The carpal tunnel syndrome is the most common entrapment neuropathy. With the report by Cannon and loves in 1946 of the favorable outcome in nine patients with median nerve entrapment at the wrist who underwent carpal tunnel release and neurolysis, the syndrome became increasingly recognized. During the next two decades, Phalen championed and immensely popularized the relatively simple operation. Carpal tunnel release is now the most common hand operation performed. Though the procedure is generally associated with low morbidity and relatively high success rates, failure of the surgeon to fully understand the anatomy, pathophysiology, and typical features of carpal tunnel syndrome, as well as the many pitfalls associated with its diagnosis and treatment, may lead to an unacceptable incidence of suboptimal results.

Anatomy

The median nerve originates from the lateral and medial cords of the brachial plexus and carries in it axons entering or leaving the spinal cord through the C6,7,8 and T1 nerve roots. It passes down the arm in the neurovascular compartment adjacent to the brachial artery but gives off no branches until the forearm and hand. In the forearm, the median nerve innervates numerous wrist and digital flexors of the preaxial muscular compartment. Though the sensory distribution of the median nerve in the hand closely approximates the C6 and 7 dermatomes, its motor fibers innervate intrinsic muscles of the hand within the C8 and T1 myotomes.

Fig-1: Topographical view of the hand -Anterior view.

1-ulnar n. et a.; 2- flexor digitorum profundus and superficialis; 3- vagina synovialis  communis mm. flexorum; 4- median n.; 5- abductor digiti minimi; 6- n. digitalis palmaris proprius; 7- flexor digiti minimi brevis; 8- arcus arteriosus palmaris superficialis; 9- nn. digitales palmaris proprii n. ulnaris; 10- aa. digitales palmares communes; 11- mm. lumbricales; 12- mesotenon; 13- vaginae synoviales tendinum digitorum; 14- vaginae fibrosa digiti manus; 15- aa.digitales palmares propriae; 16- m. interosseus dorsalis I; 17- vagina synovialis tendinis m. flexoris pollicis longi; 18- caput transversum m. adductoris pollicis; 19- nn. digitales palmares proprii; 20- ramus superficialis a. radialis; 21- m. abductor pollicis brevis; 22- m. flexor pollicis brevis; 23- nn.digitales palmares communes n. mediani; 24- ramus muscularis n. mediani. 

The abductor pollicis brevis, which abducts the thumb at a right angle to the palm, and the opponens pollicis, which flexes and opposes the thumb, are the most important of the median-innervated muscles of the hand. These two muscles of the thenar eminence are innervated by the recurrent motor branch that typically arises from the median nerve just distal to the flexor retinaculum. Damage to this nerve produces loss of thumb opposition and hence significant difficulties with grasp. Other muscles innervated include the superficial (flexor) pollicis brevis and the first and second lumbricals. The median nerve supplies sensory fibers to the radial three and one-half digits via the common palmar digital branches. The area over the thenar eminence, however, is supplied by the palmar cutaneous branch, which leaves the median nerve just proximal to and runs superficial to the transverse carpal ligament (Figure 1). Numerous variations in the origin and course of this surgically important cutaneous branch may be encountered. The branch may have origin on the ulnar side of the nerve, or it may course under or through the transverse carpal ligament.

Fig-1: The median nerve at the wrist.

The transverse carpal ligament, or flexor retinaculum, is a dense ligament measuring approximately 4 cm in Width, 5-6 cm in length, and 2.5-3.6 mm in thickness. It stretches transversely across the concavity of the carpal bones and converts their arch into a fibrous tunnel. Referred to as the carpal tunnel, here the median nerve travels in its most superficial course as it and a number synovium-invested tendons pass into the hand. In 10% of individuals, a small persistent median artery can be found coursing through this tunnel. The tendon of the palmaris longus muscle passes superficial to the transverse carpal ligament and inserts into the palmar aponeurosis, a tough stratum of connective tissue that blends into the deep palmar aspect of the transverse carpal ligament. This tendon acts as a useful landmark as the median nerve lies just radial to it. The transverse carpal ligament acts in part as a paint of origin for the muscles of the thenar and hypothenar eminences.

