Characteristic heterotopic ossification of the proximal humerus after total shoulder arthroplasty

A bony spur in a characteristic location involving the proximal humerus is identified on post-operative radiographs in some patients with history of total shoulder arthroplasty. The spur is theorized to represent heterotopic ossification near the attachment site of the pectoralis major tendon on the proximal humerus which is partially detached and then reattached during total shoulder arthroplasty. In this study, we determine the morphology, incidence, demographic associations, and clinical impact of this finding.

This is a single-center, retrospective study of 500 patients who underwent total shoulder arthroplasty (250 standard and 250 reverse technique) between 2012 and 2017. Pre- and post-operative shoulder radiographs were reviewed to identify and measure the characteristic spur; inter-observer agreement was evaluated between the two reviewers. Incidence, demographic associations, and clinical significance were then determined.

The study group included 268 men and 234 women with a mean age of 70 (42-89) years, and clinical follow-up of 25 (1-84) months. Characteristic heterotopic ossification was seen in 88 patients (17.6%) and was first noted radiographically at a mean (interquartile range) of 12.1 (11.5-12.8) months after surgery. Male sex (adjusted odds ratio (95% confidence interval), 3.00 (0.68-5.34), p < 0.001) was independently associated with heterotopic ossification. No significant relationships between heterotopic ossification and adverse clinical outcomes were observed.

Characteristic heterotopic ossification of the proximal humerus in patients status post total shoulder arthroplasty is a common imaging finding that is not associated with adverse clinical outcomes.