Sonoanatomy of the deep branch of the ulnar nerve.

INTRODUCTION: This study evaluated the sonoanatomy of the deep motor branch of the ulnar nerve (DBUN) using high-resolution ultrasonography (HRUS).
METHODS: In 60 wrists of 30 healthy adults, the gross course, cross-sectional area (CSA), and diameter of the DBUN were observed by HRUS (frequency band 3-16 MHz). Its course was assessed by using the distance from anatomical landmarks and depth from the skin.
RESULTS: The DBUN was found in all subjects with HRUS, and it branched off from the ulnar nerve before reaching the hamate bone. At the hook-of-hamate level, the mean DBUN CSA was 1.5 ± 0.2 mm2 , and the mean diameter was 1.5 ± 0.2 mm. The mean distance from the hamate hook to the DBUN was 5.4 ± 1.0 mm, and the mean depth from the skin was 8.6 ± 1.6 mm. DISCUSSION: Sonoanatomy of the DBUN obtained from HRUS may be useful in detecting or preventing DBUN lesions.