Background

Previous claims data from national US databases with 27,962 total shoulder arthroplasties (TSA) reported an incidence of bilateral TSA of 6.3%. Over the past thirteen years, we observed a greater percentage of patients electing bilateral inlay total shoulder arthroplasty (iTSA) at our institution. The purpose of this study was to determine the incidence rate of bilateral iTSA and examine related patient-reported outcomes (PROs). We hypothesized the incidence of bilateral procedures within our series of more than 500 cases exceeds the national rate of total shoulder arthroplasty.

Methods

We conducted a retrospective review of prospectively collected data from our institutional database. The study included 436 patients (515 shoulders) treated between 2011 and 2024. Postoperative timepoints were used to gain insights into PROs at the decision timepoint for a contralateral procedure. Outcomes included the American Shoulder and Elbow Surgeon’s (ASES) score and a Visual Analog Scale for Pain (VAS-Pain), and range of motion (ROM). Improvements in PROs were assessed at last follow-up stratifying the results by contralateral surgical intervention [<12 months (Group I), 12-24 months (Group II), >24 months (Group III)], gender and two age groups (Group Ia: < 65, Group IIa: >65). Comparative analyses and significance (p<0.05) were determined using Linear Model ANOVA (RStudio Team, 2024; version 2024.12.0+467). Paired t-tests were used to determine changes in pre- to postoperative scores for normally distributed data. Wilcoxon was used for non-normally distributed data.

Results

436 patients (515 shoulders) were included in this study with a bilateral incidence rate of 18.1% (79 patients, 158 shoulders). 44.3% of contralateral procedures were performed <12 months (5.3+2.5 months), 15.2% within 12-24 months (15.3+3.0 months), and 40.5% >24 months (65.1+31.4 months). There were 27 females and 52 males with a mean age of 67.1±9.5 years and a mean BMI of 28.7+5.1. Group Ia included 59 shoulders, Group IIa 101. The mean follow-up was 42.5±37.2 months. All PROs improved significantly (p<.001) with a median ASES from 33.6 (21.7-46.7) to 83.3 (60.4-95.0) and VAS-Pain from 6.9 (5.0-8.0) to 1.0 (0.0-3.0). The median ROM improved significantly (p < .001) from 90.0° (80.0-130.0) to 160.0° (145.0-170.0) in forward elevation (FE) and 20.0° (10.0-30.0) to 50.0° (40.0-60.0) on external rotation (ER). Median PROs significantly improved (p < 0.001) in all three groups prior to contralateral iTSA. Gender, age, and bilateral sequence did not impact ASES, VAS-Pain, FE, or ER (p > 0.05).

Conclusion

The incidence rate of contralateral procedures was three times higher than previously reported national rates. Significant pain relief and functional improvements were observed after staged bilateral inlay TSA. Most patients (84.8%) decided to undergo contralateral iTSA within 1 year or after 2 years following their indexed procedure. These results provide a patient-centric validation for the treatment of advanced bilateral shoulder arthritis.