00954543 /96 $0.00 ORTHOPEDICS + .20 OVERUSE SYNDROMES OF THE HAND AND WRIST Mary E. Verdon, MD Overuse syndrome is a term used synonymously with repetitive strain injury and cumulative trauma disorder. Since 1989, these syndromes have accounted for more than half of all occupational illnesses reported in the United States. This increase is attributed to improved accuracy of reporting, increased awareness of the problem by employees and employers, advances in diagnosis, and the accelerating pace of work. The term cumulative indicates that these injuries occur during periods of weeks, months, or years as the result of repeated stresses on a particular anatomic part. Persistent or recurrent musculoskeletal pain, without immediate traumatic cause within the previous 6 weeks, suggests the diagnosis of overuse Overuse syndromes typically affect the upper body, including the neck, shoulder, elbow, wrists, and hands. The wrist is a common site of overuse syndromes, and patients frequently present with work-related carpal tunnel syndrome. The incidence of carpal tunnel syndrome in the general population is less than 1%;however, it can occur in up to 15% of workers at risk.34In those settings in which workers are at risk for carpal tunnel syndrome, tendinitis is far more common, occurring at least twice the rate of carpal tunnel Certain individuals are at higher risk for overuse syndromes because of predisposing systemic conditions. These include diabetes, rheumatoid arthritis, gout, calcium pyrophosphate deposition, hypothyroidism, Dupuytren’s contracture, collagen vascular disease, tuberculosis, atypical mycobacterium, and fungal infection^.^^ Anomalous muscle bellies and tendinous interconnections can be contributing factors to overuse synd r o m e ~ . Preemployment ~* screening is not recommended because there From the Department of Family and Community Medicine, University of California, San Francisco, School of Medicine, San Francisco, California PRIMARY CARE VOLUME 23 NUMBER 2 *JUNE 1996 9 305 306 VERDON are no screening techniques that reliably predict which individuals will develop overuse syndromes of the upper extremity and such screening could be considered dis~riminatory.~~ PATHOPHYSIOLOGY Overuse is defined as a level of repetitive microtrauma sufficient to overwhelm the tissues' ability to adapt. Microtrauma refers to damage at the microscopic or molecular level. It is possible for a one-time excessive stress to cause microtrauma, but usually it results from repetitive loading episodes at a force or elongation level well within the physiologic range.7 Most musculotendinous structures are able to adapt to applied loads. Bone increases its load-bearing capabilities according to Wolff's law, in which increased growth occurs in response to external stress. Muscle increases in size and strength by hypertrophy of the existing fibers. Tendon and ligament strengths are enhanced by an increase in collagen content, collagen cross-linking, and mucopolysaccharide content. Unfortunately, this adaptive process takes time, and impatient athletes or new workers increase the distance or load attempted too quickly and cause overload of the musculotendinous unit.30 Tendons are relatively avascular structures whose gliding is facilitated by a surrounding layer of tenosynovium, which is subject to inflammation from a variety of causes. Microtrauma in overuse syndromes is one cause. Gliding over an abnormal prominence such as an osteophyte or a malunited fracture commonly gives rise to irritation. Abnormal softtissue-restraining structures such as the extensor retinaculum or an aberrant tendon also may incite inflammation around the edge in which the tendon must glide.43Tendinitis is defined as inflammation of tendons and the tendon-muscle attachment. Histologically, the inflammatory process primarily affects the synovium rather than the tendon; therefore, the term tenosynovitis is used predominantly in this article.42 The course and prognosis of overuse syndromes are understood best by reviewing the pathologic stages of the inflammatory response3o: 1. The inflammatory stage starts immediately after injury, when vasoactive and chemotactic factors are released. These factors promote vascular ingrowth, increase vascular permeability, and encourage an invasion of inflammatory cells. This stage lasts 48 hours to 2 weeks unless there is further injury, in which case it can be prolonged. The exact site of injury can be masked by inflammation of adjacent tissues. Clinical symptoms include pain, swelling, erythema, warmth, and tenderness. 2. The proliferative stage lasts 1to 2 weeks and is a time when collagen and ground substances are produced. The area is highly susceptible to injury during this stage. Only a low-level activity is encouraged, and movement should be limited to a pain-free range. 