Glenosphere Inclination and Clinical Outcomes after Reverse Shoulder Arthroplasty

Abstract Background The relationship of numerous implant design and positioning-related variables with range of motion and clinical outcomes have been investigated for reverse shoulder arthroplasty (RSA). While glenosphere inclination has been investigated with regards to implant fixation and scapular notching, little research has been done on the association between glenosphere inclination and clinical outcomes. Therefore, the primary objective of this study was to investigate the relationship between preoperative glenoid inclination, postoperative glenosphere inclination and inclination change (∆INC) from pre- to postoperative on clinical outcomes after RSA. Methods A multicenter retrospective study was conducted of RSAs with minimum 2-year clinical follow-up. All included patients had the same RSA prosthesis. Preoperative, postoperative, and ∆INC from pre-to postoperatively were measured for each patient. The primary study outcome was the minimum 2 year ASES score. Secondary outcomes were active range of motion (ROM), Constant-Murley score and WOOS at a minimum of 2 years postoperatively. Receiver-operator characteristic (ROC) curve analyses were performed to determine if any significant thresholds in inclination existed. Univariate analyses were performed with ANOVA to compare subgroup means. Finally, a multivariate logistic regression was performed to examine each inclination variable as a predictor of clinical outcome while controlling for patient and implant-related variables. Results 87 patients were included in the study. The mean age was 70 years and 53% of patients were male. The examiners had excellent reliability determined by intraclass correlation coefficients (ICCs) for all three measurements. There was no apparent correlation between preoperative inclination, postoperative inclination or ∆INC with minimum 2-year ASES scores. This was confirmed in the ROC analyses, where no significant thresholds were found for each of the three assessed measurements (p > 0.05 for all analyses). A subgroup analysis comparing patients with low preoperative inclination ( 10 degrees) stratified by the ∆INC demonstrated no significant association with inclination (P > 0.05 for all comparisons). In the multivariate regression analysis, inclination had no significant association with the minimum 2-year ASES scores. Conclusions For the studied implant system, preoperative inclination, postoperative inclination and ∆INC did not have a significant association with postoperative clinical outcomes after RSA. Level of Evidence Level III; Retrospective Comparison Study