| |||||||||||||
|
Home
|
For other articles and previous issues click here. September 12, 2005 Hand
Jive — The Mechanics of Carpal Tunnel Syndrome Learn about the hand’s complex movements and how a simple exercise could relieve pain. Our body is an amazing symphony of parts that gives us the strength, mobility, and flexibility to do fine movements such as picking up a pin. We are a perfect design of use, and most of us don’t even give it a second thought—until something goes wrong. Medical transcriptionists (MTs) call on muscles that allow them to do precision movements for hours on end every day, repetitively straining the fibers that do the motions necessary to complete the job. These are the same muscles that cause MTs to experience hand/wrist pain and numbness which could end their careers. Every MT is familiar with the term carpal tunnel syndrome, a condition that can severely hamper productivity and cause enough pain to make an MT consider changing professions. However, knowledge of the anatomy of the various muscles MTs use on a daily basis can help prevent, or even reverse, this debilitating condition. Examine your hands. Your fingers are composed of 14 small bones called phalanges that have a small bursa at every joint. The bursa, which looks like a tiny gel capsule and is located between every bone, prevents the bones from rubbing together as they move. This amazing “machine” is driven by a complex, yet simple design of pulleys and levers—muscles and tendons. The thumb—the strongest of the fingers—is really amazing. The area where the thumb meets the palm is called a saddle joint. Its unique shape allows the thumb to move in a circular direction. The thick muscle at the base of the thumb, called opponens pollicis, gives the thumb its power to grip and also plays an important role in carpal tunnel syndrome. Your wrists are even more of an amazing piece of engineering: • Eight small bones called carpal bones lie next to each other. The carpal bones—and a ligament that crosses over them like a bridge—create the carpal tunnel of the wrist. • The tendons of the flexor muscles on the under side of your forearm pass through the tunnel, bending your wrist and curling your fingers into a fist. • The tendons of the extensor muscles on the upper side of your forearm attach to the carpal bones on the top of your hand, and also to your fingers, enabling you to open your hand from the clenched position. The carpal bones, directed by the pull of various muscles attaching to them, give you the ability to move your hands in a full circle, bend, turn, and even support your weight on your palms. When the nerve is trapped within the carpal tunnel, usually because a muscle is having an impact on the bones or tendons that affect the dimensions of the tunnel, you experience the pain and numbness that is carpal tunnel syndrome. A muscle is a large grouping of individual fibers that work independently to pull on a tough fiber called a tendon. The tendon has no ability to move on its own and simply connects the muscle to the bone at a specific spot, usually just across from a joint. The muscle contracts and pulls on the tendon, which is attached to the bone, making the joint move. Muscles always pull, never push. This is an important concept to understand when seeking to find the source of a painful joint. Nerves give the body the ability to have sensation and also direct the muscles to contract and release, creating movement. When a nerve is being impinged by any other structure, you will feel tingling or numbness at the end of the nerve. You could even lose strength because the muscle is receiving an incomplete message, similar to the way a poor electrical signal will cause static on a radio. In the case of the hand and wrist, the nerves begin in the neck, pass under a tendon in the front of your shoulder, go down your arm and through your wrist (the carpal tunnel), and end in your hand. The nerves that give feeling to your hands all begin in your neck, behind a muscle called scalenes, from which problems emanate. The scalenes bring your head down, a movement you perform all day long. As you hold your head in the same position for hours at a time, the muscle actually shortens due to a phenomenon called muscle memory. When you lift your head, the now-shorter muscle presses on the bundle of nerves called the brachial plexus. The phenomenon, dubbed thoracic outlet syndrome, causes your hand to go numb. Another element of carpal tunnel syndrome is known as the Gate Theory, a term coined during World War II when physicians realized that amputees were suffering pain in limbs that no longer existed. The common phrase is phantom limb. The Gate Theory explains that when a nerve has pressure anywhere along its length, you will have numbness at the endpoint. You are experiencing the Gate Theory when you feel your fingers or wrist go numb as you work. In the case of the nerves of the neck that go down to your arm and hand, an impingement will cause numbness in your fingers. Anatomy of the Neck and Arm • You hold your head down as you are typing or reading, contracting the scalene muscles of the neck and therefore putting pressure on the brachial plexus. • The pectoralis minor muscle of your chest is responsible for pulling on your shoulder blade, allowing your arm to go forward so you can place your hands in front of you. The tendon pulls down on the coracoid process of the scapula and presses directly into the median nerve as it passes under the bone, referring numbness to the thumb and first two fingers. If the pectoralis minor is severely contracted, it will also entrap the axillary artery and the ulnar nerve, causing restricted circulation and numbness in the fourth and fifth digits. • The median nerve then travels under the biceps, with possible pressure being placed on it by this strong muscle. • The flexor muscles, which are located on the under side of your forearm, give a two-pronged impact on the median nerve. When contracting to close your hand or bend your wrist, the flexors are pressing down on the median nerve as it travels through the muscle fibers. By pulling hard on the flexor tendons to hold heavy items, the taut tendons impinge on the nerve as all the structures pass through the carpal tunnel. • The extensor muscles insert into the carpal bones on the top of the hand. As the extensors become contracted, they can put sufficient pressure on the carpal bones so they will be pulled out of alignment. This causes the carpal tunnel to change dimension and put pressure directly onto the median nerve. • The opponens pollicis muscle draws your thumb in toward your palm. You hold this muscle tightly contracted as you lift and carry various objects. Even just holding onto your car’s steering wheel puts tension in the muscle. Ultimately, the muscle fibers shorten. Since the muscle originates on the bridge over the carpal tunnel (the flexor retinaculum), it causes the ligament (bridge) of the carpal tunnel to become taut and puts pressure directly on the median nerve. The last three situations will cause you to have a false-positive electromyogram reading. The nerve is definitely being impinged within the carpal tunnel. However, the key question is, “Why?” Most physicians don’t address the why and therefore the muscles are ignored as a possible cause of the problem. Muscles are often overlooked when diagnosing conditions such as carpal tunnel syndrome, ulnar neuropathy, trigger finger, or any other repetitive strain injury. Yet, by simply locating the spasms that have formed in the muscles during the repetitive strain and then releasing the trigger points, relief is immediate. As each muscle is treated to release tension in the fibers, the strain is removed from the joint. Also, eliminating the tension in the muscles will remove the pressure from the nerves. As the nerves are freed from pressure, they stop sending incomplete messages and they also stop tingling or feeling numb. This logical solution to a complex set of conditions may restore your healthy, flexible, and pain-free hands. — Zev M. Cohen, MD, is the medical director of both centers and of Healthcheck Medical Facility. He is a recognized expert in the field of carpal tunnel syndrome and repetitive strain injuries. — Julie Donnelly, BS, LMT, is the therapeutic director of the Julstro Muscular Therapy Center and the Carpal Tunnel Treatment Center, in Nanuet, N.Y. |
 |
3801 Schuylkill Rd • Spring City, PA 19475 Publishers of For the Record All rights reserved. |