Facet Joint Opening on Computed Tomography Is a Predictor of Poor Clinical Outcomes After Minimally Invasive Decompression Surgery for Lumbar Spinal Stenosis

Study design Retrospective longitudinal cohort study. Objective To investigate the impact of facet joint opening (FJO) on clinical outcomes after minimally invasive decompression surgery for lumbar spinal stenosis. Summary of background data Although FJOs have previously been identified as indicators of segmental spinal instability, their impact on clinical outcomes after decompression alone surgery has yet to be investigated. Methods This study included 296 patients from a single institution who underwent minimally invasive surgery for lumbar spinal stenosis and were followed up for ≥5 years. Our analysis focused on identifying FJOs at the index decompression level (d-FJO) and at multiple levels (m-FJO) (i.e., ≥3 levels within the lumbar segment) using preoperative computed tomography. Clinical outcomes including reoperations, improvement ratio for Japanese Orthopaedic Association (JOA) score, and achievement of a minimal clinically important difference (MCID) in visual analogue scale (VAS) scores for low back pain (LBP) or leg pain at 5 years were compared between patients with and without d-FJO or m-FJO. Results There were 129 (44%) and 62 (21%) patients with d-FJO (more common with lateral olisthesis) and m-FJO (less common with spondylolisthesis), respectively. Reoperations were more common in patients with d-FJO than in those without (16% vs. 5%). On Cox proportional hazards analysis, d-FJO was identified as a predictor for revision at the index decompression level [hazard ratio (HR) 4.04, p = 0.03], whereas m-FJO was a predictor for revision at other lumbar levels (HR 3.71, p = 0.03). Patients with m-FJO had slightly lower rates of achieving MCID in VAS scores for LBP (34% vs. 52%, p = 0.03) and poorer improvement ratio forJOA scores (74% vs. 80%, p = 0.03) than those without. Conclusion FJO at both index decompression level and multiple level were predictors of poor outcomes; patients with FJOs require careful surgical planning or special follow-up.Level of Evidence: 3.