Risk factors for rotator cuff tears and aseptic glenoid loosening after anatomic total shoulder arthroplasty

Background: The purpose of this study is to retrospectively analyze all primary anatomic total shoulder arthroplasty (aTSA) patients within a multicenter international database of a single prosthesis to identify risk factors for patients with rotator cuff tear (RCT) and aseptic glenoid loosening. Methods: To investigate the risk factors for RCT and aseptic glenoid loosening, we retrospectively analyzed all aTSA patients with 2-year minimum follow-up from a multicenter international database of a single platform shoulder system, only excluding patients with a history of revision arthroplasty, infections, and humeral fractures. A univariate/multivariate analysis was conducted to compare primary aTSA patients who had report of: 1) a RCT and/or subscapularis failure and 2) aseptic glenoid loosening/cage glenoid dissociations, to identify the differences in (i) intrinsic patient demographics and comorbidities and (ii) implant and operative parameters. Finally, to adapt our statistical analysis for prospective identification of patients most at-risk for RCT and aseptic glenoid loosening, we stratified the dataset by multiple risk factor combinations and calculated the odds ratio (OR) to determine the impact of accumulating risk factors on the incidence rate of each complication. Results: 122 aTSA shoulders had a RCT for a rate of 3.2% and 123 aTSA shoulders had aseptic glenoid loosening for a rate of 3.3%. The multivariate analysis identified that aTSA patients with RCT were more likely to have previous shoulder surgery (P < .001) and small size glenoids (P = .002). Additionally, the multivariate analysis identified that aTSA patients with aseptic glenoid loosening were more likely to be younger (≤62 years at the time of surgery, P = .001), have small size glenoids (P = .033) and have a nonhybrid glenoids (P < .001). Stratifying patients with multiple risk factors identified multiple aTSA cohorts with ORs >2 for RCT or aseptic glenoid loosening. Discussion: This analysis of 2699 primary aTSA identified risk factors for the two most common postoperative complications: RCTs and aseptic glenoid loosening. Using these risk factors, we calculated ORs for patient cohorts with multiple risk factors to identify the patients with the greatest risk for each complication. This information is useful to guide the surgeon in their preoperative counseling and potentially mitigate the occurrence of these complications, by indicating patients with these risk-factors for alternative treatment strategies, like rTSA, instead of aTSA.