The axial cage. a pilot study for interbody fusion in higher-grade spondylolisthesis.

BACKGROUND CONTEXT: The surgical treatment of high-grade spondylolisthesis is challenging. Posterolateral fusion alone has a high rate of pseudarthrosis. Surgical stabilization of higher-grade lumbar spondylolisthesis with a fibula strut graft is an effective technique but is associated with harvest site morbidity and graft fractures.

PURPOSE: We hypothesized that a lumbar interbody fusion with a long, threaded titanium cage, packed with cancellous bone, inserted across the center of the spondylolisthesis, would provide the rigid immobilization necessary for successful arthrodesis. This would, therefore, eliminate the need for fibula harvest and possibly reduce the need for posterior instrumentation.

STUDY DESIGN/

SETTING

Prospective, study cohort of 11 consecutive patients with a minimum follow-up of 1 year.

PATIENT SAMPLE: Patients with higher-grade spondylolisthesis (grade II-IV) were considered eligible.

OUTCOME MEASURES: Pain was measured with a 10-point Numerical Rating Score (NRS). The Oswestry Disability Index (OSI) was used to assess patient function. Patients also responded to a satisfaction scale to evaluate satisfaction with their outcome. Radiographs were reviewed 1, 3, 6, 12, and, when available, 24 months after surgery.

METHODS

We reviewed our clinical results and technical outcomes in 11 consecutive patients who underwent this unique form of anterior lumbar interbody fusion with a custom axial cage.

RESULTS

There were no surgical or postoperative complications. Serial x-rays revealed no implant subsidence or loosening. There have been no implant fractures or reoperation. Clinical results have been excellent with significant pain reduction and improved function. At 1 year after surgery the mean NRS was 3.5 (range, 0-7), a significant average reduction of 5.0 points. (p<.001) All patients have been satisfied with their results.

CONCLUSIONS

The axial cage technique appears to be a significant improvement over the fibular strut graft for the treatment of higher-grade spondylolisthesis. It provides significant reduction in pain, significant improvement in function, high patient satisfaction, and avoids the morbidity and fracture risks associated with fibular strut grafting.