Improving effect of microendoscopic decompression surgery on low back pain in patients with lumbar spinal stenosis and predictive factors of postoperative residual low back pain: a single-center retrospective study

BACKGROUND: Although there are reports on the effectiveness of microendoscopic laminotomy using a spinal endoscope as decompression surgery for lumbar spinal stenosis, predicting the improvement of low back pain (LBP) still poses a challenge, and no clear index has been established. This study aimed to investigate whether microendoscopic laminotomy for lumbar spinal stenosis improves low back pain and determine the preoperative predictors of residual LBP. METHODS: In this single-center retrospective study, we examined 202 consecutive patients who underwent microendoscopic laminotomy for lumbar spinal stenosis with a preoperative visual analog scale (VAS) score for LBP of ≥40 mm. The lumbar spine Japanese Orthopaedic Association (JOA), and VAS scores for LBP, leg pain (LP), and leg numbness (LN) were examined before and at 1 year after surgery. Patients with a 1-year postoperative LBP-VAS of ≥25 mm composed the residual LBP group. The preoperative predictive factors associated with postoperative residual LBP were analyzed. RESULTS: JOA scores improved from 14.1 preoperatively to 20.2 postoperatively (p < 0.001), LBP-VAS improved from 66.7 to 29.7 mm (p < 0.001), LP-VAS improved from 63.8 to 31.2 mm (p < 0.001), and LN-VAS improved from 63.3 to 34.2 mm (p < 0.001). Ninety-eight patients (48.5%) had a postoperative LBP-VAS of ≥25 mm. Multiple logistic regression analysis revealed that Modic type 1 change (odds ratio [OR], 5.61; 95% confidence interval [CI], 1.68–18.68; p = 0.005), preoperative VAS for LBP ≥ 70 mm (OR, 2.19; 95% CI, 1.17–4.08; p = 0.014), and female sex (OR, 1.98; 95% CI, 1.09–3.89; p = 0.047) were preoperative predictors of residual LBP. CONCLUSION: Microendoscopic decompression surgery had an ameliorating effect on LBP in lumbar spinal stenosis. Modic type 1 change, preoperative VAS for LBP, and female sex were predictors of postoperative residual LBP, which may be a useful index for surgical procedure selection.