The Impact of Paraspinal Muscle Degeneration on Oswestry Disability Index Subsections Two Years After Spinal Surgery for Degenerative Lumbar Spondylolisthesis.

Study Design: Secondary analysis of prospective study.

Objective: To investigate the impact of fatty infiltration (FI) in the paraspinal muscles (PM) on postoperative Oswestry Disability Index (ODI) subsection-scores in patients undergoing elective lumbar surgery for degenerative lumbar spondylolisthesis (DLS).

Background: DLS can increase FI in the PM like the multifidus (MF), erector spinae (ES), and psoas (PS), leading to greater spinal disability and higher ODI-scores. It is unclear if increased PM FI affects all ODI subsections equally.

Methods: This study reviewed data from a single-center cohort of DLS-patients who underwent elective lumbar surgery. Overall ODI and the subsection scores were prospectively assessed before and 2 years post-surgery. FI of the PS, MF, and ES was measured using T2-weighted MRI images. The relationship between PM FI and postoperative ODI subsections were analyzed, using multivariable linear regression analysis.

Results: Overall, 229 patients (59% female, mean age of 67±8 y) were included with an overall baseline ODI of 50[40-62] and a postoperative ODI of 16.[2-34] The highest preoperative subsection-scores were seen in pain intensity (4[2-4]), changing degree of pain (4[3-4]), lifting (4[1-5]), and standing (4[3-4]). PM-measurements showed a mean FI of 41±10% for ES, 58±15% for MF, and 6±5% for PS. Patients with increased ES FI were more likely to show higher postoperative scores in all ODI subsections and in the overall ODI (Est=0.45, 95%CI 0.20-0.71, P=0.004). Increased MF FI was significantly associated with higher postoperative ODI subsection scores in standing (Est=0.02, 95%CI 0.01-0.03, P=0.033) and walking (Est=0.02, 95%CI 0.01-0.03, P=0.017).

Conclusion: Increased erector spinae fatty infiltration is significantly associated with higher ODI scores across all subsections 2 years after lumbar surgery, while higher multifidus fatty infiltration is linked to greater disability in standing and walking. These findings underscore the need to maintain paraspinal muscle health to improve surgical planning, improve rehabilitation outcomes, and reduce postoperative disability.