Fig-2: Transverse section upper third of the wrist.
1- vagina tendinis m. flexoris pollicis longus; 2- caput superficialis m. flexoris pollicis brevis; 3- retinaculum flexorum; 4- median n.; 5- tendines m. flexorum superficialis; 6- vagina synovialis communis mm. flexorum; 7 - a. et n. ulnaris; 8 - ramus palmaris  profundus  a. ulnaris et ramus  n. ulnaris; 9-m. palmaris; 10- m. flexor digiti minimi; 11. m. abductor digiti minimi; 12- m. interosseus palmaris III; 13- m. opponens digiti minimi; 14- tendo m. extensoris digiti minimi; 15- tendenes m. extensoris digitorum; 16- m. interosseus dorsais IV; 17- tendo m. extensoris digitorum; 18- m. interossius palmaris II; 19- arcus arteriosus palmaris profundus; 20- m. interossius dorsalis III; 21- tendo m.extensoris digitorum; 22- tendo m. extensoris indicis; 23- m. interosseus dorsalis II; 24- The deep fatty space; 25- m. interosseus palmaris I; 26- m. interosseus dorsalis I; 27- tendines m. flexoris digitorum profundus; 28- m. adductor pollicis; 29- tendo m. extensoris policicis longi; 30- tendo m. extensoris pollicis brevis; 31 ­ caput profundum m. flexoris pollicis brevis; 32- m. opponens pollicis; 33 - m. abductor pollicis brevis.

Like the palmar cutaneous branch, there are numerous variations in the course of the recurrent motor branch of the median nerve; however, in 95% of cases, the motor branch will take one of three courses. The most common point of origin is the radial side of the median nerve just distal to the transverse carpal ligament, frequently arising in common with the first common palmar digital nerve. The motor branch then courses directly to the thenar muscles (Figure 1). The second most common site is an origination from the median nerve as it travels beneath the transverse carpal ligament. The branch then passes around and over the distal edge of the ligament to the thenar muscles. An origin of the motor branch from beneath the transverse ligament with a transligamentous course is the third most common. In rare cases, the motor nerve may arise from the ulnar aspect of the median nerve or may even travel for a short course on top of the distal edge of the transverse ligament. In cases of persistent median artery, the median nerve may have a high division; that is, the motor branch make take origin many centimeters proximal to the wrist.

Epidemiology and Etiology

The carpal tunnel syndrome affects women somewhat more often than men, though the actual incidence in each sex is not entirely clear. Fifty percent of cases occur in the fifth and sixth decades. Frequently, the patient's occupation will require repetitive wrist motion or prolonged pressure to the "heel" of the hand. Recreational-related trauma to the hand or wrist is increasingly becoming a factor in development of this entrapment syndrome. Five to ten percent of all patients will relate a history of recent or remote injury to the wrist.

Numerous systemic diseases have been associated with an increased predisposition to development of carpal tunnel syndrome. Rheumatoid arthritis, amyloidosis, acromegaly, and hypothyroidism predispose the median nerve to compression within the carpal tunnel due to thickening and hypertrophy of the ligaments and other connective tissues. The carpal tunnel syndrome is also more likely to occur in association with diseases that produce demyelinating or ischemic neuropathies, such as diabetes mellitus, renal failure, or alcoholism. Pyridoxine (vitamin B6) deficiency has likewise been suggested to be an etiologic factor. Transient symptoms of median nerve compression are very common during pregnancy and usually resolve spontaneously after delivery. Any mass lesion within the carpal tunnel may produce median nerve impingement, such as neurofibromas, ganglion cysts, and other benign tumors. Anomalous muscles and tendons, as well as a persistent median artery or other vascular anomalies, have been reported to produce the carpal tunnel syndrome. Other local conditions, such as synovial inflammation and fibrosis (as is observed in teno­synovitis), fracture of the carpal bones, and thermal injuries to the hand or forearm may be associated with the carpal tunnel syndrome.

Phalen argues for a common etiology for many of the idiopathic cases. During the course of decompressing the carpal tunnel, Phalen biopsied the synovium of the flexor tendon lying beneath the median nerve. Chronic inflammation and fibrosis of the flexor synovialis, consistent with tenosynovitis, were found in 126 of 148 biopsy specimens. Phalen also believes a vasomotor imbalance from sympathetic dysfunction may play a role in the disease process, though there is no scientific evidence to substantiate this.

In essence, any disease process that reduces the cross-sectional area of the carpal tunnel or increases the volume of its contents may produce median nerve compression and entrapment, especially if a concurrent neuropathy predisposes the nerve to injury from compressive lesions.

