Graft Extrusion in AxiaLIF

Presented at SMISS 2009 Annual Conference
By William D. Smith MD
With William Blake Rodgers MD, FACS, Kyle Malone, Jamie Patterson

Disclosures: William D. Smith MD Grants/Research Support: NuVasive, Inc.; Consulting Fees: NuVasive, Inc., Spineology, SI-Bone, Inc.; Speakers’ Bureau: NuVasive, Inc.; Ownership Interest/Shareholder: NuVasive, Inc.; Royalty/Patent Holder: NuVasive, Inc. , William Blake Rodgers MD, FACS B; NuVasive. D; NuVasive, Alphatec. F; NuVasive., Kyle Malone None., Jamie Patterson None.

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

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

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

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

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

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

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

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