3. During the maturation stage, further healing is completed during 6 to 12 weeks. Full unrestricted activity should be avoided until OVERUSE SYNDROMES OF THE HAND AND WRIST 307 this process is complete. Flexibility exercises, isometric contractions, and a slow return to resistive exercises are safe so long as pain is not produced. If the athlete or worker pushes too hard or too fast, the inflammatory response is reinitiated. Fibrosis results from continued or repeated release of inflammatory products leading to thick, unyielding, restrictive tendon sheaths or retinacular tunnels. The result of this process, stenosing tenosynovitis, usually requires surgical treatment. Clinically, three stages can be seen with overuse syndromes.16First, there is a condition of fatigue characterized by increased aching and tiredness during the work shift or activity. The symptoms usually subside with overnight rest. This stage should be construed as a warning to protect the affected body part. In the second stage, there is persistence of the discomfort into the next day, with earlier onset of fatigue during the workday. It is a sign that injury is developing, and steps should be taken immediately to reduce the strain on the affected part. The affected part should be rested more frequently, and the work process or sport should be redesigned to avoid the offending motion. This clinical stage corresponds to repeated injury and release of inflammatory products. In the third clinical stage of overuse syndromes, chronic aching, fatigue, and weakness persist despite rest of the affected part. This is a warning that fibrosis can be developing. Key occupational risk factors for developing overuse syndromes include repetition, high force, awkward joint posture, direct pressure, vibration, and prolonged constrained posture.10,2s Repetition. Highly repetitive work may damage tendons directly through repeated stretching and elongation. Such work increases the likelihood of fatigue and decreases the opportunity for tissues to recover. Jobs that have a basic cycle time of 30 seconds or less and in which more than 50% of the work cycle involves similar patterns of upper extremity motion are considered to be repetitive. High force. Forceful hand exertions during work activities increase the risk for overuse syndromes. These include carrying or using heavy tools, employing knives or scissors to cut, using wrenches and pneumatic tools to tighten bolts, and using one's fingers or hands to shape or surface finish materials and parts. Wearing gloves may reduce strength by 20% to 30%. Slippery objects and pinch grasps can increase the amount of force needed. Awkward joint posture. Awkward upper extremity postures increase the risk of overuse syndromes. These include pinch grips, wrist deviations such as flexion or extension and ulnar or radial bending, forearm pronation or supination, and shoulder elevation or abduction. Wrist deviations from the neutral position show significant losses in grip strength, which increase the amount of force required. Direct pressure. Local mechanic stresses are caused by physical contact between soft body tissues and an object or tool. These occur when a body part is in contact with a hard or sharp object or is 308 VERDON used as a striking tool. Trigger finger is seen with tools that have hard, sharp, or small diameter handles. Tools with ringed handles (e.g., scissors) that rub on the sides and backs of fingers can compress the digital nerves. High pressure on the base of the palm can lead to median nerve compression and carpal tunnel syndrome. Vibration and temperature. Localized vibration of the upper extremities can occur with activities that involve power tools including chain saws, pneumatic drivers, and jackhammers. Exposure of the upper extremities to vibrating tools can cause hand-arm vibration syndrome. This is characterized by Raynaud's-type symptoms in the hand. Temperature extremes increase the risk of overuse syndromes. In cold temperatures, as with vibration, grip strength must be increased, and hand flexibility and manual dexterity decrease. Hot environments can cause dehydration and heat exhaustion.'O Prolonged constrained posture. Workstation layout, equipment, tool features, and worker anthropometry interact to create a working posture. If work surfaces or tools are at awkward reaches, it can cause a worker to adopt harmful body postures that can overstress the neck, shoulder, elbow, wrists, and hands. TREATMENT OF OVERUSE SYNDROMES Resting the affected body part is the mainstay of treatment and should be prescribed for at least 2 weeks.39A major goal of treatment is to prevent fibrosis. Initial treatment of tenosynovitis, in addition to rest, can include