I just found Microsoft has a fairly good guide on ergonomics dealing with computers. It is located here.
Carpal tunnel syndrome (CTS) is defined as pain and abnormal sensations of the hand in the area of distribution of the median nerve. It is a common, painful condition caused by compression of the median nerve at the wrist. CTS can lead to malfunction of the hand and wrist and tissue atrophy and death. CTS occurs three times more often in women than in men and is most common in the 40 to 70 year old age group. It is most often found in the dominant hand but is sometimes found bilaterally with the more severe condition found in the dominant hand.
CTS is most prevalent in the occupational setting. It is common for data processors, carpenters, assembly-line workers, meat processors, dental hygienist, hairdressers, truck drivers, and typist. Contributing factors are repetitive, forceful hand and arm movements (especially flexion and extension); sustained, awkward hand and wrist positions; vibration; and low temperature.
A person should expect CTS when there is pain, tingling, or numbness in the first three digits of the hand. It will occur most often at night and may be accompanied by clumsiness and loss of function.
The treatment for carpal tunnel syndrome in its early stages includes splinting, nonsteroidal anti-inflamatory drugs (NSAIDs), rehabilitation, pyridxine therapy, and corticosteroid injection. In late stages or in advanced cases of CTS a surgical procedure called a transverse carpal ligament release is performed.
There are eight small bones in the hand (wrist). These eight bones are known as the carpal bones. The rigid carpal bones intimately articulate with each other and are held together by ligamentous attachments. Together they form the floor and walls of the carpal groove (the bottom and sides of the carpal tunnel). The transverse carpal ligament also known as the flexor retinaculum is a tough, fibrous sheet which acts as the roof of the carpal groove forming the top of the carpal tunnel. Ten structures pass through this carpal tunnel: nine tendons of forearm muscles and the median nerve.
The palmar cutaneous branch of the medial nerve should also be mentioned here. It is not located in the carpal canal but just superficial to the flexor retinaculum. It is of importance because if care is not taken during surgery it is often times severed leaving no sensation in the palm of the hand.
The carpal tunnel is a fixed space with finite volume. Any condition or injury that either increases the volume of the contents of the tunnel or decreases the size of the tunnel will increase the pressure in the tunnel which could result in median nerve compression and venous and arterial obstruction.
Compression of the median nerve can be attributed to a number of things, some being hereditary, others relating to trauma. The most common cause of CTS is the thickening or fibrosis of the synovium which surrounds the tendons. Carpal tunnel syndrome commonly develops in persons whose activities include repetitive wrist motions involving flexion and extension; forceful hand and arm movements; sustained, awkward hand and wrist positions; vibration; and low temperature.
Research has shown that the following conditions may increase the risks of getting CTS.
1. Systemic diseases--such as rheumatoid arthritis, acromegaly, gout, diabetes, myxoedema, ganglion formation, and certain forms of cancer.
2. Congenital defects--including bony protrusions into carpal tunnel, anomalous muscles extending into or originating in the carpal tunnel, and the shape of the median nerve.
3. Wrist shape--recent studies of carpal tunnel syndrome patients made with the use of computerized axial tomography (CAT scanner) and standard engineering calipers suggested that there is an association between relatively square wrists and idiopathic carpal tunnel syndrome.
4. Acute trauma--Median nerve injury inside the carpal tunnel can be produced by a blow to the wrist, laceration, burn, or other acute wrist injury.
5. Pregnancy, oral contraceptives, menopause, and gynecological surgery--Because all are uniquely female-oriented, they may, in some cases, contribute to a disproportionately high incidence rate of the syndrome in females.
6. Ergonomic factors--These include frequent deviation from the neutral wrist position, frequent use of the "pinch" grasping hand position, and repetitive hand movements.
Some other injuries that could facilitate CTS are a colles' fracture and a anterior lunate dislocation changing the anatomy and shape of the carpal tunnel. Many times the exact cause of CTS is not known. Every effort should be made during the evaluation to determine the cause so that the proper treatment can be given to alleviate the problem.
Symptoms of carpal tunnel syndrome usually begin pain or abnormal sensation (numbness, tingling) in the hand and wrist. More specifically on the thumb and first two fingers. As the disorder continues, pain, numbness, and tingling intensify in these same areas. The pain is described as burning, aching, and prickling. The pain and numbness may spread up the forearm and eventually go as far as the shoulder. The pain and numbness are most severe at night often causing patients to wake after several hours of sleep. Relief of night pain can often be obtained by shaking or rubbing the hand and wrist. The patient will often complain of clumsiness in performing hand activities that require small and exact coordination. Many CTS sufferers also experience loss of grip strength, and difficulty in doing simple tasks such as turning a key, opening a bottle, or writing. The dominant hand is usually involved but there are many cases where CTS occurs bilaterally. When the disease occurs bilaterally the dominant hand usually has more severe symptoms.
