Polyethylene liner dissociation from humeral tray: impediment to closed reduction of dislocated reverse total shoulder replacement

BACKGROUND: Instability is one of the leading causes of revision for reverse total shoulder arthroplasty (RTSA). Closed reduction (CR) of a dislocated RTSA is recommended by many as initial treatment with varying degrees of success. In this study, we describe polyethylene liner dissociation from the humeral tray (PDH) as a cause of failure of CR of dislocated RTSA. METHODS: In this retrospective study, patients who underwent revision RTSA for instability were identified through our institutional database review using specific International Classification of Diseases and Current Procedural Terminology codes. Pertinent clinical information including demographics, details of instability event (early vs. late), traumatic vs. atraumatic, outcomes of CR (if performed), and intraoperative findings during revision surgery were collected and analyzed. RESULTS: Twenty-two patients met the inclusion criteria with average follow-up of 2 years. CR was attempted in 12 (55%) patients, prior to revision surgery, and was successful in 5 (23%) patients. During the revision surgery polyethylene liner dissociation from the humeral tray (PDH) was identified in 10 patients (45%). Five of these 10 patients had failed CR and the other 5 patients did not undergo CR due to primary surgeon’s preference. All patients with PDH event had onlay humeral tray RTSA system. Although not a consistent radiographic finding in our series, the presence of the metallic glenosphere in direct contact with the humeral tray on anteroposterior or axillary radiographs was diagnostic for PDH. CONCLUSION: Dissociation of polyethylene liner from the humeral tray can be associated with an RTSA dislocation and is a contraindication for CR. A radiographic finding of the metallic humeral tray articulating directly with the glenosphere is an indication that the polyethylene liner is dissociated from the humeral tray.