ice and elevation. Nonsteroidal anti-inflammatory agents (NSAIDs) and corticosteroids (usually as a. local injection) can limit the inflammatory response and decrease pain. A risk of NSAIDs is that they may encourage return to unrestricted activity. Treatment also can include splinting to limit movement to a pain-free range. Such immobilization helps patients avoid reinjury and has been proved beneficial in carpal In tenosynovitis, immobilization appears to offer no tunnel advantages over NSAIDs and injections.l*Corticosteroid injection around a tendon or into its sheath can limit the inflammatory response and break the cycle of chronic inflammation. Injection of corticosteroids directly into a tendon or ligament is detrimental and should be avoided. The injection should be followed with rest, a protected motion program, and a slowgraded return to activity. No more than three injections are recommended. Rehabilitation should follow the 10% rule, i.e., increase the weight, repetitions, or distance by no more than 10% per week.29 It is essential that the treatment of overuse syndromes includes an identification of conditions that cause or aggravate the illness. Office evaluation should include having the patient reenact his or her work or sport activity to identify any risk factors for overuse syndromes. Many workplaces now have ergonomic specialists who can assist in workstation evaluation. Ergonomics, which literally means work knowledge, involves adapting the workplace to the needs of the worker. A basic ergonomic OVERUSE SYNDROMES OF THE HAND AND WRIST 309 evaluation of the workplace includes the following measures: changing tools, designing machinery to do highly repetitive tasks, changing work posture, and controlling environmental condition^.^^ The aim of changing tools is to spread the load over as many muscle groups as possible to avoid overburdening the smaller muscle groups. The posture of the hand and forearm has a direct impact on the amount of force the muscles must generate to perform a given task. By altering hand position, the amount of force required for lifting can be reduced by four to five times. Decreasing the weight of tools, balancing tools, or providing tools with handles, thereby avoiding pinching, reduces the force on the tendons. By reducing the demands for strength, it may be possible to lower the patient's tendon forces below the threshold for mechanic irritation and pain. Sharp edges of tool handles such as scissors or pliers may fail to distribute forces over a wide enough area. Patients may complain of symptoms caused by tendinitis or nerve compression at the edge of a tool handle. Fibrosis and nerve compression occur in an area of repeated trauma. This process has been documented in the thumbs of bowling enthusiasts who develop fibrosis with digital nerve compression from continued trauma at the area where the thumb was held against the bowling ball.9 Tools requiring ulnar-radial deviation or flexion-extension of the wrist may incite tenosynovitis of the flexor or extensor tendons or lead to nerve compression. The high incidence of de Quervain's disease at one electronics manufacturer was associated with the use of needle-nosed pliers that required workers to turn their wrists in constant ulnar deviation. This was resolved through many measures including redesigning the handles of the pliers to maintain the wrist in a neutral position.21 Work posture and tool design are related directly. Changing work posture is often key in the treatment of overuse syndromes. For optimal hand and arm strength and skill, work should be placed 10 to 12 inches in front of the eyes, and elbows should be postured at an 85" to 100" angle. The shoulder should be in the vertical position, with abduction no greater than 20". The wrist should be in the neutral position, without ulnar or radial deviation and with minimal flexion or extension. Workplace design to maintain the arms at the sides prevents the need for continuous abduction of the shoulder and pronation of the wrist. Finally, environmental conditions such as temperature extremes and vibration should be minimized because they play a role in overuse syndromes. Vibration can be altered by changing tools and decreasing the hours of tool use per work shift. Symptoms of hand-arm vibration syndrome often resolve if the exposure is decreased; however, permanent neurovascular damage can result if exposure to vibration continues. Optimal working temperature is in the range of 68°F to 78°F with 20% to 60% humidity. lo A useful resource for identifying simple solutions to these problems is the Job Accommodation Network (800-526-7234), a federally sponsored program to facilitate cost-effective modifications in the workplace. It is important for clinicians to file a