Annual Meeting

Annual Meeting 2010

November 4-5, 2010
The Loews Miami Beach Hotel & M.A.R.C. Lab
Miami, FL

The 2010 SMISS Board of Directors would like to whole heartedly thank all the attendees for their time and contributions that made SMISS 2010 the success it was. We look forward to seeing you at SMISS 2011!

The SMISS 2010 Annual Meeting was held at The Loews Miami Beach Hotel & the Miami Anatomical Research Center (M.A.R.C.) in Miami, FL. This "can't miss" meeting featured a full-day hands-on cadaver lab showing the latest MIS procedures, two full days of CME-accredited didactic sessions, including lectures from MIS leaders, in-depth case discussions, oral abstracts and e-Posters on the newest research.

• A Comparison of MIS Fusion to Open Fusion for Degenerative Lumbar Disorders: A Systematic Review
  Presenting author: Y. Raja Rampersaud, MD, FRCS9(c)
  Additional authors: Rabin, MD, FRCS(C); Soo Yong Chua, MD, FRCS(C); Shawn Liu, HBSc; Oma Persaud, MSc;
  
  Presentation Summary

  Introduction:
  There are recent reports of promising outcomes in minimally invasive spine (MIS) lumbar arthrodesis. Most reports are non-comparative descriptions of heterogeneous patient populations. This study aims to compare efficacy of MIS posterior fusion surgery for lumbar spondylosis in comparison to open surgical technique.

  Methods:
  Medline, EMBASE, PubMed, Web of Science, and Cochrane databases were queried. The MeSh terms used were derivatives of the following: "Spine"; "Lumbar vertebra"; "Spinal fusion"; "Arthrodesis"; and "Minimally invasive surgical procedure". Articles were initially accepted based on title relevance. Inclusion and exclusion criteria were then applied to the remaining articles. Inclusion criteria were randomized control studies (RCT) or comparative cohort studies with more than 10 patients with at least 1 of the following: clinical outcome measures; perioperative data (blood loss, surgical time, length of hospital stay); radiographic outcomes; and complications. Study populations with traumatic, neoplastic or infectious pathology and articles describing decompression without arthrodesis were excluded. 2 spine surgeons independently reviewed the articles for inclusion and exclusion criteria. In cases of disagreement, a third surgeon reviewed the article to assess suitability. A meta-analysis was conducted on all comparative studies meeting search criteria.

  Results:
  The literature search identified 1144 articles. 54 articles were reviewed in detail, of which 8 were comparative studies. Reported data was of insufficient quality to perform a meta-analysis. Most studies reported superior clinical outcomes and perioperative outcomes in MIS patients. Radiographic fusion rates and complications appear to be equivalent.

  Conclusions:
  MIS posterior arthrodesis for lumbar spondylosis appears to be equivalent to open procedures with respect to clinical efficacy and safety. Additional comparative data is required to support any claim of superiority of one technique over another.

• A long term clinical experience with three different Nucleus Replacement Devices - Lessons Learned after 9 years follow up
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Luis Marchi, MS; Etevaldo Coutinho, MD
  
  Presentation Summary

  Introduction:
  The nucleus replacement devices have been developed for treating moderate forms of degenerative disc disease, trying to fill the gap between discectomy and fusion. The surgical goals are pain relief, maintenance of the disc height and flexibility at the index and adjacent levels. Here we show our experience after 9 years using three different nucleus replacement prostheses.

  Material and Methods:
  125 patients with moderate forms of degenerative disc disease were enrolled in this study. 80 patients had PDN disc prosthesis, 26 patients with PNR (Trans1) and 19 patients using the NUBAC (Pioneer) device. Radiographic (AP, lateral and dynamic) and clinical outcomes were collected preoperatively, 1 week and 1, 3, 6, 9, and annually through 9 years postoperatively. The VAS and ODI questionnaires were used to assess pain and functional outcomes.

  Results:
  After 9 years follow up, the global retrieval incidence was 48.8% (61/125). From these patients, 15 (57.7% of the specific device) had PNR failures, 8 (42.1% of the specific device) experienced NUBAC retrievals and 38 (47.5% of the specific device) had PDN flaws. The failures included significant loosening of the disc height at the operated level, displacement, silicon inside de canal and migration. All patients underwent fusion as a retrieval surgery.

  Conclusion:
  The retrieval rate in our series is very high. It shows that the end-plate reaction in a long period of time happens, resulting in important subsidence and mechanic back pain. The device expulsion was another cause of pain and second surgery, as shown in the literature.

• A Novel Radiographic Targeting Guide for Percutaneous Placement of Transfacet Screws in the Cervical Spine with Limited Fluoroscopy: A Cadaveric Feasibility Study
  Presenting author: David M. Jackson, MD
  Additional authors: Jacqueline Karp, MD; Greg Anderson, MD; Dan Gelb, MD; Steven Ludwig, MD
  
  Presentation Summary

  Introduction:
  There is emerging interest in developing a minimally invasive technique for instrumentation of the cervical spine. We describe and test a technique for percutaneous transfacet screw placement in the cervical spine using a unique radiographic targeting guide that eliminates the need for lateral fluoroscopy.

  Methods:
  We used previously established articular pillar morphometry to define the ideal trajectory for transfacet screw placement in the subaxial cervical spine. Using these guidelines, Kirschner wires were placed percutaneously in 10 cadaveric specimens. Wire placement in the inferior articular process of C3, C4, C5 and C6 was done entirely under modified AP fluoroscopy using a radiographic targeting device that eliminated the need for a lateral radiographic view. Following the placement of the K-wires, 4.0 mm cannulated screws were advanced across the facet joints. (See Figure) All specimens were assessed for acceptable placement or critical breach by three fellowship trained orthopedic spine surgeons using CT scans. Open dissection was used to confirm radiographic interpretation. Acceptable placement was defined as a screw crossing the facet joint, achieving purchase in the inferior and superior articular processes and not violating critical structures . Breach was defined as a violation of the transverse foramen, spinal canal or nerve root, or a fracture of the facet joint resulting in loss of fixation.

  Results:
  A total of 48 screws wires were placed across the C3-4, C4-5, C5-6 and C6-7 joints. 46 screws were acceptably placed. The three breaches included a facet fracture, a facet distraction and a 6-7 screw contacting the C7 nerve root in a specimen with a small C7 superior articular process.

  Conclusion:
  Multiple authors have championed a variety of techniques with a lack of consensus for proper trajectory in open transfacet screw placement. A previous feasibility study evaluating percutaneous transfacet screw placement showed it to be unreliable with current instrumentation and techniques. Our data shows that, with the appropriate anatomic technique and instrumentation, percutaneous transfacet screw placement, without the need for lateral fluoroscopy, is viable at C3-C7. Due to the variable morphometry of the C7 lateral mass, however, care must be taken when placing a transfacet screw at C6-7. We described a new minimally invasive technique to reliably navigate screws across the facet joints of the subaxial cervical spine in cadaveric specimens.

• Anatomic Relationships Between The L4-5 Disc Space And Pelvis: Implications For A New Trajectory During Lateral Lumbar Interbody Fusion
  Presenting author: Brian Kwon, MD
  Additional authors: Nael Shanti, MD; Ling Li, MSPH; David H. Kim, MD
  
  Presentation Summary

  Introduction:
  Lateral lumbar interbody fusion (LLIF) exploits the retroperitoneal space to access the anterior spinal column. Deformity correction, increased fusion bed area and implant size are comparable to traditional anterior surgery. Because of the pelvis, LLIF cannot be done at L5-S1 and approaching L4-5 is difficult. Because of its location near the midpoint of the L4-5 disc, L4 nerve injury during LLIF is attributed to dorsal migration of retractors and implants and possibly ischemia. We hypothesize that the L4-5 disc can be prepared and L4 nerve injury may be avoided by a more ventral approach during LLIF.

  Objectice:
  To perform an anatomic study of the relationship between the L4-5 disc space and pelvis. To describe a more ventral trajectory that is more parallel to the L4-5 disc.

  Methods:
  We studied 25 patients with pelvis CTs prior to hip arthroplasty. We examined axial and coronal images of L4-5 disc in relation to the pelvis. Measurements and correlations on coronal CT: (a) distance between top of L5 and the top of crests, (b) approach angle parallel to the L4-5 disc (Fig 1). On axial images (parallel to L4-5 disc): (d) new trajectory angle, (e) psoas entry point comparing new vs. traditional trajectories (Fig 2). Two readers made all measurements (ICC 0.60 - 0.99).

  Results:
  Location of the L5 superior endplate relative to the iliac crests in men was -9.3mm (below) and in women +6.0mm (above), p=0.009. There were significant correlations (p<0.005) between depth of L5 endplate and (b) approach angle [ICC -0.74], and (d) new trajectory angle [ICC -0.76]. Thus lower seated L4-5 discs required more ventral and caudal trajectories. Average change of approach angle was, in ventral direction, 8.7-12.5 deg in men and 2.2-2.9 deg in women, p<0.05. The % psoas penetration is measured from the ventral to dorsal most aspect of the psoas. The difference between new and old trajectories in women was not significant: 0.11 vs. 0.14, p=0.5. There was a significant difference in men: 0.33 vs. 0.46, p<0.0001, i.e. new trajectory penetrated ventral third of psoas while the old trajectory penetrated near mid-point.

  Discussion:
  Based on our data, anatomic considerations should be made when approaching the L4-5 disc during LLIF. There are significant differences between men and women in the location of the L4-5 disc in relation to the iliac crests. Choosing a more ventral trajectory in men will allow more parallel entry to L4-5, lead to a more ventral entry point into the psoas and may better avoid L4 nerve root injury.

• Axial Interbody Fusion (AxiaLIF) Patients Show Negligible Postsurgical Complications: Analysis of First 70 Consecutive Cases
  Presenting author: Atiq Durrani, MD
  Additional authors: Rachel Mistur, MS
  
  Presentation Summary

  Introduction:
  Axial Lumbar Interbody Fusion (AxiaLIF) provides a promising new approach to the treatment of lumbar degenerative disc disease, spondylolisthesis, and spinal stenosis, among other conditions. This minimally invasive procedure encourages shortened recovery times and reduced complications, as compared to traditional open techniques for lumbar fusion. Preliminary data suggest minimal complications in 70 consecutive AxiaLIF cases, providing support for the use of this pre-sacral approach.

  method:
  We performed a retrospective chart review of our first 70 consecutive patients who received L5-S1 AxiaLIF implants between 1/2009-12/2009. All patients received a minimum of two follow-up evaluations to assess wound healing, hardware placement, and potential postsurgical complications. All complications were carefully addressed and documented in patient charts. These complications were later reviewed for purposes of this study.

  Results:
  The present study included 23 males and 47 females with an average age of 52.1 years. Complications were identified in 12.8% of these first 70 cases. Of these cases, 4 patients had wound dehiscence/ infection (44.4%), 4 patients had extrusion of bone graft (44.4%), and 1 patient had coccydynia (11.1%), which was resolved with steroid injections. There were no documented vascular or rectal bowel complications. Most postsurgical complications were minor and did not necessitate additional surgery. It is also important to note that 100% of patients experiencing complications noted a decrease in pain levels following surgery, as assessed by the visual analogue pain scale (VAS).

