Heterotopic ossification after minimally invasive rotator cuff repair

Heterotopic ossification is a common phenomenon after spinal cord injury, head injury, neurologic disorders, burns and other trauma, and joint arthroplasty. Periarticular ossifications after shoulder surgery have been known to occur since the 19th century, at an incidence of up to 27%. After arthroscopic and minimally invasive shoulder surgical procedures were introduced and came into broad use, reports about heterotopic ossification became very rare. We describe here a case of heterotopic bone formation in the subdeltoid fascia after arthroscopic subacromial decompression, acromioclavicular joint resection, and mini-open rotator cuff reconstruction were performed with 2 absorbable suture anchors 3 months postoperatively. Computed tomography (CT) confirmed a massive heterotopic ossification of the deltoid muscle. During revision surgery, a 4 x 6.5-cm bone shell that consisted primarily of immature trabecular bone and lamellar bone in smaller proportions was removed. The case presented here is unique in the scientific literature. Although risk factors have been identified, the underlying pathomorphogenetic mechanism of such heterotopic bone formation remains unclear. Prophylactic administration of nonsteroidal anti-inflammatory drugs (NSAIDs) or radiation for arthroscopic or minimally invasive shoulder surgery is not justified, given the low incidence of heterotopic ossification and the known adverse effects. Apparently, information on basic science and on evidence-based therapy is lacking.