workers' compensation report for any patient with a suspected work-related illness. These allow federal sur- 310 VERDON veillance organizations to identify high-risk jobs and work sites. Such reports are also essential for the worker to obtain compensation and workstation adjustment. A designation of an illness as work related is based on the legal standard of causation. If the clinician believes there is a likelihood of 51% or more that the condition is caused by work, a workers’ compensation claim should be filed. A survey by the California Occupational Health Program indicated significant underreporting of carpal tunnel syndrome by health care providers in Santa Clara County, with only 71 workers’ compensation reports filed for the 3413 work-related cases found in the survey.6 SPECIFIC OVERUSE SYNDROMES OF THE HAND AND WRIST Specific overuse syndromes of the hand and wrist include tenosynovitis of the dorsal wrist extensor compartments, tenosynovitis of the flexor tendons of the wrist, trigger finger, and carpal tunnel syndrome. Treatment consists of that outlined for overuse syndromes in general. Specific alterations for a given diagnosis are discussed. Extensor tenosynovitis can occur at any of the extrinsic extensor tendons and tendon groups found in any of the six dorsal compartments. These compartments and their associated syndromes are as follows: 1. Abductor pollicis longus (APL) and extensor pollicis brevis (EPB) (de Quervain’s) 2. Extensor carpi radialis longus (ECRL) and brevis (ECRB) (intersection syndrome) 3. Extensor pollicis longus (EPL) 4. The four extensor digitorum communis tendons and the extensor indicis propius (EIP) tendon 5. Extensor digiti minimi 6 . Extensor carpi ulnaris (ECU) Compartments 3 through 6 have tenosynovitis syndromes that bear the name of the respective tendon. de Quervain’s Syndrome This is a common condition in primary care practice. First described in 1895by de Quervain, it is associated with activities that require forceful grasp coupled with ulnar deviation or repetitive use of the thumb. Those at risk include golfers, fly fishers, racquet sport players, knitters, laboratory technicians, filing clerks, and mail sorters. Tenosynovitis develops in the APL and EPB tendons that are held in a groove of the radius by a firm segment of the extensor retinaculum. In approximately 30% of the population, the APL and EPB tendons are divided by a septum. Patients with de Quervain’s syndrome are much more likely to have this anatomic variation, and it may play a role in the cause of the condition.22 OVERUSE SYNDROMES OF THE HAND AND WRIST 311 The presenting symptom of de Quervain’s syndrome is pain in the radial aspect of the wrist and thumb, often intensified by movement of the wrist and thumb. Pain also may extend up the forearm. The dorsal sensory branch of the radial nerve passes directly over these tendons. If inflammation is severe, the dorsal sensory branch of the radial nerve can become irritated, and patients complain of pain and paresthesias radiating to the thumb, dorsum of the hand, and index finger. There is an increased frequency of trigger finger and carpal tunnel syndrome in patients with de Quervain’s syndr0me.4~ On physical examination, patients with this syndrome show swelling and tenderness 0.5 in proximal to the radial styloid. There rarely can be dramatic crepitus or triggering. In chronic de Quervain’s syndrome, palpable fibrous thickening or nodules can occur, occasionally associated with a ganglion. In these cases, when the thumb is flexed and adducted, a trigger effect or popping sensation may occur as a result of nodules on the tendon surface slipping through fibrosed parts of the tendon sheath. de Quervain’s syndrome is associated with a positive Finkelstein’s test or pain when the thumb is flexed into the palm while the examiner ulnarly deviates the wrist. This causes maximum excursion of the APL and EPB tendons.39 Treatment of de Quervain’s syndrome follows the standard protocol for overuse syndromes. The majority of patients improve with conservative treatment, including corticosteroid injection. Splinting with a thumb spica splint worn full-time is recommended by some authors; however, the only controlled studyla using immobilization showed no benefit. A total lack of progress after 6 to 8 weeks and palpable fibrous thickening are indications that surgical release may be necessary. The risks of surgery include damage to the dorsal sensory branch of the radial nerve, persistent symptoms, tendon adhesions, tendon subluxation, and inadequate decompression.2 Intersection Syndrome (Extensor Carpi Radialis Longus and Brevis) Tenosynovitis of the second dorsal compartment of the wrist may be triggered by a traumatic event or repetitive wrist flexion and extension. It