  Conclusion:
  Data suggests that complications as a result of AxiaLIF are negligible and easily resolved with conservative treatment. Despite complications, all patients report an improvement or complete alleviation of symptoms following the AxiaLIF procedure. These 70 patients represent our earliest cases and complication rates in our patient population are expected to decrease over time. Overall, this analysis provides support for the use of AxiaLIF in the treatment of lumbar degenerative disc disease and other conditions requiring L5-S1 fusion.

• Biomechanical Evaluation of a Standalone Lumbar Interbody Cage with Integrated Screws
  Presenting author: Frank M. Phillips, MD
  Additional authors: Martin B. Kornblum, MD; Michael A. Zatushevsky, MD; Alexander W. Turner, PhD; G. Bryan Cornwall, PhD
  
  Presentation Summary

  Introduction:
  Anterior lumbar interbody fusion (ALIF) devices with integrated fixation provide the opportunity to increase fusion construct stability, potentially allowing for standalone use. The purpose of this study was to evaluate an interbody cage with integrated fixation screws (Brigade?, NuVasive, Inc.) to resist motion and to compare the construct rigidity to traditional ALIF fixation methods and cages without supplemental fixation.

  Methods:
  Eight human lumbar spines (L2-S1) were tested with unconstrained pure moments at ?7.5 Nm in flexion-extension (FE), lateral bending (LB) and axial rotation (AR). Intervertebral motions were measured with an optoelectronic system. Conditions tested were: (i) intact, (ii) cage (0 screws) at L4-5, (iii) cage (0 screws) + anterior plate, (iv) cage (0 screws) + bilateral pedicle screws, (v) cage (3 screws), (vi) cage (4 screws), and (vii) cage (3 screws) + spinous process plate. Range of motion (ROM) at L4-5 was measured optoelectronically. Differences in ROM between test conditions were evaluated using repeated-measures ANOVA and Holm-Sidak multiple paired comparisons with significance set at p < 0.05.

  Results:
  The standalone cage with supplemental integrated screw fixation was significantly more rigid than the cage alone (p < 0.02). The addition of a 4th screw did not significantly increase stability when compared to a 3-screw construct (p > 0.11), although there was a trend towards more motion in flexion-extension and axial rotation with 3 screws. The cage with screws (3 or 4) was not significantly different (p > 0.05) from the cage (0 screws) and anterior plate, or the cage (3 screw) and spinous process plate in lateral bending or axial rotation. The cage with 3 screws and spinous process plate provided the most rigid construct in flexion-extension. This construct was also not significantly different from the cage (0 screws) with bilateral screws in any direction (p > 0.25). Bilateral pedicle screws provided the most rigid construct in lateral bending and axial rotation.

  Conclusion:
  The results indicate that the standalone cage with integrated screws provides more post-operative initial stability than a standalone cage and provides comparable stability to traditional ALIF constructs, particularly in LB and AR. Additional of the spinous process plate was shown to further increase stability.

• Biomechanical Evaluation of XLIF Supplemental Fixation Including a Combination of Lateral and Spinous Process Plates
  Presenting author: Guy R. Fogel
  Additional authors: MD; Huy T. Duong, MD; Andrew Cappuccino, MD; Alexander W. Turner, PhD; G. Bryan Cornwall, PhD
  
  Presentation Summary

  Introduction:
  Previous testing has shown the high biomechanical stability of the XLIF approach interbody cage alone compared with the intact spine. The 2-bolt lateral plate has been shown to add stiffness in lateral bending and axial rotation, but little in flexion-extension. The stability offered by the spinous process plate should reduce motion in the flexion-extension plane, and therefore a combination of lateral and spinous process plates may increase stability in all directions; potentially to the extent of bilateral pedicle screws.

  Methods:
  Ten spines (L1-L5) were subjected to multidirectional non-destructive flexibility testing. Each spine was tested under the following conditions: (1) intact, (2) L3-4 discectomy with XLIF cage, (3) lateral plate, (4) lateral + spinous process plates, (5) spinous process plate, (6) ipsilateral pedicle screws, (7) bilateral pedicle screws. ROM was evaluated and differences were examined using repeated-measures ANOVA and Holm-Sidak comparisons.

  Results:
  The interbody cage alone significantly reduced ROM in all directions with respect to intact. Bilateral screws provided the most rigid supplemental fixation. The lateral plate was not significantly different from the cage alone in flexion-extension, but was more rigid in lateral bending and axial rotation. The spinous process plate significantly improved flexion-extension rigidity over standalone, but was not significantly more rigid in lateral bending or axial rotation. The addition of the spinous process plate to the lateral plate combined to reduce motion in all planes, providing rigidity not statistically different from bilateral pedicle screws.

  Conclusions:
  The clinical question is how much rigidity is necessary to prepare the best environment for interbody fusion. This study demonstrates the increased rigidity of supplemental fixation including the combination of lateral and spinous process plates, which provided improved rigidity in all directions that was not statistically different from bilateral pedicle screws.

• Biomechanics of Minimally Invasive Interlaminar Lumbar Instrumented Fusion (ILIF) Technique for the Treatment of Lumbar Spinal Stenosis
  Presenting author: Hyun W. Bae, MD
  Additional authors: Ben B. Pradhan, MD; Michael A. Zatushevsky, MD; Alexander W. Turner, PhD; G. Bryan Cornwall, PhD
  
  Presentation Summary

  Introduction:
  Interlaminar Lumbar Instrumented Fusion (ILIF™, NuVasive, Inc.) is a potentially less invasive alternative to segmental laminectomy and posterolateral fusion with pedicle screw (PS) fixation techniques. In this study, biomechanical stability of the ILIF procedure in a multi-segmental cadaveric model was compared with more invasive traditional approaches using a hybrid testing protocol.

  Methods:
  Eight L1-L5 cadaveric specimens were subjected to multi-directional testing. Intervertebral motions were measured optoelectronically. After testing the intact spine to ±7.5 N•m, subsequent conditions evaluated at L3-4 were tested to the intact ROM: (1) bilateral PS, (2) bilateral laminotomy, (3) ILIF (bilateral laminotomy + ExtenSure® H2 allograft + Affix™ spinous process plate), (4) wide laminectomy, (5) wide laminectomy + unilateral PS, (6) wide laminectomy + bilateral PS, (7) Gill laminectomy, (8) Gill laminectomy + bilateral PS. Ranges of motion were evaluated using repeated measures ANOVA and Holm-Sidak comparisons.

  Results:
  The most rigid construct in all directions was bilateral pedicle screws without any destabilization. In flexion-extension (see Figure), no statistical difference existed between ILIF and the bilateral PS conditions (p > 0.9). Unilateral PS with wide laminectomy provided less rigidity than ILIF and bilateral pedicle screws (p < 0.004). In lateral bending, ILIF was not significantly different from unilateral PS fixation (p = 0.16), however bilateral PS were more rigid than both of these conditions (p < 0.05). Under axial rotation ILIF was significantly different from bilateral PS alone (p = 0.012), but not significantly different from unilateral PS (p = 0.771) or laminectomy with bilateral PS (p > 0.496). Furthermore, none of the fixation conditions were significantly different from intact (p > 0.15) with the exception of bilateral PS without destabilization (p = 0.002).

  Conclusions:
  While bilateral pedicle screws provided the most stable construct under these testing conditions, the ILIF construct provided rigidity in flexion-extension and axial rotation that was not significantly different from bilateral screws with wide or Gill laminectomy. In lateral bending, ILIF was not significantly different from laminectomy with unilateral screws. The ILIF technique provides surgeons with the ability to perform a minimally invasive, single-approach, posterior decompression.

• Clinical Performance Evaluation of a Modular Interbody Fusion Device
  Presenting author: Jesse Butler
  Additional authors: Paul Adsourian, MD; Arnold Schwartz, MD; Jeffrey Felt, MD
  
  Presentation Summary

  introduction
  Interbody Fusion Devices inserted from a posterior approach have historically been limited to only partial endplate coverage dictated by the dimensions of the posterior access channel. Many surgeons believe that a broader footprint would lead to greater stability, less subsidence, and a lower migration rate. The Vertebral Technologies, Inc. (VTI) InterFuse® implant is an FDA cleared interbody fusion device that uses several modules connected by rail and slot dovetailed junctions to build a full footprint implant horizontally across the endplates. Each module is about 8mm in the medial/lateral dimension and can be placed through a unilateral PLIF approach, thus minimizing nerve root or dural irritation.

  methods
  We are reporting the results of imaging studies on the first 104 cases for which we have the imaging data. The patients are unselected except that they have had a C.T. scan and a flexion/extension x-ray performed six to nine months post operatively. Bone morphogenic protein was used in less than half of the patients. The films were read by an independent spine radiologist and evaluated for fusion, migration, subsidence and hardware loosening. The criteria for fusion were based on stability and the presence of bridging bone. Migration was read as positive if more than 3mm of anterior/posterior displacement of any module was present. Subsidence was read as positive if more than 3mm of settling of the end plates had occurred and hardware loosening was determined by the presence of lucent lines around the screws.

  Results: Of the 104 cases with flexion/extension x-rays and CT scan, 101 were read as showing definite fusion. All 104 films and CT scans were read as negative for subsidence, migration or hardware loosening determined by the presence of lucent lines around the screws.

  results
  Of the 104 cases with flexion/extension x-rays and CT scan, 101 were read as showing definite fusion. All 104 films and CT scans were read as negative for subsidence, migration or hardware loosening.

  Conclusions:
  In this study the modular InterFuse implant resulted in a high fusion rate and no subsidence, migration, or hardware loosening.

• Comparison of Clinical and Radiological Outcomes between Open and MIS TLIF
  Presenting author: Wai Mun Yue, MBBS, FRCSEd, FAMS(Ortho Surg)
  Additional authors: Kong Hwee Lee; William Yeo; Henry Soeharno; Seang Beng Tan
  
  Presentation Summary

  Introduction:
  Open TLIF has been performed for many years with good results. MIS TLIF techniques have recently been introduced with the aim of smaller wounds, less tissue trauma and faster recovery. At the same time it is hoped that MIS TLIF will also achieve the same good long term results of open TLIF, in terms of fusion and clinical outcomes.

  Methods:
  MIS TLIF has been performed in Singapore General Hospital since 2005. The clinical and radiological outcomes are tracked prospectively at the Orthopaedic Diagnostic Centre. 68 such patients with single level MIS TLIF followed for at least 2 years were matched with another 69 patients who had Open TLIF performed.The indications for surgery were: 1) Grade 1 or 2 spondylolisthesis and 2) degenerate discs presenting with mechanical low back pain and radicular symptoms. Clinical assessment in terms of NASS, ODI, SF-36 and VAS scores, were performed preoperatively, 6 month and 2 year postoperatively. Fusion rates based on Bridwell grading were assessed at 6 months and 2 years.

