Repetitive Motion Disorders
Repetitive motion disorders
Repetitive motion disorders are a group of syndromes caused by injuries to muscles, tendons, nerves, or blood vessels from repeated or sustained exertions of different body parts. Most of these disorders involve the hands, arms, or neck and shoulder area. Other names for repetitive motion disorders include repetitive trauma disorders, repetitive strain injuries (RSIs), overuse syndrome, work-related disorders, and regional musculoskeletal disorders.
Repetitive motion disorders are characterized by pain , loss of strength and coordination, numbness or tingling, and sometimes redness or swelling in the affected area. The symptoms come on gradually, and are usually relieved temporarily by resting or avoiding the use of the affected body part. Repetitive motion disorders are commonly thought of as work related, but they can occur as a result of academic, leisure-time, or household activities as well.
The demographics of repetitive motion disorders vary according to the specific syndrome. As of 2004, about 50% of all industrial injuries in the United States and Canada are attributed to overuse disorders. Professional athletes, dancers, and musicians experience one of these disorders at a much higher percentage at some point in their careers. The Institute of Medicine's 2001 study, Musculoskeletal Disorders and the Workplace, reported that nearly a million American workers were treated in 1999 for work-related pain or impaired function in the arms, hands, or back. Other experts estimate that overuse injuries cost the United States economy between $27 million and $45 million every year.
Race is not known to be a factor in repetitive motion disorders. Gender has a significant effect on the demographics of some disorders, but it is not clear whether the higher incidence of some disorders in women reflects different occupational choices for men and women, or whether it reflects biological differences. For example, de Quervain's syndrome is a common overuse disorder in women involved with childcare, because repeated lifting and carrying of small children places severe strains on the wrist joint. On the other hand, some researchers think that the greater frequency of this disorder in women is related to the effects of female sex hormones on connective tissue, as women's ligaments are slightly looser during pregnancy and at certain points in the menstrual cycle.
Some repetitive motion disorders appear to be age related. Carpal tunnel syndrome is more common in middle-aged than in younger women, and trigger finger is most common in people aged 55–60. It is not yet known whether the widespread use of computers in the workplace will change the age distribution of repetitive motion disorders as present workers grow older.
Causes and symptoms
SOFT TISSUE DAMAGE Repetitive motion disorders are the end result of a combination of factors. One basic cause of repetitive motion disorders, however, is microtraumas, which are tiny damages to or tears in soft tissue that occur from routine stresses on the body or repeated use of specific muscles and joints. When microtraumas are not healed during sleep or daily rest periods, they accumulate over time, causing tissue damage, inflammation, and the activation of pain receptors in peripheral nerves.
NERVE COMPRESSION Some repetitive motion disorders are associated with entrapment neuropathies, which are functional disorders of the peripheral nervous system . In an entrapment neuropathy, a nerve is damaged by compression as it passes through a bony or fibrous tunnel. Carpal tunnel syndrome, de Quervain's syndrome, ulnar nerve syndrome, and thoracic outlet syndrome are examples of entrapment neuropathies.
Compression damages peripheral nerves by limiting their blood supply. Even slight pressures on a nerve can limit the flow of blood through the smaller blood vessels surrounding the nerve. As the pressure increases, transmission of nerve impulses is affected and the patient's sensation and coordination are affected, with further increases in nerve compression producing greater distortion of sensation and range of motion.
TECHNOLOGICAL AND SOCIAL FACTORS Economic and social factors that have affected people's occupations and leisure-time activities over the past two centuries have contributed to the increase in repetitive motion disorders. The Industrial Revolution led to increased job specialization, which meant that more and more workers were employed doing one task repeatedly rather than many different tasks. In addition, industrialization brought about the invention of complex tools and machinery that affect the tissues and organs of the human body in many ways. The high levels of psychological and emotional tension in modern life also contribute to repetitive stress injuries by increasing the physical stresses on muscles and joints.
INDIVIDUAL RISK FACTORS Risk factors that are associated with repetitive stress injuries include the following:
- Awkward or incorrect body postures. Each joint in the body has a position within its range of motion in which it is least likely to become injured. This position is called the neutral position. Any deviation from the neutral position puts increased strain on body tissues. Inadequate work space, using athletic or job-related equipment that is not proportioned to one's height, or improper technique are common reasons for RSIs related to body posture.
- Use of excessive force to perform a task. Pounding on piano keys or hammering harder than is necessary to drive nails are examples of this risk factor.
