Thursday, July 19, 2007

The Fingers & Repetitive Strain Injuries

Continuation of RSI series - the fingers ...

"Repetitive Strain Injuries (RSIs) from computer use or desk work can cause headaches, eyestrain, and pain through the neck, shoulders, arms and back. "The Fingers" is part of a series that takes a closer look at the mechanism of injury and specific injury prevention techniques for particular pain areas.

Anatomy

The fingers have no actual muscles in them. Rather, the movement of bending the fingers is caused by the muscles in the forearm contracting and pulling on the tendon (the long, rope-like structure that connects muscle to bone) that attach to the fingers. These muscles start at the inside edge of the elbow.

The muscles that straighten the large knuckles of the hand are also forearm muscles that start at the outside edge of the elbow.

There are small muscles within the hand (palm area) that straighten the finger tips and provide fine motor control.

Trigger Finger

The tendons that bend the fingers run through a pulley system within the finger itself. The pulley system is necessary to hold the tendon close to the bones and prevent bowstringing of the tendon. This system maximizes the efficiency, motion, and strength of grip.

Unfortunately, one of the most common repetitive hand injuries occurs within this pulley system. Over the front of the palm, at about the level of where the large knuckles bend, the tendon passes underneath a ligament bridge. If the tendon becomes swollen and inflamed, it does not pass smoothly underneath this ligament. The resulting friction may cause the tendon to “hitch”, get caught, snap, and feel as if it is not working effortlessly. The finger may also “lock” when the swollen tendon pops through the tightness but is unable to pass back underneath. If this happens often enough, or if the finger is painful or the swelling tight enough, the finger can actually begin to contract at the joint and it may become physically stiff. The palm area at the site of this inflammation can also become quite tender and painful. This triggering can occur in any of the fingers and the thumb."    (Continued via BellaOnline, Marji Hajic)    [Ergonomics Resources]

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