and personal efficiency.

  Introduction:
  The AHA released data in April 2009 stating that 59% of hospitals have reported either a moderate or significant decrease in elective procedures.1 Efficiency is more crucial than ever in the healthcare industry. This study examines the effect of transition to MISS from traditional open methods on a spine surgeon's efficiency.

  Methods:
  Key performance indicators (KPIs) were defined as determining factors of a single surgeon’s efficiency. KPIs included length of stay (LOS) and complication rate, cases per day, patient encounters, and personal hours saved per day. Clinical data from a single-site series of 121 2 level MIS lumbar fusions (2 level XLIFS and XLIF-AxiaLIF combinations at L4-S1) were prospectively collected from 2007-2009 and evaluated in comparison with a retrospective database of 109 open 2-level PLIF patients from the same practice, captured from 2005-2007. Case quantity and patient encounter data from a surgeon’s practice were prospectively collected from 2005-present and retrospectively reviewed to measure KPIs and calculate efficiency.

  Results:
  Clinical performance indicators showed an increase in efficiency with MIS fusions. In the MIS group, average LOS was 27.6 hours ,and the rate of complications was 4.9% with no infections; in the open group, LOS 75.8 hours, and rate of complications 13.6% with 3 infections. OR time for 2 level XLIFs was 103.3 minutes, and OR time for XLIF-AxiaLIF combinations was 137.6 minutes, which includes placing posterior instrumentation. OR time for the open group was 107 minutes. Reoperation rate in the MIS group was 2.2%; in the open group, 12.7%. Cases per day in 2008 were 5.2, compared to 3.9 in 2005. From 2006 to 2008, patient encounters increased 51.2%. Personal hours saved per day, compared to years prior to 2007, was 2.32 hrs – 10%-20% of a work day.

  Conclusion:
  The advent of MIS techniques in a single surgeon’s practice has greatly improved efficiency. This efficiency, defined by improved clinical outcomes, an increase in cases per day and patient encounters, and personal hours saved, has lead to increased profitability of the surgeon’s practice and may advantageously affect the profitability of hospitals and related institutions, potentially counteracting the decrease.

• Outcomes of minimally invasive surgery (MIS) compared to open fusion for spondylolisthesis
  Presenting author: Y. Raja Rampersaud, MD
  Additional authors: Mladen Djurasovic, MD, Leah Carreon,MD, Oma Persaud, Paul Anderson, MD, Steven Glassman, MD
  
  Presentation Summary

  Summary:
  Spondylolisthesis is a well-defined and focal structural abnormality that can cause significant mechanical back pain, neurogenic claudication, and radiculopathy. The efficacy and outcomes of open spinal decompression and fusion has been validated for spondylolisthesis, however the morbidity associated with open surgery is undesirable. MIS techniques, such as MIS transforaminal lumbar interbody fusion (MIS-TLIF), have been shown to reduced acute surgical morbidity, however, due to very limited comparative data, the clinical efficacy of this techniques remains unproven.

  Introduction:
  The primary objective of this study was to compare patient reported outcomes (PRO) following MIS or Open fusion for spondylolisthesis.

  Methods:
  A multicentered retrospective cohort study of prospectively collected data was performed. Consecutive patients from academic spine centers were used. The primary clinical outcome measure was change in ODI at 1 year, secondary measures were pain scores and SF-36 PCS/MCS. One level instrumented fusions for low grade (I-II) spondylolisthesis from 3 centers, using either a posterior MIS (2 centers: TLIF-n=59) or Open technique (2 centers: TLIF-n=43 / posterolateral-n=87), with a minimum of 1 year follow-up and baseline patient reported outcomes (PROs) were compared.

  Results:
  As shown in table 1, both groups demonstarted significant clinical improvement, however, there were greater improvements in the MIS compared to Open group in ODI and PCS at 1 and 2 years. Using ODI as the dependent variable, linear regression demonstrated that MIS, revision status and baseline PRO were significant factors at one year and MIS and baseline PRO at 2 years. Age, sex, BMI, co-morbidity, type of spondylolisthesis (degenerative or isthmic) and complications did not affect ODI. Significantly more patients (p<0.05) reached the minimum clinically important difference in the MIS group at 6m for back (81 vs 62%) / leg (88 vs 65%) pain; at 1year for leg pain (83 vs 60%), ODI (72 vs 52%) and PCS(78 vs 59%); and 2years for ODI (82 vs 64%) and PCS (85 vs 59%). Significantly more patients (p<0.05) reached the substantial clinical benefit in the MIS group at 6m for back (75 vs 49%) / leg (84 vs 56%) pain, and PCS (66 vs 46%); at 1year for leg pain (73% vs 42%), ODI (62 vs 42%) and PCS (76 vs 54%); and 2year for ODI (68 vs 47%) and PCS (82 vs 55%).

  Conclusion:
  In this multicentered cohort study, the MIS technique independently demonstrated superior outcomes at 1 and 2 years postoperatively compared to open fusion for spondylolishtesis. Based on the results of this study, MIS fusion for spondylolisthesis, should be considered a viable surgical management option. Further follow-up with increased patient numbers and participating centers are required to further validate the generalizability of these findings.

• Outcomes of MIS Spinal Fusion: 12 and 24 Months
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  12 and 24 month outcomes are presented from a single surgeon's series of 660 XLIFs.

  Introduction:
  The XLIF approach provides a minimally disruptive alternative to anterior column access that allows for large graft placement, disk height restoration, and indirect decompression. Outcomes at 1 year are presented and are compared with initial 2 year data.

  Methods:
  Of our single-site consecutive series of 660 XLIF patients, 266 have presented for 12 month follow-up, and 34 for 24 month follow-up. Clinical and radiographic measures were prospectively collected and evaluated to assess pain scores, changes in disk height and alignment, listhesis, and fusion. A patient questionnaire was used to collect satisfaction data at 12 months.

  Results:
  Of the patients who have returned for follow-up at one year, age ranged from 27-87 years (average 62.6 years). Comorbidities included smoking (31%), chronic steroid use (12%), diabetes (22%), CAD (52%), and COPD (4%). 129 patients (48%) were obese (BMI>30), 40 of those morbidly obese (BMI>38). Average VAS improved from 8.7 at pre-op to 2.5 at 12 months. Disk height improved from 6.2mm to 10.3mm at post-op, settling about 1mm to 9.2mm by 12 mos. Listhesis was reduced from 4.2mm to 0.7mm, maintained at 12 mos. Definitive signs of fusion (Lenke 1-2) were present in 90% at 3 months, 97% at 6 months, and 99% at 12 months. 65 patients had CT scans at 1 year postop. Fusion by CT criteria of >50% area fused was achieved in all but 3 levels (96.5%). Early 24 month outcomes indicate maintenance of 12 month clinical outcomes. Average VAS at 24 months was 2.5, average disk height was 9.7mm, and slip was 0.7mm. At 12 months, 85% were very satisfied or satisfied with their surgery. 89% would definitely or likely do the surgery again. 81% were considered excellent or good outcomes by the surgeon.

