Acromion to greater tuberosity distance as a predictor of functional outcomes after reverse shoulder arthroplasty

Background: Rotator cuff arthropathy is characterized by pain and pseudoparalysis, for which reverse shoulder arthroplasty (RSA) is an established treatment. Appropriate deltoid tensioning is critical to functional outcomes, yet objective radiographic surrogate measures of tensioning remain limited. This study aimed to evaluate the association between acromion to greater tuberosity distance (AGTD) as a surrogate for deltoid tension and postoperative motion, functional outcomes, and pain following RSA. Methods: We conducted an observational retrospective case series, examining 61 patients who underwent RSA. Patients were evaluated using Constant-Murley shoulder score, visual analog scale pain score, Oxford shoulder score, and the University of California, Los Angeles shoulder score. Postoperative assessments were performed at 6-month and 1-year intervals. The AGTD was measured by two independent observers based on postoperative plain radiographs. Results: Mean patient age was 69.9±8.3 years. At 1 year postoperative, significant improvements were observed in forward flexion, abduction, pain, and all functional outcome scores (all P<0.001). Spline modeling demonstrated a non-linear association between AGTD and outcomes, with superior function and lower pain observed within an intermediate AGTD range centered near 45 mm. Both shorter and longer distances were associated with less favorable results. Conclusions: In our study, an intermediate AGTD centered near 45 mm was associated with more favorable functional outcomes, whereas shorter or longer distances demonstrated poorer results. Our findings provide further confirmation that RSA is a dependable treatment option for rotator cuff arthropathy. Level of evidence: IV.