Paraspinal Muscle Cross-Sectional Area, Sacral Slope and Canal Diameter as Predictor for Clinical Improvement Following Decompression and Fixation of Degenerative Lumbar Canal Stenosis

Lumbar degenerative disease was associated with paraspinal muscle atrophy, alterations in spinal alignment and sagittal balance, and narrowing of the spinal canal. This study aimed to evaluate the paraspinal muscle cross-sectional area (CSA), sacral slope (SS), and canal diameter (CD) as predictors of functional outcome improvement measured by the Oswestry Disability Index (ODI) following decompression and fixation for degenerative lumbar stenosis. A retrospective case–control study was conducted involving 40 patients with degenerative lumbar canal stenosis who underwent decompression and fusion surgery. Preoperative radiographic evaluations included sacral slope, multifidus muscle CSA (MFCSA), erector spinae muscle CSA (ESCSA) at the L4–L5 level, and canal diameter at the stenotic level. The ODI was assessed preoperatively and postoperatively on the first, second, fourth, and sixth days, as well as at the eighth postoperative week. Patients with an ESCSA of at least 900 mm² demonstrated a significant improvement in ODI scores at postoperative weeks 2, 4, 6, and 8 (p < 0.005). No significant differences in postoperative ODI improvement were observed between patients with MFCSA below or above 600 mm² or between those with sacral slope below or above 30 degrees (p > 0.05). Preoperative canal diameter showed a significant correlation with postoperative ODI improvement at weeks 2, 4, 6, and 8 (p < 0.05). In conclusion, a larger erector spinae muscle CSA and a narrower preoperative canal diameter were significant predictors of postoperative functional improvement in patients with degenerative lumbar stenosis undergoing decompression and fixation. Multifidus muscle CSA and sacral slope were not significant predictors of ODI improvement in this study. Keywords: Canal Diameter, Degenerative Lumbar Stenosis, Oswestry Disability Index, Paraspinal Muscle Cross-Sectional Area, Sacral Slope