Flexor tendon tears affect tendons in the forearm and palm side of the arm, causing difficulty or inability to flex the wrist and fingers. Injuries include deep cuts, carpal tunnel syndrome, and acute strains. Surgery is often required to repair severed tendons.
A flexor tendon tear affects the tendons in the forearm, the tendons on the palm side of the arm that cross the wrist joint and insert on the bones of the fingers. The tendons are what allow the muscles to flex, or curl inward, in the wrist and fingers. Injuries to these tendons include deep cuts in the wrist or hand that can sever the tendons and inflammatory repetitive stress injuries such as carpal tunnel syndrome. Acute forms of flexor tendon injury, such as muscle strains, can also affect these tendons if the wrist is bent backward sharply, such as when catching during a fall.
Located in the anterior compartment of the forearm, flexor muscles with tendons spanning the wrist joint include the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, flexor digitorum profundus, and longus flexor thumb. There are nine flexor tendons in all, with four belonging to the flexor digitorum superficialis and one to each of the other muscles. Six of these tendons, those belonging to the flexor digitorum superficialis, flexor digitorum profundus, and flexor digitorum longus, lie deep in the wrist and pass through a space between the set of carpal bones at the base of the hands known as the carpal tunnel. The remaining three, those belonging to the flexor carpi radialis, palmaris longus, and flexor carpi ulnaris, are closer to the surface and cross the palmar side of the wrist close to the skin.
One type of flexor tendon injury that affects the superficial tendons is a deep cut on the wrist. These tendons can potentially be severed, snapping them back in both directions like rubber bands. Because the superficial tendons attach to the hand near the wrist joint, a deep cut will result in difficulty or a complete inability to flex the wrist. A deep cut on the palm of the hand or the palm surfaces of the fingers can likewise damage any of the deep flexor tendons that attach to the bones in the fingers, resulting in an inability to curl the fingers. Severed tendons almost always require surgery to repair, because the severed ends stretch so far apart.
Another very common form of flexor tendon injury is carpal tunnel syndrome. A repetitive stress injury (RSI) brought on by frequent, repetitive, and prolonged flexion of the wrist joint over time, carpal tunnel can be initiated by behaviors ranging from typing on a keyboard to sleeping with wrist curls. It is caused by inflammation of the deep flexor tendons, which swell and pinch the median nerve, a large nerve that also passes through the carpal tunnel. Symptoms include pain, numbness, and tingling in the hand that may radiate down the arm, particularly to the thumb side.
Flexor tendon injury can also result from sudden trauma that forcefully bends the wrist backwards, straining the tendons. An example is catching yourself when you fall. Strains are felt as pain, stiffness, and tenderness within the wrist joint, symptoms that may be accompanied by bruising and swelling if the pulling on the tendons is severe.
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