No impact of osteoporosis on stemless reverse shoulder arthroplasty stability

It remains unclear whether altered bone density may be a stability issue in stemless reverse shoulder arthroplasty (RSA).

This was a retrospective multicentric study. Patients with stemless RSA with two-year postoperative shoulder X-ray and clinical data were included. Measurement of proximal humeral cortical bone thickness (CBT avg) on postoperative radiography was used to assess bone density.

68 patients (mean age, 67.0 years) were included. CBT avg < 6 mm (osteoporosis) at two years was reported in 22.2% (2/9) of patients with humeral loosening and 35.6% (21/59) without humeral loosening (p = 0.7073). After adjustment for age and body mass index (BMI), CBT avg < 6 mm was not significantly associated with humeral loosening at two years (OR 0.37; 95% CI 0.04-2.21). Factors associated with humeral loosening vs. no humeral loosening at two years were BMI (24.2 vs. 27.9 kg/m²; p = 0.0131), cervico-diaphyseal angle < 140° at two years (66.7% vs. 16.9%; p = 0.0039) and lateralization of polyethylene (100% vs. 59.3%; p = 0.0217).

These results suggest that radiological evaluation of bone density does not predict early migration of stemless RSA implants. Some clinical factors such as BMI or implant configuration were associated to early implant migration, but never led to implant removal.