Early clinical outcomes following reverse shoulder arthroplasty or InSpace balloon implantation for irreparable massive rotator cuff tears: An exploratory retrospective cohort study

Purpose To compare early pain, functional, and perioperative outcomes following reverse total shoulder arthroplasty (RTSA) or InSpace balloon implantation for irreparable massive rotator cuff tears (IRCTs), interpreting differences as exploratory, non-causal associations.Methods This single-center retrospective cohort included 29 patients treated between June 2023 and June 2025 (RTSA, n = 15; InSpace, n = 14). Treatment was non-randomized. Operative measures and visual analog scale (VAS), American Shoulder and Elbow Surgeons (ASES), and Constant-Murley scores were compared at 6 weeks and 3 months using exploratory time-point analyses with Holm adjustment for the six postoperative score comparisons.Results The InSpace group had shorter median operative time (72.5 versus 130.0 min; p = .013) and lower median blood loss (20.0 versus 200.0 mL; p < .001). Median VAS, ASES, and Constant-Murley scores were more favorable in the InSpace group at both postoperative assessments (all p ≤ .021); the 95% CIs for all six postoperative between-group comparisons excluded zero, and all six comparisons remained statistically significant after Holm adjustment. These were unadjusted time-point associations; the analysis did not estimate between-group differences in recovery trajectory.Conclusions In this small, non-randomized cohort, the observed early between-group differences may reflect differences in clinical indication, rehabilitation exposure, and other residual confounding. They do not establish causal treatment effects, clinical superiority, comparable safety, or durability. The findings are hypothesis-generating and require confirmation in adequately powered prospective randomized studies with longitudinal analysis and long-term follow-up. For physiotherapists, these findings support a 4–6-week protection phase before active motion after reverse total shoulder arthroplasty versus earlier tolerated motion after InSpace implantation, with strengthening introduced at approximately 6 weeks when pain control and movement quality permit; they do not establish the superiority of either rehabilitation pathway.