Accelerometry evaluation of shoulder movement and its association with patient-reported and clinical outcomes following reverse total shoulder arthroplasty

Background: Accelerometers provide a new method to objectively measure recovery of movement and physical activity in patients following reverse total shoulder arthroplasty (RTSA) and may overcome common limitations associated with patient-reported outcome measures (PROMs). The aim of this study was to assess changes in upper limb movement using accelerometers following RTSA and investigate their association with other clinical outcome measures. Methods: Thirty-six patients who underwent RTSA wore accelerometers on both wrists and arms for 3 days at 3, 6, and 12 months postsurgery. PROMs (Constant score, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, visual analog scale for pain, Single Assessment Numerical Evaluation, Shoulder Activity Level) and isometric shoulder strength were also assessed. Accelerometer outcomes were calculated to quantify counts of forearm and arm activity and the contribution of both arms to activity (limb symmetry and magnitude ratio). Changes and differences in all clinical measures and objective movement measures were evaluated with within-subjects analysis of variance. Correlations between limb activity and other clinical measures were investigated using Spearman correlation coefficients. Results: Objective movement of the operated arm increased from 3-6 months postsurgery (P =.004), but not from 6-12 months (P =.240). Limb asymmetries were observed at 3 and 6 months and improved by 12 months postsurgery. No associations were demonstrated between PROMs and objective upper limb movement at 12 months postsurgery. Discussion: Despite early recovery of function and pain relief assessed by PROMs, objective movement using accelerometers showed delayed recovery of the operated arm postoperatively, before normalizing by 12 months postsurgery. Accelerometers provide a unique insight into functional recovery following RTSA.