Clinical Diagnosis Symptoms

Carpal tunnel syndrome is characterized by a typical discomfort and numbness of the lateral three digits (radial half of the hand). The pain is often described by the patient as bothersome "pins and needles" paresthesias, though occasionally the pain will have more of a deep, aching quality. The pain may affect the entire hand or, in atypical cases, radiate proximally into the forearm, upper arm, or even the shoulder, producing symptoms that can be confused easily with a C6 nerve root compression syndrome. The syndrome is frequently bilateral, though the symptoms are usually worse in the dominant hand.

A feature quite distinctive of carpal tunnel syndrome is nocturnal exacerbation of the symptoms. The patient frequently complains of being awakened by pain during the early morning hours. Shaking and massaging the affected hand often relieve the discomfort. It has been suggested that akinesia during sleep leads to venous stasis in the extremities, which exacerbates compression of the median nerve within the already restrictive carpal tunnel. By shaking and moving the hands, venous return is improved, causing a reduction in the pressure within the tunnel, thus relieving the uncomfortable paresthesias. Strenuous use of the hands, especially with repetitive or forceful flexion movements of the wrist, may also aggravate the symptoms.

In contrast to ulnar neuropathy at the elbow, it is unusual for weakness and atrophy to be present in the early stages of carpal tunnel syndrome. Thenar atrophy and weakness of thumb opposition are hallmarks of advanced disease. Interestingly, the rare patient who initially presents with weakness and atrophy frequently has little pain.

Findings

The history alone usually establishes the diagnosis of carpal tunnel syndrome. Abnormal findings on neurologic examination may support the diagnosis in patients with less typical symptoms, though objective abnormalities are generally sparse except in more advanced cases. Hypesthesia in the median nerve distribution may be found, except over the thenar eminence and base of the palm. This is due to the palmar cutaneous branch of the median nerve arising proximal to and passing superficial to the transverse carpal ligament. This sensory branch is frequently spared the effects of entrapment within the carpal tunnel. Motor deficits are seen less frequently. The two most important muscles innervated by the distal median nerve are the opponens pollicis and the abductor pollicis brevis. The first is tested by having the patient oppose the thumb to the palm and draw it medially toward the base of the fifth digit against resistance. The latter is tested by resisting active abduction of the thumb away from the plane of the palm. Significant and long-standing denervation to these muscles leads to atrophy of the thenar eminence.

Two-thirds of patients will experience electrical sensations radiating into the palm and first three digits when the median nerve at the wrist crease is percussed. This is known as Tinel's sign, which classically has been associated with median nerve entrapment at the wrist; however, recent reports suggest this test to be of dubious value in establishing the diagnosis of carpal tunnel syndrome due to a high incidence of false-positive results in otherwise asymptomatic individuals. A more accurate predictor of carpal tunnel syndrome is Phalen wrist-flexion test. The patient is asked to hold the forearms up in a vertical orientation with the wrists flexed for 60 seconds. Reproduction of the patient's painful dysesthesias provides a high degree of certainty of the diagnosis. Likewise, inflating a blood pressure cuff placed around the arm may reproduce the symptoms. Again, symptom exacerbation in this test is likely due to venous distention within the rigid confines of the carpal tunnel.

Electrodiagnostics

Electromyography and nerve conduction velocities should be obtained to confirm, not to establish, the diagnosis of carpal tunnel syndrome. Indications for surgery should not rest solely on the results of this test, but rather should be based on clinical judgment. Electrodiagnostic studies are helpful in differentiating the carpal tunnel syndrome from other disorders, such as cervical nerve root impingement or syndromes of the thoracic outlet.

The most sensitive and the earliest abnormality found is a prolonged sensory conduction latency across the wrist. Normally, the distal latency through the carpal tunnel to the abductor pollicis brevis is less than 4.5 milliseconds. A prolonged motor latency generally occurs later in the entrapment process. The amplitude of the action potential is frequently diminished. Denervation potentials in the opponens pollicis and abductor pollicis brevis indicate advanced and probably irreversible damage to the median nerve.

Nerve conduction velocities and latencies are subject to a number of physiologic variables, such as the age and metabolic status of the patient, as well as the temperature, vascular supply, and extent of edema in the arm. Numerous technical problems are associated with the determination itself. The treating physician or surgeon is responsible for being aware of the variability of the test and for assessing the results in light of the patient's clinical evaluation. Should the electrodiagnostic studies be equivocal, it might be prudent to wait up to 4­6 weeks to repeat the study before embarking on a course of surgical management. Though electrical abnormalities may not be evident in up to 10% of clinical cases of carpal tunnel syndrome. Many surgeons will not consider decompression of the carpal tunnel without electrodiagnostic confirmation.