  Conclusion:
  Our data shows satisfactory intermediate term clinical outcomes in our series of XLIF at 12 months. VAS scores improved, disk height was restored and maintained, and slip was adequately reduced. Patient and surgeon satisfaction scores at 12 months are encouraging. Early data shows maintenance of these outcomes at 24 months. More follow-up will be beneficial to determine long-term outcomes.

• Outpatient Microscopic Lumbar Discectomy Using a Fixed Tubular Retractor: 6 Month Results
  Presenting author: Raymond Gardocki, MD
  
  Presentation Summary

  Summary:
  Retrospective review with 6 month follow up of 35 outpatient microscopic lumbar discectomies done on an outpatient basis using a fixed 16-18mm tubular (MetRx) retractor.

  Introduction:
  Minimally invasive surgery is sometimes criticized as minimally effective surgery. We are presenting the 6 month follow up data of a cohort of 35 patients who underwent outpatient Microscopic Lumbar Discectomy (MLD) using a fixed tubular retractor. We intend to show that the results of MLD using the fixed tubular retractor on an outpatient basis are at least equivalent to traditional microscopic lumbar discectomy.

  Methods:
  Between January 2007 and September 2008 35 outpatient primary microscopic lumbar discectomies with a fixed tubular retractor were performed by a single surgeon. The analysis included patients with unilateral disc herniation confirmed by MRI who had symptomatic radiculopathy attributable to the herniation by history and physical exam. Patients with prior lumbar surgery were excluded from the analysis. Six month follow up data was obtained by retrospective chart review.

  Results:
  Average operative time was 65 minutes and average EBL was 48cc. Pain scores decreased from a pre-operative average of 7.44 on a 0-10 100mm Visual Analogue Pain Scale (VAS) to 1.67 (p<0.01) at 6 months follow up. Oswestry Disability Index (ODI) decreased from a pre-operative average of 46.9 to 9.7 (p<0.01) at 6 months follow up. Narcotic usage decreased from 60% of patients pre-operatively to 0% (p<0.01) at six months. There were three recurrent herniations in the first 6 months for a 9% incidence of recurrent HNP, all treated with MLD using the same fixed tubular retractor system. On average we saw at least a 75% improvement in VAS, ODI, motor grade, nerve tension and narcotic usage by 3 months post-operative and these results were maintained out past 6 months follow up.

  Conclusion:
  Outpatient MLD using a fixed tubular retractor system is a viable procedure with quick recovery and good results. Performing MLD with a fixed tubular retractor system can ease the transition from open lumbar surgery to minimally invasive TLIF and decompression procedures.

• Outpatient Microscopic Lumbar Discectomy Using a Fixed Tubular Retractor: Pain on Day of Surgery and at Time of Discharge
  Presenting author: Raymond Gardocki, MD
  
  Presentation Summary

  Summary:
  Retrospective review which describes Pre-Op VAS and Post-Op VAS at time of discharge, narcotic requirements, hours observed post operatively, average blood loss and average operative time using a fixed tubular retractor (MetRx) for outpatient primary lumbar discectomies.

  Introduction:
  Safety profile, potential complications and adequacy of pain control in the immediate post operative period determine whether procedures can be performed on an outpatient basis. Microscopic Lumbar Discectomy (MLD) is an accepted procedure commonly performed on an outpatient basis. To our knowledge, nobody has described the pain response on the day of surgery after outpatient MLD using a fixed tubular retractor.

  Methods:
  Between January 2007 and September 2008 we performed 35 outpatient primary microscopic lumbar discectomies with a fixed tubular retractor. The analysis included patients with unilateral disc herniations confirmed by MRI who had symptomatic radiculopathy attributable to the herniation by history and physical exam. Patients with prior lumbar surgery were excluded from the analysis. Curettage of the disc space was not performed. All data was obtained by retrospective chart review.

  Results:
  Average operative time was 65 minutes and average EBL was 48cc. Pain scores decreased from a pre-operative average of 7.44 on a 0-10 100mm Visual Analogue Pain Scale (VAS) to 0.6 (p<0.01) at time of discharge. On average, patients were discharged just under 2 hours post operatively (average = 1.85 hours, SD = 0.78). Patients received an average of 1.84 mg morphine equivalents intravenously post operatively on the day of surgery (median = 0, range = 0-14, SD = 3.2). No dural tears were encountered.

  Conclusion:
  MLD using a fixed tubular retractor can be safely performed on an outpatient basis with adequate pain control in the immediate post-operative period using minimal narcotic medication.

• Percutaneous anterior column stabilization of focal metastatic lesions of the spine: the value of plasma-mediated radiofrequency ablation before cement injection
  Presenting author: Bassem Georgy, MD
  
  Presentation Summary

  Summary:
  The study is performed to assess if cavity creation in the anterior 2/3 of the vertebral bodies affected by metastasis can result in control over cement deposition before vertebroplasty. cement deposition in the anterior 2/3 of the vertebral bodies affected by metastasis can alter treatment and avoid extensive anterior corpectomy.

  Introduction:
  This study assessed the value of creating a cavity in the anterior 2/3 of the vertebral body using plasma-mediated radiofrequency ablation prior to cement injection, aiming to stabilize the anterior column.

  Methods:
  Retrospective assessments of CT images were performed pre- and post-procedure in 24 patients with 27 levels with different metastatic lesions of the spine. Patients were classified into two main groups, group I with focal anterior lesions and group II with focal posterior lesions. Computed Tomography imaging was performed immediately before and after the procedure. Pain alleviation was measured using visual analogue scale (VAS) scores. A void was created in the anterior portion of the tumor-infiltrated vertebral body using a bipolar plasma-mediated radiofrequency-based wand (ArthroCare Corporation, Austin, TX) before standard vertebroplasty. Pain was recorded both pre-procedure and 2-4 weeks afterwards using a visual analogue scale (VAS).

  Results:
  In 11/12 levels with anterior lesions (group I), cement was deposited inside the lesion. Cement was also successfully deposited anterior to the lesion in 13/15 levels with posteriorly-located lesions (group II). VAS pain scores were available for 21 patients: 19 reported significant pain relief while 2 exhibited no change. No clinically significant leakage was observed.

