Heterotopic Ossification Complicating Traumatic Ulnar Nerve Palsy in a Child

Heterotopic ossification (HO) refers to the process of forming bony tissues in extra-skeletal sites such as muscles and soft tissues. This pathological process most commonly commences following trauma, surgery, and fractures. Rarely, HO can compress nearby neurovascular structures. To the best of our knowledge, however, no previous reports exist of HO serving as second-hit to partially injured ulnar nerve in the pediatric population. We present a case of a 6-year-old girl with complete high ulnar nerve palsy caused by medial epicondylar fracture followed by development of HO around the elbow. The patient was initially managed conservatively. Four months after the first visit, she presented with complete ulnar nerve palsy that was not evident on the initial presentation. Based on further investigations, she was taken to OR for release of the cubital tunnel and anterior transposition of ulnar nerve. On further follow-up, the patient regained sensory and motor functions of the ulnar nerve with minimum sequalae. Post-traumatic ulnar nerve injury is well described in the literature as resulting from initial trauma or as an iatrogenic injury following fracture reduction and fixation. HO in the pediatric age group is considerably rare, occurring after trauma and burn injuries. Surgical timing of HO release remains controversial. No previous reports of HO complicating traumatic ulnar nerve palsy in pediatric patients exist. In the current case report, partial ulnar nerve injury was initially due to medial epicondylar fracture, but it had progressed to full blown ulnar palsy secondary to superimposed HO. Early HO takedown combined with decompression of ulnar nerve are crucial to ensure complete nerve recovery.