Back Muscle Mass as a Predictor of Postoperative Complications in Posterior Lumbar Interbody Fusion Surgery †

Background: There is a lack of studies on utilising skeletal muscle mass via preoperative lumbar computed tomography or magnetic resonance imaging as a predictor of postoperative complications of posterior lumbar interbody fusion (PLIF) surgery in elderly patients. Methods: Patients aged >65 years who underwent PLIF were enrolled. The sum of the cross-sectional areas of the erector spinae muscles (CSA(Both)) was presented as the skeletal muscle mass. Postoperative complications were assessed using CSA(Both), pulmonary function testing, and prognostic nutritional index (PNI). Results: Patients with postoperative complications showed significantly lower values of CSA(Both) (median 2266.70 (2239.73–2875.10) mm(2) vs. 3060.30 (2749.25–3473.30) mm(2), p < 0.001), functional vital capacity, forced expiratory volume at 1 s, and PNI. However, multiple logistic regression analysis identified American Society of Anaesthesiologists Physical Status (ASA PS) I (odds ratio 0.307 (95% confidence interval 0.110–0.852), p = 0.023), ASA PS III (4.033 (1.586–10.254), p = 0.003), CSA(Both) (0.999 (0.999–1.000), p < 0.001), and postoperative red blood cell (RBC) transfusion (1.603 (1.193–2.152), p = 0.002) as risk factors for postoperative complications after PLIF surgery. Conclusions: CSA(Both), ASA PS III, and postoperative RBC transfusion might be used as predictors of postoperative complications after PLIF in patients aged >65 years.