  Conclusion:
  Cavity creation using plasma-mediated radiofrequency ablation can be performed percutaneously before standard vertebroplasty, and results in more control over cement deposition in the anterior part of the vertebral body, regardless of the lesion location. This approach could treat focal metastatic lesions while avoiding the more invasive standard technique of extensive anterior surgical debulking and reconstruction. In cases displaying neurological deficit, it can complement a simpler posterior decompression laminectomy and fusion.

• Percutaneous Interspinous Process Implanted in Prone Position 24 months follow up
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Etevaldo Coutinho, MD, Luis Marchi, MSc Leonardo Oliveira, MD
  
  Presentation Summary

  Summary:
  The lumbar spinal stenosis is considered one of the causes of Neurogenic Intermitent claudication. Using an interspinous spacer we were able to treat the pathology using a minimal invasive percutaneous approach to the lumbar spine, shortening the surgery time, hospital stay and rehabilitation.

  Introduction:
  Neurogenic Intermittent Claudication (NIC) can be a consequence of lumbar spinal stenosis. The literature shows symptom reliefs in flexion and worsening in extension. This new technology allows lateral insertion of a novel interspinous device using a minimally invasive percutaneous approach, shortening the surgery time, hospitalization stay and rehabilitation.

  Methods:
  14 patients (9 male; 5 female) with a median age of 69.6 (48-82) years and central stenosis with neurological claudication were enrolled. The operated levels were between L2-S1, totalizing 19 prosthesis due to 5 two-level operations. Operative time, blood loss and hospital stay were recorded. Subjects were evaluated preoperatively and postoperatively at 1 and 6 weeks, 3, 6, 12 and 24 months. Analysis consists of clinical outcomes and radiological assessment of disc and foraminal height through x-ray films and CT evaluation by an independent radiologist, pain assessment by means of VAS responses and functional assessment by means of ODI.

  Results:
  The posterior disc height increased by 38% after 12 months, while foraminal height increased 27% in the same period. The mean surgical time was 34.3 minutes and mean blood loss was less than 50 cc. The mean hospital stay was 23.4 hours. The mean VAS and ODI preoperative score was decreased in the postoperative quantifications.

  Conclusion:
  This novel percutaneous approach offers a less invasive surgical option, maintaining the supraspinous ligament and preserving the interspinous ligament at adjacent levels, with minimal management of the interspinous ligament at the index level. This procedure allows short operative time, minimal blood loss and reduced hospitalization time. The lateral interspinous device is an excellent option to maintain motion, while improving disc and foraminal height, reducing the painful symptoms of lumbar stenosis.

• Percutaneous vertebroplasty for osteoporotic fractures: Experience with high viscosity cement using a hydrolic injection device, the CONFIDENCE system.
  Presenting author: Bassem Georgy, MD
  
  Presentation Summary

  Summary:
  Vertebroplasty in osteoporotic fractures using a highly viscus cement that can be safely controled and injected via a hydrolic system can be performed safely without significant complications.

  Introduction:
  Vertebroplasty is a widely used technique to treat painful osteoporotic vertebral compression fractures, however, precise control of cement delivery is necessary to minimize the risk of cement leakage. The study is conducted to assess the clinical feasibility of performing vertebroplasty on osteoportic compression fractures using an ultraviscous cement injected by a hydrolic device, CONFIDENCE Vertebral Augmentation System, to further control cement deposition.

  Methods:
  A retrospective evaluation of series of 94 consecutively treated patients were identified for the review. There were a total of 163 levels which ranged from T3 to S1 vertebral bodies. The degree of leakage, seen in the post-operative films, was assessed at each treated level using a strict 4-point scale (none, minimal, moderate, severe). The pattern of any observed leakage was also characterized as: discal, venous, paravetebral, or epidural.

  Results:
  Pre-operatively the mean degree of vertebral collapse was 29. A bi-pedicular approach was used for 82% (133/163) levels and unipedicular in 18% (30/163). There was no leakage in 50%, minimal leakage in 42%, and moderate leakage noted in 8% of cases. Both unipedicular and bi-pedicular approaches showed leaks in 50% of cases. The most frequent pattern of leak was venous indicated in 52% of leaks, the adjacent disc in 46%, and paravertebral in 5%. The pattern of leakage was always limited to one region except in two cases. There were no symptomatic leaks that required surgical intervention.

  Conclusion:
  Vertebroplasty in osteoporotic fractures using a highly viscus cement that can be safely controled and injected via a hydrolic system can be performed safely without significant complications.

• Perioperative complications of single-level instrumented mini-open transforaminal lumbar interbody fusion for degenerative spondylolisthesis: analysis of risk factors
  Presenting author: Dong Yeob Lee, MD
  Additional authors: Sang-ho Lee, MD, PhD
  
  Presentation Summary

  Summary:
  Consecutive 207 patients who underwent single-level instrumented mini-open transforaminal lumbar interbody fusion (TLIF) for degenerative spondylolisthesis were analyzed. Perioperative complications occurred in 16.9% of the patients. Surgeon's level of experience with minimally invasive spinal surgery (MISS) was the only significant risk factor for complication.

  Introduction:
  The purpose of this study was to analyze the incidence and risk factors for perioperative complications of single-level instrumented mini-open TLIF for degenerative spondylolisthesis.

  Methods:
  The authors analyzed data obtained in consecutive 207 patients who underwent single-level instrumented mini-open TLIF for degenerative spondylolisthesis between 2005 and 2006. The operations were performed by 13 surgeons, who were divided into two groups based on their level of experience with MISS. Operation was performed using tubular retractor or Casper retractor system according to the preference of the surgeon. The series comprised 43 men and 164 women whose mean age was 61.7 years (range 43-75 years). The fusion level was at L4-5 in 194, L3-4 in 10, and L5-S1 in three. Minor or major adverse events within four weeks of the surgery were considered as perioperative complication.

  Results:
  The mean operating time was 202.9 minutes (range 105-345 minutes). The mean estimated blood loss was 580.3 ml (range 250-1700 ml). Transfusion was performed in seven cases (3.4%). A total of 35 patients (16.9 %) experienced perioperative complication. Transient sensory disturbance was the most common complication (24 cases, 11.6%), followed by permanent sensory disturbance (three cases, 1.4%), screw malposition (two cases), wound infection (two cases), epidural hematoma (one case), unintended durotomy (one case), and miscellaneous (two cases). No patient experienced either transient or permanent motor weakness. Five patients (2.4%) underwent revision surgery due to complication. Statistical analysis revealed that surgeon's level of experience with MISS was the only significant risk factor for complication (p=0.034, Odds ratio=6.895) among clinical variables (age, sex, symptom duration, diabetes mellitus, hypertension, smoking, body mass index, spinal level, Meyerding classification, operationg time, estimated blood loss, type of retractor, and surgeon experience).

