Revision rates between obese and nonobese total shoulder arthroplasty patients: an Australian registry data study.

BACKGROUND

Obesity is an epidemic more apparent in many developed countries, like Australia. The effect on total shoulder replacement (TSA) is not clear, with different studies reporting varying conclusions. This registry-based study offers a large-scale analysis of the effects of obesity on the risk of revision in anatomic TSA (aTSA) and reverse TSA (rTSA) for various indications.

METHODS

This is an observational cohort analysis of data from a national arthroplasty registry. Primary aTSA for osteoarthritis and primary rTSA for cuff arthropathy or fracture performed between January 2015 and December 2022 in Australia were included. Procedures were stratified by body mass index (BMI) groups and the cumulative percentage of revision was compared between groups. The analyses were undertaken using Kaplan-Meier estimates of survivorship and hazard ratios (HRs) from Cox proportional hazards models.

RESULTS

There were 9,549 primary aTSAs for osteoarthritis, 13,920 primary rTSAs for cuff arthropathy, and 4,685 primary rTSAs for fractures. In rTSA indicated for fracture, obese class III had an increased all-cause revision risk compared with normal-BMI patients (HR 1.87, 95% CI 1.13-3.10, P = .014) throughout the entire follow-up period. In contrast, all-cause revision rates for aTSA for osteoarthritis and rTSA for rotator cuff arthropathy across BMI categories were not significantly different. There was an increased risk of revision for instability or dislocation in BMI class III compared with normal-BMI patients after rTSA for fracture (HR 2.84, 95% CI 1.43-5.63, P = .002). Obese class 1 and obese class 2 patients receiving aTSA for osteoarthritis had a higher rate of revision for cuff insufficiency compared with normal-BMI patients (entire period HR 2.30, 95% CI 1.17-4.55, P = .016, and entire period HR 2.10, 95% CI 1.00-4.40, P = .049, respectively).

CONCLUSION

Obesity has an increased risk of all-cause revisions and revision for instability or dislocation in patients receiving rTSA indicated for fractures. BMI was not associated with an increased risk of revision in primary aTSA indicated for osteoarthritis, nor for primary rTSA indicated for rotator cuff arthropathy. We recommend BMI class III patients undergoing rTSA for fracture to be counseled on their complication risks during the informed consenting process.