Anatomy of the Carpal Tunnel

Abstract

The carpal tunnel is an inelastic fibroosseous tunnel defined by the carpal bones and the flexor retinaculum. Theosseouscomponentsofthecarpaltunnelforman arch,defined by four bony prominences — proximally by pisiform and tubercle of scaphoid and distally by hook of the hamate and tubercle of trapezium.Superficially the palmaris longus tendon passes anterior to the flexor retinaculum to become continuous with the palmar fascia.Deep to the palmar fascia,a thick ligamentous band forms the superficial border of the carpal tunnel,also referred to as the transverse carpal ligament.The flexor retinaculumand the transverse carpal ligament are considered by some authors synonymous terms [1-3 ].The anatomic zone of the flexor retinaculum extends from the distal radius to the proximal metaphysis of the third metacarpal.It is firmly attached to the hook of the hamate and pisiformbones on the ulnar (medial)side of the carpal tunnel and the tubercle of thetrapeziumanddistalpoleofthescaphoidontheradial (lateral)side of the carpal tunnel.The flexor retinaculum may be divided into three distinct components.The proximal portion is a direct continuation ofthe deep antebrachial fascia.Distally,the transverse carpal ligament represents the central portion of the flexor retinaculum.Most distally is an aponeurosis between the thenar and hypothenar muscles [4 ](Fig.2.1).