  Conclusion:
  Perioperative complication occurred in 16.9% of the patients after single-level instrumented mini-open TLIF for degenerative spondylolisthesis. Proper training and considerable clinical experience for MISS are important to reduce the incidence of perioperative complications.

• Post Discectomy Annular Augmentation and Stabilization: A novel technique and implant
  Presenting author: Juan Dipp, MD
  Additional authors: Ricardo Flores, MD, Ricardo Flores, MD, Scott Conner,MD, Ali Araghi, MD, Peter Davis, MD
  
  Presentation Summary

  Summary:
  Initial Disc Annular Repair Technology (DART) clinical results are reported. The DART implant seals the annulus fibrosus and structurally maintains disc height. The device is delivered by open or MIS surgery post discectomy and is seated intradiscally and posteriorly resides against the vertebral lips. Acute clinical results demonstrate successful implantation. Early follow-up shows an improvement in ODI, VAS and SF36. There has been no implant migration, no disc re-herniations and disc height has been measured.

  Introduction:
  Disc re-herniation and height loss can lead to patient reoperation and are precursors for greater disc degeneration. After a standard discectomy and disc preparation, a new PEEK implant can be inserted through the annular defect to provide structural integrity while sealing the annulus. The implant has three SUmmary: key elements (an anchor in the disc space, a tail for load bearing along the apophyseal ring and an extradiscal flange) and can be implanted minimally invasively. A clinical study has been initiated with acute and early success. Patients enrolled have shown reduced pain and an improved quality of life.

  Methods:
  Six patients undergoing a posterior lumbar discectomy were implanted with the DART after removal of the extruded or protruded disc fragments. Patients met the study inclusion and exclusion criteria and consented to the procedure. Baseline ODI, VAS and SF36 scores were assessed. Operative time, blood loss, analgesics and unanticipated events were recorded. Patient follow-up includes routine office visits, score assessments and imaging at regular intervals. Images were evaluated by the investigators and outside lab for reherniation and disc height. Score assessments were compared at baseline and follow-up intervals.

  Results:
  Six patients, ages 38-80, were enrolled. All patients had successful implant procedures performed in open or minimally invasive surgeries. Average surgical time was 82 minutes. Average blood loss was 116cc. There were no intra-operative adverse events. All patients were discharged one day post surgery and have completed at least two week follow-up. There have been no disc re-herniations and no implant migration. Outcome measure averages have improved (pre vs 2wk f/u); ODI 68 vs 24, VAS 5.9 vs 3.2 and SF36 Physical Function 28 vs 42.

  Conclusion:
  In early clinical results, six patients have achieved improvements in outcomes after discectomy. The implant procedure is simple, having no effect on the primary discectomy procedure, and is delivered without incident. Blood loss and procedure times compare to SPORT Surgical Treatment for Lumbar Disc Herniation results. Imaging results and pain scores confirm implant retention. There has not been any noted subsidence.

• Preliminary Findings from a Single Site Investigating the Use of Extreme Lateral Interbody Fusion as a Treatment for Adjacent Segment Disease
  Presenting author: Jim Youssef, MD
  Additional authors: Michelle Renza, Mira Emmanuel-ogier, Catherine Patty
  
  Presentation Summary

  Summary:
  Between 2007 and 2009, we respectively reviewed 16 patients with adjacent segment disease (ASD), mean age of 68 years, who underwent a 1- level extreme lateral interbody fusion (XLIF) procedure. Anterior instrumentation included: interbody implant without instrumentation, a tabbed interbody implant with vertebral body screws, and those who received an interbody implant and adjuvant titanium plate with vertebral body screws.

  Introduction:
  Little evidence exists supporting the use of XLIF as an effective treatment for ASD. The purpose of this study is report the preliminary radiographic and clinical results of patients that underwent XLIF to treat ASD.

  Methods:
  Thirteen patients underwent XLIF with anterior instrumentation (XLIF only) and 3 of these patients received posterior spinal fusion (PSF) including pedicle screw instrumentation (XLIF/PSF group); 3 of which underwent concomitant laminectomies. At a mean follow-up of 8 months, CTs and flexion/extension radiographs were reviewed to assess the progress of fusion.

  Results:
  No procedural complications were reported. The mean blood loss was 57cc for XLIF only patients and 258cc for XLIF/PSF patients. The infection rate was zero. The average length of hospital stay was similar for both groups: XLIF only (avg. 1.6 days) and XLIF/PSF patients (avg. 1.5 days). At 2 weeks, all patients were able to walk 1 mile as instructed and have continued to increase in activity. One patient reported left psoas weakness (5-/5 motor grade) and numbness immediately after surgery that resolved by 7 weeks post-operatively. Another patient developed L2 unstable burst fracture status post L2-L3 XLIF procedure, which failed non-operative alternatives. At 2 months post-operatively, the patient was treated with corpectomy of L2, anterior arthrodesis at L1-L3 with application of anterior expandable cage and PSF T10 to L3. One patient developed a mild superior endplate fracture and treated with a brace at all times for 8 weeks, the fracture was considered to be stable at 2 months and healed at 3.5 months. At 8 months, CT and flexion/extension radiographs showed evidence that 7/16 patients had solid arthrodesis and no subsidence. All other patients are demonstrating further consolidation of their fusion status without complications.

  Conclusion:
  These preliminary results suggest that XLIF is a viable treatment option for the treatment of ASD due to decreased blood loss, decreased length of hospital stay, increased activity after surgery and maintenance of early radiographic fusion. We anticipate reporting on final radiographic and clinical outcome data when all patients achieve longer follow-up.

• Safety and the Learning Curve of Trans-Sacral Fusion (AxiaLIF) at L5-S1: Complications in the first 160 Surgeries of a Single Surgeon Series
  Presenting author: William Blake Rodgers, MD
  Additional authors: Edward Gerber, MD, Jamie Patterson
  
  Presentation Summary

  Summary:
  Complications and clinical outcomes are reviewed of a surgeons' series of 160 AxiaLIF trans-sacral fusions, during the 'learning curve.'

  Introduction:
  Trans-sacral fusion of L5-S1 has been well described.1,2 Improvements in the technique and instrumentation have been implemented to reduce the risk of complications, particularly during the 'learning curve.' To our knowledge, the early complications during the adoption phase for AxiaLIF have not been reported in detail.

