Early Postoperative Magnetic Resonance Imaging in Detecting Radicular Pain After Lumbar Decompression Surgery: Retrospective Study of the Relationship Between Dural Sac Cross-sectional Area and Postoperative Radicular Pain

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Study Design:A retrospective analysis.Objective:To evaluate the association between early postoperative dural sac cross-sectional area (DCSA) and radicular pain.Summary of Background Data:The correlation between postoperative magnetic resonance imaging (MRI) findings and postoperative neurological symptoms after lumbar decompression surgery is controversial.Methods:This study included 115 patients who underwent lumbar decompression surgery followed by MRI within 7 days postoperatively. There were 46 patients with early postoperative radicular pain, regardless of whether the pain was mild or similar to that before surgery. The intervertebral level with the smallest DCSA was identified on MRI and compared preoperatively and postoperatively. Risk factors for postoperative radicular pain were determined using univariate and multivariate analyses. Subanalysis according to absence/presence of a residual suction drain also was performed.Results:Multivariate regression analysis showed that smaller postoperative DCSA was significantly associated with early postoperative radicular pain (per −10 mm2; odds ratio, 1.26). The best cutoff value for radicular pain was early postoperative DCSA of 67.7 mm2. Even with a cutoff value of <70 mm2, sensitivity and specificity are 74.3% and 75.0%, respectively. Early postoperative DCSA was significantly larger before suction drain removal than after (119.7±10.1 vs. 93.9±5.4 mm2).Conclusions:Smaller DCSA in the early postoperative period was associated with radicular pain after lumbar decompression surgery. The best cutoff value for postoperative radicular pain was 67.7 mm2. Absence of a suction drain at the time of early postoperative MRI was related to smaller DCSA.

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