Impact of accumulating risk factors on the acromial and scapular fracture rate after reverse total shoulder arthroplasty with a medialized glenoid-lateralized humerus onlay prosthesis.

Abstract

Identifying risk factors for acromial and scapular fractures improves our understanding about which variables are relevant to these fracture complications; however, these data are difficult to integrate into clinical practice because the majority of reverse total shoulder arthroplasty (rTSA) patients have ≥1 risk factor. The goal of this study was to better facilitate preoperative identification of patients at risk of acromial and scapular fractures and quantify the impact of accumulating risk factors on the incidence of fracture. We retrospectively analyzed 9079 rTSA patients from a multicenter database of rTSA procedures performed with a single medialized glenoid-lateralized humerus onlay rTSA prosthesis to quantify the rate of acromial and scapular fractures. Univariate and multivariate analyses were performed to identify risk factors for fracture. Next, we quantified the number of patients with 1 or multiple significant risk factors for fracture. Finally, to facilitate preoperative identification of patients most at risk of fracture, we stratified our data set using multiple combinations of age, sex, and diagnosis risk factors and calculated the odds ratio for each cohort to quantify the impact of accumulating risk factors on the incidence of fracture. A fracture of the acromion or scapula was radiographically identified in 138 of 9079 patients, for a rate of 1.52%. Patients with fractures were more likely to be older, of female sex, to have a diagnosis of rheumatoid arthritis and/or cuff tear arthropathy, and were less likely to have a diagnosis of diabetes. Eighty-five percent of rTSA patients had ≥1 fracture risk factor. Individually, age, sex, or diagnosis failed to identify any patient cohort with an odds ratio >2.5. Use of multiple combinations of patient risk factors refined the identification of at-risk patients better than any individual risk factor or 2-risk factor combination and demonstrated that the patients with the greatest fracture risk were female patients with a rheumatoid arthritis diagnosis who were aged >70, >75, and >80 years. This 9079-rTSA multicenter study demonstrated that 1.52% of patients experienced acromial and/or scapular fractures with a single medialized glenoid-lateralized humerus onlay rTSA prosthesis. Our analysis identified numerous risk factors and quantified the impact of accumulating risk factors on fracture incidence. Patients who are considering rTSA and who have these age, sex, and diagnosis risk factors should be made aware of their elevated complication risk.