- Extended periods of static work. This type of work requires muscular effort, but no movement takes place. Instead, the muscles contract, preventing blood from reaching tissues to nourish the cells and carry away waste products. Over time, the muscle tissue loses its ability to repair microtraumas. Examples of static work include sitting at a desk for hours on end or holding the arms over the head while painting a ceiling.
- Activities that require repetitive movements. Assembly-line work and word processing are examples of job-related repetitive motion. In addition, such leisure-time activities as knitting, embroidery, gardening, model construction, golf or tennis, etc. can have the same long-term effects on the body as work-related activities.
- Mechanical injury. Tools with poorly designed handles that cut into the skin or concentrate pressure on a small area of the hand often contribute to overuse disorders.
- Vibration. There are two types of vibration that can cause damage to the body. One type is segmental vibration, which occurs when the source of the vibration affects only the part of the body in direct contact with it. An example of segmental vibration is a dentist's use of a high-speed drill. Overexposure of the hands to segmental vibration can eventually damage the fingers, leading to Raynaud's phenomenon. The second type is whole-body vibration, which occurs when the vibrations are transmitted throughout the body. Long-distance truckers and jackhammer operators often develop back injuries as the result of long-term whole-body vibration.
- Temperature extremes. Cold temperatures decrease blood flow in the extremities, while high temperatures lead to dehydration and rapid fatigue . In both cases, blood circulation is either decreased or redirected, thus slowing down the process of normal tissue recovery.
- Psychological stress. People who are worried, afraid, or angry often carry their tension in their neck, back, or shoulder muscles. This tension reduces blood circulation in the affected tissues, thus interfering with tissue recovery. In addition, emotional stress has been shown to influence people's perception of physical pain; workers who are unhappy in their jobs, for example, are more likely to seek treatment for work-related disorders.
- Structural abnormalities. These abnormalities include congenital deformities in bones and muscles, changes in the shape of a bone from healed breaks or fractures, bone spurs, and tumors. Overdevelopment of certain muscle groups from athletic workouts may result in entrapment neuropathies in the shoulder area.
- Other systemic conditions or diseases. People with such disorders as rheumatoid arthritis (RA), joint infections, hypothyroidism, or diabetes are at increased risk of developing repetitive motion disorders. Pregnancy is a risk factor for overuse disorders affecting the hands because of the increased amount of fluid in the joints of the wrists and fingers.
The symptoms of repetitive motion disorders include the following:
- Pain. The pain of an RSI is typically felt as an aching sensation that gets worse if the affected joint(s) or limb is moved or used. The pain may be severe enough to wake the patient at night.
- Paresthesias. Paresthesia refers to an abnormal sensation of pricking, tingling, burning, or "insects crawling beneath the skin" in the absence of an external stimulus.
- Numbness, coldness, or loss of sensation occur in the affected area.
- Clumsiness, weakness, or loss of coordination result.
- Impaired range of motion or locking of a joint occur.
- Popping, clicking, or crackling sounds in a joint are experienced.
- Swelling or redness in the affected area are observed.
History and physical examination
The diagnosis of a repetitive motion disorder begins with taking the patient's history, including occupational history. The doctor will ask about the specific symptoms in the affected part, particularly if the patient suffers from rheumatoid arthritis, diabetes, or other general conditions as well as overuse of the joint or limb.
The next step is physical examination of the affected area. The doctor will typically palpate (feel) or press on the sore area to determine whether there is swelling as well as pain. He or she will then perform a series of maneuvers to evaluate the range of motion in the affected joint(s), listen for crackles or other sounds when the joint is moved, and test for weakness or instability in the limb or joint. There are simple physical tests for specific repetitive motion disorders. For example, the Finkelstein test is used to evaluate a patient for de Quervain's syndrome. The patient is asked to fold the thumb across the palm of the affected hand and then bend the fingers over the thumb. A person with de Quervain's will experience sharp pain when the doctor moves the hand sideways in the direction of the elbow. Tinel's test is used to diagnose carpal tunnel syndrome. The doctor gently taps with a rubber hammer along the inside of the wrist above the median nerve to see whether the patient experiences paresthesias.
Laboratory tests of blood or tissue fluid are not ordinarily ordered unless the doctor suspects an infection or wishes to rule out diabetes, anemia, or thyroid imbalance.
Imaging studies may be ordered to rule out other conditions that may be causing the patient's symptoms or to identify areas of nerve compression. When surgery is being planned, x rays may be helpful in identifying stress fractures, damage to cartilage, or other abnormalities in bones and joints. Magnetic resonance imaging (MRI) can be used to identify injuries to tendons, ligaments, and muscles as well as areas of nerve entrapment.