Differential Diagnosis

The surgeon should be aware of the similarity between carpal tunnel syndrome and other pathologic processes that cause pain and neurologic dysfunction of the radial aspect of the forearm and hand. These include brachial plexopathy from tumor, trauma, or inflammation, and, less often, thoracic outlet syndrome. The most common of these, however, is C6 and C7 radiculopathy caused by cervical disk herniation or spondylosis. Typically, this pain seems to originate in the neck and shoulder and radiates down the arm in a lancinating fashion into the radial aspect of the hand. Exacerbation of the pain with movement of the cervical spine is a significant diagnostic factor in this pain syndrome. In general, C6 and C7 nerve root compression produces motor deficits in the upper arm, such as biceps or triceps weakness, and diminished deep tendon reflexes. The intrinsic hand muscles are relatively unaffected.

The median nerve may become entrapped at locations other than the carpal tunnel. The pronator syndrome is produced by median nerve compression at one of a number of locations around the distal humerus, elbow, and proximal forearm. Entrapment at these sites produces pain on the volar surface of the forearm and hypesthesia of the radial half of the hand. Weakness of the thenar muscles is observed less often. Symptoms are usually aggravated by exertion, especially with forceful flexion of the elbow or pronation of the forearm. Phalen's wrist-flexion test is typically negative. Likewise, the anterior interosseous syndrome causes pain in the proximal forearm. This pain is exacerbated by exercise and relieved by rest. Because it affects the anterior interosseous branch distal to where it leaves the median nerve in the cubital fossa, the motor and sensory innervation of the hand is not directly affected, though pain may be referred into the hand.

Carpal tunnel syndrome may coexist with other lesions of the nerve roots, brachial plexus, or median nerve. Concurrent cervical radiculopathy has been found in over 10 % of electrically proven carpal tunnel syndrome. This is referred to as the double-crush syndrome. This syndrome is based on the concept that proximal compression of a nerve may weaken the nerve's ability to withstand a more distal compression.

Management

Nonoperative Therapy

Many cases of carpal tunnel syndrome, especially mild cases or those that present early in the evolution of the disease process, are self-limiting and resolve spontaneously without need for surgical intervention. In cases related to systemic illnesses, such as hypothyroidism or acromegaly, treatment of the underlying illness may result in improvement or even resolution of entrapment symptoms.

The occurrence of the carpal tunnel syndrome in pregnancy is thought to be related to fluid retention in connective tissues about the wrist. Nocturnal and exertional dysesthesias in the radial half of the palm occur in 10% to 25% of pregnant women. When the carpal tunnel syndrome occurs, the symptoms are more often bilateral. Onset of symptoms is typically during the third trimester. Relief occurs spontaneously, within a few weeks of delivery, in the majority of cases. Because of its transient nature, carpal tunnel syndrome during pregnancy is best treated by using conservative measures, such as splinting and analgesics.

In the rare case of severe pain refractory to nonoperative therapy, it is reasonable to proceed with carpal tunnel decompression using a local anesthetic. That subsequent pregnancies are frequently associated with repeated episodes of carpal tunnel syndrome confirms the association of carpal tunnel syndrome and pregnancy.

Short-term immobilization of the wrist by splinting is among the most commonly used of nonoperative therapies. In general, the splint is worn only at night, though patients with diurnal dysesthetic pain should wear the splint at all times. It is important that the splint be constructed such that no pressure overlies the median nerve at the wrist. If symptoms are not alleviated or improved after 6-8 weeks of splinting. further conservative management is unproductive. The patient is then offered the option of surgical decompression.

Diuretics may prove helpful in patients with carpal tunnel syndrome related to excessive fluid retention, such as is observed in congestive heart failure. Control of hyperglycemia in diabetics and weight loss in obese patients also may be of benefit in alleviating symptoms. Adequate analgesia may be obtained from nonsteroidal anti-inflammatory drugs. though their long-term efficacy in the treatment of carpal tunnel syndrome has not been determined. Pyridoxine administration has not gained wide­spread acceptance as a useful therapy. If development of the syndrome is occupation related, an alteration of work activities or even a change of occupation may be necessary.

