Heterotopic Ossification and Entrapment of the Tibial Nerve Within the Tarsal Tunnel: A Case Report.

Heterotopic ossification has been reported to occur after musculoskeletal trauma (including orthopedic procedures). This has been known to cause nerve entrapment syndromes and persistent pain, limiting joint mobility. We present a case of a 19-year old female collegiate athlete who had previously undergone ankle arthroscopy and arthrotomy to remove 2 ossicles. At approximately 1 year postoperatively, the patient developed pain when planting and pivoting her foot. Imaging revealed a radiodense lesion at the posteromedial ankle consistent with heterotopic ossification and entrapment of the tibial nerve within the tarsal tunnel. The patient underwent surgical resection and postoperative indomethacin prophylaxis. At the 1-year follow-up visit, the patient remained asymptomatic, without evidence of recurrence of the heterotopic ossification. In our review of the published data, we found no previously reported cases of heterotopic ossification causing entrapment of the tibial nerve within the tarsal tunnel. In the present case report, we describe this rare case and the postulated etiologies and pathophysiology of this disease process. In addition, we discuss the clinical signs and symptoms and recommended imaging modalities and treatment.