# Posttraumatic Compressive Neuropathy of the Deep Motor Branch of the Ulnar Nerve Caused by Heterotopic Ossification

## TL;DR

A patient developed nerve compression in the ulnar nerve due to abnormal bone growth after an injury, which was successfully treated with surgery.

## Contribution

This case highlights a rare cause of ulnar nerve dysfunction due to heterotopic ossification.

## Key findings

- The patient developed muscle atrophy and claw deformities due to nerve compression.
- Surgery to remove the abnormal bone and decompress the nerve improved symptoms.
- Computed tomography and electromyography were key in diagnosing the condition.

## Abstract

We report a case of posttraumatic compressive neuropathy of the deep motor branch of the ulnar nerve occurring in the setting of heterotopic ossification following a direct blow to the hypothenar eminence. Over several weeks, the patient developed ring and little finger claw deformities and atrophy of his first dorsal interosseous and adductor pollicis muscles with sparing of sensation. Electromyography and nerve conduction study localized the area of injury, and computed tomography confirmed the presence of heterotopic bone near the deep motor branch of the ulnar nerve. Intraoperatively, the deep motor branch of the ulnar nerve was under tension as it traversed volarly over the hook of hamate and heterotopic bone. Decompression of the deep motor branch of the ulnar nerve with resection of heterotopic bone and the hook of hamate was performed. Six months postoperatively, the patient demonstrated resolution of clawing and improving strength of his ulnar nerve innervated intrinsic muscles.