Carpal Tunnel Syndrome



Carpal tunnel syndrome (CTS) is the most commonly diagnosed and treated entrapment neuropathy. The syndrome is characterized by pain, paresthesias, and weakness in the median nerve distribution of the hand. Surgical and nonsurgical treatments exist that can produce excellent outcomes for patients.

History of the Procedure: Sir James Paget first reported median nerve compression at the wrist following a distal radius fracture in 1854. In 1880, James Putnam presented the first series of patients with pain and paresthesias in the median nerve distribution of the hand. In 1913, Pierre Marie and Charles Foix described the pathology of median nerve compression underneath the transverse carpal ligament (TCL). In 1933, Sir James Learmonth reported the first TCL release to treat median nerve compression at the wrist. Since these early reports, much work has described the signs and symptoms of CTS as well as its treatments.

Frequency: CTS is common in the general population. CTS previously has been reported with acute onset following trauma to the wrist or as a gradual progression of symptoms typically occurring in women who are in the late middle-aged years of life. More recently, a new population at risk has been reported to be industrial workers, whose hands and wrists are subjected to repetitive motion and trauma.

Controversy exists regarding the clinical and electrophysiologic findings necessary to diagnose CTS. Despite this controversy, several surveys have been conducted to determine the prevalence of CTS in the general population. In the Netherlands, the prevalence of undetected CTS was 5.8% in women and 0.6% in men. In Sweden, the overall prevalence of CTS in the population was 2.7%. These prevalence rates were based both on clinical and electrophysiologic criteria and probably represent minimum prevalence rate estimates.

Etiology: The etiology of CTS is multifactorial, with both local and systemic factors contributing to varying degrees. Symptoms of CTS are a result of median nerve compression at the wrist, with ischemia and impaired axonal transport of the median nerve across the wrist. Compression results from elevated pressures within the carpal canal. Elevated pressures can develop within the carpal canal despite it not being a separate closed compartment within the upper extremity. Direct pressure or a space-occupying lesion within the carpal canal can increase pressure on the median nerve and produce CTS. Fracture callus, osteophytes, anomalous muscle bodies, tumors, hypertrophic synovium, gout and other inflammatory conditions, and infection can produce increased pressure within the carpal canal. Extremes of wrist flexion and extension also elevate pressure within the carpal canal.

Compression of a nerve affects intraneural blood flow. Pressures as low as 20-30 mm Hg retard venular blood flow in a nerve. Axonal transport is impaired at 30 mm Hg. Neurophysiologic changes manifested as sensory and motor dysfunction are present at 40 mm Hg. Further increases in pressure produce increasing sensory and motor block. At 60-80 mm Hg, complete cessation of intraneural blood flow is observed. The carpal canal pressures in patients with CTS averaged 32 mm Hg compared to only 2 mm Hg in control subjects.

Pressure on the median nerve at a second site remote from the wrist, termed the double crush syndrome, can further lower the median nerve’s pressure threshold for producing symptoms of CTS. If a nerve is compressed at multiple sites, traction within the nerve with joint motion may be produced. In addition to pressure, traction or stretch has been demonstrated to produce alterations in intraneural circulation. Elongation of only 8% can impair venular flow, and all intraneural microcirculation can cease at 15% nerve elongation.

Many systemic conditions are strongly associated with CTS. These conditions may directly or indirectly affect microcirculation, pressure thresholds for nerve conduction, nerve cell body synthesis, and axon transport or interstitial fluid pressures. Perturbations in the endocrine system, as observed in individuals with diabetes and hypothyroidism and in women who are pregnant, are linked to CTS. Conditions affecting metabolism (eg, alcoholism, renal failure with hemodialysis, mucopolysaccharidoses) also are associated with CTS.

The international debate regarding the relationship between CTS and repetitive motion and work is ongoing. The Occupational Safety and Health Administration (OSHA) has adopted rules and regulations regarding cumulative trauma disorders. Occupational risk factors of repetitive tasks, force, posture, and vibration have been cited. However, the American Society for Surgery of the Hand has issued a statement that the current literature does not support a causal relationship between specific work activities and the development of diseases such as CTS.

Psychosocial and socioeconomic issues increasingly are being studied. In a study of risk factors for CTS in women, the strongest link was a previous history of another musculoskeletal complaint. Perceptions of health and tolerance to pain also may influence the development of CTS.

