Humeral and glenoid component malposition in patients requiring revision shoulder arthroplasty: a retrospective, cross-sectional study

Background: The purpose of this study was to assess the incidence of glenoid and humeral component malposition in failed primary shoulder arthroplasty requiring revision. We hypothesized that glenoid and humeral component malposition would be a prevalent feature in cases requiring revision arthroplasty for primary anatomic total shoulder arthroplasty (TSA), primary reverse shoulder arthroplasty (RSA), and primary hemiarthroplasty procedures. Methods: A retrospective cross-sectional study was performed focusing on identifying the incidence of malpositioned components in shoulder arthroplasty in quantitative and qualitative reviews. A total of 234 consecutive cases from 3 institutions were included in the study. Past surgical and radiographic data relative to the primary and revision surgeries were collected by each of the 3 investigative institutions, and radiographs were reviewed by an independent reviewer. Descriptive data are summarized as means, ± standard deviations, or frequency (%). An Exact McNemar's test was used to compare frequencies between the independent reviewer and the institutions when appropriate, with significance set at P = .05. Results: Quantitative analysis demonstrated that the majority of glenoid components in these revision cases were malpositioned in both TSA (51%) and RSA (93%) when all measures were considered. Similarly, there was humeral component malposition in 57% of TSA cases, 62% of RSA cases, and 54% of hemiarthroplasty cases when all measures were considered. When asked if there was glenoid component malposition, the independent reviewer considered 17% of glenoid components to be malpositioned in TSA cases and 54% in RSA cases. The investigative institutions reported similar rates (P = .585). For the humeral side, the independent reviewer felt that 71% of TSA cases, 24% of RSA cases, and 74% of hemiarthroplasty implants were malpositioned in some direction. The investigative institutions reported similar rates (P = .087). Discussion and Conclusion: The data from this study suggest that component malposition is frequently present among patients requiring revision arthroplasty. Component malposition was not just frequently present, but also occurred in consistent patterns. Moreover, while significant attention has been placed on the impact of glenoid malposition, this study highlights the previously underappreciated high incidence of humeral component malposition in cases requiring revision arthroplasty.