occurs in active people who lift weights, row, or canoe and in industries requiring repetitive wrist motion. Patients with intersection syndrome complain of pain, tenderness, swelling, and crepitus over the radiodorsal aspect of the distal forearm 4 to 8 cm proximal to the dorsal wrist crease. In this area, the ECRL and ECRB tendons cross under the more oblique muscle bellies of the EPB and APL tendons. It is postulated that the syndrome is caused by friction produced by the APL and EPB muscle bellies rubbing on the radial wrist extensors. Published ~ t u d i e s of ’ ~ operative reports describe tenosynovitis of the ECRL and ECRB tendons in intersection syndrome. In addition to standard measures for overuse syndromes, treatment of intersection syndrome can include splint immobilization at 20” of ex- 312 VERDON tension. According to one report,15conservative therapy was successful in the majority of patients, and those who required surgery had a good outcome with few complications. Extensor Pollicis Longus EPL tenosynovitis usually presents as pain in the upper (medial) edge of the anatomic snuff-box, which is aggravated by motion of the thumb. The pain occasionally radiates throughout the dorsal aspect of the forearm. It can develop with activities that require repetitive thumb and wrist motion. It rarely occurs as an isolated condition; predisposing factors include rheumatoid arthritis, direct trauma, and fractures of the radius. EPL tenosynovitis requires early diagnosis because tendon rupture can occur, which is prevented by early operative intervention. Overuse is an unusual cause of rupture; it usually occurs following a Colles’ fracture or occurs in patients with rheumatoid arthritis. Treatment of EPL tenosynovitis is the same as de Quervain’s, except injections are discouraged because of the theoretic possibility of pressureinduced circulatory compromise in a zone of the tendon that already is vascularized poorly.36 Extensor lndicis Proprius Syndrome or Tenosynovitis of the Common Digital Extensors Tenosynovitisof the fourth dorsal compartment presents as pain, tenderness, and swelling over the dorsum of the hand, which is aggravated by strenuous activity of the wrist and hand. It can affect only the EIP or all the common digital extensors. In EIP syndrome, the pain is reproduced by full passive wrist flexion and resisted active index finger extension. With tenosynovitis of the common digital extensors, pain is elicited with the wrist in a neutral position and resisted extension of the index, long, ring, or little fingers.41In addition to standard treatment, a forearm-based splint can be employed. The splint should eliminate most of the extensor tendon excursion by immobilizing the wrist and metacarpophalangeal joints. Because symptoms may be slow to resolve, at least 8 to 12 weeks should be allowed before considering s~rgery.~O Extensor Digiti Minimi Tenosynovitis This is extremely uncommon, although it has been reported after wrist trauma and overuse. It presents as pain and swelling on the dorsum of the wrist, just distal to the head of the ulna. This tenosynovitis can be associated with the inability to extend the little finger at the metacarpophalangeal joint. Injection into the fifth dorsal compartment is diagnostic and therapeutic. An ulnar gutter splint has been recommended in addition to standard treatment.19 OVERUSE SYNDROMES OF THE HAND AND WRIST 313 Extensor Carpi Ulnaris This is another rare tenosynovitis that presents with pain, swelling, and crepitus with motion along the dorsal ulnar aspect of the wrist just distal to the ulnar head. Symptoms are exacerbated by resisted wrist extension. It develops in activities requiring repetitive wrist motion or a snap of the wrist. Trauma or repetitive hypersupination with ulnar deviation of the wrist can cause this condition. Inflammatory involvement of the dorsal sensory branch of the ulnar nerve can cause numbness over the dorsal ulnar aspect of the hand. In addition to standard treatment, splint immobilization in a position of wrist dorsiflexion, pronation, and radial deviation has been ~uggested.’