Early outcomes after first reverse total shoulder arthroplasty better prognosticate contralateral success compared with early outcomes after anatomic total shoulder arthroplasty

Abstract

The ideal timing between bilateral total shoulder arthroplasty (TSA) is unclear. The purpose of this study is to determine whether early outcomes after first TSA can be used to predict clinical outcomes after TSA of the contralateral shoulder and to evaluate the ideal time after TSA to perform the contralateral shoulder. A single-institution prospectively collected shoulder arthroplasty database was reviewed. Patients who underwent bilateral primary anatomic or reverse TSA (aTSA+rTSA) without an indication of fracture, tumor, or infection were identified. Included patients had minimum 2-year follow-up on their second TSA and postoperative follow-up after their first TSA at 3 months, 6 months, 1 year, or 2 years. Our primary outcome was whether outcome scores and motion at 3-month, 6-month, 1-year, and 2-year follow-up after first TSA predicted clinical success after second TSA at final follow-up, defined as achieving the patient acceptable symptomatic state (PASS=the highest level of symptoms beyond which patients consider themselves well). Outcomes included the American Shoulder and Elbow Surgeons and Constant scores, abduction, forward elevation, and external/internal-rotation. Multivariable logistic regression determined whether postoperative outcomes after first TSA were predictive of achieving the PASS after second TSA independent of age, sex, and body mass index. Receiver operating characteristic analysis determined cutoffs of postoperative outcomes after first TSA at each time point that best predicted achieving the prosthesis-specific PASS after second TSA. One hundred thirty-four patients were included in the final analysis (110 aTSA and 158 rTSA). Range of motion and outcome scores at late (1- or 2-year) follow-up after first aTSA were more predictive of achieving the second TSA PASS compared with early (3- or 6-month) outcomes. In contrast, outcomes after early and late follow-up after first rTSA were similarly predictive of achieving the second TSA PASS. Specifically, the Constant score threshold at 2 years after first aTSA (79.4; area under the curve [AUC]=0.804) better differentiated achieving the second TSA PASS vs. the 6-month threshold (72.0; AUC=0.600). In contrast, the Constant score threshold at 2 years after first rTSA (76.4; AUC=0.703) was similarly discriminant of achieving the second TSA PASS compared with the 6-month threshold (65.8; AUC=0.711). Patients with good outcomes after first rTSA can be counseled on contralateral TSA as early as 3 months postoperatively with confidence of a similar result on the contralateral side. In contrast, success after first aTSA does not reliably predict contralateral success until ≥1 year.