Recurrent Dislocation Following Reverse Total Shoulder Arthroplasty for Acute Proximal Humeral Fracture: Salvage With Large-Head Bipolar Hemiarthroplasty and Brachial Plexus Neuropraxia.

Reverse shoulder arthroplasty (RSA) is commonly performed for complex proximal humeral fractures in older adults when fixation or anatomic reconstruction is unlikely to provide reliable outcomes. Recurrent instability following RSA remains a devastating complication, particularly in medically frail patients with poor bone quality and compromised soft tissue balance. Salvage strategies after repeated failed revisions are limited and often associated with poor functional outcomes. A 75-year-old man with severe chronic obstructive pulmonary disease, hypertension, hypercholesterolaemia, transitional cell carcinoma, rectal polyposis, active smoking history, and frailty sustained a comminuted, displaced left proximal humeral fracture with subglenoid humeral head dislocation following a mechanical fall. He underwent hybrid reverse-polarity total shoulder replacement. One week postoperatively, the shoulder developed anterior instability requiring closed manipulation under anaesthesia. Despite a temporary reduction, recurrent instability persisted during rehabilitation, necessitating two subsequent open revision procedures, including liner exchange with adjustment of implant inclination and later glenosphere cup modification. Persistent instability led to referral and multidisciplinary review at a tertiary shoulder centre. The failed RSA was ultimately converted to a large-head bipolar hemiarthroplasty as a salvage procedure. The hemiarthroplasty later dislocated anteriorly, with migration of the prosthetic head into the anterior deltopectoral/coracoid region and severe upper-limb dysfunction suggestive of brachial plexus neuropraxia. Given the patient's significant comorbidities and elevated operative risk, further reconstruction was deemed unsuitable after shared decision-making, and conservative management was pursued. The patient subsequently developed septic arthritis of the contralateral shoulder, further worsening overall functional status. Serial imaging through 2025 demonstrated persistence of the dislocated bipolar implant without evidence of implant fracture or gross stem loosening. This case illustrates the catastrophic progression of recurrent instability following fracture-related RSA in a medically frail patient with compromised bone and soft tissue conditions. It underscores the importance of careful patient selection, accurate restoration of implant positioning and soft tissue tension, prompt tertiary multidisciplinary involvement after failed stabilisation, and realistic counselling regarding the limited salvage potential and persistent complications associated with hemiarthroplasty conversion after failed RSA. This case highlights that, in medically frail patients with multiple risk factors for instability, early recognition of recurrent dislocation and timely referral to specialist shoulder centres may help guide management decisions, optimise patient expectations, and avoid repeated interventions with diminishing likelihood of durable success.