Fracture of pyrocarbon humeral head resurfacing implant: a case report

We report a case of a pyrocarbon humeral head resurfacing implant fracture, occurring 6 years after its implantation, without any obvious trauma or dislocation. Initial radiographs showed a proud and oversized pyrocarbon resurfacing implant. On clinical examination, the patient had a painful and pseudoparalyzed shoulder with subscapularis insufficiency. Imaging studies confirmed implant fracture and severe fatty infiltration (Goutallier, grade 4) of the subscapularis muscle. Intraoperatively, the implant was found to be fractured with multiple pyrocarbon debris in the glenohumeral joint. The implant was loose, and gross inspection showed no visible bony adhesion or ongrowth. Histologic analysis showed multiple seats of metallosis in the synovial tissue and cancellous bone of the humeral head. Successful management of this complication was managed with a thorough debridement and irrigation and revision to reverse shoulder arthroplasty. Our observation put into question the use of pyrocarbon as a humeral head resurfacing implant. The material seems to be too fragile to be used as a resurfacing implant and cannot achieve fixation of the implant to bone.