Much has been written about the use of corticosteroid injections into the carpal tunnel, but few objective reports of positive results are available. Patients with mild and early symptoms noted a beneficial effect after 3 weeks: however, those patients with more profound symptoms failed to respond to this therapy. Others feel steroid injections may alleviate symptoms though only temporarily. In the last three decades, enthusiasm for this treatment modality has waned. Its primary indication, however, may remain as a means of controlling symptoms during temporary or reversible causes of carpal tunnel syndrome, such as is observed during pregnancy, or following failed carpal tunnel syndrome surgery.

Administration of corticosteroids into the carpal tunnel must be precise in order to avoid injury to the median nerve. A 25-gauge needle is inserted into the wrist at a point 1 cm proximal to the flexion crease between the tendons of the palmaris longus and the flexor carpi radialis and at an angle of 45 degrees to the long axis of the forearm. The needle is advanced approximately 1 cm until the flexor retinaculum is pierced. If painful dysesthesias in the distribution of the median nerve are produced, the needle is withdrawn and reinserted at a slightly different location. One to two milliliters of a mixture of triamcinolone or a similar corticosteroid and 1 % lidocaine are slowly injected. If the patient does not obtain relief following the first injection, further injections, in general, should not be pursued.

Fig-2: Incisions described by several authors (A-E). G- The mini-incision in red used by the author.

Surgical Therapy

The indications for carpal tunnel release are (1) rapidly progressive thenar wasting and hand dysfunction, or (2) substantial symptoms that are unrelieved by conservative measures. The surgeon should be confident of the diagnosis and have thoroughly excluded other causes of hand dysfunction and pain.

In cases of bilateral carpal tunnel syndrome, it is rarely necessary to operate on both hands simultaneously. The more severely affected hand (or in the case of symmetric disease, the nondominant hand) should be decompressed first. Surgery on the contralateral hand may be performed 6 weeks later, after the first hand has recovered and has regained full function. Most would agree that the patient undergoing simultaneous bilateral procedures would be rendered functionally impaired and quite dependent, albeit for a short period of time. Often the symptoms in the less severely affected hand will spontaneously resolve in the interim and will not require operative intervention. One-third of patients with bilateral carpal tunnel syndrome require bilateral operations. When bilateral surgery was needed, an interval between operations of at least 3 weeks was allowed.

Rarely does a patient require general anesthesia to undergo carpal tunnel release. A regional block or, if the anesthesiologist is not well versed in this technique, a locally administered anesthetic agent is used. The use of a tourniquet is unnecessary.

There are as many methods of incision as there are surgeons performing carpal tunnel releases (Figure 2). The type of incision is of little importance as long as it follows three basic guidelines: (1) The incision should be designed to avoid potential division of the palmar cutaneous branch of the median nerve; (2) It should be carried far enough into the palm to confidently divide the most distal aspect of the ligament in its entirety; and (3) If it is to cross the flexion crease of the wrist, it should not do so in a perpendicular fashion.

A simple transverse wrist incision, though widely used in the past, is discouraged. This incision does not offer adequate exposure of the deep palm in order to ensure that the thickest and most distal portion of the transverse carpal ligament has been completely divided. In addition, the palmar cutaneous branch of the median nerve may be inadvertently divided, producing numbness over the thenar eminence or pain related to neuroma formation. As has been previously and eloquently stated, "There is no doubt that unless the transverse carpal ligament is seen throughout its course, the completeness of division will remain a matter of hope, faith, and speculation.

Once the incision is made, sharp dissection is carried through the subcutaneous fatty tissue to the underlying anterior antebrachial fascia in the distal forearm and wrist and the palmar aponeurosis in the hand. Loupe magnification and headlamp illumination improve the visualization of anatomic structures. Hemostasis is maintained throughout the procedure by coagulating and dividing the small subcutaneous vessels using bipolar electrocautery. The division of the transverse carpal ligament begins just radial to this easily identifiable tendon. Rarely, the palmaris longus tendon may overlie and appear to compress the median nerve when the wrist is extended.

The transverse carpal ligament is sharply divided using a No. 11 blade or fine Metzenbaum scissors. The division is performed under direct vision. The incision is made on the ulnar side of the median nerve where the palmar cutaneous and the recurrent motor branches are less likely to be encountered. As the dissection crosses the wrist into the palm, the transverse carpal ligament becomes noticeably tougher and thicker. The muscles of the thenar and hypothenar eminences originate from the transverse ligament at this site.

