Inclination correction is associated with improved clinical outcomes in anatomic total shoulder arthroplasty

Abstract

BackgroundWhile retroversion of the glenoid in anatomic total shoulder arthroplasty (TSA) has been increasingly studied, the effect of glenoid inclination on clinical outcomes has received less attention. The goal of this study was to examine the influence of pre- and postoperative inclination on clinical outcomes after anatomic TSA. MethodsPatients undergoing primary anatomic TSA with minimum 2-year outcomes were included from a multicenter prospectively maintained database of shoulder arthroplasties from 2015 to 2017. Preoperative and postoperative radiographs were independently evaluated to assess native glenoid inclination and postoperative prosthetic glenoid inclination using the previously described TSA angle. A receiver-operator characteristic (ROC) curve analysis was performed to determine if a significant threshold existed for preoperative inclination, postoperative inclination, or amount of inclination correction. A linear regression analysis assessing the correlation between each of these measurements and the postoperative Constant score was performed. For final analysis, means and standard deviations of the Constant scores for patients above and below the calculated inclination thresholds for each group were compared using SPSS. ResultsSeventy-two anatomic TSAs with minimum 2-year follow-up were included. ROC analysis determined a significant threshold of 10 degrees of postoperative inclination for prediction of the 2 year postoperative Constant score (AUC = 0.682), P= .010. This finding was additionally supported in the linear regression analysis, where postoperative inclination was significantly associated with the postoperative Constant score (P= .046). Patients below the postoperative inclination threshold of 10 degrees had significantly improved Constant scores compared to those above the threshold (mean 65.3, P= .005; Table 2). Two degrees of inclination correction was predictive of the 2 year postoperative Constant score (AUC = 0.754; P< .001; sensitivity 68%, specificity 74%). Inclination correction was significantly associated with postoperative Constant score (P= 0.003). Patients above the inclination correction threshold of 2 degrees had significantly improved Constant scores (mean 75.4) compared to those below the threshold (mean 65.9, P= .003). ConclusionsWhen appropriately corrected, preoperative inclination over 10 degrees does not appear to significantly influence postoperative outcome of anatomic TSA. There is a significant association between postoperative inclination and 2 year Constant scores. Inclination correction is particularly associated with postoperative Constant score. These results encourage the need for future studies with detailed analysis as to how to best predict and correct inclination to produce favorable and durable outcomes after anatomic TSA. Level of EvidenceLevel III; Retrospective Comparative Study