Study Design. Retrospective cohort study Objective. To determine the relationship between preoperative physical therapy (PT) and postoperative mobility, adverse events (AEs), and length of stay (LOS) among patients with low normalized total psoas area (NTPA) undergoing ASD surgery. Summary of Background Data. Sarcopenia as defined by low NTPA has been shown to predict poor perioperative outcomes following adult spinal deformity (ASD) surgery. However, there is limited evidence correlating the benefits of PT within the sarcopenic patient population. Methods. NTPA was analyzed at the L3 and L4 mid-vertebral body on preoperative magnetic resonance imaging (MRI). Receiver operating characteristic (ROC) curve analysis was used to determine gender-specific NTPA cut-off values for predicting perioperative AEs. Patients were categorized as having low NTPA if both L3 and L4 NTPA were below these cut-off values. Perioperative outcomes were compared between patients with low NTPA that underwent documented formal PT within 6 months prior to ASD surgery with those that did not. Results. 103 patients (42 males, 61 females) met criteria for low NTPA for inclusion in the study, of which 42 underwent preoperative PT and 61 did not. The preoperative PT group had a shorter LOS (111.2±37.5 vs. 162.1±97.0 h, P &lt;0.001), higher ambulation distances (feet) on postoperative day (POD) 1 (61.7±50.3 vs. 26.1±69.0, P &lt;0.001), POD 2 (113.2±81.8 vs. 62.1±73.1, P =0.003), and POD 3 (126.0±61.2 vs. 91.2±72.6, P =0.029), and lower rates of total AEs (31.0% vs. 54.1%, P =0.003) when excluding anemia requiring transfusion. Multivariable analysis found preoperative PT to be the most significant predictor of decreased LOS (OR 0.32, P =0.013). Conclusion. Sarcopenic patients may benefit from formal preoperative PT prior to undergoing ASD surgery to improve early postoperative mobility, decrease AEs, and decrease LOS. Level of Evidence. 3

Preoperative Physical Therapy is Associated with Decreased Length of Stay and Improved Postoperative Mobility in Patients with Sarcopenia Undergoing Adult Spinal Deformity Surgery