The most common electrodiagnostic tests used to evaluate repetitive motion disorders are electromyography (EMG) and nerve conduction studies (NCS). In EMG, the doctor inserts thin needles in specific muscles and observes the electrical signals that are displayed on a screen. This test helps to pinpoint which muscles and nerves are affected by pain. Nerve conduction studies are done to determine whether specific nerves have been damaged. The doctor positions two sets of electrodes on the patient's skin over the muscles in the affected area. One set of electrodes stimulates the nerves supplying that muscle by delivering a mild electrical shock; the other set records the nerve's electrical signals on a machine.
A mild repetitive motion disorder may be treated by a primary care physician. If conservative treatment is ineffective, the patient may be referred to an orthopedic surgeon or neurosurgeon for further evaluation and surgical treatment. Patients whose disorders are related to job dissatisfaction, or who have had to give up their occupation or favorite activity because of their disorder, may benefit from psychotherapy.
Physical therapists and occupational therapists are an important part of the treatment team, advising patients about proper use of the injured body part and developing a home exercise program. Some patients benefit from having their workplace and equipment evaluated by the occupational therapist or an ergonomics expert. Professional athletes, dancers, or musicians usually consult an expert in their specific field for evaluation of faulty posture or technique.
Conservative treatment for overuse injuries typically includes:
- Resting the affected part. Complete rest should last no longer than two to three days, however. What is known as "relative rest" is better for the patient because it maintains range of motion in the affected part, prevents loss of muscle strength, and lowers the risk of "sick behavior." Sick behavior refers to using an injury or illness to gain attention or care and concern from others.
- Applying ice packs or gentle heat.
- Oral medications. These may include mild pain relievers (usually NSAIDs); amitriptyline or another tricyclic antidepressant; or vitamin B6.
- Injections. Corticosteroids may be injected into joints to lower inflammation and swelling. In some cases, local anesthetics may also be given by injection.
- Splinting. Splints are most commonly used to treat overuse injuries of the hand or wrist; they can be custom-molded by an occupational therapist.
- Ergonomic corrections in the home or workplace. These may include changing the height of chairs or computer keyboards; scheduling frequent breaks from computer work or musical practice; correcting one's posture; and similar measures.
- Transcutaneous electrical nerve stimulation (TENS). TENS involves the use of a patient-controlled portable device that sends mild electrical impulses through injured tissues via electrodes placed over the skin. It is reported to relieve pain in 75–80% of patients treated for repetitive motion disorders.
Repetitive motion disorders are treated with surgery only when conservative measures fail to relieve the patient's pain after a trial of six to 12 weeks. The most common surgical procedures performed for these disorders include nerve decompression, tendon release, and repair of loose or torn ligaments.
Complementary and alternative (CAM) treatments
CAM treatments that have been shown to be effective in treating repetitive motion disorders include:
- Acupuncture . Studies funded by the National Center for Complementary and Alternative Medicine (NCCAM) since 1998 have found that acupuncture is an effective treatment for pain related to repetitive motion disorders.
- Sports massage, Swedish massage, and shiatsu.
- Yoga and tai chi. The gentle stretching in these forms of exercise helps to improve blood circulation and maintain range of motion without tissue damage.
- Alexander technique. The Alexander technique is an approach to body movement that emphasizes correct posture, particularly the proper position of the head with respect to the spine. It is often recommended for dancers, musicians, and computer users.
- Hydrotherapy. Warm whirlpool baths improve circulation and relieve pain in injured joints and soft tissue.
Recovery and rehabilitation
Recovery from a repeated motion disorder may take only a few days of rest or modified activity, or it may take several months when surgery is required.
Rehabilitation is tailored to the individual patient and the specific disorder involved. Rehabilitation programs for repetitive motion disorders focus on recovering strength in the injured body part, maintaining or improving range of motion, and learning ways to lower the risk of re-injuring the affected part. Professional musicians, dancers, and athletes require highly specialized rehabilitation programs.
As of early 2004, there were four clinical trials related to repetitive motion disorders sponsored by the National Institutes of Health (NIH) that are recruiting subjects. One is a comparison of amitriptyline (an antidepressant medication) and acupuncture as treatments for CTS. A second study will evaluate the effectiveness of a protective brace in preventing overuse disorders associated with hand-held power tools. The third study will evaluate the effects of fast-paced assembly-line work on the health of rural women. The fourth study is a comparison of surgical and nonsurgical treatments for CTS.
