Anatomical variations of the carpal tunnel structures

Abstract

There are many anatomical variations in and around the carpal tunnel that affect the nerves, tendons and arteries in this area. Awareness of these variations is important both during the clinical examination and during carpal tunnel release. The purpose of the present review is to highlight recognized anatomical variations within the carpal tunnel including variation in nerve anatomy, tendon anatomical variants, vascular anatomical variations and muscle anatomical variations.

Keywords: Anatomical variations; Carpal tunnel; Carpal tunnel release; Median nerve; Ulnar nerve.

Figure 1)

A 23-year-old man with a bifid median nerve identified at time of carpal tunnel release. No other anomalies were noted

Figure 2)

A 57-year-old woman with a bifid median nerve. The radial median nerve had its own compartment within the carpal tunnel that required separate release. The arrows show the two distinct branches

Figure 3)

Variations in the takeoff of the median nerve motor branch. A Normal anatomy of the median nerve motor branch: extraligamentous and recurrent pattern. B Variation of the median nerve motor branch: subligamentous pattern. C Variation of the median nerve motor branch: transligmentous course. D Variation of the median nerve motor branch: ulnar takeoff. E Variation of the median nerve motor branch: superficial course. Reproduced from reference with permission

Figure 4)

Linburg-Comstock syndrome: Anomalous tendon slips from the flexor pollicis longus to the flexor digitorum profundus resulting in an inability to actively flex the interphalangeal joint of the thumb without simultaneously flexing the distal interphalangeal joint of the index finger. Reproduced from reference with permission

Figure 5)

An anomalous palmaris longus tendon was noted to pass through the carpal tunnel and insert into the palmar aponeurosis. It has been transected proximally and is held by a clamp

Figure 6)

Superficial ulnar artery identified during forearm flap elevation, proximal to the carpal tunnel. The artery may be at risk in extended carpal tunnel release incisions or in repeat surgeries

Figure 7)

An anomalous palmaris longus muscle belly identified within the carpal tunnel, likely representing an accessory palmaris muscle