A radiographic analysis of the effects of glenosphere position on scapular notching following reverse total shoulder arthroplasty

Background: Multiple biomechanical studies have analyzed the potential influence of inferior glenosphere tilt on scapular notching in reverse total shoulder arthroplasty (RTSA). The purpose of this study was to clinically determine the likelihood of scapular notching in a series of shoulders, with the glenospheres placed in neutral versus inferior tilt. Methods: From a database of all RTSA performed by the senior author, shoulders with a Delta III-type prosthesis and minimum 12-month follow-up (71 shoulders) were included. Notching in shoulders with neutrally placed glenosphere base plates (Group 1) was compared to notching with 10-15 degrees inferiorly tilted base plates (Group 2). The prosthesis-scapular border angle (PSBA) was also defined and used to determine whether the radiographically quantified amount of inferior tilt was predictive of scapular notching independent of group assignment. Results: There were no significant differences in the grade of notching or incidence of notching between groups 1 and 2 after adjusting for length of follow-up and prosthesis selection. The PSBA was also not predictive of scapular notching. Conclusion: Despite previous biomechanical studies' predictions that inferiorly tilting the glenosphere might reduce inferior scapular neck impingement and subsequent scapular notching, our data showed no difference at 1-year follow-up. Level of evidence: Level III, Retrospective Case Control Study, Treatment Study. (C) 2011 Journal of Shoulder and Elbow Surgery Board of Trustees.