Patients Undergoing Anatomic Total Shoulder Arthroplasty Achieve Clinically Significant Outcomes Faster Than Those Undergoing Reverse Shoulder Arthroplasty

Background: Clinically significant outcome (CSO) benchmarks have been previously established for outcome assessment after total shoulder arthroplasty. However, the time required to achieve CSO improvement is not well understood. The purpose of this study was to (1) determine the time-dependent achievement of the minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptom state (PASS) in patients undergoing either anatomic total shoulder (TSA) or reverse total shoulder arthroplasty (RTSA) and compare the results of the 2 populations and (2) identify variables associated with earlier or delayed achievement of each CSO.

Methods: A prospectively maintained institutional registry was retrospectively queried for all patients receiving a primary TSA or RTSA between September 2, 2016-October 31, 2017. The American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) was administered to all patients preoperatively and at standardized postoperative time periods: 5-7 months (6-month time point), 11-13 months (1-year time point), and 23-25 months (2-year time point). Cumulative percentages of CSO achievement were calculated using Kaplan-Meier survival curve analysis with interval censoring. A Weibull parametric survival regression analysis was used to investigate the influence of demographic and clinical variables on delayed or earlier CSO achievement.

Results: A total of 153 patients (157 shoulders) undergoing TSA (n = 76) and RTSA (n = 81) were included in the study population. The RTSA cohort was older (70.2 ± 7.5 vs. 61.0 ± 8.4, P < .001), had a lower BMI (28.8 ± 5.9 vs. 31.5 ± 6.5, P = .006), and a greater proportion of females (53.1% vs. 32.9%, P = .017) relative to TSA. For SCB, there was a significant difference in the cumulative percentage of TSA and RTSA patients reaching this threshold at both the 6-month (77.3% vs. 59.0%, P = .024) and 2-year (92.0% vs. 79.5%, P = .048) time periods, with similar findings demonstrated for PASS. There was a significant difference in the average time required to achieve the PASS (TSA: 6.1 months vs. rTSA: 11.6 months, P = .009), but not the MCID (P = .407) or SCB (P = .153). Factors significantly associated with earlier achievement of more than 1 of the CSO benchmarks were regular preoperative physical exercise and diagnosis of rotator cuff tear without osteoarthritis.

Conclusion: Patients undergoing RTSA had lower rates of achieving SCB and PASS at both 6 months and 2 years compared to patients undergoing TSA. Patients undergoing RTSA on average required nearly double the time to achieve PASS compared with those undergoing TSA. In both groups, clinically significant improvement continued for the entire 2-year duration of study follow-up.