Correlation Between Clinical Improvement and Dural Sac Cross-Sectional Area Expansion in Biportal Endoscopic Lumbar Decompression

Study Design: – Retrospective study. Objective: – To correlate the changes in the dural area on MRI and clinical outcome after unilateral biportal endoscopic (UBE) decompression. Summary of Background Data: – Clinical outcomes after UBE decompression have been published for up to 2 years for patients with isolated spinal stenosis at 1 level. Serial dural expansion after UBE decompression has not been published as well as correlation to clinical outcomes. Method: – We retrospectively reviewed the clinical and radiologic outcomes of 86 patients who underwent UBE decompression for spinal stenosis. Preoperative and postoperative visual analog score (VAS) and Oswestry Disability Index (ODI) were analyzed, and MRI was used for radiologic evaluation before surgery, 3 days after surgery, and 2 years after surgery. The correlation of dural spinal area CSA (preoperative-final) and difference of clinical outcome (preoperative-final) were analyzed. Result: – None of the 86 patients had permanent neurological complications. Back VAS, leg VAS, and ODI showed improvement in symptoms postoperatively and 2 years postoperatively. The postoperative CSA of the dural sac on MRI was statistically significantly increased after surgery at all time points. VAS leg was moderately correlated with change in CSA, while ODI and VAS back were weakly correlated. Correlations were all statistically significant. Conclusion: – UBE decompression showed good clinical outcomes similar to previous studies, and the CSA of ​​the dural sac on MRI significantly increased in the late postoperative phase compared with the early postoperative phase. This technique is viable option to achieve radiographic dural expansion and improvement in clinical outcomes in degenerative lumbar spinal stenosis. However, there is at best only a moderate correlation with change in CSA and clinical outcomes.