Deeper in the palm, the fibers of the palmar aponeurosis begin to blend with those of the transverse ligament, thus increasing its thickness and tenacity. Here it is of utmost importance to proceed cautiously and with vigilance for an aberrant course of the recurrent motor branch. A grooved dissector may be placed beneath the ligament in order to guide the knife blade through the tissues. The ligament may be incised likewise with a scissors throughout its' entire length. The decompression is incomplete until the transverse ligament is divided in its entirety. The median nerve itself is then examined for pseudoneuroma formation or compression from adjacent masses, such as neurofibromas or ganglion cysts. The underlying flexor synovialis is also examined; presence of severe tenosynovitis is of prognostic importance. Internal neurolysis or epineurolysis is not routinely performed unless the procedure is a re-exploration with the only significant finding being scarring in and about the nerve. The wound is then closed with a subcutaneous or subcuticular absorbable suture, taking care not to reapproximate the transverse carpal ligament over the median nerve. Nylon suture is used to reapproximate the thick palmar skin. Steristrips are placed over the incision at the wrist and distal forearm. A bulky dressing is placed and the hand wrapped lightly with an elastic bandage. It is important that the patient be reminded to keep the hand elevated above the level of the heart for at least 24 hours to limit postoperative edema and venous congestion.

Postoperative Management

The patient's hand should be bandaged with bulky dressing material in the palm for I week after surgery. Active flexion and extension of the digits as well as thumb abduction and op­position are encouraged to prevent the effects of prolonged immobilization. Bulky dressings are discontinued and the sutures are removed 1-2 weeks after surgery. The hand is placed back into night splints for the next few weeks. The patient is allowed to gradually increase the use of the hand but is discouraged from strong gripping or other exertional uses until 6 weeks postoperatively, at which time the patient is allowed to resume full activities. In patients with significant motor deficits, physiotherapy or hand rehabilitation is instituted at 4-6 weeks following surgery.

Generally, relief of painful dysesthesias occurs almost immediately following carpal tunnel release. Should the pain and tingling persist, the possibility of incomplete division of the transverse carpal ligament or of erroneous diagnosis should be entertained. A deep, aching sensation exacerbated by activity may develop in the thenar and hypothenar eminences and distal forearm related to swelling at the base of the palm. Referred to as "pillar pain," the condition is self-limiting and generally resolves within a few months. Sensory deficits should show definite improvement by 6- 12 weeks, though motor deficits are much slower to resolve. In cases of severe denervation and atrophy, complete recovery of motor function should not be expected.

Outcome

Results of Nonoperative Therapy

One-half obtain relief of their symptoms with nonoperative therapy. In those patients unrelieved by splinting and nonsteroidal analgesics, additional benefit may be obtained from steroidal injections into the carpal ligament; however, the effect is generally only temporary and 65% to 90% of patients undergoing this treatment modality will experience recurrence of symptoms.

Results of Surgery

Relief of pain and improvement in motor and sensory deficits occur in 90% of patients undergoing carpal tunnel release. Complete or near complete resolution of signs and symptoms usually achieved in 82 % of cases with an additional 10% obtaining moderate relief. The remaining 8% achieving little or no relief or worse. Poor surgical outcomes fall into two main categories: (1) failure to relieve symptoms and (2) adverse effects and complications. The former is more common, probably related to failure to completely divide the transverse carpal ligament or to adequately manage other compressive lesions within the carpal tunnel. A significant number of surgical failures, however, may be due to misdiagnosis, such as mistaking cervical radiculopathy, brachial plexopathy, or diabetic neuropathy for carpal tunnel compression. This may be especially true if surgical indications are based on electrodiagnostic tests alone without appropriate regard for the clinical presentation and physical findings.

Postoperative failures are classified into four groups: (1) neurologic complications, such as injury to the palmar cutaneous branch and other neural elements, (2) vascular injury, including palmar hematomas, (3) tendon problems, such as bowstringing, tendon adhesions, and trigger finger, and (4) wound complications, including infection, wound dehiscence, and hypertrophic or painful scarring across the wrist crease. Except in cases of incomplete sectioning of the ligament and wound problems, re­exploration following failed carpal tunnel release may prove disappointing and of limited benefit.

