Does achieving clinically important thresholds after first shoulder arthroplasty predict similar outcomes of the contralateral shoulder?

Abstract

Patients are increasingly undergoing bilateral total shoulder arthroplasty (TSA). At present, it is unknown whether success after the 1st TSA is predictive of success after contralateral TSA. We aimed to determine whether exceeding clinically important thresholds of success after primary TSA predicts similar outcomes for subsequent contralateral TSA. We performed a retrospective review of a prospectively-collected shoulder arthroplasty database for patients undergoing bilateral primary anatomic (aTSA) or reverse (rTSA) total shoulder arthroplasty since January 2000 with preoperative and 2- or 3-year clinical follow-up. Our primary outcome was whether exceeding clinically important thresholds in the American Shoulder and Elbow Surgeons (ASES) score for the 1st TSA was predictive of similar success of the contralateral TSA; thresholds for the ASES score were adopted from prior literature and included the minimal clinically important difference (MCID), the substantial clinical benefit (SCB), 30% of maximal possible improvement (30%MPI), and the patient acceptable symptomatic state (PASS). The PASS is defined as the highest level of symptom beyond which patients consider themselves well, which may be a better indicator of a patient's quality of life. To determine whether exceeding clinically important thresholds was independently predictive of similar success after 2nd contralateral TSA, we performed multivariable logistic regression adjusted for age at 2nd surgery, sex, BMI, and type of 1st and 2nd TSA. Of the 134 patients identified that underwent bilateral shoulder arthroplasty, 65 (49%) had bilateral rTSAs, 45 (34%) had bilateral aTSAs, 21 (16%) underwent aTSA/rTSA, and 3 (2%) underwent rTSA/aTSA. On multivariable logistic regression, exceeding clinically important thresholds after 1st TSA was not associated with greater odds of achieving thresholds after 2nd TSA when success was evaluated by the MCID, SCB, and 30%MPI. In contrast, exceeding the PASS after 1st TSA was associated with 5.9-times greater odds (95% CI = 2.5-14.4, P<0.001) of exceeding the PASS after 2nd TSA. Overall, patients that exceeded the PASS after 1st TSA exceeded the PASS after 2nd TSA at a higher rate (71% vs. 29%, P<0.001); this difference persisted when stratified by type of prosthesis for 1st and 2nd TSA. Patients that achieve the ASES score PASS after 1st TSA have greater odds of achieving the PASS for the contralateral shoulder regardless of prostheses type.