Pathophysiology: The pathophysiology of CTS typically is demyelination. In more severe cases, secondary axonal loss may be present. The most consistent findings of biopsy specimens of tenosynovium in patients undergoing surgery for idiopathic CTS have been vascular sclerosis and edema. Localized amyloid deposition in the tenosynovium also has been reported in persons with idiopathic CTS. Inflammation, specifically tenosynovitis, is not part of the pathophysiologic process in chronic idiopathic CTS.

Clinical: Acute CTS can develop following a major trauma to the upper extremity (typically a distal radius fracture), a carpal dislocation, or a crush injury. Swelling, pain, and paresthesias in the median nerve distribution of the hand (palmar and radial) are observed.

In the more common idiopathic or chronic CTS, symptoms are more gradual in onset. Pain and paresthesias in the median nerve distribution of the hand are common. Symptoms often are worse at night and can wake a patient from sleep. As the condition worsens, daytime paresthesias become common and often are aggravated by daily activities like driving, holding a book or the phone, and combing the hair. Weakness can be present. With long-standing or severe cases of CTS, thenar atrophy frequently is observed. Because of the motor and sensory disturbances, manual dexterity is diminished, and difficulty with daily activities (eg, buttoning clothes, holding small objects) often is encountered. Pain and paresthesias also can occur proximally in the forearm, elbow, shoulder, and neck in up to one third of patients. Pain and paresthesias in the hand are not always isolated to median nerve distribution but can involve the ulnar aspect or the entire hand.

INDICATIONS


Acute CTS can be thought of as a compartment syndrome of the carpal canal, and decompression should be performed as soon as possible, assuming reduction of associated fractures or dislocations or removal of tight splints does not relieve the symptoms. Other medical and surgical factors may impact the opportunity to operate emergently, but relieving pressure on the median is a priority to reduce the risk of permanent nerve injury. Acute CTS can be diagnosed through history and physical examination alone. Electrophysiologic studies are not required. Sometimes, carpal canal pressure measurements are made to help support the diagnosis of acute CTS, and pressures greater than 30 mm Hg are consistent with the diagnosis.

Chronic CTS presents over time and is treated in both an operative and nonoperative fashion. Patients with milder symptoms and shorter nerve conduction delays on electrodiagnostic studies respond most favorably to nonoperative treatments. Patients with more severe symptoms of duration longer than one year, weakness, atrophy, radial-sided hand numbness, 2-point discrimination greater than 6 mm, and longer nerve conduction delays often do not benefit from nonoperative care. Failure or findings predictive of failure of nonoperative treatment are indications for surgical treatment of CTS.

 

Relevant Anatomy: The carpal canal is a fibroosseous tunnel at the wrist through which 9 flexor tendons and the median nerve pass. The carpal bones define the dorsal aspect of the carpal canal and are shaped in a concave arch. The palmar aspect of the carpal canal is defined by the TCL, which bridges from one side of the carpal arch to the other. Both intrinsic and extrinsic ligaments of the wrist and hand further stabilize the carpal bones. The carpal canal is narrowest at the level of the hook of the hamate, where the canal averages 20 mm in width.

The TCL attaches to the scaphoid tuberosity and trapezial crest on the radial side of the wrist and to the pisiform and hook of the hamate on the ulnar side of the wrist (see Image 1). The TCL is 1.5 mm thick and 21.7 mm in length on average. Proximally, the TCL is a continuation of the antebrachial fascia in the forearm, and, distally, the TCL attaches to the fibers of the midpalmar fascia. The TCL is under tension and helps to maintain the carpal arch. It serves as a retinacular pulley for the flexor tendons. Cutting the TCL increases the volume of the carpal canal. Cutting the TCL has also been postulated to alter the kinematics of the carpus, risk bowstringing of the flexor tendons, and decrease grip strength.

A combination of the lateral (C6-7) and medial (C8-T1) cords of the brachial plexus forms the median nerve. At the wrist and into the palm, the median nerve divides into terminal motor and sensory branches with some anatomic variability. The variability is due in part to the branching point of the recurrent motor branch. An extraligamentous pattern, with a branching point distal to the TCL, is the most common. The recurrent motor branch also can divide from the median nerve underneath the TCL in a subligamentous fashion and then either wrap around the distal end of the TCL or pass directly through the TCL to innervate the thenar muscles. Other less common patterns, such as a branch point proximal to the TCL, exist as well. These variations can have major surgical implications.

The ulnar nerve is the other major motor and sensory nerve of the hand. The ulnar nerve does not pass through the carpal canal but instead through the Guyon canal located adjacent to the carpal canal at the wrist. Division of the TCL will change the morphology of the Guyon canal from triangular to ovoid.