  Methods:
  All AxiaLIF patients were prospectively followed to evaluate clinical and radiographic outcomes. Surgical and postoperative complications were also documented and highlighted here, with respect to type and severity. Preliminary 12 month postoperative data is reported (n=37).

  Results:
  160 patients (62M, 77F; age 55.2 yrs, range 22-88 yrs; BMI 31.1) were treated by a single surgeon (WBR) using the AxiaLIF technique to achieve fusion at the lumbosacral junction. 122 procedures were single level; 38 procedures involved concomitant fusion at L45 (via XLIF). All fusion but one involved supplemental posterior pedicle screw fixation. OR time averaged 91.4 min (69.1 min for single level procedures and 137.6 min for AxiaLIF-XLIF combinations). Length of stay averaged 27.2 hrs (1.13 days). Hemoglobin change was 1.79 g. There were 18 complications in the perioperative period: Hardware (1, screw revision at POD 1), graft herniation (3, all required laminotomy), pneumonia (1), wound dehiscence at incision (4, 3 treated with local care, 1 treated with wound VAC), cardiac (1, CHF), urinary rentention (1), gastritis (1), infection (1, I&D), transfusion (3), nonunion (2, revised at 10 and 12 mos). There have been 3 reoperations for adjacent segment disease. There were no visceral, vascular, or neurologic complications. Disk height improved from 4.4 mm preop to 7.7 mm postop; minimal subsidence was noted at 6 mos with some settling at 12 mos (disk height 5.6mm). Listhesis was reduced from 4.5 mm preop to 1.1 mm postop with slight settling to 2.1mm at 12 mos. VAS decreased from 8.7 preop to 3.4 at 3 mos and further to 3.1 at 12 mos.

  Conclusion:
  The adoption phase and learning curve for trans-sacral fusion shows very few complications compared to traditional open techniques.

• Safety of extreme lateral approach in thoracic and lumbar interbody fusion
  Presenting author: Murat Pekmezci, MD
  Additional authors: Sheri Rocha, Vedat Deviren, MD
  
  Presentation Summary

  Summary:
  Extreme lateral interbody approach is associated with a low complication rate and a safe method to acheive interbody fusion at thoracic and lumbar levels.

  Introduction:
  Extreme lateral approach is a novel minimal invasive technique that allows thoracic and lumbar interbody fusion. The aim of this study is to review the perioperative complications observed in a series of patients operated by a single surgeon.

  Methods:
  Thoracic and lumbar extreme lateral interbody fusion procedures that were performed by a single surgeon between 2007 and 2009 were reviewed. Patient demographic information, diagnosis, blood loss, perioperative complications and clinical outcome scores were recorded.

  Results:
  The study group included 38 female and 28 male patients. The average age was 62 (26-82) years. The average follow-up was 6.4 months (3-26). One hundred and ten lumbar and 14 thoracic procedures were performed. The procedure was performed at a variety of leves ranging from T5-T6 to L4-L5. The average blood loss per level was 576cc for thoracic procedures and 117cc for lumbar procedures. There were no perioperative complications in the thoracic levels. In the lumbar group, 10 patients had weakness in the psoas and/or quadriceps ipsilatereal to the approach side and only one was persistent weakness. Eight patients had numbness/pain in the anterolateral thigh all of which were temporary. One patient sustained a compression fracture between the adjacent implants, but did not require further intervention. These complications did not affect the clinical outcome.

  Conclusion:
  Extreme lateral approach is a safe and effective method to achieve interbody fusiond in the thoracic and lumbar spine.

• Short term follow up, complications and observations from 100 consecutive XLIF procedures
  Presenting author: Nicholas Wills, MD
  Additional authors: Manuel Pinto, MD
  
  Presentation Summary

  Summary:
  Retrospective review of 100 consecutive XLIF (Extreme lateral interbody fusion NuVasive San Diego, CA) procedures done by a single surgeon.

  Introduction
  In a time of shared decision making, surgeons, especially those who are performing new techniques, must critically evaluate and discuss their results. This helps the surgeon understand his or her possible areas for improvement and also may give insight to other surgeons who can then set realistic expectations for their patients.

  Methods:
  A retrospective chart review of 100 consecutive XLIF procedures performed by one surgeon over a two year period. We compiled information on age, medical history, smoking history, BMI and complications.

  Results:
  Average age and BMI of the patients was 54.7 and 30.57 respectively. 19 patients admitted to being smokers and 6 were diabetics. 88% had at least one medical comorbidity. 89% of the surgeries utilized anterior and posterior technique and 11 were anterior only. 47 were multi-level and 53 were single level. Complications not related to the lateral approach: 2 posterior wound infections that required I&D. 2 posterior malpositioned screws. 2 patients required reoperation for fracture of posterior instrumentation. 1 posterior incidental durotomy. Problems associated with the lateral approach: 11 patients described thigh numbness which resolved in all patients except one by 3 months. 2 patients had ileus lasting longer than 3 days which required no invasive interventions. 1 patient had a psoas hematoma that required readmission and 2 units of blood for anemia and no surgical intervention. 6 patients had grade 4/5 or weaker iliopsoas ipsilateral to the approach 6 weeks after surgery. All were resolved by four months except 1 patient. 2 patients had life-threatening vascular lacerations that required immediate laparotomy and vascular repair. Neither patient had long term sequelae but did require multiple units of blood. 3 patients had new quadriceps weakness, one did not resolve by 3 months and is ongoing.

  Conclusion:
  Overall, XLIF-related serious or persistent complications were few. The vascular risk and iliopsoas weakness however, do merit patient discussion.

• Short-term results of laminectomy preserving paraspinal muscles for lumbar canal stenosis
  Presenting author: Hiroyuki Hashidate, MD
  Additional authors: Jun Takahashi, MD, Hiroki Hirabayashi, MD, Nobuhide Ogihara, MD, Hiroyuki Kato, MD, Ph.D
  
  Presentation Summary

  Summary::
  N/A

  Introduction:
  We evaluated the efficacy of laminectomy without exfoliation of paraspinal muscles for preserving posterior structures while 2 years.

  Methods:
  A conventional laminectomy (CL) was performed in 13 patients, and a laminectomy preserving paraspinal muscles (LPPS) was performed in 23 patients with lumbar spine stenosis. The operation time, blood loss, use of analgesics, duration of bed rest, changes in the laboratory data, and the JOA score were evaluated and compared between the two groups.

  Results:
  The mean operation times were 99.9 and 135.0 min for patients with LPPS and CL. The mean blood loss was 93.8 and 160.4ml, the use of analgesics were 2.5 and 3.8 times, the duration of bed rest was 2.0 and 4.1 days. Above these subjects deference were statistically significant. The translation of CRP were 0.84-2.05-0.66 and 1.42-3.35-1.28 mg/dl and CPK were 151.8-103.7-79.6 and 295.4-119.9-70.3 U/l (postoperative 1-4-7 days). The mean recovery rates of JOA score were 61.7 and 51.5%.