~ FLEXOR TENDINITIS SYNDROMES Flexor Carpi Radialis Tenosynovitis This tendon lies over the scaphoid and trapezoid bones and underneath the transverse carpal ligament. FCR tenosynovitis presents as pain, tenderness, and crepitus just proximal to the wrist crease overlying the FCR tendon or at the base of the thenar eminence. The pain may radiate proximally and is increased with passive extension and resisted flexion of the wrist. This condition can be associated with a nodule or trigger wrist. The differential diagnosis of FCR tenosynovitis includes a ganglion or Linburg’s syndrome. A rupture of this tendon can masquerade as a ganglion. A ganglion is found between the FCR and radial artery, is minimally tender to palpation, and transilluminates. Needle aspiration produces gelatinous material. Standard treatment for tenosynovitis can be augmented with wrist immobilization for the FCR tendon. Patients who do not respond to conservative therapy can be referred for surgery.” Linburg’s Syndrome Linburg’s syndrome was described in 1979 by Linburg and Comand is described as pain and tenderness over the distal radial forearm with repetitive use. At surgery, a tendinous interconnection is found between the flexor pollicis longus and the flexor digitorum profundus tendons. The pathognomonic sign for this condition is simultaneous index finger interphalangeal joint flexion when the thumb is flexed actively across the palm. Up to 30% of people have this unilaterally. Patients with Linburg’s syndrome complain of distal forearm pain when joint flexion of the distal index finger is blocked at the same time that the thumb actively is flexed in the plane of the palm. Standard treatment for tenosynovitis may be helpful in the acute presentation. In cases of chronic Linburg’s syndrome with clinical evidence of the anomaly, surgical excision of the anomaly and tenosynovectomy should be considered.32 Another tendinous anomaly involves the fifth or small finger super- 314 VERDON ficialis, which often is functionally deficient. In one study? 43% of subjects showed variable deficiencies in proximal interphalangeal joint flexion of the small finger when the adjacent fingers were held in full extension. In the same study, when the ring finger was allowed to flex, proximal interphalangeal flexion of the small finger improved in 18% of subjects, suggesting a tendinous interconnection between the digits. Flexor Carpi Ulnaris Tenosynovitis This is seen more commonly than FCR tenosynovitis and presents with pain along the volar-ulnar side of the wrist with activities that require repetitive wrist flexion in ulnar deviation. The pain is exacerbated by wrist flexion and ulnar deviation against resistance. The tendon becomes inflamed in the region of the pisiform or over the flexor carpi ulnaris (FCU)just proximal to pisiform. The differential diagnosis includes pisotriquetral arthritis and pisiform fractures, both of which are associated with a positive pisotriquetral grind test. This test involves grasping the pisiform and sliding it radially and ulnarly on the triquetrum; in a positive test, crepitus is noted. Some authors recommend a hand radiograph that may show a calcific deposit along the FCU tendon or narrowing of the pisotriquetral joint and subchondral sclerosing with advanced arthritis. In addition to standard treatment, a dorsal splint in 25" of wrist flexion may be helpful. Patients who do not respond to standard treatment may need surgery. Surgical treatment is the same for tenosynovitis and arthritis and involves removal of the p i ~ i f o r m . ~ ~ Trigger Finger This condition results from thickening of the proximal portion of the flexor tendon sheath because of direct pressure from a sports racquet or another forcefully grasped tool that incites an inflammatory response. The symptoms include pain to triggering to frank locking at the level of the metacarpal head. The finger locks because the digital extensors are weaker than the digital flexors. Corticosteroid injection should be the initial treatment, directed into the fibro-osseous tunnel rather than the flexor tendon itself. Rest, splinting, and anti-inflammatory agents are ineffective. A second injection can be helpful if the first has produced some improvement. Surgery is recommended if there is no response to injection and if symptoms have been present for more than 3 months at the first visit.20 Carpal Tunnel Syndrome This syndrome is so common that it is considered the most frequent compression neuropathy seen by clinician^.^^ The tunnel is formed by carpal bones on three sides. The roof of the tunnel is formed by the flexor retinaculum extending from the hook of the hamate and pisiform ulnarly to the trapezium and scaphoid radially. The contents of the carpal tunnel OVERUSE SYNDROMES OF THE HAND AND WRIST 315 include the nine extrinsic flexor tendons of the wrist and fingers (eight flexor profundus and superficialis tendons and the flexor pollicis longus tendon) and the median nerve. The volume of the tunnel is only slightly greater than the volume of its soft-tissue contents. Any process that decreases the volume of the tunnel (deformity secondary to a fracture, arthritic spurs, tumor, or thickening of the flexor retinaculum) or increases the volume of its contents (simple fluid retention, fat deposition, tumor, ganglion or synovial proliferation) crowds the median nerve, interferes with its blood supply, and causes it to m a l f ~ n c