Contraindications: No specific contraindications exist for surgical treatment of CTS. Medical conditions should be stabilized prior to surgery. Pregnancy should be allowed to proceed to term, as CTS often resolves after the pregnancy. Unrealistic expectations can influence surgical outcomes, and risk factors for poor outcomes should be sought preoperatively. Those individuals with severe CTS should be cautioned that their numbness may persist, at least to some degree, despite a complete surgical release. Patients receiving worker's compensation have a lower return-to-work rate. Higher preference for improved strength preoperatively also has been associated with lower satisfaction.

 

WORKUP

Imaging Studies:

  • Radiographs
    • Wrist radiographs should not be performed routinely in patients with CTS due to the low yield of useful information.
    • Only 0.4% of routine wrist radiographs for CTS were demonstrated to have findings of therapeutic significance.
    • Patients with a history of systemic disorders, wrist trauma, arthritis, or abnormal findings (eg, limited motion) on physical examination for CTS are much more likely to have radiographic findings; use in these patients may be indicated.

Other Tests:

  • A thorough physical examination of the neck and upper extremity should be performed. Clinical tests to evaluate for CTS include sensory evaluations and provocative maneuvers that attempt to elicit signs or symptoms of median nerve compression at the wrist. The lists below include the more commonly used tests in the workup.
  • Sensory examinations: Threshold tests (Semmes-Weinstein pressure monofilaments and vibratory sensibility) reflect gradual decreases in nerve function, while the innervation density tests (2-point discrimination) can remain normal until nearly all sensory conduction has ceased.
    • Semmes-Weinstein pressure monofilaments: Monofilaments of increasing diameter are pressed perpendicularly against the palmar aspect of each finger until the monofilament bends to determine the sensory threshold for each finger. Values greater than 2.83 may be indicative of CTS.
    • Vibratory sensibility: A 256-cycle per second tuning fork is struck against an object, causing it to vibrate, and the fork's prong then is placed against the patient’s fingertips. The median and ulnar fingers of both hands are tested. The test is considered positive if decreased sensation is perceived.
    • Static and moving 2-point discrimination: This is the minimum separation between 2 points (either static or moving) that can be perceived. Failure to discriminate more than 6 mm (static) or 5 mm (moving) is a positive finding.
  • Provocative tests
    • Phalen wrist flexion test: The patient’s elbows are placed on a table, the forearms are perpendicular to the table, and the wrists are flexed. This position is held for 60 seconds. The test is positive if numbness or paresthesias develop in radial-sided digits.
    • Tinel test: The examiner taps along the course of the median nerve on the volar aspect of the wrist. The test is positive if paresthesias are elicited in the median nerve distribution.
    • Carpal compression test: Direct application of pressure of 150 mm Hg or even pressure from both thumbs of the examiner is exerted on the patient’s carpal canal and is maintained for 30 seconds. The test is positive if pain, numbness, or paresthesias develop in the radial-sided digits.
  • Electrophysiologic diagnostic studies: Nerve conduction
    • Median motor and sensory latencies and conduction velocities are measured across the wrist. A sensory latency of greater than 3.5 millisecond or a motor latency of greater than 4.5 millisecond is considered an abnormal finding. Comparison to the contralateral hand and also to ulnar motor and sensory latencies and conduction velocities can provide additional evidence supporting the diagnosis of CTS.
    • Distal compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes may be decreased in persons with CTS.
    • Minimum F wave latencies of the median nerve can be prolonged in individuals with CTS.
  • Electrophysiologic diagnostic studies: Electromyography
    • This study must be performed with a clinical differential diagnosis in mind, and the abductor pollicis brevis is the key muscle to evaluate.
    • Positive findings in persons with CTS include sharp waves, fibrillation potentials, and increased insertional activity.
  • When interpreting electrophysiologic studies, remembering that CTS is a clinical diagnosis is important. CTS is a constellation of signs and symptoms caused by compression and slowing of the median nerve at the wrist, and electrodiagnostic studies should not be used independently in making a diagnosis.

Diagnostic Procedures:

  • Direct pressure measurement
    • A catheter is inserted directly into the carpal canal to measure pressure.
    • This test typically is used to evaluate acute CTS and can help differentiate between median nerve contusion and compression.
    • Thirty mm Hg is a guide used to determine if the pressure is critically elevated, but physical examination and patient-specific factors can modify the critical pressure.