  Conclusion:
  Preservation of paraspinal muscles may be less invasive procedure in short-term results.

• Spinous Process Fusion is Safe, Minimally Invasive, Fast and Significantly Reduces VAS and ODI Scores
  Presenting author: W. Warren, MD
  
  Presentation Summary

  Summary:
  30 patients were followed for 3 months after interspinous fusion using the Aspen device. VAS and ODI data are presented showing significant improvement in these patients. These data show that spinous process fusion is a viable alternative to interbody fusion in many patients. The spinous process should be viewed by spine surgeons as a part of the palette of choices in lumbar fusion, and should not be routinely sacrificed during decompression procedures.

  Introduction:
  The spinous process has a long history of being used in a variety of spinal fusion procedures. Though it has largely been supplanted in recent years by pedicle screws and interbody devices, two devices resurrected interest in the interspinous region. Rigid fixation using the Spire clamp has been shown to be biomechanically sound and effective. Extension blockade and indirect foraminal decompression has been proven to be effective using the X-Stop device. The Aspen device provides rigid fixation, interspinous fusion, indirect decompression of the canal and compares favorably to all other types of instrumentation in biomechanical testing in a sheep model. Many patients have anatomy which makes pedicle screws difficult to place, and in some cases previous surgery has made the pedicles unavailable or inadequate to achieve solid fixation. In these patients, options for fixation are limited. Many surgeons routinely sacrifice the spinous process while decompressing the spinal canal, eliminating a choice for solid instrumentation later and wasting a large, stable area of cortical bone that could be very useful in future operations. Given the proven success of minimally invasive unilateral approaches for decompression of the canal by traveling underneath the spinous process, preservation of the spinous process is possible in most cases.

  Methods:
  Using the Aspen device along with posterior bone graft, 30 patients were operated for single and multi-level degenerative disk disease, spinal stenosis, and/or ruptured disks. 2 week, 6-week, and 3-month follow-up data, including VAS and Oswestry Disability Index data were collected and are presented.

  Results:
  Average surgical time per level was 13 minutes, blood loss average was 50cc, and no patient stayed in the hospital more than 24 hours. VAS scores on average were reduced 75% and ODI scores reduced 60% at 3 months.

  Conclusion:
  This study demonstrates the efficacy of interspinous fusion using the Aspen device, and argues for a paradigm shift in training spine surgeons to view the spinous process as an important available instrumentation option. The spinous process can be instrumented quickly and rigidly, and successful fusion and decompression are reliably achieved.

• Spinous Process Splitting Laminectomy
  Presenting author: David Ryan, MD
  Additional authors: Michael Macmillan, MD
  
  Presentation Summary

  Summary:
  We performed a cadaveric biomechanical comparison of the traditional laminectomy technique to a ligament preserving (spinous process splitting) laminectomy technique. Our hypothesis was that the inherent stability of a spine after a laminectomy done by preserving the posterior ligaments would be greater than the stability of a spine without these soft tissues. The clinical relevance would be the theory that this may decrease the incidence of post laminectomy instability.

  Introduction:
  Post laminectomy instability syndrome or the concept of increased instability at the level of the laminectomy, is a common pathology that is seen in the spine clinic. Traditionally the laminectomy has been performed by taking down the majority of the posterior ligamentous structures and, therefore, disrupting a static stabilizer of the spine. Performing a spinous process splitting laminectomy (SPSL), where the dissection is performed by splitting the supraspinous ligament longitudinally followed by a longtitudinal osteotomy of the spinous process, preserves the integrity of the supraspinous ligament and a posterior portion of the interspinous ligament. We hypothesize that the SPSL leaves the patient a more biomechanically sound spine than does a traditionally laminectomy and thereby may prevent or at least delay the onset of post laminectomy instability syndrome.

  Methods:
  We obtained five fresh cadaveric spine specimens of two levels each and performed biomechanical comparative testing. Each specimen was tested as an intact spine, then after performing a SPSL (as described above), and finally after removing the spinous process and posterior ligamentous structures (a traditional laminectomy). Each specimen was tested in sagital and coronal plane bending and finally in axial rotation. Standard forces were applied. Comparative results were obtained for range of motion and construct stiffness.

  Results:
  In the sagital bending and axial rotation planes the SPSL model behaved more like an intact spine in both range of motion and construct stiffness than the traditional laminectomy model. In the coronal bending plane the models all behaved similarly. The results were, however, not statistically significant in any of the models as the power of the study was too small.

  Conclusion:
  Although the overall mechanical stability of the SPSL specimens was greater than the traditional laminectomy specimens, the limited number of specimens tested did not allow the results to reach statistical superiority. Despite the lack of statistical significance, we believe that this study does show a trend toward the SPSL behaving more like an intact spine. Therefore, the SPSL may eventually prove to be a more biomechanically advantageous laminectomy approach.

• The Mini- Open Posterior Lumbar Interbody Fusion and spinal instrumentation in patients with high-grade spondylolisthesis
  Presenting author: Nasir Quraishi, FRCS
  Additional authors: Y. Raja Rampersaud, MD
  
  Presentation Summary

  Summary:
  A minimal access technique can be effectively and safely performed for high grade spondylolisthesis with the added benefit of reduced soft tissue disruption. Our results suggest that ability to correct focal deformity and radiographic fusion rates are similar to the open procedure.

  Introduction:
  Minimally invasive or ??oeminimal access surgery? (MAS) is being utilized with increasing frequency to reduce approach related morbidity in the lumbar spine. The objectives of this study were to describe a new technique using a MAS approach for posterior lumbar interbody fusion (PLIF) and spinal instrumentation in 3 patients with high-grade spondylolisthesis grade (Myerding Grade III-IV) at a minimum follow-up of two years.

  Methods:
  The patients, one male/two females, mean age 43.4 years (24-60 years) underwent a ‘mini-open’ decompression, a PLIF, partial reduction of focal kyphotic deformity and instrumented pedicle screw fixation for high grade spondylolisthesis at L4-L5 (n=1) and L5-S1 (n=2). Operative findings and radiographic parameters were also noted and all patients recorded their level of back and leg pain on a Visual Analogue Scale (VAS) and completed an Oswestry Disability Index (ODI). All patients were followed up for a minimum of two years.

