The Wrist & Repetitive Strain Injuries

The wrist joins the hand to the forearm. It is able to move forward and back, side-to-side, and in circular movements. This variety of motion allows the hand to reach objects and function in a wide range of motion. In addition, a strong and stable wrist is important during grip activities.The wrist is a complex joint where the two long bones of the forearm meet the eight small carpal bones of the wrist. These carpal bones are essentially arranged in two rows of 4 bones. The eight small wrist bones then meet the five long finger bones in the palm of the hand. Most of the muscles that move the wrist, fingers and thumb are located in the forearm. The tendons (the cords that connect muscle to bone) that bend and straighten the wrist and the fingers must cross through the wrist joint on their way from the elbow towards the hand.Many of the repetitive strain injuries associated with computer work occur at the wrist. In fact, according to the National Occupation Research Agenda for Musculoskeletal Disorders, the most frequently reported upper-extremity musculoskeletal disorders affect the hand and wrist region.

Carpal Tunnel Syndrome is the most commonly diagnosed nerve injury in the arm. The nerves are the power cords for the arms, providing strength to the muscles and sensation to areas of skin. Carpal tunnel syndrome is the compression of the median nerve as the wrist as it passes from the neck to the fingers. Carpal Tunnel Syndrome can cause pain at the base of the hand and in the bulky muscles in the palm right below where the thumb meets the palm. Also, people often say they feel as if they have a tight band around their wrists. Numbness in the thumb, index and middle fingers is common. The pain may feel as if it is traveling up the arm and into the shoulder and neck

Pain where the thumb meets the wrist may be caused by a tendinitis of the muscles that pull the thumb back (as if you were hitchhiking). People who type tensely are prone to developing this tendinitis as they hold their thumbs over the keyboard with tension. Pain at the base of the thumb can also be caused by arthritis in the joint where the long palm bone meets one of the tiny wrist bones of the thumb.

Tendinitis of the wrist and finger flexors (the bending/closing muscles) and extensors (the straightning muscles) and benign ganglion cysts also occur fairly frequently at the wrist.

RSI Prevention

  • Maintain a neutral wrist position.
    • The wrist should be flat in relationship to the forearm; it should not be bent forward or back.
    • For each 15 degrees that the wrist is out of alignment, the pressure on the median nerve increases.
    • The middle finger should be in alignment with the forearm, not angled toward the thumb or the small finger.
    • Wrist supports can provide proper positioning during the night.
    • Do not fight against a wrist support. It is better to remove the brace and perform activities carefully than to wear a brace that prevents necessary movement.
    • Softer, neoprene braces without the rigidity provide support but also allow for some movement and may be a better choice is the task requires wrist movement.
    • Using a wrist brace can cause the body to compensate for loss of motion by moving the elbows differently. Monitor for a shift in pain symptoms in other body areas.
  • Ergonomics
    • Using a split keyboard can align the wrists into a more neutral position.
    • Try a negative tilt of the keyboard where the row of keys closest to you is slightly higher than the row farthest away.
    • The keyboard height should allow the wrists to be neutral while the shoulders are relaxed and the elbows are open slightly greater than 90 degrees.
    • Use the upper arm to manipulate the mouse. Do not activate the mouse by using side-to-side movements of the wrist.
    • The mouse should be located by the keyboard. Do not reach forward to activate the mouse positioned on a different level than the keyboard or positioned out of easy reach.
    • Keep the fingers and thumb relaxed on the keyboard. Use only the minimum necessary force to activate the keys. Do not float the fingers stiffly over the keyboard.
Advertisements

The Fingers & Repetitive Strain Injuries

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.

Arthritis

Other than trigger finger, the most commonly occurring, non-traumatic injuries that occur in the hand tend to be arthritic in nature. Osteoarthritis is caused by wear and tear on the joints. This type of arthritis is not necessarily caused by actual age, but by the mileage (physical stressors) put on the hands over the years. That said, there does seem to be a genetic predisposition towards developing osteoarthritis. Although not directly a repetitive strain injury, arthritic joints can become inflamed and painful with work activity.

Heberden’s nodules are calcifications caused by arthritis at the top joint of the fingers. Bouchard’s nodules are calcifications caused by arthritis at the middle joints of the fingers. These nodules can enlarge the joints and make them painful and unstable. Once the fingers have had joint changes due to the arthritic process, the joint cannot return to its normal state.

With arthritis, the goal is to prevent joint changes by using the hands more gently or in a supportive way. Joint protection techniques, energy conservation techniques, and the use of adaptive equipment are all prevention methods that are associated with the attempt at preventing arthritic joint changes.

Below are some ergonomic techniques that will help prevent the overuse activities that can cause inflammation or trigger finger and the physical stressors that can promote osteoarthritis.

Ergonomics

Avoid sustained gripping or pinching activity. 

  • Use a larger grip if possible;  for example, use pens with a larger barrel such as the Dr. Grip; or use kitchen utensils designed with the Good Grip handles – these are comfortable to use and take the stress off the hands.
  • Do not hold/squeeze the mouse with any force.
  • Rather than holding a book, place it on a surface (such as a bean-bag lap tray) and use the palms to hold it open; or use a weighted book mark to hold it open for you.
  • Use specially designed ergonomic tools with larger and softer grips; check industry catalogs for equipment specific to your type of occupation/work.
  • Use electric tools and gadgets (e.g., can opener) rather than manual tools

Avoid repetitive gripping (opening and closing the hand).

  • Use the lightest touch possible to activate the keyboard.
  • Use rotary scissors or self-opening scissors.
  • Open bottles/jars using the flat palm of the hand rather than a large, finger grip hold.

Pacing Activity

  • If unable to avoid the above activities, take frequent micro-breaks.
  • If possible, rotate activities throughout the day so that you are not performing any one type of hand-intensive activity for any length of time.
  • Do not go home after performing heavy or repetitive work and immediately perform leisure or housework activity that uses similar motions.
  • Use a cold pack for 10 minutes after any activity that causes pain.

Joint Protection and Energy Conservation

The general principles of Joint Protection and Energy Conservation are to avoid a sustained position, use leverage versus a grip when possible, use the largest joint possible for the activity, respect pain, and balance work and rest. Visit Hand Health Resources for detailed information on tendon and joint protection principles.

Exercises

Stretch often.

  • A great stretch for the hand and forearm is to put your arm out in front of you with the palm down then pull the wrist back as if you are saying “stop”. Gently increase the stretch by pulling the wrist and fingers back with the other hand. Hold for 30 seconds.
  • You can also open your hand and spread your fingers open as widely as you can.
  • Gently pull each finger back using the other hand.
  • A great stretch for the smaller muscles within the palm area of the hand – make a hook fist (try to touch the fingers to the very top edge of the palm as if you are holding a briefcase or a grocery bag; the large knuckle should be straight and the two end knuckles of the fingers are hooked into a fist). Maintaining the hook, gently push the large knuckle back into more extension using the other hand.
  • If having hand/finger pain, do not exercise the hand by using grippers or squeezing a ball. Rather, use a rubber band placed at the tip of the fingers for light resistance as you open the hand. This works the opposite muscle groups and creates balance, rather than stressing muscles that are already over-worked.

Neutral Position

  • There is a natural, soft curve to the fingers.
  • Many people are tense sleepers who tend to make a tight fist at night. Try to sleep with the fingers mostly straight. If needed, use a splint such as the Pil-O-Splint to keep the fingers from fisting in the night.