  Results:
  The mean age for MIS and Open procedures were 51.5 and 56.9 years respectively. Female:male distribution were 20:49 for the Open group and 19:49 for the MIS group. There was no difference in the operative time (MIS: 168.2 minutes, Open: 180.6 minutes, p<0.05). Fluoroscopic time (MIS: 50.6 seconds, Open: 15.6 seconds, p<0.05) was longer in MIS cases. There was less blood loss and postoperative drainage in MIS (50.7ml, 0.2ml) versus Open (418.2ml, 532ml) procedures (p<0.05). The total morphine used for MIS cases (3.9mg) was less compared to Open (33.2mg, p<0.05). MIS patients have shorter time to ambulation (1.2 days vs 3.5 days, p<0.05) as well as shorter hospitalisation compared to Open (3.2 days vs 6.9 days, p<0.05). Both MIS and Open groups showed significant improvement in ODI (p<0.05), back pain and lower limb symptoms (NASS and VAS scores, p<0.05) and Quality of Life scores (SF-36, p<0.05) at 6 months and 2 years but there was no significant difference between the two groups. At 6 months, 56.9% of MIS and 51.5% of Open TLIF levels achieved Grade 1 fusion (p>0.05). By 2 years, 96.8% of MIS and 98.4% of Open TLIF levels achieved Grade 1 fusion (p>0.05).

  Conclusion:
  MIS TLIF has similar good long term clinical outcomes and high fusion rates of OPEN TLIF with the additional benefits of less initial postoperative pain, less blood loss, early rehabilitation and shorter hospitalization.

• Complications In A Mini-open, 90? Lateral, Retroperitoneal, Transpsoas Approach For Discectomy And Fusion In The Lumbar Spine: Two-year Results
  Presenting author: William D. Smith
  Additional authors: Ginger Christian, B.S.; Sherrie Serrano, B.S.
  
  Presentation Summary

  Introduction:
  Complications of spine surgery are an unfortunate reality, though the benefits of intervention have been shown to outweigh risks. Outside of the general risks of surgery, spinal fusion procedures carry different risks based on the type of procedure being performed and the extent of exposure used. Among other things, anterior lumbar interbody fusion (ALIF) is regularly associated with increased risk of vascular injury, while posterior approaches generally carry a greater risk of neural injury. Open procedures are also associated with greater intraoperative blood loss and higher associated complication rates than minimally invasive procedures. Lateral approach surgery is less studied, but widely performed as a less invasive approach to the anterior spine. This study aims to detail long-term complications using a lateral approach for lumbar interbody fusion.

  Methods:
  Lateral pproach surgery is less studied, but widely performed as a less invasive approach to the anterior spine. This study aims to detail long-term complications using a lateral approach for lumbar interbody fusion.

  Results:
  559 of the 801 patients (69.8%) completed at least 24-month follow-up. Average treatment variables included 96 minute operative time with <50cc blood loss and a 2.1 day hospital stay. A total of 57 complications (10.2%) were observed in 48 (8.6%) patients with 29 (5.2%) reoperations. Complications included 11 (2.2%) pseudoarthroses, nine (1.6%) instances of clinical subsidence, four (0.7%) adjacent segment disease revisions, four (0.7%) lower extremity dysesthesias, and one (0.2%) femoral nerve palsy.

  Conclusions:
  Low blood loss, operative time, and length of stay suggest mini-open XLIF minimizes collateral tissue damage. Vascular and visceral complications common to anterior procedures were not encountered, and neural injuries were fewer than commonly reported rates in posteriorly approached procedures. The single instance of nerve injury in this series supports the required use of advanced neuromonitoring modalities. The overall complication and reoperation rate in this study is in-line with the least complicated approaches in the literature.

• Degenerative Spondylolisthesis: Superior Results with Minimally Invasive Transforaminal Lumbar Interbody Fusion Without Posterior Spinal Fusion
  Presenting author: Raymond, J. Gardock, MD
  Additional authors: Adam M. Kennedy, M.D
  
  Presentation Summary

  Introduction:
  The management of symptomatic degenerative spondylolisthesis often involves surgical intervention. Decompression, instrumentation, and posterolateral fusion have been well established as the universal standard of care. With the advent of minimally invasive interbody fusion using BMP, the neccessity of a posterolateral fusion has been called into question. To evaluate minimally invasive transforaminal lumbar interbody fusion (MITLIF) without posterior fusion in the treatment of degenerative spondylolisthesis and to objectively compare our patient outcomes with published results, a retrospective review was undertaken.

  Methods:
  Between March 2008 and August 2010, 31 patients with degenerative spondylolisthesis underwent MI-TLIF with posterior instrumentation. Visual analog score, SF-36 mental and physical scores, and Oswestry Diability Index were all obtained before surgery and at 6 weeks and 3, 6, 12 and 24 months postoperatively. Operative time, blood loss, hospital stay, and narcotic use were also recorded.

  
  Final follow up averaged 8.5 months. Preoperative and 12 month VAS for back pain were 6.6 and 2.52, respectively. Preoperative and final VAS for leg pain were 6.64 and 0.95, resepectively. SF-36 preoperative and final scores were 29 and 63, respectively, for PCS; MCS was 48 and 70. Preoperative physical function and bodily pain scores were 22 and 23, respectively, and they increased to 66 and 65 at final follow up. The Oswestry Disability Index preoperatively was 48.4 and 16 at most recent followup. Morbidity was represented by operative duration, intra-operative blood loss, and hospital stay. Operative time averaged 128 minutes and the estimated blood loss was 116 cc?s. The average hospital stay was 24 hours. This compares to the SPORT study with average operative times of 210 minutes, 570 cc estimated blood loss, and hospital stays of 4.8 to 6.9 days. Fewer than ? of our patients were using narcotics at the 6-month mark.

  
  Patients with degenerative spondylolisthesis treated with MI-TLIF using BMP without posterior fusion demonstrated excellent results, with less morbidity and subjectively better outcomes compared to standard treatment. Fusion rates were comparable to those reported for decompression, stabilization, and posterolateral fusion.

• Early Results Of Minimally Invasive Surgical Sacroiliac Joint Arthrodesis
  Presenting author: Mark Reiley, MD
  
  Presentation Summary

  Purpose:
  According to literature, over 22% of individuals who presented with low back complaints had problems in their SI joint. Despite the large number of patients with SI joint symptoms, most low back pain treatments focus on the disc. A recent publication on lumbar fusion patients (Ha, et al., Spine, 2008) indicated that 75% developed CT documented SI joint degeneration within 5 years post-fusion. Diagnosis of SI joint has been challenging and open surgical fusion has been highly morbid and technically demanding. A new, intramedullary MIS implant coated with porous plasma spray that acts as an interference surface to treat the SI joint has been evaluated.

  Methods:
  59 patients were diagnosed with symptomatic SI joint pain based on interpretation of a patient?s history, clinical exam, and imaging studies. Joint asymmetry may be seen on CT and MRI. Image guided anesthetics injection provides confirmation of SI pain The MIS procedure is performed under general anaesthesia prone. Ideally three 4.0mm or 7.0 mm triangular implants are inserted across the SI joint through a 2-3cm incision. The drills, broaches, and implants are cannulated to allow precise placement over a guide pin. Patients are kept non-weight bearing for 6 weeks and followed by 4 weeks of partial weight bearing. Routine activities are allowed at 12 weeks. Radiologic studies include post-op films, 3, 12, and 24 month X-rays. CT is recommended at 3, 12, and 24 months to document implant position and to observe bone growth across the joint.

  Results:
  59 patients included in this report. Patients were evaluated pre-operatively, and at 3, 6, 12 and 24 months. All patients were able to return to full and unrestricted activity at three months. Symptoms were measured by VAS and showed consistent improvement from pre-op to follow-up. Some patients exhibited evidence of SI joint fusion as early as 2 months post-op, as seen on sagittal CT view. 90% of patients indicated they would have this MIS procedure again. Complications included three self-resolving hematomas and one (bent) guide pin puncture of the obdurator artery, which required arterial injection.

  Conclusion:
  SIJD syndromes are common. Several treatments available have shown limited efficacy. This study reinforces awareness that the SI joint produces symptoms. In some patients with residual symptoms after hip or lumbar spine procedures, it may be the SI joint that is the symptom generator. With the advent of this new MIS procedure, surgeons may now be able to successfully treat patients refractory to conservative medical therapy.

• Endoscopic Transformainal Decompression: A Single Surgeon Experience At Two Or More Years F/u.
  Presenting author: Daniel T. Laich;
  Additional authors: Carol E. Talisse, PA-C; Fred H. Geisler, MD, PhD; Jerrel Boyer, DO
  
  Presentation Summary

  Introduction:
  Despite reported benefits by Hijikata, Kambin, and more recently Iprenburg & Yeung the efficacy of transforaminal decompression has remained questioned as equal to the more traditional open methods of microdiscectomy or laminoforaminotomy. This is a retrospective review of 122 consecutive patients performed at a single institution for three distinct subsets of patients: LBP with LE radiculitis secondary to HNP; LBP and LE radiculitis secondary to foraminal stenosis; LBP as primary complaint with DDD/HNP.

  Methods:
  122 consecutive patients deemed appropriate for, and operated via endoscopic transforaminal decompression were retrospectively reviewed. These patients were all from a single institution, and surgery was performed all by a single surgeon. F/U was a minimum of two years.

  Results:
  122 patients: 57females, 65males.77% had pre-op motor deficit, 79% pre-op sensory deficit. Post-op deficits were 3% and 4% respectively. Pre-op VAS was 3.5-9.3, post-op VAS 1.6-4.6. Pre-op ODI 40%, post-op 20%. Treatment failure, 'intent to treat' resulted in subsequent surgery in 29%. Of these failures 32 underwent reconstructive procedures and 3 decompressive procedures. Of this 29% 18 were reoperations. 10 of 18 failed. 10 of these 10 had LBP as primary complaint. 1 had residual sensory deficit. Successful 'intent to treat': 8 of 10 with foraminal stenosis and radiculitis, and 75 of 77 of HNP with radiculitis found relief.

  Conclusion
  Failures with the endoscopic transforaminal approach seem associated with selection process more than surgical technique. Endoscopic transforaminal decompression shows results at least equal to the historical gold standard for open microdiscectomy or laminoforaminotomy.

• Five-year Experience with Computer Navigation Without Neuromonitoring for Direct Lateral Interbody Fusion
  Presenting author: Michael MacMillan, MD
  Additional authors: D. McCormick, MD
  
  Presentation Summary

  Introduction:
  Records were reviewed of 99 patients who had undergone 129 levels of interbody fusion through a direct lateral approach performed by a single surgeon using computer navigation without neuromonitoring. Five surgeries were completed with the assistance of fluoroscopic navigation, 36 with isocentric fluoroscopic navigation, and 58 performed with intra-operative computer tomographic navigation.

