Radiographic Predictors of Clinical Improvement following Extreme Lateral Interbody Fusion: A Multi-institutional Analysis of 101 Consecutive Levels

Presented at SMISS Annual Forum 2016
By Robert E. Isaacs MD
With

Disclosures: Robert Isaacs MD A; NuVasive. B; NuVasive, Providence Medical Technology. C; Association for Collaborative Spine Research. D; SafeRay Spine, LLC, SafeWire, LLC, VilaSpine LTD, Vertera Spine, Providence Medical Technol

Introduction

The extreme lateral interbody fusion (XLIF) approach facilitates indirect spinal decompression via a lateral transpsoas approach, with initial studies demonstrating promising clinical and radiographic results. Despite recent reports of successful indirect decompression following the XLIF procedure, a subset of patients continues to have same-level persistent pain and functional disability. Accordingly, identifying preoperative radiological factors that are predictive of failure to achieve substantial clinical benefit would facilitate better patient selection and improve patient outcomes. 

Aims/Objectives

Determine preoperative radiographic factors that are predictive of failure to achieve substantial clinical benefit for patients undergoing the XLIF procedure.

Methods

Radiographic measurements were recorded for patients who met inclusion criteria. Radiographic variables measured included: (1) anterior and posterior disc height, (2) foramen height and area, (4) central canal diameter, (5) central canal area, (6) right and left subarticular diameters, (7) facet arthropathy grade and (8) presence of bony lateral recess stenosis. Only the spinal levels involved in the XLIF were included in radiographic analysis. Demographic data and surgical levels were recorded. At 1-year follow-up, patients who experienced greater or equal-to 20-point improvement in ODI score were considered to have reached substantial clinical benefit. Preoperative radiographic measurements were then compared between those patients who reached substantial clinical benefit and those who did not. 

Results

A total of 45 patients (age 65.6 ± 10.5 years, 14 male) involving 101 spinal levels were included in this study. A total of 32 (71.1%) patients reached substantial clinical benefit (SCB) at 1-year follow-up. There were no statistically significant differences in age, sex, or number of vertebral levels between those who SCB and those who did not. Average ODI improvement for those who reached SCB was 32.0 points compared to 15.0 points for those who did not reach SCB (p < 0.001). Analysis of preoperative radiographic measurements demonstrated that patients who reached SCB were significantly more likely to have smaller left (2.11 vs. 3.05mm, p = 0.036) and right (1.69 vs. 2.73mm, p = 0.042) subarticular diameter, and worse central canal stenosis at L2-L3 (6.95 vs. 9.77mm, p = 0.046) and L4-L5 (6.74 vs. 9.14mm, p = 0.025). All other preoperative radiographic factors were statistically similar between the two groups. 

Conclusions

A large majority of patients undergoing XLIF reached substantial clinical benefit at 1-year follow-up. Patients with significant central canal stenosis and reduced subarticular diameter are less likely to demonstrate significant functional improvement, and thus may benefit from direct decompression.