Quantifying success after first revision reverse total shoulder arthroplasty: the minimal clinically important difference, substantial clinical benefit, and patient acceptable symptomatic state

Background: When patients require revision of primary shoulder arthroplasty, revision reverse total shoulder arthroplasty (rTSA) is most commonly performed. However, defining clinically important improvement in these patients is challenging because benchmarks have not been previously defined. Our purpose was to define the minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptomatic state (PASS) for outcome scores and range of motion (ROM) after revision rTSA and to quantify the proportion of patients achieving clinically relevant success.

Methods: This retrospective cohort study used a prospectively collected single-institution database of patients undergoing first revision rTSA between August 2015 and December 2019. Patients with a diagnosis of periprosthetic fracture or infection were excluded. Outcomes scores included the ASES, raw and normalized Constant, SPADI, SST, and University of California, Los Angeles (UCLA) scores. ROM measures included abduction, forward elevation (FE), external rotation (ER), and internal rotation (IR) score. Anchor-based and distribution-based methods were used to calculate the MCID, SCB, and PASS. The proportions of patients achieving each threshold were assessed.

Results: Ninety-three revision rTSAs with minimum 2-year follow-up were evaluated. Mean age was 67 years, 56% were female, and average follow-up was 54 months. Revision rTSA was performed most commonly for failed anatomic TSA (n = 47), followed by hemiarthroplasty (n = 21), rTSA (n = 15), and resurfacing (n = 10). The indication for revision rTSA was most commonly glenoid loosening (n = 24), followed by rotator cuff failure (n = 23), subluxation and unexplained pain (n = 11 for both). The anchor-based MCID thresholds (% of patients achieving) were as follows: ASES, 20.1 (42%); normalized Constant, 12.6 (80%); UCLA, 10.2 (54%); SST, 0.9 (78%); SPADI, -18.4 (58%); abduction, 13° (83%); FE, 18° (82%); ER, 4° (49%); and IR, 0.8 (34%). The SCB thresholds (% of patients achieving) were as follows: ASES, 34.1 (25%); normalized Constant, 26.6 (43%); UCLA, 14.1 (28%); SST, 3.9 (48%); SPADI, -36.4 (33%); abduction, 20° (77%); FE, 28° (71%); ER, 15° (15%); and IR, 1.0 (29%). The PASS thresholds (% of patients achieving) were as follows: ASES, 63.5 (53%); normalized Constant, 59.1 (61%); UCLA, 25.4 (48%); SST, 7.0 (55%); SPADI, 42.4 (59%); abduction, 98° (61%); FE, 110° (56%); ER, 19° (73%); and IR, 3.3 (59%).

Conclusions: This study establishes thresholds for the MCID, SCB, and PASS at minimum 2-years after revision rTSA, providing physicians an evidence-based method to counsel patients and assess patient outcomes postoperatively.