  Records were reviewed for intra-operative complications, post-operative neurologic sequelae, and rates of fusion. Of the 99 patients, there was one intra-operative complication consisting of a single anterior graft dislodgment in a two-level procedure. Neurologic sequelae were found in 25 patients. Eighteen patients reported sensory dysesthesia symptoms which resolved in 15 patients within one year after surgery. Hip flexion weakness reported in 8 patients had resolved in 7 by 3 months post-operatively. Quadriceps weakness reported in 8 patients had resolved in 7 patients at 6 months post-operatively and in all at 1 year.

  Of the 129 levels which underwent implantation, 11 levels did not fuse and required revision surgery. Four different Interbody devices were used. Fusion rates were not noticeably different between devices.

  Computer navigation for the direct lateral approach to the lumbar spine appears to result in a low percentage of intra-operative complications and an acceptable level of post-operative neurologic events. This study confirms the feasibility of using computer navigation for the direct lateral approach.

• Indirect Decompression of Lumbar Spondylolisthesis Using Anterior Lumbar Interbody Fusion and Minimally Invasive Pedicle Screw Fixation
  Presenting author: Jessica Shellock, M.D
  Additional authors: D. Guyer, M.D.; Michael S. Hisey, M.D.; W. Daniel Bradley, M.D.; Carlos Kugler, M.D.; Donna D. Ohnmeiss, Dr.Med.
  
  Presentation Summary

  Introduction:
  Lumbar spondylolisthesis is a common disorder for which numerous surgical strategies exist. One technique that has received little attention is anterior lumbar interbody fusion (ALIF) combined with posterior instrumentation without decompression.

  Purpose:
  The purpose of this study was to evaluate the clinical and radiographic outcome of a group of patients with symptomatic lumbar spondylolisthesis who underwent ALIF and minimally invasive pedicle screw fixation without direct posterior decompression. Materials and Methods: Radiographs and charts were reviewed for the consecutive series of 41 patients with spondylolisthesis, unresponsive to nonoperative management, who underwent ALIF and minimally invasive pedicle screw placement. Clinical outcome measures included visual analog scales (VAS) separately assessing back and leg pain. The Oswestry Disability Index was also used to evaluate outcome. The mean length of clinical follow-up was 19.2 months.

  Results:
  For the degenerative group (n = 15) mean operative time was 154.9 minutes, estimated blood loss was 63.7 cc, and length of hospital stay was 1.9 days. For the lytic group (n = 26) mean operative time was 160.3 minutes, estimated blood loss was 89.6 cc, and length of hospital stay was 1.9 days. Back and leg pain scores improved significantly from pre- post-operative in both groups (Table 1). In addition, mean Oswestry score improved significantly for the lytic group. In the degenerative group, the Oswestry improved, but not statistically significantly. Radiographically, the amount of slip was significantly reduced and disc space height increased. Fusion was achieved in 37 (86%) of patients, 2 (4.7%) were not confirmed, and 3 (7%) incorporating. There were no cases of pseudarthrosis, malpositioned or broken pedicle screws. One patient underwent reoperation for a wound infection and three patients underwent pedicle screw removal after fusion was achieved.

  Discussion:
  This study found that indirect decompression using ALIF combined with percutaneous pedicle screws resulted in significantly improved pain and radiographic measures. These results suggest that this is a viable technique for treating spondylolisthesis without the need for a formal posterior decrompression.

• Intraoperative Evoked EMG to Assess Nerve Function after Minimally Invasive Lumbar Decompression: A Pilot Study
  Presenting author: Kevin T. Foley, M.D.
  
  Presentation Summary

  Introduction:
  Compressed nerves are known to require elevated thresholds to evoke a compound muscle action potential (CMAP) on EMG. Reduction in evoked EMG threshold after surgical decompression may therefore be indicative of improvement in nerve function and may correlate with clinically adequate neural decompression. The purpose of this IRB-approved study was to determine what, if any, changes in evoked EMG thresholds occurred following minimally invasive lumbar nerve root decompression and whether or not there was any clinical correlation with the electrophysiological findings.

  Methods:
  17 consecutive patients with unilateral lumbar radiculopathy underwent minimally invasive decompression of the symptomatic nerve root utilizing a 16 mm diameter tubular retractor. Evoked EMG thresholds were measured utilizing the NeuroVision Intraoperative Monitoring System. An insulated probe was used to stimulate the nerve proximal to its point of compression, once the nerve root of interest was initially exposed. The EMG threshold required to evoke a response from the corresponding myotome was recorded as the baseline threshold. After the decompression was completed, a second threshold was recorded after stimulating the nerve at the same proximal location. Pre-op, immediately post-op, and 4-6 weeks after surgery, ODI, VAS, and neurologic exams were collected.

  Results:
  11 males and 6 females (average age 50 years, range 35-64) were included. Average symptom duration prior to surgery was 7.9 months (range 1-24). Average evoked EMG threshold prior to decompression was 6.9 mA (range 2-14). Average evoked EMG threshold after decompression was 4.7 mA (range 2-10). Average pre- and post-decompression threshold values were significantly different (p=0.014). Patients with an EMG threshold reduction ≥ 2 mA (n=10) after decompression experienced greater average improvements in VASleg (51.6 mm vs 44.7 mm, p=0.659) and significantly greater improvements in ODI scores than those with a threshold change < 2 mA (29.8 vs. 14.0, p=0.018).

  Conclusion:
  This pilot study demonstrated a reduction in evoked EMG threshold values after minimally invasive decompression of lumbar nerve roots. There were significantly greater early improvements in ODI scores in those patients with an EMG threshold reduction of ≥ 2 mA after decompression. These findings suggest that the results of EMG threshold testing of lumbar nerve roots may provide verification of clinically successful nerve root decompression. Intraoperative improvement in stimulation thresholds for evoked EMG may carry prognostic implications for such patients.

• Is The Less Invasive Far Lateral Approach A Safe Way To Reconstruct The Anterior Spinal Column In Advanced Adult Deformity Surgery? A Minimum 2-year Follow-up Study
  Presenting author: Behrooz A. Akbarnia, MD
  Additional authors: Gregory M. Mundis, MD; Pooria Salari, MD; Ramin Bagheri, MD; Nima Kabirian, MD
  
  Presentation Summary

  Summary:
  16 adult patients with an average Cobb angle of 47° were treated with an anterior release and spinal fusion via a less invasive lateral interbody fusion. While there are predictable perioperative sequelae, there was significant improvement of curve magnitude and various clinical outcome measures at two year post-op.

  Introduction:
  Anterior reconstruction of the adult spine is a widely accepted approach to improve fusion rate and achieve coronal and sagittal correction. We present our experience using the less invasive far lateral interbody fusion (LIF) to achieve these goals.

  Methods:
  This was a retrospective review of adult deformity patients undergoing LIF. Of 58 patients, 16 met the inclusion criteria: Cobb ≥30°, initial surgery for scoliosis, and minimum 2-year follow up. Exclusion criteria included add-on disease and primary diagnosis other than scoliosis. Clinical, radiographic and outcomes data were analyzed.

  Results:
  There were 15 females and 1 male. Mean age was 56 (23-84) yrs, 7 were idiopathic and 9 were degenerative scoliosis. Mean co-morbidities were 2.6 per patient. Main curve improved from 47° to 17°, the L4 tilt significantly corrected from 23° to 10°. Change in spinal balance, lordosis (L1-S1) or amount of lordosis across the LIF was not significant (Table 1). 5 of 16 developed a total of 8 complications associated with LIF: 3 abdominal wall bulging, 3 post-op quadriceps weaknesses, 1 anterior dislodgment of a cage requiring revision, and one pleural effusion resolved with chest tube. All patients regained quadriceps function within 6 months of surgery. 9/16 (56%) experienced anterior thigh numbness (2 permanent) and 8/16 (50%) anterior thigh pain for at least 4 weeks post-op. Post-operative improvement at two year follow up for VAS (6.5 to2.5), ODI (60 to 24) and SRS-22 (2.6 to 3.8) were all statistically significant.

  Conclusion:
  LIF approach is a safe and effective alternative to open surgery for adult scoliosis. Patients with advanced spinal deformities should be made aware of possible post-op thigh numbness, pain and/or transient weakness as sequelae of the less invasive LIF technique.

• Microscopic Assisted Transpsoas Interbody Fusion
  Presenting author: K. Khurana, MD
  Additional authors: Robert S. Bray, MD; Amir Vokshoor, MD
  
  Presentation Summary

  Introduction:
  The Lateral Extracavitary approach for lumbar interbody fusion is an accepted minimal access method for achieving interbody fusion. Theoretical drawbacks of this approach include muscular trauma of the iliopsoas and inability to monitor sensory branches (ie genitofemoral nerve) within the iliopsoas. Anecdotal reports of persistent nerve pain despite normal nerve surveillance have been reported. Anatomic lumbar plexus variations, particular at L4-5 have provide an anatomic basis for unexplained neural trauma. Our modified microscope-based lateral interbody approach allows direct visualization of the iliopsoas and avoidance of neural structures. The direct visualization afforded by the operating microscope combined with neurophysiologic monitoring provides superior confidence in neural avoidance and protection during the surgical procedure.

  Methods:
  From 2007 to 2010 , 75 extreme lateral interbody fusions were performed utilizing the microscopic-based psoas dissection technique. The conditions treated included spondylolisthesis, pseudoarthrosis, scoliosis, and degenerative disc disease. Cases ranged from 1 level to 3 fusion levels. Follow up was performed at 2 weeks, 3 months, and 6 months by the surgeon. Specific assessment of groin, thigh and leg pain was made.

  Results:
  We found 1 reported case of persistent thigh or groin discomfort after the 3 month and 6 month clinical assessments. No visceral, vascular, or neural injuries were noted and fusion rates were all excellent.

  Conclusions:
  The addition of the microscope to lateral interbody fusions has proven to be a valuable supplement to the widely used neuromonitoring technique for extreme lateral interbody fusion. Our group's technique has migrated to this modification of the exisiting technique with reproducible and excellent clinical outcomes.

• Mini-open TLIF Followed By Pedicle Screw Fixation For Lumbar Spondylolisthesis: Minimum 5-year Fu
  Presenting author: Jin-Sung Kim
  Additional authors: -Ho Lee, MD, PhD; Hyung-Lea Cho, MD; Sun Kwon, MD
  
  Presentation Summary

  Introduction:
  Instrumented single level mini-TLIF has become a widely accepted surgical treatment for lumbar degenerative and ithmic spondylolisthesis. This study was done to investigate the long-term results of instrumented mini-TLIF for the treatment of back and leg pain in adult spondylolisthesis.

  Methods:
  A total of 55 patients who had undergone instrumented mini-TLIF for the treatment of adult low-grade spondylolisthesis in the lumbar spine (L3-4:3, L4-5:35, L5S1:16) at our institute, between Aug 2003 and Feb 2005, was retrospectively reviewed by chart review and telephone survey.

