Corpus: Carpal tunnel

The carpal tunnel is an anatomical passage at the wrist that serves as a passageway for nerves and tendons travelling from the forearm to the palm.

The carpal tunnel is bordered dorsally by the sulcus carpi of the carpus and the ligamentum carpi radiatum, palmarly by the retinaculum flexorum, which stretches out as a taut band of fibres between the following elevations (eminentiae):

• the eminentia carpi ulnaris, formed by the os pisiforme and the hamulus of the os hamatum and
• the eminentia carpi radialis, formed by the tuberosities of the scaphoid and trapezium bones

The median nerve and the 9 tendons of the following muscles pass through the osteofibrous carpal tunnel:

• Musculus flexor digitorum profundus (4 tendons)
• Musculus flexor digitorum superficialis (4 tendons)
• Musculus flexor pollicis longus (1 tendon)

The tendon of the flexor carpi radialis muscle runs radially from the carpal tunnel in its own tendon sheath, separated from the carpal tunnel by a layer of connective tissue. Some authors cite the flexor carpi radialis muscle as one of the contents of the carpal tunnel.

Tendon sheaths[Bearbeiten]

The tendons of the above-mentioned muscles are surrounded by tendon sheaths. The following subdivisions can be made:

• Radial sac (vagina tendinis musculi flexoris pollicis longi): This tendon sheath surrounds the flexor pollicis longus muscle and extends to just before the insertion of its tendon at the end phalanx of the thumb.
• Ulnar sac (vagina communis tendinum musculorum flexorum): This tendon sheath includes the flexor digitorum superficialis muscle and the flexor digitorum profundus muscle. The tendons are rearranged in this part of the carpal sac. One tendon each of the superficial and deep flexor, which lead to the same finger, lie next to each other. However, the ulnar sac only extends to the proximal end of the respective metacarpal bones. The tendons that lead to the little finger are excluded from this. They behave similarly to the tendon sheath on the radial side and end just before the attachment of the tendon to the end phalanx of the little finger.

The two tendon sheaths do not communicate with each other. Their extent varies greatly from person to person.

A constriction of the median nerve in the carpal tunnel can lead to a bottleneck syndrome known as carpal tunnel syndrome.

• Carpal tunnel (Snackable)

• Waldeyer et al. Human Anatomy: Textbook and Atlas in One Volume (De Gruyter Studium) (19th totaly rev. ed.), De Gruyter, 2012

• Image source podcast: © Roman Odintsov / Pexels