t i o nThe . ~ ~pressure inside the carpal tunnel can increase from 3 to 30 mm Hg, with the wrist in extreme extension or flexion.I3 The most common cause of this condition is flexor tenosynovitis, usually associated with repeated forced hand movements noted in cashiers, electronic assembly workers, grinders, typists, keypunch operators, seamstresses and cutters, musicians, packers and bricklayers, housekeepers, cooks, and carpenters.6There is an increased incidence of carpal tunnel syndrome in patients with diabetes, thyroid disease, amyloidosis, and rheumatoid arthritis and in pregnancy.37 The median nerve at the wrist is 94% sensory and only 6% motor; therefore, dysfunction at the wrist usually is manifested by sensory changes. Motor changes occur with chronic or severe median nerve compression. Early malfunction causes dysesthesia or pain, paresthesia, numbness, or a pins-and-needles sensation in the median nerve distribution of the hand. This distribution is described classically in the thumb, index finger, middle finger, and radial aspect of the ring finger. Symptoms can be isolated to one or two digits, and atypical presentations appear to be the rule rather than the exception. Nocturnal paresthesias and pain are almost universal for carpal tunnel syndrome. In severe or late malfunction of the median nerve, thenar atrophy and weakness of abduction and opposition of the thumb develop.27 The physical examination of a patient with suspected carpal tunnel syndrome traditionally includes two signs: Tinel’s and Phalen’s. Tinel’s sign involves percussion of the median nerve at the wrist. A positive sign is associated with painful tingling into the thumb and index or into the middle fingers. Phalen’s involves 90” palmar flexion at the wrist; if symptoms are reproduced within 60 seconds, it is considered positive. In a recent studyz5of patients referred for nerve conduction testing, Tinel’s and Phalen’s signs had low positive predictive values (0.55 and 0.48, respectively). The use of a hand diagram, in which the patient indicates the site of pain and paresthesias, is associated with a higher positive predictive value (0.59).26 The earliest objective sensory finding in carpal tunnel syndrome is diminished vibratory sensation, tested with a 256-cycle tuning fork. More severe median nerve involvement results in abnormal two-point sensory discrimination. The physical examination always must include testing of the motor strength of the median-innervated thenar muscles. Weakness or atrophy is a sign of significant compression and usually warrants immediate surgery without a trial of conservative treatment. Approximately one fourth of patients with work-related carpal tunnel syndrome have 316 VERDON accompanying disorders such as ulnar neuropathy at the wrist, trigger finger, de Quervain's tenosynovitis, or arthritis of the basal joint of the thumb.44 In the diagnostic workup of carpal tunnel syndrome, hand or wrist radiographs are not indicated routinely. Most texts recommend nerve conduction studies for all patients suspected of having carpal tunnel syndrome because such studies represent the only completely objective test for this condition. The lack of an abnormal nerve conduction test does not exclude a diagnosis of carpal tunnel syndrome, especially early in the course of the process. Sensitivity for electrodiagnostic tests of the median nerve ranges from 49% to 84%, whereas specificities of 95% or greater have been reported. Accuracy depends on the methods used and the normal values selected by the laboratory? Practice standards for the care and treatment of patients with carpal tunnel syndrome were published by the American Academy of Neurology3in 1993. These standards recommend electrodiagnostic tests only if the diagnosis is uncertain or there is no response to conservative treatment. A recent by the Ambulatory Sentinel Practice Network, a primary care research network of more than 70 practices, studied more than 500 cases of carpal tunnel syndrome. Clinicians judged 43% of cases to be job related and ordered nerve conduction tests in only 13% of patients. Treatment typically included splinting and NSAIDs, and most cases improved in 4 months. Only 2% of cases of carpal tunnel syndrome were injected in that study, suggesting primary care physicians are unfamiliar or uncomfortable with that therapy. The treatment of carpal tunnel begins with a resting splint that puts the wrist in neutral flexion. It is most effective at night while sleeping. Injection is indicated if symptoms persist and have been present less than 6 months.14 Injection is done at a 45" angle, 1 cm proximal to the volar wrist crease, between the flexor carpi radialis and the palmaris longus tendons. The median nerve lies just ulnar to the flexor carpi radialis tendon and radial to the palmaris longus tendon.27Surgery is indicated if symptoms progress, there is no improvement during 6 weeks, or thenar muscle weakness or atrophy is present. Surgery is effective in the majority of cases, with an 86% success rate reported in a recent study.' Pyridoxine hydrochloride has been suggested as a potential treatment for work-related carpal tunnel syndrome; however, based on existing there is no evidence that it works. The differential diagnosis of carpal tunnel syndrome includes flexor tenosynovitis, cervical radiculopathy, thoracic outlet syndrome, and pronator teres s y n d r ~ m eFlexor .