  Results:
  Clinical follow-up and radiological follow-up with dynamic lumbar X-ray, three-dimensional CT scans, and lumbar MRI for checking the adjacent segmental disease were completed in 55 and 43 patients respectively. Radiological results including the intervertebral disc height, the degree of listhesis, segmental lumbar lordosis, and whole lumbar lordosis were analyzed by statistical analysis.

  Conclusion:
  Instrumented single level mini-TLIF demonstrated good long-term clinical and radiologic outcomes. The fusion rate was comparable with the published results of the other lumbar interbody fusion techniques. Therefore, the results of this study suggest that instrumented single level mini-TLIF is a safe and effective surgical technique for the lumbar spondylolisthesis.

• Minimally Invasive Lumbar Fusion (XLIF) using a ?TCP-HA Bone Graft Substitute (FormaGraft): Fusion Rates out to 2 Years
  Presenting author: William B. Rodgers, M.D, F.A.C.S.;
  Additional authors: J. Gerber, PA-C; Jody A. Rodgers, M.D., F.A.C.S.
  
  Presentation Summary

  Summary:
  The use of a beta-tricalcium phosphate/hydroxyapatite (FormaGraft) with bone marrow aspirate (BMA) was prospectively studied in 57 consecutive 1- and 2-level XLIF procedures. Outcomes were encouraging; XLIF has proven to be a safe and effective procedure, and now 24-month results using ?TCP-HA bone graft substitute confirm fusion, maintenance of improvements, and overall patient satisfaction.

  Introduction:
  Good short-term outcomes after XLIF have been shown, however, no reports to date have focused specifically on fusion rates associated with XLIF, or on the graft materials used in XLIF. Issues related to early resorption and hospital cost with bone morphogenic protein in lumbar fusions have fueled continued evaluation of other bone graft substitutes.
  The use of a beta-tricalcium phosphate/hydroxyapatite (FormaGraft) with bone marrow aspirate (BMA) was prospectively studied in 57 consecutive 1- and 2-level XLIF procedures. Radiographic outcomes were evaluated to demonstrate fusion and were compared with clinical results.

  Results:
  Patient age ranged from 25-79yrs (average: 55.9yrs). Primary diagnoses included stenosis(31), DDD(12), spondylolisthesis(8), and HNP(6). Comorbid conditions included previous spine surgery(47.4%); smokers(40.35%); diabetes(22.81%); chronic steroid use(8.77%); obesity/morbid obesity(52.6%). 64 levels were treated: 50=1-level, 7=2-level; 1@T8-9, 4@L1-2, 6@L2-3, 16@L3-4, 37@L4-5. Graft included equal amounts by volume FormaGraft and BMA, aspirated from the adjacent vertebral body under lateral exposure. All included supplemental fixation. Hgb change and hospital stay averaged 1.20g and 1.04days. Complications included one iatrogenic HNP requiring secondary decompression. One patient died at 10months post-op, unrelated to his surgery. Average disk height improved from 6.35mm to 10.86mm, and was maintained at 10.0mm at 24 months. Fusion by Lenke score=1 and 2 was 90.0% at 24 months. Average VAS pain scores decreased from 9.0 at pre-op to 3.2 and 3.6 at 12 and 24 months respectively. 89% expressed satisfaction with their procedures at 12months, and 89% said they would do it again.

  Conclusion:
  XLIF has proven to be a safe and effective procedure, and now 24-month results using ?TCP-HA bone graft substitute confirm fusion, maintenance of improvements, and overall patient satisfaction.

• Minimally Invasive Posterior Spinal Instrumentation for Pediatric Spinal Deformity: One Year Follow-Up with CT Scans of First 30 Cases
  Presenting author: Atiq Durrani, MD
  Additional authors: Rasesh Desai; Vivek Sharma, MD; Alvin H. Crawford, MD
  
  Presentation Summary

  Introduction:
  Results from 30 cases with scoliosis/kyphosis treated by minimally invasive (MIS) posterior spinal instrumentation show robust fusion in all patients with no loss of correction at 1 year. Our objective was to study the feasibility, safety, morbidity and efficacy of MIS posterior spinal instrumentation and fusion for the treatment of scoliosis/kyphosis and to assess fusion at one year with CT scans.

  Methods:
  After obtaining IRB approval, we performed a retrospective chart review of 30 consecutive patients treated by MIS posterior spinal instrumentation for either scoliosis or kyphosis from 11/01/07 through 12/31/08. Patient demographics and perioperative data were reviewed. Preoperative and postoperative Cobb angles were compared. CT scans with 3D reconstruction and radiographs collected at one year follow-up were reviewed by independent radiologists to assess fusion.

  Results:
  Patients included 23 females and 7 males with a mean age of 16.6 years. These cases included 25 scoliosis and 5 kyphosis patients. Three patients (2 kyphosis, 1 scoliosis) had an additional video assisted thoracoscopic surgery (VATS) at the same stage. The mean preoperative and postoperative Cobb angles were 51 and 17 degrees, respectively. The mean number of segments fused was 11, with an average of 16 screws per patient. The mean duration of surgery was 4 hrs 57 minutes and the average hospital stay was 3 days. The mean blood loss was 261.5 ml. Four patients had intraoperative spinal cord monitoring changes, three of which returned to baseline before the end of surgery. One patient had postoperative leg weakness, which resolved completely in two days. At one year, the mean Cobb angle was 19 degrees with an average loss of only 2 degrees. CT scans with 3D reconstruction showed robust fusion in all patients with no evidence of non-union, as assessed by radiologists.

  Conclusion
  To our knowledge, this is first study outlining the safety, feasibility and efficacy of fusion using MIS posterior spinal instrumentation for the treatment of spinal deformities in children and adolescents. CT scans and radiographic data at one year show solid fusion with no loss of correction. Short term data suggest decreased morbidity of MIS posterior spinal instrumentation for pediatric spinal deformity.

• Minimally Invasive Technique and Outcomes for Reconstruction of Adult Thoracolumbar Deformity
  Presenting author: Stefan Renaud, D.O.
  Additional authors: Reginald Q. Knight, M.D.; Jeffrey S. Roh, M.D.
  
  Presentation Summary

  Introduction:
  Both interbody devices and posterior instrumentation have been applied using MIS techniques to treat adult degenerative conditions. Literature is building to support claims of decreased blood loss; shortened hospital stays, and better tolerated surgeries by using MIS. Despite this, there is little literature describing multilevel circumferential reconstruction of adult degenerative scoliotic deformity. We aim to outline an effective and reproducible MIS technique.

  Methods:
  16 patients (15 female,1 male) underwent one or two stage surgical reconstruction.Age ranged from 24-82(Mean age= 60).All surgeries were carried out by two of the contributing authors at one center.The surgical technique will be described in the body of the paper.Coronal and sagital Cobb angles were measured preop and postop.Operative times, EBL, transfusions, length of stay, complications; ODI and VAS were recorded.

  Results:
  Preoperative coronal cobb range was 21-60?,average=44?. Postoperative coronal cobb angles ranged from 1-27?,average=14.?Average curve correction was 62?.Preoperative Sagital Cobb angles measured from T12-S1 averaged 33?(range -15(kyphotic) to 70).Average post op angle =40?of lordosis(range 21-60).Estimated intraoperative blood loss for the combined surgeries averaged 270cc (150-650); for stage I average was 256cc (25-800); stage II 377cc(50-1200). All surgeries together averaged 520cc blood loss (150-1900). The average transfusion for all patients in the study was 1.7 u PRBC. Average hospital length of stay was 6.8 days (2-10). VAS improved 50% for both back and leg symptoms. Complications included one L3-4 durotomy, one ileus requiring NG tube placement, and one distal junctional kyphosis requiring reoperation 9 months later. No pseudoarthrosis.

  Conclusion:
  Large magnitude and symptomatic adult deformity can be treated using circumferential MIS techniques. Patients tolerated to procedures well with only 1.7 units of PRBC transfusion, few complications, and shosrt hospital stays. This is only the second paper describing similar technique and results.

• Minimally Invasive Tlif In Young Adolescent Competitive Athletes With Spondylolitheses And Discogenic Back Pain: 1 Year Outcomes And Early Safe Return To Pre-operative Competition
  Presenting author: Chad Prusmack, MD
  Additional authors: David Whatmore, PA; Mike Richards; Ryan Winters, PhD
  
  Presentation Summary

  Introduction:
  Many feel that a lumbar fusion in an adolescent should be avoided because of poor outcomes, complication rates and long term adjacent level disease. Some also feel that a fusion should be a contraindication to participation in high level athletics. minimally invasive transforaminal lumbar fusions (MISTLIF) has shown is some studies have lower complication rates, shorter hospital stats and faster recoveries than traditional open fusion surgery. In addition there is more muscle sparing in this technique. We report on 7 adolescent athletes who underwent single level MISTLIF. there were six girls and 1 boy. All had back pain and leg pain and had been treated conservatively for more than 16 months. Three had isthmic spondylolithesis and four had positive disco grams. One was at L4-5 the rest were at L5-S1. Average operative EBL=146cc, op time=155min, Avg. Hospital stay=1.8 days, avg. flouro time=198sec. There was no complications. Average pre-op ODI=19.5, post op 3 mo = 1.5, 1year=0.5. numerical pain score went from 8.5 to 0. They all went through a rigorous 2 phase pt program. Average return to competitive play was 15 weeks to skating, soccer or basketball. All patients fused at one year on CT. Mistlif is a safe effective operation for discogenic lbp or spondylolithesis in athletic adolescents who want to compete again at the same preoperative level.

• Minimally Invasive Treatment Of Adjacent Segment Degeneration Via Xlif
  Presenting author: William B. Rodgers, M.D., F.A.C.S.
  Additional authors: Edward J. Gerber, PA-C; Jody A. Rodgers, M.D., F.A.C.S.
  
  Presentation Summary

  Summary:
  In a large single-site series of XLIFs, 276 patients were treated for ASD. Overall clinical and radiographic outcomes and are reported; results were encouraging.

  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 with XLIF are presented.

  Methods:
  Of our single-site consecutive series of 932 XLIF patients, 276 were treated for ASD. Clinical and radiographic measures were prospectively collected and evaluated.

  Results:
  Results: Age ranged from 29-91 years (average 61.6 years). 90.6% had one or more comorbidity. 144 patients (52%) were obese or morbidly obese. All but one case included supplemental fixation: 47% unilateral pedicle screws, 4% bilateral pedicle screws, 12% lateral embroidered plate, and 43% 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 1.3 days, with 2 blood transfusions and one wound infection. Complications included intraoperative hardware failure (4, revised during same procedure with no incident), ileus (5), gallstone pancreatitis (1), urinary retention (3), kidney stone (1), peritoneal catheter occlusion (1), pulmonary embolism (1), subcutaneous hematoma (1), delirium (1), atrial fibrillation (3), MI at 6 weeks post-op (1), compression fracture at an adjacent level (5), sacral fracture (1), and postoperative quadriceps weakness (1, resolved within 4 weeks of surgery). Average VAS scores improved by 4.6 points from pre-op to 12 months. Average disk height improved from 6.4 to 10.6 at post-op, settling to 8.7mm at 24 mos; slip from 3.5 to 0.6mm. Definitive signs of fusion (Lenke 1-2) were present in 74% at 3 months, 91% at 6 months, 96% at 12 months and 95% at 24 months.

