Carpal Tunnel Anatomy – Boundaries and Relations of Carpal Tunnel

Carpal Tunnel Anatomy

In Carpal Tunnel Anatomy, The carpal tunnel is an osteo-fibrous canal (narrow passageway) Found on the Anterior Aspect of the wrist. It’s the entrance to the palm for several tendons and Median Nerve.
The boundaries are the carpal bones forming the floor, and the flexor retinaculum (or transverse carpal ligament) forming the roof. The retinaculum is about 3–4 cm wide and inserts into the scaphoid tuberosity and into the pisiform (proximal carpal tunnel) and subsequently into the trapezium and the hook of the hamate (distal carpal tunnel). On the radial side, it divides into two layers, a superficial layer and a deep layer to accommodate the tendon of the flexor carpi radialis.

The carpal tunnel is formed by two layers: 1) a deep carpal arch and, 2) a superficial flexor retinaculum.

 

Carpal Arc: –

– Base/sides: – Concave on the palmar side.
– Laterally: – Scaphoid and Trapezium tubercles
– Medially: – hook of the hamate and the pisiform

 

Flexor Retinaculum: –

– Roof: – Thick connective tissue.
– Turns the carpal arch into the carpal tunnel by bridging the space between the medial and lateral parts of the arch.
– Originates: – Lateral side
– Inserts: – Medial side of the carpal arch.

The carpal tunnel contains nine tendons and a nerve: The flexor pollicis longus, the four flexor digitorum superficialis, the four flexor digitorum profundus as well as the median nerve.
The flexor pollicis longus has its own synovial sheath, whereas the flexor digitorum superficialis and profundus have a common synovial sheath (single synovial sheath).

Synovial sheath: – These sheaths allow free movement of the tendons.

Sometimes you may hear that the carpal tunnel contains another tendon, the flexor carpi radialis tendon, but this is located within the flexor retinaculum and not within the carpal tunnel itself!

Clinical Case or Management: – Carpal tunnel syndrome is a syndrome characterized by tingling burning and pain (needle, pin) through the course of the median nerve particularly over the outer fingers and radiating up the arm, that is caused by compression of the carpal tunnel contents. It is associated with repetitive use, rheumatoid arthritis, and several other states. It can be detected using Tinel’s sign and the Phalen maneuver. It may be treated non-surgically by splinting and/or corticosteroid injection, though definitive management often requires surgical division of the flexor retinaculum, which forms the roof of the carpal tunnel. Carpal tunnel symptoms can sometimes be caused by tight muscles in the neck and shoulder region.