Functional Outcomes After Anatomic and Reverse Shoulder Arthroplasty Assessed using a Novel Objective Method

Introduction Anatomic shoulder arthroplasty replicates joint anatomy, while Reverse Total Shoulder Arthroplasty (RSA) is preferred for rotator cuff deficiency or bone loss. This study compares pre- and post-operative function after TSA and RSA using outcome measures and the Kinesiological Instrument for Normal and Altered Reaching Movement (KINARM). Methods A cohort of 81 shoulders in 74 patients (mean age 71 ± 8) underwent Total Shoulder Arthroplasty (TSA) or Reverse Total Shoulder Arthroplasty (RSA). Outcomes included lateral and forward elevation; WOOS, Constant, Oxford, and SF-36 scores; and Kinarm sensorimotor tasks (visually guided reaching, object hit, arm position matching). Patients were evaluated pre-operatively and at 6 weeks, 3, 6, and 12 months. Analyses used paired and independent t-tests, ANOVA, and Pearson correlation. Results ROM improved at 3, 6, and 12 months in TSA and at 6 and 12 months in RSA (p < 0.01), with TSA showing better ROM at 3 months (p < 0.01). Both groups showed improvement in WOOS, Oxford, and Constant scores (p < 0.01). The TSA group had higher SF-36 mental scores, while the RSA had higher physical scores beyond 3 months. TSA showed better early WOOS, Oxford, and Constant scores. Kinarm tasks improved at 1 year in both groups (p < 0.01), and RSA showed greater improvement in arm matching. Kinarm scores correlated strongly with WOOS, Constant, and Oxford. Discussion Early recovery favored TSA; by 12 months, outcomes converged. Kinarm offers an objective complement to PROMs. Conclusion TSA and RSA showed similar 1-year outcomes, with earlier recovery after TSA. Kinarm is a reliable objective tool for pre- and post-operative upper extremity assessment. Level of Evidence: Level II.