  Results:
  All patients had resolution of back and leg symptoms. The mean EBL, OR time and post-op hospital stay were 633mls, 3.7 hours and 5.3 days respectively. The mean slip percentage and slip angle improved from a pre-op mean of 60.3% and 9.7° kyphosis to 17% and 16.7° lordosis respectively. The mean ODI improved from 61.1% to 17.3% at two years. There were no complications associated with the procedures and CT scans showed good placement of all pedicle screws and bone graft (at 6 months).

  Conclusion:
  A minimal access technique can be effectively and safely performed for high-grade spondylolisthesis with the added benefit of reduced soft tissue disruption. In addition, we have found virtual fluoroscopy to be a safe and valuable adjunct to instrumented fusions in patients with high-grade spondylolisthesis. Our results of this technique suggest that the ability to correct focal deformity, radiographic fusion rates as well as clinical outcome are similar to the open procedure.

• The Occurrence and Degree of Cement Leakage Following Vertebral Body Augmentation: A Comparison of the CONFIDENCE Vertebral Augmentation System and Kyphoplasty.
  Presenting author: Bassem Georgy, MD
  
  Presentation Summary

  Summary:
  Leakage rate using ultra viscous cement in vertebroplasty is equivalent to Kyphoplasty.

  Introduction:
  Vertebroplasty was known for relatively high cement leakage rates compared to kyphoplasty. Advances in delivery systems and new high viscosity cements provide enhanced control and uniformity of cement filling during vertebroplasty compared to the previously available technology.This study was done to assess the incidence and pattern of cement leakage with Confidence system (ultra viscous cement) compared to kyphoplasty.

  Methods:
  A series of 65 consecutively treated patients were identified for the review. There were a total of 105 levels, 58 Confidence and 47 kyphoplasty–treated levels, which ranged from T5 to L5. The degree of leakage was assessed at each treated level using a strict 4-point scale (none, minimal, moderate, severe). The pattern of any observed leakage was also characterized as: discal, venous (paravetebral), or epidural. The radiographic reviewer was blinded to the treatment group. Each film was assessed for percent collapse, evidence of cement leakage, as well as degree and pattern of any noted leak.

  Results:
  The average vertebral collapse was 26% in the Confidence group vs. 25% in the kyphoplasty group. There was no or minimal leakage in 91% Confidence and 85% kyphoplasty cases (minimal: 36% Confidence vs. 38% kyphoplasty). Severe leakage was only reported in 1 (2%) Confidence and 1 (2%) kyphoplasty cases. In both cases, the severe leakage was found in the disc space. No significant leakage was noticed that required any surgical intervention.

  Conclusion:
  The leakage rate with the high viscosity Confidence Vertebral Augmentation System is comparable to that of kyphoplasty. High viscosity cements and specialized delivery systems may reduce the risk of leaks for standard vertebral body augmentation.

• Transcorporeal tunnel approach for unilateral cervical radiculopathy: A 2 year follow-up, review and results
  Presenting author: Gun Choi, MD, PhD
  Additional authors: Sang-ho Lee, MD, PhD, Nikhil j Arbatti,MD, Ho jae Kim, MD,PhD, Sung hui Myung, MD
  
  Presentation Summary

  Summary:
  We report 2-years follow-up results of a functional disc surgery in which decompression for cervical radiculopathy is done by drilling a hole in the upper vertebral body. Thirty patients with unilateral cervical radiculopathy who did not respond to conservative treatment, underwent this procedure. Post-op NDI improved 89.44% (P<0.05). Arm and neck pain improved (VAS) 87.5% and 69.6% respectively (P<0.05). This procedure is an effective minimally invasive treatment for cervical radiculopathy avoiding unnecessary violation of the disc space.

  Introduction:
  The conventional treatment for cervical spondylotic radiculopathy has been discectomy and fusion. Jho developed an anterior unco-foraminotomy approach which we have modified to make it ‘an anterior transcorporeal tunnel approach’ for cervical spondylotic radiculopathy. We here report our experiences with this technique with more than 2 years of follow-up.

  Methods:
  Between April 2004 and August 2006, 30 patients operated for unilateral cervical radiculopathy were considered. There were 20 males and 10 females. The mean age was 52.4 years and the average duration of symptoms was 14 weeks. The selection criteria was 1) patients having unilateral cervical radiculopathy only, without myelopathy, which the radiological findings correlates with clinical findings and 2) patients not responding to conservative management. After submitting an informed consent, all patients underwent a transcorporeal tunnel approach through the affected side. Follow-ups were done after 6 weeks, 3 months, 6 months, 1 year and then after every 6 months. Stress view and plain X-rays were taken at each follow-up and VAS, ODI and disc height were measured and compared with the pre-operative value.

  Results:
  The average operating time was 93 minutes, the average blood loss was 159 cc. The average duration of post-operative stay was 4.3 days. The pre-op NDI mean was 55.16% and the post-operative mean was 5.82%. The mean improvement was 89.44%, which was statistically significant (P<0.05). While the average pre-operative VAS scores for arm and neck were 8.15 and 4.05 respectively, the average post-operative VAS was 1.05 and 1.23 respectively showing an improvement of more than 87.5% for VAS arm and 69.6% for VAS neck pain respectively, both of which were statistically significant (P<0.05). There was a reduction in the disc height from a 6.97(mm) pre-operative mean to 6.34(mm) post-operatively, which though was statistically significant. No patients reported any symptoms which could be associated with it. There were no complications like vascular or neural injury.

  Conclusion:
  This procedure appears as a good alternative minimally invasive procedure to conventional discectomy and fusion for cervical spondylotic radiculopathy case.

• Tree Year Follow Up in a Metal-on-Metal Lateral Disc Replacement: A Shift Paradigm
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Etevaldo Coutinho, MD, Luis Marchi, MSc Leonardo Oliveira, MD
  
  Presentation Summary

  Summary:
  Current lumbar total disc replacement (TDR) devices require an anterior approach for implantation. Placement of a TDR device from a true lateral (XLIF) approach allows for easier, less invasive access to the disc space, with fewer lesions of the adjacent tissues.

  Introduction:
  Current lumbar total disc replacement (TDR) devices require an anterior approach for implantation. This approach has inherent limitations, including risks to abdominal structures, and resection of the anterior longitudinal ligament (ALL). Placement of a TDR device from a true lateral (XLIF) approach allows for easier, less invasive access to the disc space. Lateral implantation of TDR also preserves the stabilizing ligaments, which are a natural restraint to excessive rotations and translations, and thereby help to minimize facet stresses. Importantly, implantation from a lateral approach leaves greater opportunity for safer revision surgery, if necessary, by avoiding scarring of anterior vasculature. Additionally, the footprint of the lateral TDR device capitalizes on the biomechanical support of the ring apophysis.