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

• Minmally Invasive Versus Open Transforamininal Lumbar Interbody Fusion for the Treatment of Single Level Degenerative Spondylolisthesis
  Presenting author: Zachary Kelly, MD
  Additional authors: Regional Q. Knight, MD, Jefrey Roh, MD, David Hanscom M.D.
  
  Presentation Summary

  Introduction:
  We retrospectively reviewed the perioperative course in 60 patients who underwent a transforaminal lumbar interbody fusion (TLIF) with instrumentation for the treatment of single level degenerative lumbar spondylolisthesis. The surgeries were carried out by three experienced surgeons; two surgeons used a minimally invasive technique, and the third used an open approach. The patients were placed into two groups. The first group consisted of 47 patients who received a TLIF through minimally invasive tubular retractors with placement of an interbody cage and percutaneous pedicle screws with rods. The minimally invasive surgeons used BMP and local bone for grafting. The second group of 13 patients had a TLIF with placement of an interbody cage, and pedicle screws with rods through an open approach. This surgeon used iliac crest bone for graft. The mean estimated blood loss was 189 ml and 492 ml for the MIS procedures and open procedures, respectively (p < 0.001). Also, 6 of 13 or 46% of patients in the open group received a postoperative blood transfusion versus none in the MIS group. The length of hospitalization averaged 2.72 in the MIS group, and patients who received open surgery remained inpatient an average of 5.15 days (p < 0.001). There was no statistical difference in operative time. The only significant complications were two dural tears in the MIS group.

  Conclusion
  : Minimally invasive transforaminal lumbar interbody fusion results in less blood loss and need for postoperative blood transfusions versus open procedures. Also, a decreased length of hospital stay is seen with TLIFs performed minimally invasively. However, there may be an increased risk of dural tears when performing the procedure minimally invasively, but this complication did not cause an increased length of stay when compared to the length of stay for open procedures.:

• Mis For Traumatic Spinal Pathologies: A Mini-open, Lateral Approach In The Thoracic And Lumbar Spine
  Presenting author: William D. Smith, M.D
  Additional authors: Juan S. Uribe, M.D., F.A.C.S.; Elias Dakwar, M.D.; Tien V. Le, M.D.; Ginger Christian, B.S.; Sherrie Serrano, B.S.
  
  Presentation Summary

  Introduction:
  Examples of high-quality literature examining treatment methods for acute traumatic thoracic and lumbar fractures are few and what do exist contain insufficient samples to make broad conclusions. Despite this, we do know that conventional surgical techniques often include large, morbid exposures. More recent advancements in less invasive surgical techniques have greatly decreased the associated morbidities of conventional approach, namely thoracotomy. The objective of this study was to examine patient outcomes using a mini-open, lateral approach for the treatment of traumatic thoracic and lumbar fractures.

  Methods:
  Fifty-two patients were treated at one of two institutions for traumatic thoracic or lumbar fractures with a mini-open lateral approach for corpectomy. Patients were prospectively followed for clinical outcomes, with treatment and in-hospital complications collected retrospectively.

  Results:
  The vast majority of patients (94.2%) presented with traumatic burst fractures with instability and neurologic deficit. Patients were treated with mini-open, lateral corpectomies from T7 to L4, with the majority at T12 and L1 and followed two years postoperatively. Supplemental internal fixation was used in all patients: 75% anterolateral plating and 46.1% percutaneous transpedicular fixation (15 combined). Median operative time, estimated blood loss, and hospital stay were 128 minutes, 300 cc, and 4 days, respectively. Complications were observed in 13.5% of patients and no reoperations occurred. Neurologic status, assessed using American Spinal Injury Association categorization, improved significantly postoperative with 73% of patients either completely neurologically intact or with only slight residual deficits. No patient experienced neurological deterioration. Expandable wide-footprint titanium cages were used in 34.6% of patients, which resisted radiographic subsidence seen in some patients treated with expandable cylindrical titanium cages. One example of an L2 burst fracture and corpectomy using a mini-open lateral approach is included as figures.

  Introduction:
  The mini-open lateral approach for thoracic and lumbar corpectomy was shown to be safe and effective in this series while avoiding many of the associated morbidities of thoracotomies for anterior column reconstruction and open posterior approaches.

• O-Arm Image Guided Pedicle Screw Insertion: Revision And Reoperation Rates In 2,068 Screws
  Presenting author: Jonathan N. Sembrano, M.D
  Additional authors: R.G. Santos, M.D.; David W. Polly, Jr., M.D.
  
  Presentation Summary

  Introduction:
  Pedicle screws are widely used in the treatment of various spine disorders. The advent of image guidance has increased the accuracy of screw placement. The O-arm is an intra-operative scanner that provides real-time images for navigation, and allows intra-operative assessment of pedicle screw position. The objective of the study was to determine the accuracy of O-arm image guided screw insertion in our institution, looking specifically at screw revision rates and reoperation rates for 2068 pedicle screws.

  Methods:
  All consecutive cases from October 2006 to March 2010 where O-arm image-guided pedicle screw insertion was performed were reviewed. Operative notes and charts defined the incidence of screw revision and the incidence of reoperation. We also sought any neurologic or vascular complications which resulted from any screw malposition.

  Results:
  There were a total of 166 patients with a mean age of 46.7 (range 7 to 88 years). There were 75 male and 91 female patients. A total of 2068 screws were placed using the O-arm image-guided technique. The average number of screws inserted per patient was 12 (range 2 to 32). Sixty of 2068 screws (2.90%) were revised for an accuracy rate of 97.1%. Reoperation rate was 0%. There were no major neurovascular complications from malpositioned screws.

  Conclusions:
  The technique of O-arm image guided screw insertion yields a 2.9% intra-operative revision rate, reflecting an accuracy rate that is higher than previously reported in a recent meta-analysis (Kosmopoulos, 2007). The ability to perform intra-operative scans enabled revision of the screws during the same procedure, eliminating the need for a second surgical intervention (8.8% in a recent series, Amato 2010) and preventing major neurovascular complications.

• Perioperative Outcomes an d Complications Following XLIF for the Treatment of Adult Scoliosis: Results of a Prospective, Non-randomized, Multi-center Evaluation
  Presenting author: Robert E. Isaacs, MD;
  Additional authors: Jonathan Hyde, MD; J. Allan Goodrich, MD; W. Blake Rodgers, MD; Frank M. Phillips, MD; SOLAS Degenerative Study Group
  
  Presentation Summary

  Introduction:
  The surgical treatment of adult scoliosis presents a treatment challenge. Neural decompression with combined anterior/posterior instrumented fusion is often performed. These procedures have been reported to carry a high risk of complication, particularly in the elderly patient population. Over the past decade less invasive surgical approaches to neural decompression and fusion have been popularized and have recently been applied in the treatment of degenerative scoliosis. To date there has been little published evaluating these treatment approaches.

  Methods
  In a prospective multicenter nonrandomized IRB-approved observational study of patients who underwent the XLIF procedure with or without supplemental posterior fusion for the treatment of degenerative scoliosis, perioperative measures were compiled to identify the short-term results and complications of the procedure. Intraoperative data collection included surgical procedural details, operative time, estimated blood loss, and surgical complications. Postoperative complications, length of hospital stay, and neurological status were recorded. This report focuses on perioperative complications following surgery.

  Results:
  107 patients (mean age 68 years; range 45-87) were treated with XLIF. 28% had at least one comorbidity. A mean of 4.4 levels/patient (range 1-9) were treated. Supplemental pedicle screw fixation was used in 75.7% of patients, 5.6% had lateral fixation and 18.7% had standalone XLIF. Mean operative time and blood loss were 178min (58min/level) and 50-100cc. Mean hospital stay was 2.9 days (unstaged), 8.1 days (staged; 16.5%), 3.8 days overall. 5 patients (4.7%) received a transfusion, 3 (2.8%) required ICU admission, 1 (0.9%) required rehabilitation services. Major complications occurred in 13 patients (12.1%): 2 (1.9%) medical, 12 (11.2%) surgical. Of procedures that involved only less invasive techniques (XLIF standalone or with percutaneous instrumentation), 9.0% had one or more major complications. In those with supplemental open posterior instrumentation, 20.7% had one or more major complication. Early reoperations (3) (all for deep wound infections) were associated with open posterior instrumentation procedures.

  Conclusions:
  The morbidity in adult scoliosis surgery is minimized with less invasive techniques. The rate of major complications in this study (12.1%) compares favorably to that reported from other studies of surgery for degenerative deformity.

• Posterior Less Invasive Decompression and Stabilization for the Treatment of Benign and Malignant Neoplasms of the Thoraco-lumbar Spine
  Presenting author: Bruce M. Frankel, MD
  
  Presentation Summary

  Introduction:
  The treatment of patients with neoplasms affecting the axial spine, both benign and malignant, can be approached in a variety of ways, each with its own risks and benefits. In an effort to reduce patient morbidity, blood loss and hospital length of stay, we have employed several posterior less-invasive techniques to decompress and stabilize the thoraco-lumbar spine in patients with a variety of spinal neoplasms.

  Methods:
  The author has retrospectively reviewed the charts of 28 patients treated with one of three posterior less-invasive methods (MIS) of decompression including: micro-tubular decompressive laminectomy and facetectomy, micro-tubular transpedicular partial or complete corpectomy, or micro-tubular costo-transverse partial or complete corpectomy. In these patients anterior column reconstruction was performed, where necessary, using either Polymethyl-methacrylate (PMMA) or VBR cage insertion. Three-column fixation was performed using percutaneous pedicle screw insertion and augmented with PMMA where indicated. Results were compared with a separate cohort of patients treated with ?open? posterior decompression and stabilization procedures.

  Results:
  The mean age of the MIS group was 54 years as compared to 47.5 years of the ?open? group. A variety of disparate pathologies were treated including benign (schwannoma, neurofibroma, meningioma, giant cell tumor), and malignant (breast, prostate, GI, renal cell, and thyroid metastases, multiple myeloma and sarcoma) tumors. All lesions resulted in preoperative pain and neurological deficits. There were no cases of new postoperative neurological deficits; deficit stabilization or improvement was seen in all patients. There was one case of hardware failure in each group, requiring reoperation within one month postoperatively. The mean postoperative length of stay was significantly less in the MIS group (3 days) as compared to the ?open? group (9.4 days). Additionally, mean blood loss was significantly less in the MIS as compared to ?open? group, 736 cc?s vs. 2500 cc?s, respectively.

  Conclusions:
  Posterior less invasive techniques of decompression and stabilization of the thoraco-lumbar spine should be considered as a treatment option for patients with both benign and malignant neoplasms involving the spine. Length of hospitalization and blood loss is significantly less in the MIS as compared to open group.

