Atraumatic scapular body fractures after reverse total shoulder arthroplasty: a case series

ObjectiveIndications for reverse total shoulder arthroplasty (RSA) are expanding, and utilization of this procedure is projected to increase. While improvements in implant design, surgical techniques, and patient selection have decreased the rate of major complications such as instability and baseplate failure, new complications are becoming evident. There is a case report of a single patient with a "floating glenoid" from an atraumatic scapula fracture that required revision to hemiarthroplasty. We present a case series of three patients with a history of RSA that developed a similar type of atraumatic periprosthetic scapular body fractures.MethodsUsing a single surgeon's database of patients that underwent RSA, we identified three patients with a unique periprosthetic fracture morphology distinct from acromial stress fractures and scapular spine fractures. We performed a chart review of patient history, functional outcome scores, imaging, and range of motion data.ResultsThree patients were identified. All three patients were over 70 years old. One patient underwent a primary RSA for cuff tear arthropathy while the other 2 underwent revision RSA for failed shoulder arthroplasty. The fracture pattern varied. One patient developed an incomplete fracture inferior to the baseplate. One patient developed a fracture inferior to the baseplate and extending medially before exiting the scapular spine. The final patient developed a stellate glenoid vault fracture that extended and exited the medial border of the scapula. Two patients had a stable glenoid implant and were treated with sling immobilization and healed the fracture with resolution of pain and return to baseline functional range of motion. One patient had a loose glenoid baseplate and was revised to a hemiarthroplasty. She healed the fracture and had a complete resolution of pain with an adequate return to function.ConclusionAs the number of RSA is increasing, there are newer rare complications seen, despite advances in technique and implant design mitigating other known complications. Atraumatic scapular body fractures could be a result of stress from load-sharing of the glenosphere around the baseplate, as seen in one patient with a hooded glenosphere. Another potential cause may be long term scapular notching, which was seen as the potential reason for fraction in one patient. Finally, poor bone quality from osteoporosis and glenoid bone loss from failed arthroplasty may be a cause for these fractures when trying to achieve adequate baseplate fixation with screws. Nonoperative treatment in two patients with a stable implant was successful, and revision to hemiarthroplasty was performed in a patient with a loose glenoid baseplate with success. Further biomechanical and implant design research on this topic is warranted to identify the true causes of this fracture.