Comparing the Use of Axillary Radiographs and Axial Computed Tomography Scans to Predict Concentric Glenoid Wear

BACKGROUND: Axillary radiographs traditionally have been considered sufficient to identify concentric glenoid wear in osteoarthritic shoulders; however, with variable glenoid wear patterns, assessment with use of computed tomography (CT) has been recommended. The purpose of the present study was to compare the use of axillary radiographs and mid-glenoid axial CT scans to identify glenoid wear. METHODS: Preoperative axillary radiographs and mid-glenoid axial CT scans for 330 patients who underwent anatomic total shoulder arthroplasty were reviewed. Five independent examiners with differing levels of experience characterized the glenoid morphology as either concentric or eccentric. The morphologies determined with use of axillary radiographs and CT scans were assessed for correlation, and both intraobserver and interobserver consistency were calculated. RESULTS: Concentric wear identified with use of radiographs was confirmed with use of CT scans in an average of 61% of cases (range, 53% to 76%). Intraobserver consistency averaged 75% for radiographs and 73% for CT scans. There was significant interobserver consistency, as higher levels of training corresponded with greater consistency between imaging analyses (p < 0.001). The most senior observer identified the highest proportion of concentric wear on radiographs (p < 0.001), showed the greatest consistency between attempts when using CT (p < 0.001), and had the greatest agreement of radiographs and CT evaluating glenoid morphology (p < 0.001). CONCLUSIONS: For the experienced shoulder surgeon, concentric glenoid wear identified on axillary radiographs will appear concentric on 2-dimensional CT in approximately 75% of cases. Obtaining a CT scan to confirm glenoid wear patterns most greatly benefits less-experienced surgeons. Across all levels of experience, axillary radiographs and single-slice, mid-glenoid CT scans appear insufficient for consistently predicting wear patterns. LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.