The carpal tunnel is composed anteriorly at the wrist by a deep arch created by the carpal bones and the flexor retinaculum.
The base of the carpal arch is composed medially by the pisiform and the hook of the hamate and laterally by the tubercles of the scaphoid and trapezium.
The flexor retinaculum is a thick connective tissue ligament that bridges the space between the medial and lateral sides of the base of the arch and converts the carpal arch into the carpal tunnel.
The 4 tendons of the flexor digitorum profundus, the 4 tendons of the flexor digitorum superficialis, and the tendon of the flexor pollicis longus go through the carpal tunnel, as does the median nerve.
The flexor retinaculum holds the tendons to the bony plane in the wrist and keeps them from “bowing.”.
Free movement of the tendons in the carpal tunnel is eased by synovial sheaths, which surround the tendons. All the tendons of the flexor digitorum profundus and flexor digitorum superficialis are encompassed by just one synovial sheath: a different sheath surrounds the tendon of the flexor pollicis longus. The median nerve is anterior to the tendons in the carpal tunnel.
The tendon of the flexor carpi radialis is encompassed by a synovial sheath and goes through a tubular compartment created by the connection of the lateral aspect of the flexor retinaculum to the margins of a groove on the medial side of the tubercle of the trapezium.
The ulnar artery, ulnar nerve, and tendon of the buddy – maris longus enter the hand anterior to the flexor retinaculum and thus don’t go through the carpal tunnel. The tendon of the palmaris longus isn’t encompassed by a synovial sheath.
The radial artery enters dorsally around the lateral side of the wrist and is located adjacent to the external surface of the scaphoid.
The extensor tendons enter the hand on the medial, lateral, and posterior surfaces of the wrist in 6 compartments defined by an extensor retinaculum and lined by synovial sheaths:.
– The tendons of the extensor digitorum and extensor indicis share a compartment and synovial sheath on the posterior surface of the wrist.
– The tendons of the extensor carpi ulnaris and extensor digiti minimi have individual compartments and sheaths on the medial side of the wrist.
– The tendons of the abductor pollicis longus and extensor pollicis brevis muscles, the extensor carpi radialis longus and extensor carpi radialis brevis muscles, and the extensor pollicis longus muscle go through 3 compartments on the lateral surface of the wrist.
Carpal Tunnel Syndrome.
Carpal tunnel syndrome is an entrapment syndrome caused by pressure on the median nerve inside the carpal tunnel. The etiology of the illness is usually vague, though in certain cases the nerve injury might be an immediate effect of increased pressure on the median nerve caused by overuse, swelling of the tendons and tendon sheaths (example, rheumatoid arthritis), and cysts originating from the carpal joints. Increased pressure in the carpal tunnel is considered to cause venous blockage that generates nerve edema and anoxic damage to the capillary endothelium of the median nerve itself.
Patients normally report pain and pins and needles sensations in the distribution of the median nerve. Weakness and loss of muscle mass of the thenar muscles could also take place. Lightly tapping over the median nerve (in the region of the flexor retinaculum) easily creates these symptoms (Tinel’s sign).
First treatment is directed at lessening the inflammation and removing any persistent abuses that create the symptoms. If this doesn’t result in progress, nerve conduction studies will likely be essential to support nerve entrapment, which might necessitate surgical decompression of the flexor retinaculum.