An Unusual Case of Onlay Reverse Shoulder Arthroplasty Disassembly Due to Cement Interposition. A Case Report

INTRODUCTION: Reverse shoulder arthroplasty (RSA) complication rates range between 1.4% and 28% depending on the nature of the indication. Even though glenosphere dissociation is the third most frequent complication after RSA, with an incidence that can rise to just over 12%, there is no evidence in the literature describing the disassembly between the humeral stem and its metaphysics. CASE REPORT: It is reported a novel early failure type in a reversed shoulder arthroplasty of a healthy 72-year-old female patient, involving the disassembly of the metaphysis from an onlay tray system due to cement interposition in a reversed shoulder prosthesis. CONCLUSION: This case highlights a rare form of early failure after RSA as a result of a disassembly between the humeral stem and its metaphysis due to the presence of interposed cement. To prevent this complication, a two-step implantation procedure is recommended, which consists of cementing the stem before inserting the metaphyseal tray.