• Preclinical Evaluation of a Modular Structural Nucleus Replacement System
  Presenting author: Jeffrey Felt, MD
  Additional authors: Paul Asdourian, MD; Manuel Pinto, MD; Jonathon Kalla, MD; Britt Norton, MD;
  
  Presentation Summary

  Introduction:
  Preclinical testing was performed to characterize a modular nucleus replacement device that utilizes a novel rail and slot engagement and delivery system.

  Methods:
  An elastomeric nucleus replacement uses multiple 7.6mm-wide modules for assembly in situ into a monolithic load-bearing structure via a unilateral posterior approach. The modules possess a rigid substructure of rails and slots that serve both as a delivery and interconnection system. Each module is overmolded with low modulus polyurethane to provide a physiologic compressive modulus. The number of segments used can be varied to accommodate a wide range of disc widths.

  Devices were assessed via finite element (FE) analysis and subjected to mechanical, biomechanical and biocompatibility testing. The FE analysis simulated 1300N static compression on a 5-module device between incompressible plates, with maximum stress calculated. Mechanical testing was comprised of simple axial dynamic compression of three 5-segment devices between 0N and 1300N for 5 million cycles at 2Hz in a 50% bovine serum solution at 37C, followed by mechanical and visual evaluation. Biomechanical testing was performed using six cadaver lumbar motion segments with cyclic preconditioning to 100N followed by loading each motion segment five times to 1,300N in straight compression, flexion and extension (10?) and right and left lateral bending (5?) in each of three disc states: intact, enucleated, and implanted. Each specimen was implanted with a 5-segment device, and displacement v. load data were analyzed for differences between disc states. The polyurethane overmold was evaluated via MEM elution and agarose overlay cytotoxicity testing, and was also subjected to acute systemic injection and intracutaneous reactivity testing. The overmolded substructure was subjected to a 26 week muscle implantation test in rabbits.

  Results:
  The maximum stress on the endplate determined via FE analysis was < 0.6MPa, less than 1/6 the failure stress of the cancellous bone of the vertebra. All samples tested via dynamic compression retained their functionality and showed no visual degradation. When comparing intact, enucleated and implanted states in the biomechanical assessment via paired t-tests, differences were statistically significant (p < 0.05) for each specimen, with device implantation recovering an average displacement of 73% of the intact state under compressive load, 66% in flexion, and 47% - 64% in lateral bending. Recovery in extension was negligible. The urethane overmold material and the overmolded substructure passed all biocompatibility tests.

• Predictors of Persistent Leg Pain Following Minimally Invasive Surgery For Lumbar Radiculopathy
  Presenting author: John W. German, MD
  Additional authors: Anthony G. Conte, BA
  
  Presentation Summary

  Introduction:
  Minimally invasive approaches to the lumbar spine are being increasingly utilized with good efficacy. To further improve the clinical outcomes of patients undergoing surgery for lumbar radiculopathy all pre-operative factors should be considered to determine which subset of patients are at risk for doing poorly. Understanding these risk factors can then be used to improve the treatment paradigm.

  Methods:
  A retrospective review was undertaken of 140 patients undergoing surgery for lumbar radiculopathy. Medical records were reviewed and data was abstracted for demographics, past medical history, past surgical history, psychiatric co-morbidities, neurologic co-morbidities, anatomic factors, and intra-operative factors. Six month outcomes were available for patient derived outcomes included leg visual analog score (VAS). Outcomes were analyzed using the peri-operative change in which outcomes were classified as success (?VAS?-2.0) or failure (?VAS<-2.0) as well as a threshold method in which outcomes were classified as success (VAS<4.0) or failure (VAS>4.0). Statistical analyses included a t-test for continuous variables and a Chi square test for categorical variables. Significance was set at p<0.05.

  Results:
  Six month outcomes were available for 56 patients. Using the peri-operative change method 18.1% of patients were classified as failures while the threshold method classifed 32% patients were classified as failures. Bivariate analysis of the leg VAS peri-operative change method suggests that the risk factors for failure were: female sex, presence of depression, and presence of anxiety. Bivariate analysis of the leg VAS threshold method suggest that the risk factors for failure were: presence of depression, presence of neurologic co-morbidity, absence of CSF leak, absence of foraminotomy, absence of sequestrectomy, and absence of annulotomy.

  Conclusion:
  Minimally invasive surgery for lumbar radiculopathy results in a successful outcome in 68 to 82% of patients at six months. The common risk factor for persistent post-operative leg pain using the two analyses methods is a pre-operative self-reported history of depression.

• Preliminary (6-month) Results Of Minimally Invasive Transforaminal Lumbar Interbody Fusions In An Outpatient Setting
  Presenting author: Raymond J. Gardocki, M.D.
  
  Presentation Summary

  Introduction:
  The purpose of minimally invasive transforaminal lumbar interbody fusion (MITLIF) is to spare normal tissue function and allow quicker recovery due to diminished postoperative 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 MITLIF to be performed on a 23-hour stay basis with quick recovery and excellent results.

  methods:
  Between September 2008 and August 2010, 23 MITLIF procedures with BMP (Infuse) were done by a single surgeon 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 were collected by retrospective chart review and included the VAS, ODI, SF-36 and narcotic usage, with an average of 6 months follow-up.

  Results:
  Average operative time was 118 minutes and average EBL was 96cc. Back pain scores (VAS) decreased from a preoperative average of 5.53 on a 0-10 100mm Visual Analogue Pain Scale (VAS) to 2.09 (p<0.01) at 6 month follow up for a 62% average improvement in VAS. Leg pain decreased from 6.06 to pre-operatively to 0.68 at six months. Oswestry disability index (ODI) scores decreased from a pre-operative average of 48.4 to 12.9 at six months. Pre-operative physical component (PCS) and mental component (MCS) scores from the SF-36 were 32 and 52 respectively. Both PCS and MCS improved to 51 and 72 at three months post-operative. Physical function and bodily pain components respectively increased from 27 and 25 pre-operatively to 73 and 84 at three months post-operatively. Narcotics use decreased from 100% of patients at time of surgery to 40% at three months (similar to pre-op levels) and 15% at six months.

  Conclusion:
  Using a 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 such as degenerative spondylolisthesis.

• Radiographic and Clinical Outcomes Following Minimally Invasive Decompression and Fusion in patients with Spinal Cord Compression from Metastatic Carcinoma.
  Presenting author: David Hong, MD
  Additional authors: Fadi Delly, MD; Neena I. Marupudi, MS, MD; Jay Jagannathan, MD; Hazem Eltahawy, MD, PhD
  
  Presentation Summary

  Object:
  In spite of Class I evidence which demonstrates improved outcomes for patients who undergo early decompression for metastatic spinal cord compression, cancer patients are often not medical candidates for major surgical procedures. In this paper we examine outcomes following minimally invasive decompression and fusion in patients with epidural metastases.

  Methods:
  A prospective study of 11 patients who underwent surgery at our institution (Karmanos Cancer Institute). All patients had either pain (11 patients) or neurologic findings (8 patients) or both (8 patients). In addition to pre-operative MR-imaging all patients underwent plain radiographs to measure focal and segmental (Cobb) angulation. Clinical outcomes were assessed in terms of recovery of neurologic function, pain control and changes in post-operative Cobb angle.

  Results:
  Four patients had metastatic lung cancer, 3 patients had renal cell carcinoma, 2 patients had prostate cancer and 2 patients had multiple myeloma. Mean pre-operative VAS score was 9.2 (Range, 6-10), and mean Cobb angle was 16.3 degrees (kyphosis). All patients had widely metastatic disease, with at least 3 systems involved. In patients with neurologic deficits, the mean time to surgery was 12.4 hours (27 hours for the entire cohort). Four patients underwent decompressions alone, while 7 patients underwent decompression as well as fixation for disease which appeared to cause symptomatic deformity. Mean surgical time was 90 minutes (Range, 45-150 minutes), and blood loss was 150cc?s (Range, 25-500cc?S). Mean follow-up was 4.5 months (Range, 3-8 months). At final follow-up 1 patient died (14 days after surgery) from complications of a bowel obstruction. Of the 10 surviving patients, mean VAS pain score was 2.3 and mean Cobb angle was 5.1 degrees (kyphosis). Of the 8 patients with neurologic deficits, 6 showed an improvement in neurologic function while 2 remained unchanged.

  Conclusion:
  Minimally invasive decompression and fixation is ideal in patients with epidural metastatic disease from cancer. The rates of neurologic improvement and changes in angulation are comparable to open surgery, and the operative morbidity in relation to blood loss and tissue retraction is significantly less.

• Radiographic Comparison Of Lateral Fusion (LLIF) vs. Standard Fusion Methods (ALIF, TLIF And PSF): Analysis Of Segmental Sagittal Contour Change
  Presenting author: Jonathan N. Sembrano, M.D.
  Additional authors: Amit K. Sharma, M.D.; Ryan D. Horazdovsky, M.D.; Bieta Azmoudeh, B.S.; Edward R.G. Santos, M.D.; David W. Polly, Jr., M.D.
  
  Presentation Summary

  Introduction:
  Potential advantages of minimally-invasive lateral lumbar interbody fusion (LLIF) include reduced morbidity and blood loss, decreased post-op pain, and faster recovery. Improvement in sagittal parameters is considered an important goal in lumbar fusion. There are no studies comparing restoration of sagittal parameters utilizing the LLIF approach versus standard approaches.

  Methods:
  This is a comparative x-ray analysis of 4 lumbar fusion approaches. In a 2-year period, 245 levels in 167 patients were fused: LLIF (43 patients; 63 levels); ALIF (41 patients; 67 levels); TLIF (56 patients; 74 levels); and PSF (30 patients; 41 levels). The following parameters were measured on pre- and post-op standing radiographs: segmental lordosis; overall lumbar lordosis (L1-S1); anterior and posterior disk heights. Comparison of measurement changes between groups were performed using student?s t-test.

  Results:
  All interbody procedures produced significantly greater lordosis change compared to posterior fusion alone (ALIF p=0.007; TLIF p=0.019; LLIF p=0.03). The 3 interbody approaches were not significantly different (ALIF vs. TLIF p=0.15; ALIF vs. LLIF p=0.28; TLIF vs. LLIF p=0.80). Only ALIF showed significant improvement in overall lumbar lordosis (p=0.0017). Significant differences were noted in terms of anterior disk height restoration, in the following order: ALIF > LLIF > TLIF > PISF.

  Conclusion:
  LLIF provides similar segmental sagittal contour change compared to ALIF and TLIF, and significantly greater compared to posterior fusion alone. Overall lumbar lordosis remains unchanged after LLIF.

• Radiographic Results of the MIS Lateral Interbody Fusion Technique for the Treatment of Multi-level Spinal Stenosis with Degenerative Scoliosis
  Presenting author: W. Kim, M.D., Ph.D.
  Additional authors: Niraj Patel; Gilad Regev; Yu-Po Lee, M.D.; Steven R. Garfin, M.D.
  
  Presentation Summary

  Introduction:
  The minimally invasive lateral interbody fusion technique (MIS Lateral) is being increasingly utilized for the treatment of patients with adult degenerative scoliosis with stenosis. This study aims to delineate the characteristics of deformity correction in the sagittal and coronal planes.

