Chief Scientific Officer Medical Metrics, Inc Medical Metrics, Imaging Core Laboratory Olympia, WA, US
Disclosure(s):
John A. Hipp, PhD: No relevant disclosure to display
Introduction: While static and dynamic spondylolisthesis have been widely studied, limited evidence supports an objective diagnostic test for dynamic spondylolisthesis to guide treatment planning. We hypothesize that changes in a standardized Spondylolisthesis Index (SI), which accounts for disc angle and disc height relative to healthy discs, may help predict patient outcomes following decompression surgery for spondylolisthesis with stenosis.
Methods: Preoperative flexion-extension radiographs for 48 patients from a previously reported prospective study were analyzed using automated, FDA-cleared methods. SI was calculated in both flexion and extension. Based on a previous study, a SI value of < -2 or > 2 indicates abnormal sagittal plane offset relative to healthy discs. The change in SI between flexion and extension was correlated with patient satisfaction as a potential diagnostic test for dynamic spondylolisthesis. Additionally, we compared the change in SI with the translational instability metric that had been used in the prospective study.
Results: Patient satisfaction with decompression surgery was 40% when the change in SI between flexion and extension exceeded 8 (10/48 patients), compared to 69% satisfaction when the change was ≤ 8 (P = 0.05). The relationship between the change in SI and a traditional measure of translational instability was significant (P < 0.0001), although the R² was low (0.2).
Conclusion : Translational instability is typically the primary radiographic criterion for determining when fusion, in addition to decompression, is necessary for lumbar spondylolisthesis and stenosis. The low coefficient of determination (R²) in the comparison between the traditional metric of translational instability and SI suggests that the change in SI measures aspects of intervertebral motion distinct from the standard measure. Our post hoc analysis of a previous prospective study suggests that the presence of dynamic spondylolisthesis, measured using an automated, objective SI metric, may help predict suboptimal outcomes for patients undergoing decompression alone. Additional research is required to determine if the findings can be repeated and have prospective clinical efficacy.
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