Anyone suffering from what they think may be CTS should consult a physician for a complete evaluation. This evaluation may include one or more of the following tests.
1. Phalen's wrist flexor test. With the elbows on the table and the forearms vertical, the patient holds both wrists in complete but unforced flexion. If numbness or tingling are produced in areas listed above within 60 seconds the test is positive. Wrist extension should bring relief.
2. Tinel's sign test. This test is also known as the median nerve percussion test. The examiner taps over the wrist area along the course of the median nerve using a reflex hammer. A positive sign is elicited if the patient reports a "pins and needles" feeling in the thumb or first two fingers with each tap.
3. Tourniquet test. A blood pressure cuff is applied above the elbow and inflated above systolic blood pressure. In a normal person (no CTS), a tingling sensation develops over the ulnar aspect of the hand after two to three minutes and tingling in the thumb and first two fingers after ten minutes. If the person does have CTS there will be pain and numbness in the thumb and first two fingers within 30 to 60 seconds.
If these tests give positive results electrodiagnostic tests should be done to confirm the diagnosis.
Electromyography and MRIs are both used to help diagnose CTS. Both should be utilized before surgery is perscribed.
Carpal tunnel can be treated operatively or nonoperatively. The first step in treating CTS is to treat that which is causing the elevated pressures in the carpal tunnel. This may include things such as fixing a fracture, giving antibiotic for an infection, or splinting to prevent the movements of flexion and extension. Only after the cause of the syndrome has been established can effective treatment begin. Otherwise only the symptoms are being treated. As a general rule, conservative therapy can be used whenever there is no muscle weakness or atrophy. Conservative therapy can include one or more of five different things.
The first step in treatment is to put the wrist in a splint in a neutral position. Splints can be bought by prescription in orthopedic and medical supply houses. Many therapist prefer to make their own using lightweight material which they can custom fit. The lighter, better fitting splints that can be made offer better patient compliance. This splinting is usually done for a period of three weeks both day and night and pending successful results an additional three weeks of night only splinting. Splinting has proved very successful.
The second thing that can be done is to start physical therapy which is directed at decreasing swelling, reduction of scar tissue, and decreasing pain. These things can be accomplished with exercise regimens and a wide variety of modalities such as fluidotherapy, TENS, high-volt galvanic stimulation, iontophoresis, ice, and ultrasound.
The third step is the administration of pyridoxine (vitamin B6). Although there have been no accurate studies to prove this theory it is used quite often due to the fact that there are no side effects. Some of the studies show a success rate greater than 68%. Due to the reported success rate and having no side effects it should be used in cases of CTS. 100mg orally twice daily for a period of 12 weeks seems to be most effective.
The use of Nonsteroidal anti-inflammatory drugs (NSAIDs) are recommended for pain control as well as the anti-inflammatory response. This keeps the patient more pain free and comfortable and also decreases the pressure in the canal by decreasing swelling.
The last treatment that can be done which still fits under the conservative heading is the injection of a corticosteroid into the carpal tunnel to decrease swelling. It has been proven that this is a good option for short term relief yet there is controversy over its effectiveness over a longer period of time. Upon injection there will be early numbness which will last for a few hours. This will slowly subside and the symptoms of CTS will recur and usually will be significantly worse for 24 to 48 hours following the injection. After the 24 to 48 hour period the full effect of the injection should be felt and relief obtained.
When the methods of conservative therapy have failed or in severe cases involving muscle loss one must look at the surgical process of the transverse carpal ligament release. This can be done with the use of local anesthetic, regional nerve block, or general anesthetic. The surgical procedure is simple and fast and in most cases the relief of pain is immediate and permanent. A qualified hand surgeon should perform this release and care should be taken to dissect out the palmar cutaneous branch of the medial nerve to avoid it being severed. Care should be taken by the surgeon to completely visualize all structures before any incision is made so as to protect important structures. The most common error in this surgery is that the flexor retinaculum in not transected in its entirety. In these cases a second surgery is needed to complete the transection. In most patients the surgery is successful and eliminates any further signs and symptoms of carpal tunnel syndrome.
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