The Hand: Focused US Anatomy and Examination Technique

Abstract

There are nine flexor tendons for each hand, a flexor digitorum superficialis and a flexor digitorum profundus for each finger, from the second to the fifth. The thumb is provided with a single flexor tendon only. The flexor digitorum profundus tendon originates from the anterior and medial aspects of the ulna, while the flexor digitorum superficialis tendon has two heads: humero-ulnar and radial. Both muscles originate from long tendons that proximally enter the carpal tunnel and then insert on the fingers. Deep tendons run straight up to the bases of the distal phalanges, where they insert. Superficial tendons run up to the middle of the proximal phalanges, where they split into two branches that surround the deep tendons and insert on the head of the middle phalanges. The superficial and deep tendons have common tendon sheaths. Flexor tendons are kept in place by several fibrous bands referred to as pulleys.