The prognosis for recovery from repetitive motion disorders depends on the specific disorder, the degree of damage to the nerves and other structures involved, and the patient's compliance with exercise or rehabilitation programs. Most patients experience adequate pain relief from either conservative measures or surgery. Some, however, will not recover full use of the affected body part and must change occupations or give up the activity that produced the disorder.
National Research Council and Institute of Medicine (IOM). Musculoskeletal Disorders and the Workplace: Low Back and Upper Extremities. Washington, DC: National Academy Press, 2001.
"Neurovascular Syndromes: Carpal Tunnel Syndrome." The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.
"Tendon Problems: Digital Tendinitis and Tenosynovitis." The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.
Andersen, J. H., J. F. Thomsen, E. Overgaard, et al. "Computer Use and Carpal Tunnel Syndrome: A 1-Year Follow-Up Study." Journal of the American Medical Association 289 (June 11, 2003): 2963–2969.
Fuller, David A., MD. "Carpal Tunnel Syndrome." eMedicine October 15, 2003 (March 23, 2004). <http://www.emedicine.com/orthoped/topic455.htm>.
Hogan, K. A., and R. H. Gross. "Overuse Injuries in Pediatric Athletes." Orthopedic Clinics of North America 34 (July 2003): 405–415.
Kaye, Vladimir, MD, and Murray E. Brandstater, PhD. "Transcutaenous Electrical Nerve Stimulation." eMedicine January 29, 2002 (March 23, 2004). <http://www.emedicine.com/pmr/topic206.htm>.
Kern, R. Z. "The Electrodiagnosis of Ulnar Nerve Entrapment at the Elbow." Canadian Journal of Neurological Sciences/Journal canadien des sciences neurologiques 30 (November 2003): 314–319.
Kryger, A. I., J. H. Andersen, C. F. Lassen, et al. "Does Computer Use Pose An Occupational Hazard for Forearm Pain; from the NUDATA Study." Occupational and Environmental Medicine 60 (November 2003): e14.
Leclerc, A., J. F. Chastang, I. Niedhammer, et al. "Incidence of Shoulder Pain in Repetitive Work." Occupational and Environmental Medicine 61 (January 2004): 39–44.
Meals, Roy A., MD. "De Quervain Tenosynovitis." eMedicine April 15, 2002 (March 23, 2004). <http://www.emedicine.com/orthoped/topic482.htm>
Nourissat, G., P. Chamagne, and C. Dumontier. "Reasons Wh Musicians Consult Hand Surgeons." [in French] Revue de chirurgie orthopÈdique et rÈparatrice de l'appareil moteur 89 (October 2003): 524–531.
Stern, Mark, MD, and Scott P. Steinmann, MD. "Ulnar Nerve Entrapment." eMedicine 8 January 2004 (March 23, 2004). <http://www.emedicine.com/orthoped/topic574.htm>.
Strober, Jonathan B., MD. "Writer's Cramp." eMedicine January 18, 2002 (March 23, 2004). <http://www.emedicine.com/neuro/topic614.htm>.
Strum, Scott, MD. "Overuse Injury." eMedicine September 14, 2001 (March 23, 2004). <http://www.emedicine.com/pmr/topic97.htm>.
Tallia, A. F., and D. A. Cardone. "Diagnostic and Therapeutic Injection of the Wrist and Hand Region." American Family Physician 67 (February 15, 2003): 745–750.
Valachi, B., and K. Valachi. "Mechanisms Leading to Musculoskeletal Disorders in Dentistry." Journal of the American Dental Association 134 (October 2003): 1344–1350.
National Institute of Neurological Disorders and Stroke (NINDS). NINDS Thoracic Outlet Syndrome Information Page. (March 23, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/thoracic_doc.htm>.
American Academy of Orthopaedic Surgeons (AAOS). 6300 North River Road, Rosemont, IL 60018-4262. (847) 823-7186 or (800) 346-AAOS; Fax: (847) 823-8125. <http://www.aaos.org>.
National Institute for Occupational Safety and Health (NIOSH). Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333. (404) 639-3534 or (800) 311-3435. <http://www.cdc.gov/niosh/homepage.html>.
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) Information Clearinghouse, National Institutes of Health. 1 AMS Circle, Bethesda, MD 20892-3675. (301) 495-4844 or (877) 22-NIAMS; Fax: (301) 718-6366. [email protected]. <http://www.niams.nih.gov>
National Institute of Neurological Disorders and Stroke (NINDS). 9000 Rockville Pike, Bethesda, MD 20892. (301) 496-5751 or (800) 352-9424. <http://www.ninds.nih.gov>.
Rebecca J. Frey, PhD