TREATMENT

Medical therapy: Steroid injection and wrist splinting have been used effectively in patients with milder symptoms. Complete relief of all symptoms was observed in 76% of hands at 6 weeks after treatment but deteriorated to only 22% with complete relief at more than 12 months of follow-up. Similar positive results have been reported with steroid injection alone in a double-blind placebo-controlled trial. Other nonoperative treatments have been proposed but not studied as rigorously and include nonsteroidal anti-inflammatory drugs (NSAIDs), vitamins (B complex), workstation redesign, ergonomic tool modification, acupuncture, and yoga.

Surgical therapy: Open and endoscopic surgical techniques have been described for treatment of CTS. Both operative techniques are effective for the treatment of chronic CTS. Potential benefits of the endoscopic technique, including a more rapid functional recovery, have to be weighed against the increased cost and higher complication rate of the endoscopic technique. Reliability and good visualization of the open technique continue to make it the preferred operation for many hand surgeons. Both techniques are described below. Open release with an extended surgical incision is recommended for acute CTS.

Intraoperative details:

Open carpal tunnel release

General, regional, or local anesthesia can be used. Surgery is performed with a tourniquet inflated around the arm to control bleeding in the operative field.

  • A longitudinal incision in the base of the palm is used (see Image 2). The incision is made in line with the flexed ring finger. The intersection of this longitudinal line with the Kaplan line (a line parallel to the ulnar aspect of the extended thumb) marks the distal extent of the incision. Proximally, the incision ends a few millimeters distal to the distal wrist flexion crease.

  • Following the incision, the subcutaneous fat is retracted radially and ulnarly, exposing the superficial palmar fascia. The superficial palmar fascia is divided sharply in line with the skin incision. Retractors are placed deeper to expose the TCL.

  • A blunt curved hemostat clamp or similar instrument can be passed deep to the distal edge of the TCL to help confirm position and protect the contents of the carpal canal. The TCL is divided sharply along its ulnar aspect. Distally, the superficial palmar arch marks the end of the TCL and must be protected. Proximally, the ligament is transected to the level of the distal wrist crease under direct vision.

  • Blunt dissecting scissors are used to spread both superficial and deep to the antebrachial fascia. Angled retractors are placed proximally under the skin flap so that the antebrachial fascia now can be divided for 2-3 centimeters proximally under direct vision, using the blunt scissors partially opened in a pushing fashion.

  • If visualization is poor, the skin incision may need to be extended proximally. If the incision needs to extend across the distal wrist crease, it should be angled.

  • Tenolysis, neurolysis, synovectomy, or reconstruction of the TCL is not performed routinely.

  • Prior to closure, the tourniquet is deflated and hemostasis is obtained with bipolar electrocautery. No deep sutures are used. The skin is closed with 4-0 nylon. A soft sterile dressing is applied.

Postoperative splinting has been recommended to prevent prolapse of nerve, entrapment of nerve in scar tissue, or tendon bowstringing. However, splinting has not been demonstrated to have any beneficial effect and can increase pain and scar tenderness.

Endoscopic carpal tunnel release

One- and 2-incision (ie, portal) techniques are described.

  • In both techniques, the first incision is made transversely just proximal to the wrist flexion crease between the palmaris longus and the flexor carpi ulnaris (see Image 3).

  • In the 1-incision technique, the blade assembly and viewing device are inserted into the carpal canal anterograde through the proximal incision. With the wrist in extension, the device is advanced to the distal edge of the TCL. Video picture, ballottement, and translumination confirm the position. When correctly positioned, the cutting blade is elevated, and the device is withdrawn, cutting the distal half of the ligament. The device then is reinserted to inspect ligament division, and additional passes then are made to complete the division of the remaining proximal portions of the ligament. The skin incision is sutured closed.

  • In the 2-incision technique, the second incision is made transversely in the palm on a line bisecting the angle formed by lines drawn along the distal border of the fully abducted thumb and the third web space (see Image 3). Blunt dissection is performed in the palm to identify the superficial palmar arch, the common digital nerves, and the distal edge of the TCL. Following the axis of the forearm, a blunt curved instrument is inserted into the carpal canal through the proximal incision to free soft tissues from the undersurface of the TCL.

  • A trocar and sheath assembly is passed anterograde from the proximal incision to the distal incision through the carpal canal. The fingers and wrist then are extended and secured in a custom holder. The trocar is removed, and the endoscope is inserted into the sheath through the proximal incision.

  • The distal half of the ligament then is divided with special upward and reverse cutting knives placed in the distal sheath while viewing through the endoscope.