~ tenosynovitis can cause carpal tunnel syndrome when the inflammation causes compression of the median nerve in the carpal tunnel. It also can occur outside the carpal tunnel and mimic carpal tunnel syndrome. Repetitive digital flexion leads to swelling just proximal to the wrist flexion creases. Pain aggravated by finger motion can be reported along the volar surface of the forearm. Median nerve compression also can occur with severe pain. Electrodiagnostic tests may be normal if done acutely, despite findings of median nerve irritability such as a positive Tinel's sign or Phalen's maneuver. Treatment is the OVERUSE SYNDROMES OF THE HAND AND WRIST 317 Table 1. SURVEILLANCE CASE DEFINITION FOR THE WORK-RELATED CARPAL TUNNEL SYNDROME A. One or more symptoms of carpal tunnel syndrome present for at least a week, paresthesias, hypoesthesia, pain, or numbness affecting at least part of the median nerve distribution of affected hand(s). B. Objective findings 1. Positive Tinel’s sign or Phalen’s test or decreased or absent sensation to pinprick in median nerve distribution of the hand, or 2. Findings of median nerve dysfunction across the carpal tunnel on electrodiagnostic testing. C. Evidence of work relatedness-history of a job involving one or more of the following activities on the affected side before the development of symptoms. 1. Frequent, repetitive movements 2. Regular tasks requiring generation of high force 3. Regular or sustained tasks requiring awkward hand positions 4. Regular use of vibrating hand-held tools 5. Frequent or prolonged pressure over the wrist or base of the palm A temporal relation of symptoms to work or an association with cases of the carpal tunnel syndrome in coworkers performing similar tasks also is evidence of work relatedness. Adapted from Centers for Disease Control: Occupational disease surveillance: Carpal tunnel syndrome. MMWR CDC Surveil1 Summ 38:485-489, 1989. same as for carpal tunnel syndrome except splinting is in slight wrist extension.30 Pronator teres syndrome occurs because the median nerve can be compressed at the level of the pronator teres along the volar forearm just distal to the elbow where it travels between the two heads of the pronator teres. Symptoms are purely sensory and identical to carpal tunnel syndrome. Usually Tinel’s is negative at the wrist and positive in the forearm, whereas Phalen’s sign is negative. Treatment includes long-arm splinting with the elbow in 90” of flexion and midposition rotation.I2 Some authorsz7question if carpal tunnel syndrome is truly a workrelated and compensable illness. Because of issues of compensation, a case definition has been developed and is detailed in Table 1. The purpose of the definition is surveillance, so it maximizes sensitivity at the expense of specificity. In summary, overuse syndromes are some of the most common occupational illnesses that primary care providers treat. Their pathophysiology follows that of tenosynovitis, and basic medical treatment includes rest, NSAIDs, and corticosteroid injections. Risk factors at work include repetition, high force, awkward joint posture, direct pressure, and vibration. Treatment also should include identification and adjustment of such factors. Specific overuse syndromes discussed include tenosynovitis of the dorsal wrist extensor compartments and of the flexor tendons of the wrist, trigger finger, and carpal tunnel syndrome. References 1. Adams ML, Franklin GM, Barnhart S: Outcome of carpal tunnel surgery in Washington state workers’ compensation. Am J Ind Med 25:527-536,1994 318 VERDON 2. Arons MS: de Quervain’s release in working women: A report of failures, complications, and associated diagnoses. J Hand Surg 12A:540-544, 1987 3. American Academy of Neurology: Practice parameter for carpal tunnel syndrome (Summary statement). Neurology 43:2406-2409, 1993 4. American Academy of Neurology, American Association of Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation: Practice parameter for electrodiagnostic studies in carpal tunnel syndrome (Summary statement). Neurology 4332404-2405,1993 5. 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