Design Analysis: Modular Reverse Total Shoulder Prosthetic Failure Without Proximal Bone Support

Reverse total shoulder arthroplasty (RSA) serves as an effective alternative to total shoulder arthroplasty (TSA), especially for patients with rotator cuff deficiency [1]. Long-term performance of RSA has been limited by a variety of complications including dislocation, infection, humeral fracture, glenoid loosening, glenoid unscrewing, scapular erosion and polyethylene debris [1–2]. Dissociation between the proximal metaphyseal component and distal humeral prosthetic stem (disaphysis) in modular RSAs has been reported with low frequency (1–2%) [2]; however, cases have led to severe consequences including in vivo disassembly [3]. Most cases of unscrewing have occurred due to insufficient support for the prosthesis resulting from proximal humeral bone deficiency [4–5]. In this study, we evaluate a retrieved RSA that unscrewed and subsequently fractured in vivo in a patient with proximal bone deficiency.