Avoidance of Complications

Adverse effects and complications of carpal tunnel release are under-reported. Only those authors who deal with a large volume of patients referred for failure of prior decompressions have adequate data for evaluation. In a group of patients, 26 of whom had undergone prior carpal tunnel release that resulted in postoperative complications. Fourteen patients had painful neuromas related to division of the palmar cutaneous branch, making this the most common complication. In two patients, failure to relieve symptoms was related to the use of transverse wrist incisions. Painful and hypertrophic scarring from perpendicular wrist incisions was observed in three patients. Two patients experienced stiffness of the interphalangeal joints following prolonged immobilization, two had neuromas of the superficial branch of the radial nerve, and three experienced dysesthesia, possibly secondary to reflex sympathetic dystrophy. In a series of 186 patients, there were 34 complications in 22 patients. The complications included 12 cases of incomplete division of the transverse carpal ligament (in 8 of these cases, a transverse incision was used), 11 injuries to the palmar cutaneous branch of the median nerve, 4 cases of reflex sympathetic dystrophy, 2 each of hypertrophic scarring (from perpendicular incisions), palmar hematoma, and "bowstringing" of the flexor tendons, and 1 case of adherence of flexor tendons. Superficial wound infections have been reported to occur in 0.5 % to 6% of cases. Fortunately, injury to the recurrent motor branch is a rarely reported complication.

In analyzing sub­optimal results of carpal tunnel release, over one-half of the patients evaluated were involved in litigation concerning Worker's Compensation or automobile, machinery, or medical malpractice liability.

Retinaculotomy

In 1983, Paine and Polyzoidis described an innovative method of carpal tunnel release using a retinaculotome. In their technique, a small transverse wrist incision is made centered over the palmaris longus tendon. The flexor retinaculum is opened medial to the median nerve and the retinaculotome is inserted. This instrument has a blunt foot plate beneath a sharp vertically oriented blade and is designed to acutely incise the ligament while deflecting the underlying median nerve. The instrument is passed beneath the transverse carpal ligament, dividing the ligament as it is advanced more distally into the palm. The procedure is repeated in a proximal direction to divide the remaining ligament. Adequacy of ligament division is determined by feel and sound, which the authors describe as being quite characteristic. In their review of 516 "closed" procedures using the retinaculotome, 89% of their patients reported satisfactory results. Their few failures were thought to be due to incomplete division of the ligament. Wound hematomas occurred in less than 1% of the cases. They reported no injuries to the recurrent motor branch.

Pagnanelli and Barrer reported a series of 577 hands decompressed using a slight modification of the Paine and Polyzoidis "closed" retinacultotomy. Satisfactory results were obtained in 93 % of cases. Complications were minor and few; no injuries to the median nerve or its branches occurred. Length of post­operative recovery appeared to be shorter with this technique as compared to the more traditional "open" procedure, and incisional discomfort was perhaps lessened.

Despite the comparable results achieved by closed retinaculotomy, it has not gained wide­spread acceptance among surgeons performing carpal tunnel release. However, the limited experience with this innovative technique challenges surgical dogma that the transverse carpal ligament must be divided its entire length under direct visualization. Further experience is needed to evaluate the role of this procedure in the surgical treatment of carpal tunnel syndrome.

Summary

Carpal tunnel syndrome is a common affliction, especially among persons whose occupations require repetitive wrist motion. Numerous systemic disease processes can predispose to the development of this disorder. Symptoms are quite characteristic as are physical findings; however, because of occasional similarity between other nerve compression syndromes, electrodiagnostic tests may be necessary to confirm the diagnosis of carpal tunnel syndrome. Early and mild cases are frequently self-limiting and resolve with time or conservative measures. This is especially true with regard to pregnancy-induced carpal tunnel syndrome. Symptoms are adequately managed in one-half of the cases by using wrist splinting, analgesics, physiotherapy, and occasionally steroid injections into the carpal tunnel. In those cases unrelieved by nonoperative means, surgical decompression of the carpal tunnel can be undertaken with an 80% to 90% success rate. Surgical failures can be minimized if care is taken to avoid injury to the palmar cutaneous and recurrent motor branches of the median nerve, and if an incision is made that avoids hypertrophic scarring in the wrist yet allows adequate visualization for division of the distal extent of the transverse carpal ligament.

With a proper understanding of the anatomy, pathophysiology, clinical presentation, and available treatment modalities for median nerve entrapment at the wrist, the surgeon can expect to offer substantial relief to the majority of his or her patients afflicted with carpal tunnel syndrome.