Quantitative Paraspinal Muscle Morphology and Risk of 90-Day Complications After Lumbar Instrumentation Surgery

Retrospective cohort study.

To investigate the association between paraspinal muscle morphology and postoperative complications after lumbar instrumentation surgery for degenerative lumbar spine disease.

Paraspinal muscle degeneration may influence outcomes after lumbar spine surgery; however, quantitative imaging-based predictors of postoperative complications remain limited.

In this retrospective cohort study, 89 patients who underwent lumbar instrumentation surgery were analyzed. Paraspinal muscle cross-sectional areas of the multifidus and erector spinae at the L4-L5 level were measured using a region-of-interest technique on preoperative MRI. Muscle ratios, a composite Paraspinal Muscle Index (SMI), and asymmetry indices were calculated. Logistic regression and receiver operating characteristic (ROC) analyses were used to evaluate associations with 90-day postoperative complications.

Postoperative complications occurred in 19 patients (21.3%). Patients with complications demonstrated lower mean multifidus ratio (P=0.005), erector spinae ratio (P=0.010), and SMI (P=0.004), whereas multifidus asymmetry was significantly higher (P=0.012). In multivariable analysis, diabetes mellitus and operative time remained independent predictors. The addition of muscle parameters increased model discrimination from AUC 0.771-0.820; however, this improvement did not reach statistical significance (P=0.150).

Reduced paraspinal muscle ratios and increased muscle asymmetry were associated with postoperative complications. Quantitative evaluation of paraspinal muscles on routine MRI may contribute to perioperative risk stratification.