  Methods:
  A TDR device designed for implantation through a true lateral, retroperitoneal, transpsoas approach (XLIF) was implanted in 36 patients with discography-confirmed 1- or 2-level DDD. Clinical and radiographic outcomes assessments were prospectively collected.

  Results:
  Patients included 16 males and 20 females, average age 43 yrs (24-60). Surgeries included 14 1-level, 3 2-level, and 19 hybrid TDR/ALIF cases. The surgery was performed through a 4cm lateral incision in an average of 134 minutes (90-300) and with an average 58cc blood loss (30-150). There was no intra-op or post-op complications. Postoperative x-rays showed good device placement, with restoration of disc height, foraminal volume, and sagittal balance. All patients were up and walking within 12 hours of surgery. VAS pain scores improved from an average of 9.3 at pre-op to 2.27 after 3 years. Oswestry Disability Index improved from an average of 57 at pre-op to 16.5 after 3 years.

  Conclusion:
  Our results of a laterally placed TDR device demonstrate maintenance of pain relief and functional improvement. The benefits of this technique – minimal morbidity, avoiding mobilization of the great vessels, preserving the anterior longitudinal ligament, biomechanically stable orientation, and broader revision options – suggest a promising new direction for TDR procedures.

• Vertebral Augmentation Treatment of Painful Osteoporotic Compression Fractures with the Kiva System
  Presenting author: Ricardo Escamilla, MD
  Additional authors: Luis Rosales olivarez, MD, Juan Dipp, MD, Harrison Stubbs,PhD, Jon Block, MD
  
  Presentation Summary

  Summary:
  Vertebral compression fractures (VCFs) cause significant pain and functional impairment. This multi-center pilot study evaluated the clinical outcomes associated with the use of an innovative vertebral augmentation device, the Kiva?, VCF Treatment System (Benvenue Medical, Santa Clara, CA), in the management of symptomatic osteoporotic VCFs. These pilot findings suggest robust and durable clinical improvement following the novel vertebral augmentation procedure using the Kiva System in patients with painful VCFs.

  Introduction:
  Vertebral compression fractures (VCFs) cause significant pain and functional impairment. This multi-center pilot study evaluated the clinical outcomes associated with the use of an innovative vertebral augmentation device, the Kiva™ VCF Treatment System (Benvenue Medical, Santa Clara, CA), in the management of symptomatic osteoporotic VCFs.

  Methods:
  The Kiva System deploys a coiled PEEK-Optima Implant into the vertebral body via a transpedicular cannula, and is designed to restore height, preserve native cancellous bone, reduce volume of and contain PMMA bone cement injected within the Implant. Forty patients (mean age: 69.8 ± 9.7 y) with radiologically-confirmed VCFs underwent vertebral augmentation for persistent back pain. There were 35 one-level, 4 two-level and 1 three-level case(s), representing 46 treated levels. Back pain severity was evaluated as a primary endpoint using a standard 100 mm Visual Analog Scale (VAS). A secondary endpoint, condition-specific functional impairment was evaluated with the Oswestry Disability Index (ODI). Evaluations were performed prior to device implantation and at 6 weeks, 3 months and 12 months.

  Results:
  Marked clinical improvements were realized in back pain and functional impairment through 12-months. The mean (± SD) VAS score improved from 8.1 ± 1.6 pre-treatment to 2.2 ± 2.1, 2.1 ± 2.6 and 2.3 ± 2.3 at 6 weeks, 3 and 12 months, respectively. The average decrease at 12 months was 5.2 ± 2.5 or approximately 70% (p < 0.0001). Similarly, the mean ODI score improved from 70.5 ± 17.1% pre-treatment to 25.4 ± 18.2%, 21.4 ± 19.4% and 19.6 ± 11.5%, representing an average change of 41.1 ± 12.9 percentage points or approximately 68% at 12 months. Clinical success rates based on a ? 2-point improvement in VAS were 97%, 93% and 91% at 6 weeks, 3 and 12 months. The vertebral augmentation procedure required 2.2 ± 0.12 ml cement per vertebral body. There were 4 cases (10%) of cement extravasation identified radiographically although none were correlated with clinical symptoms.

  Conclusion:
  These pilot findings suggest robust and durable clinical improvement following the novel vertebral augmentation procedure using the Kiva System in patients with painful VCFs.

• XLIF Indirect Decompression for the Treatment of Lumbar Stenosis: Lessons Learned
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Etevaldo Coutinho, MD, Luis Marchi, MSc Leonardo Oliveira, MD
  
  Presentation Summary

  Summay:
  Symptomatic lumbar stenosis presents as a consequence of a narrowed spinal canal and nerve roots. Using a lateral retroperitoneal approach we were able to indirect decompress the canal and nerve roots in a minimal invasive way, preserving all posterior elements of the spine.

  Introduction:
  Symptomatic lumbar stenosis presents as a consequence of different factors that narrows the lumbar spinal canal and the nerve roots. Its most common symptoms are weakness, numbness/tingling, radicular pain and neurogenic claudication in almost equal proportions. Traditional treatment includes laminectomy with spinous processes, laminae and pedicles removal. The purpose of this paper is to present a lateral retroperitoneal minimal invasive approach for the indirect treatment of lumbar central and lateral stenosis without the morbidity of a larger procedure.

  Methods:
  The extreme lateral approach was done through the retroperitoneal space and through psoas muscle avoiding vascular lesions. A partial discectomy was done and the end-plate cleaned preserving ALL, keeping the spine more stable than the traditional surgery. 20 patients with central or lateral stenosis underwent the XLIF Stand Alone procedure with 18mm cage (standard) and 20 patients with 22mm cage (Wide). Dynamic X-rays, MRI and clinical outcome assessments using Oswestry and VAS scores were performed preoperatively, 1 and 12 weeks after surgery. The measurements were done using medical imaging software.

  Results:
  We used a t-test to compare the average and standard deviation of the preoperative and postoperative data. All parameters were statistically significant (p < 0.05), showing the improvement of the disc height, canal area and foraminal space. VAS pain scores improved from an average 8.9 at pre-op to 3.25 at 3 months. Oswestry scores improved from an average 56.40 at pre-op to 32.5 three months after surgery. The only statistical difference found between both groups was subsidence rate. The standard group had 31% of subsidence while the Wide group presented only 10% of subsidence rate.

  Conclusion:
  The XLIF procedure provides the necessary decompression for the treatment of central and/or lateral stenosis in a minimally invasive way, preserving the ALL and all posterior elements of the lumbar canal with a wider implant preventing subsidence in a stand alone construction.