Fig. 4

Deep branch impingement against an unrecognized hamate hook fracture in a 40-year-old male with motor impairment in the territory of the ulnar nerve after a blunt trauma over the palm. a Short-axis 22–8-MHz US image demonstrates severe edematous changes and swelling of the deep branch (arrow) as it runs on the ulnar side of the hamate hook (HH). A small piece of fractured bone (asterisk) is shown avulsed from the tip of the hook. The terminal divisions of the superficial branch (arrowheads) present a normal appearance as they run in between the palmaris brevis (PM) and the abductor digiti minimi (ADM) and flexor digiti minimi (FDM). Outlined arrow, ulnar artery. b Long axis 22-8MHz US image shows a swollen deep branch (arrowheads) presenting a distorted path around the level of the hamate hook. Note the abrupt change in caliper of the nerve at the hiatus (arrow), related to the impingement. c Transverse turbo Spin-Echo T1-weighted and d transverse turbo Spin-Echo fat suppressed T2-weighted MRI scans confirm swelling and edematous changes of the deep branch (outlined arrowhead) and the presence of a fracture of the hamate hook (asterisk). The ulnar artery (arrow) and the superficial branch (arrowhead) have a normal appearance