Long-Term Outcomes of Inverted-Bearing Reverse Shoulder Arthroplasty with Large Polyethylene Glenospheres

Background: Inverted-bearing reverse total shoulder arthroplasty (rTSA), using a polyethylene glenosphere with a metal humeral liner, may reduce polyethylene wear, osteolysis, and scapular notching. This study evaluated long-term survivorship, complications, radiographic findings, and clinical outcomes of a large-glenosphere inverted-bearing rTSA design. Methods: A retrospective single-surgeon cohort included 394 primary rTSAs (363 patients; mean age 73.8 ± 8.5 years) performed between 2006 and 2018 using the same implant system. Clinical follow-up was available for 123 patients at a mean of 9.4 years. Outcomes included ASES, Oxford Shoulder Score (OSS), Subjective Shoulder Value (SSV), and pain VAS. Radiographs obtained at ≥8 years were assessed for scapular notching, glenoid loosening, and humeral osteolysis/stress shielding. Kaplan-Meier survival analysis was performed. Results: Thirty of the 257 rTSAs with revision follow-up (11.7%) underwent revision, most commonly for glenoid loosening or instability. Among patients with long-term radiographs, scapular notching occurred in 8.3% of all-polyethylene glenospheres and was limited to grade 1. Humeral osteolysis/stress shielding was present in 36%, although no humeral components were revised for loosening. Median final follow-up PROMs were ASES 75.8, OSS 42, SSV 78, and pain VAS 1. Conclusions: Large-glenosphere inverted-bearing rTSA demonstrated satisfactory long-term outcomes, low notching rates, and acceptable survivorship. The favourable notching profile should be interpreted in the context of the larger eccentric glenosphere design, which precludes attribution of this finding to bearing material alone.