  Methods:
  Early radiographic results were obtained through retrospective review of multiple measurements taken from pre-operative and post-operative AP and lateral radiographs of the lumbar spine in 39 patients.

  Results:
  Thirty-nine patients with an average of 3-levels of involvement underwent reconstructive surgery using minimally invasive direct lateral anterior interbody fusion technique (MIS Lateral). Regional coronal correction of the lumbar spine was 8.5?4.6? and focal coronal correction was 4.1?4.7?. Lumbar lordosis increased slightly from 40.8? to 41.9?. Local disc angle/sagittal wedging increased 4.0?. The average follow-up was 32 months (range 16 - 56 months). There were 14 complications, including 3 patients with hip flexor weakness and anterior thigh numbness. The hip flexor weakness was temporary in all cases, resolving in an average of 18.7 weeks (range 12-32 weeks). Major complications included 1 patient with multi-system organ failure, sepsis, and subsequent death, 1 patient with iliopsoas abscess, and 1 patient with pleural effusion. Pseudoarthrosis requiring refusion was required in 2 of 39 patients during the follow-up period.

  Conclusions:
  The minimally invasive lateral interbody fusion technique enables correction of degenerative lumbar scoliosis maximally in the coronal plane. Sagittal plane correction is modest. Although minimally invasive, multi-level spinal reconstruction in elderly patients continues to be associated with significant morbidity and mortality. Careful patient selection along with meticulous adherence to surgical technique optimizes its safety and efficacy.

• Rhabdomyolysis and Acute Renal Failure Following Minimally Invasive Lateral Spine Surgery
  Presenting author: Elias Dakwar, MD
  Additional authors: Ildemaro J. Volcan, M.D.; J Allan Goodrich, M.D.; Juan S. Uribe, M.D.
  
  Presentation Summary

  Introduction:
  Minimally invasive spine surgery has become increasingly employed to treat various spinal pathologies with the goal of minimizing destruction of surrounding tissues. Rhabdomyolysis (RM) is a rare but known complication of spine surgery. Rhabdomyolysis is characterized by muscle necrosis with resultant leakage of various intracellular constituents. Acute renal failure is a potential complication of severe rhabdomyolysis. We report the first known cases of RM and acute renal failure after minimally invasive lateral spine surgery.

  Methods:
  A retrospective review was conducted at two medical centers of all patients who underwent a minimally invasive lateral approach to the spine and developed acute renal failure secondary to rhabdomyolysis postoperatively. All patient data was recorded including age, gender, BMI, co-morbidities, medications and pre-operative renal function. The procedure performed, operative time, CPK level, as well as the method of treatment for the acute renal failure was evaluated.

  Results:
  A total of five patients (4 males, 1 female) have been identified with rhabdomyolysis and acute renal failure after undergoing minimally invasive lateral spine surgery. The mean age was 62.6 with a range of 60-70. The CPK ranged from 5,000 to 56,000 u/l. The mean BMI of the patients was 30.6 and ranged from 25-40 kg/m2 and the mean operative time was 418 and ranged from 315 to 600 minutes. Two of the five patients required temporary hemodialysis while three patients only required aggressive fluid resuscitation. There were no deaths.

  Conclusion:
  Rhabdomyolysis is a rare but known potential complication of spine surgery. We report the first cases associated with the minimally invasive lateral approach. Surgeons need to be aware of the possibility of post-operative RM and ARF, particularly in morbidly obese patients and in procedures associated with prolonged operative times.

• Safety and Complication Profile of Percutaneous Lumbosacral Axial Interbody Fusion
  Presenting author: Neel Anand, MD,
  Additional authors: Eli M. Baron, MD
  
  Presentation Summary

  Introduction:
  The trans-1 AxiaLIF system is an innovative procedure of achieving fusion across the L5?S1 and L4-5 disc space in a minimally invasive manner. Through this approach, the disc is radically excised and interbody fusion is performed while preserving the integrity of muscles, ligaments and annulus. Considerable concern has been raised from complications such as viscus and vascular injury, though the true incidence of complications resulting from this technique has not clearly been reported to date.

  Methods:
  We review complications as per the US Food and Drug Administration (FDA) medical device reporting (MDR) data provided through the FDA?s website in 10,000 cases of Trans1 AxiaLIF performed in the United States from January 1, 2005 to June 30, 2010. Results:
  In the aforementioned time periods, 65 MDR injuries were noted (0.65% complication rate). There were 51 bowel injuries (0.51% injury rate) necessitating 31 temporary colostomies. There were 20 bowel injuries treated with antibiotics alone. Seven infections were noted, as were 3 vascular injuries, 1 ureteral injury, 1 sacral fracture and 1 posterior foraminal placement. In terms of adverse incidents in surgery 9 broken cutters were noted, 8 cases of hypotension, and 1 discitis. In 2010 only 3 bowel injuries were reported and no adverse incidents have been noted to date Conclusion:
  Trans 1 AxiaLIF is a very safe minimally invasive method of achieving discectomy and interbody fusion at L5-S1. Based on a very large clinical experience of 10,000 cases in the United States, its safety profile is significantly better than anterior lumbar interbody fusion when compared with the literature.

• The Effect Of Minimally Invasive Posterior Cervical Approaches Versus Open Anterior Approaches On Neck Pain And Disability.
  Presenting author: Jeffrey A. Steinberg, BS
  Additional authors: John W. German, MD
  
  Presentation Summary

  Introduction:
  Traditional surgical dictum suggests that patients with myelopathy or radiculopathy and significant axial pain should be treated with an anterior interbody fusion as a posterior decompression alone may exacerbate their neck pain. To date the effect of a minimally invasive posterior cervical approach (miPC) on neck pain has not been compared to that of an anterior cervical diskectomy or corpectomy with interbody fusion (ACF).

  methods:
  A retrospective review was undertaken of 89 patients undergoing either a miPCD (n=49) or ACF (n=40) for the treatment of myelopathy or radiculopathy. Medical records were abstracted for demographic information, medical history, surgical details, and complications. Clinical outcomes were assessed by patient derived neck visual analog scores (VAS) and neck disability index (NDI). Outcomes were analyzed using: 1) a threshold in which outcomes were classified as success (NDI<40; VAS<4.0) or failure (NDI>40; VAS>4.0) and 2) the peri-operative change in which outcomes were classified as success (?NDI?-15; ?VAS?-2.0), and failure (?ODI<-15; ?VAS<-2.0). Groups were compared using Chi square tests with significance taken at p<0.05.

  Results:
  At last follow-up the percent of patients classified as successful using the threshold criteria were as follows: neck VAS (miPC: 75%; ACDF: 70%; NS) and NDI (miPC: 71%; ACDF: 58%; NS). The percent of patients classified as successful using the peri-operative change criteria were as follows: neck VAS (miPC: 55%; ACDF: 56%; NS) and NDI (miPC: 42%; ACDF: 23%; p<0.05).

  Conclusion:
  In this small retrospective analysis miPCD is associated with similiar neck pain and disability than that of ACF. Given the avoidance of cervical instrumentation and interbody fusion in the miPCD these results suggest that further comparative effectiveness study is warranted.

• The Efficacy of Silicated Calcium Phosphate Bone Graft Substitute (Actifuse) in Minimally Invaseive Lumbar Inter-body Fusion Procedures
  Presenting author: Vamsi V. Nagineni, MD.
  Additional authors: Chrstoph Hofstetter, MD, PhD, Harry Gebhard, MD. Roger, Hartl, MD
  
  Presentation Summary

  Study Design:
  Retrospective study

  Objective:
  Silicated calcium phosphate (Si-CaP, Actifuse, ApaTech? US, UK) is a calcium phosphate bone graft with specific substitution of phosphate ions by silicate ions resulting in a biomaterial with 0.8 wt% silicate ions. Several studies have suggested that controlled local silicate release appears to promote bone formation. We sought to evaluate the efficacy of Si-CaP as an alternative to autograft in minimally invasive lumbar Inter-body fusion procedures.

  Method:
  47 patients who underwent minimally invasive lumbar inter-body fusion were included. Surgical approaches included transforaminal lumbar inter-body fusion (TLIF- 20 patients), Axial lumbar inter-body fusion (AxiaLIF- 15 patients) and Extreme lateral inter-body fusion (XLIF- 12 patients). Demographic, surgical, radiographic and clinical data were retrospectively reviewed. Clinical outcomes were assessed using a visual analog scale (VAS) and Oswestry Disability Index (ODI) before surgery and up to 24 month after surgery.

  strong>Results
  The fusion rate based on CT imaging was 80% (38/47 patients) at a mean (? S.D) of 11.2 ? 5 months. Fusion rates by approach: TLIF- 85% fusion, (17/20), AxiaLIF- 73% (11/15) and XLIF- 83% (10/12). There was a significant improvement in ODI of 20 points (44 ? 16 vs. 24 ? 11, mean ? S.D pre-operative vs. post-operative, respectively), VAS back of 4.1 points (7.3 ? 4 vs. 3.2 ? 3) and VAS leg of 4.4 points (6.5 ? 4 vs. 2.1 ? 2) after surgery. This magnitude of improvement correlates with a clinically significant improvement. Radiographic non-union did not correlate with a poor clinical outcome. There were four cases requiring revision surgery, three in the TLIF group and one in AxiaLIF group. Three were for incomplete resolution of symptoms and one for screw repositioning, none for non-union.

  Conclusion:
  Silicated calcium phosphate bone graft may be a feasible alternative to other accepted bone graft sources. We saw acceptable fusion rates at relatively short follow-up. Longer f/u data are needed to determine final fusion rates and clinical outcome.

• The Importance Of All In Lumbar Disc Arthroplasty. 36 Month Follow Up Experience In Extreme Lateral Total Disc Replacement
  Presenting author: Luiz Pimenta, MD, PhD
  Additional authors: Leonardo Oliveira, BSc; Luis Marchi, MS; Etevaldo Coutinho, MD
  
  Presentation Summary

  Introduction:
  Current lumbar total disc replacement (TDR) devices require an anterior approach for implantation. The anterior approach to place lumbar TDR devices has inherent biomechanical limitations and surgical risks 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, as has been shown in reports of XLIF for fusion procedures. 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 is performed through a 4cm lateral incision in an average of 134 minutes (90-300) and with an average 58cc blood loss (30-150). There has been no intra-op or post-op complications. Postoperative x-rays show good device placement, with restoration of disc height, foraminal volume, and sagittal balance. All patients were up and walking within 12 hours of surgery and all but 9 were discharged the next day (7/9 were hybrid TDR/ALIF cases). 5/36 patients (13.8%) had psoas weakness and 3/36 (8.3%) had anterior thigh numbness postoperatively, both resolving within 2 wks. 4/36 (11%) had postoperative facet joint pain, all in hybrid cases. Clinical outcomes improved significantly from preop. Average postoperative ROM remains steady, not significantly different from preoperative values.

  Conclusion:
  Mid-term 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.