Risk factors for eccentric glenoid wear after humeral head replacement for cuff tear arthropathy

Background: In our previous report, glenoid wear (GW) after humeral head replacement for cuff tear arthropathy was classified with modified Goya’s classification (grade 0-3), and, among 3 subtypes of grade 3 (glenoid bone erosion), grade 3B (superior eccentric erosion) showed significantly more pain and limited active flexion postoperatively compared to grade 3C (concentric erosion). The purpose of this study was to detect individual risk factors for the progression to grade 3B GW. Methods: Seventy-nine shoulders in 70 patients who were followed up for a mean of 8.2 years (range, 5.0-13.2 years), including 29 men and 41 women, with a mean age at the surgery of 71.1 years (range, 54-87 years), were reviewed. Atrophy and fatty degeneration of torn cuff muscle, preoperative humeral head displacement (superior translation ratio [STR], anterior translation ratio, and other several parameters) on preoperative magnetic resonance imaging, and other individual factors were analyzed as possible risk factors. Results: GW at the final follow-up was grade 0: 5 shoulders, grade 1: 17, grade 2: 20, and grade 3: 37 (3A: 4, 3B: 22, and 3C: 11). Preoperative higher STR was defined as a risk factor for grade 3 GW (odds ratio, 35.5; 95% confidence interval, 1.8-693.0; P = .018). Comparison among the three subtypes of grade 3 showed that patients with grade 3B GW had larger STR than 3C (41.4 ± 14.2% vs. 23.5 ± 13.3 % P = .006). Conclusion: Patients with preoperative high STR are considered to have a risk for grade 3B GW, which possibly relates to poor clinical outcome and future revision.