Ulnar Nerve Compression at the Wrist Secondary to Heterotopic Ossification following a Minor Trauma: A Case Report.

Introduction: Heterotopic ossification (HO) is a known complication in the rehabilitation setting, involving the abnormal formation of bone in soft tissues. Ulnar nerve compression at the wrist due to HO is a rare occurrence, not widely reported in the literature. This case report highlights the unusual presentation of HO leading to ulnar nerve compression at the wrist, adding significant insight into the potential complications and management strategies for such cases. Case Report: A 52-year-old woman of Caucasian ethnicity presented with a painful lump on the ulnar side of the volar aspect of her left wrist, 1 year after minor trauma. The patient initially forcefully dorsiflexed her wrist against a bus railing to prevent a fall, leading to a soft-tissue injury diagnosed through radiographs. Over the following months, she developed swelling, pain, and tingling in the ring and little fingers. Clinical examination revealed a firm 3 × 4 cm swelling associated with the flexor carpi ulnaris tendon and ulnar neurovascular bundle, indicated by increased pain on movement and a positive Tinel's sign. Imaging showed calcific deposits and a lesion compressing the ulnar nerve. Surgical excision of the lesion was performed, and histopathology confirmed the diagnosis of HO. The patient experienced complete resolution of symptoms post-surgery, with no complications or recurrence observed at follow-up. Conclusion: This case report discusses the importance of considering HO as a differential diagnosis for chronic ulnar-sided wrist pain with swelling post-trauma. The unusual presentation of ulnar nerve compression due to HO at the wrist enriches the orthopedic literature by highlighting a rare but significant complication.