Morphology and morphometry of the ulnar head of the pronator teres muscle in relation to median nerve compression at the proximal forearm

Abstract

Introduction: The pronator syndrome is a rare compression neuropathy of the median nerve. Ulnar head of the pronator teres muscle may cause compression at proximal forearm. Hypothesis: Detailed morphologic and morphometric studies on the anatomy of the ulnar head of pronator teres is scarce. Material and methods: We dissected 112 forearms of fresh cadavers. We evaluated the morphology and morphometry of the ulnar head of pronator teres muscle. Results: The average ulnar head width was 16.3 +/- 8.2 mm. The median nerve passed anterior to the ulnar head at a distance of 50.4 +/- 10.7 mm from the interepicondylar line. We classified the morphology of the ulnar head into 5 types. In type 1, the ulnar head was fibromuscular in 60 forearms (53.6\%). In type 2, it was muscular in 23 forearms (20.5\%). In type 3, it was just a fibrotic band in 18 forearms (16.1\%). In type 4, it was absent in 9 forearms (8\%). In type 5, the ulnar head had two arches in 2 forearms (1.8\%). In 80 forearms (71.5\%: types 1, 3, and 5), the ulnar head was either fibromuscular or a fibrotic band. Discussion: Although the pronator syndrome is a rare compression syndrome, the ulnar head of pronator teres is reported as the major cause of entrapment in the majority of the cases. The location of the compression of the median nerve in relation to the ulnar head of pronator teres muscle and the morphology of the ulnar head is important for open or minimally-invasive surgical treatment. (C) 2016 Elsevier Masson SAS. All rights reserved.