  • The endoscope then is removed and reinserted into the sheath through the distal incision, and the reverse cutting knife is inserted into the sheath through the proximal incision. By withdrawing the reverse cutting knife, the proximal half of the ligament is released. Skin incisions are sutured closed.

In both the 1- and 2-incision techniques, if visualization is not satisfactory, the technique should be abandoned and converted to an open carpal tunnel release.

NEW FINDINGS

Compared with wrist splinting, open carpal tunnel release surgery results in better outcomes, Dutch researchers report in the September 11th issue of the Journal of the American Medical Association.

Dr. Annette A. M. Gerritsen from Vrije Universiteit Medical Center, Amsterdam, and colleagues randomly assigned 176 patients with idiopathic carpal tunnel syndrome to open carpal tunnel release surgery or at least 6 weeks of nighttime wrist splinting.

During 18 months of follow-up, the researchers evaluated overall improvement, severity of symptoms and the number of nights when symptoms caused the patient to wake up. Treatment success was defined as a general improvement score by the patient of "completely recovered" or "much improved."

Intention-to-treat analysis found that those allocated to open carpal tunnel release surgery had better outcomes on all measures compared with patients allocated to splinting.

At 3 months, 80% of the patients in the surgery group reported treatment success, compared with 54% of the patients in the splint group (p < 0.001).

After 18 months, treatment was successful for 90% of the 68 patients in the surgery group who could be evaluated, compared with 75% of the 79 patients in the splint group (p=0.02). However, Dr. Gerritsen's group notes that by 18 months, 41% of the patients (n=32) in the splint group had undergone open carpal tunnel release surgery.

In an additional analysis, after 18 months, surgery was successful in 94% of the 32 patients in the splint group who underwent surgery, whereas splinting was successful in 62% of the remaining 47 patients who did not undergo surgery.

"The study by Gerritsen et al. strongly reinforces findings that indicate splinting is an excellent adjunctive treatment in early cases, but is ineffective on a long-term basis for treating this condition [carpal tunnel syndrome]," Dr. E. F. Shaw Wilgis from Union Memorial Hospital, Baltimore, comments in an accompanying editorial.

"The findings of Gerritsen et al. also suggest that there is no need for patients with carpal tunnel syndrome to continue to have pain, functional limitations, or sleep loss when surgery produces such a favorable outcome," Dr. Wilgis adds.

 

COMPLICATIONS

Complications are not common following either open or endoscopic surgical techniques. Major complications with either technique can include nerve laceration, vessel laceration, and tendon laceration. Laceration of the palmar cutaneous branch of the median nerve with painful neuroma formation is reported to be the most common complication of open carpal tunnel release.

Incomplete release of the TCL is reported to be the most common complication of endoscopic carpal tunnel release. Loss of grip strength and tenderness of scars following open carpal tunnel release tend to resolve with time.

The general consensus among surgeons is that nerve injuries occur with greater frequency with an endoscopic method than with an open release. Nerve injuries with the endoscopic technique are not necessarily related to the skill and experience of the surgeon but may be related to the nature of the procedure, the anatomy of the carpal canal, and the device used.

OUTCOME AND PROGNOSIS

Lasting relief of pain, numbness, and paresthesias can be expected in more than 90% of patients treated with open or endoscopic carpal tunnel release, and patient satisfaction is high. The endoscopic technique is associated with a shorter interval to return to work and less incisional pain. The primary reason for a poor result is an error in diagnosis.

FUTURE AND CONTROVERSIES

The etiology of CTS and its relationship to the workplace will continue to be better understood in the coming decades. It already is apparent that the etiology of CTS is multifactorial, and while work-induced repetitive trauma may not be the major cause of CTS, it may contribute in some way.

A realized goal of the less invasive endoscopic technique is to return individuals to work sooner. Presently, concerns over safety and cost have prevented current endoscopic techniques from being widely accepted and used. In the future, safer endoscopic techniques and new less invasive or nonoperative techniques to provide safe and lasting treatment for CTS hopefully will be developed.

IMAGES

Caption: Picture 1. Cross sections of the carpal canal at the levels of the proximal and distal carpal rows are depicted. The transverse carpal ligament bridges the carpal tunnel and is under tension.

Click to see larger picture

 

 

Picture Type: Image

Caption: Picture 2. Surgical incision for an open carpal tunnel release is depicted. The incision can be extended proximally across the wrist flexion crease for a more extended exposure.

Click to see larger picture

 

 

Picture Type: Image

Caption: Picture 3. Surgical incisions for an endoscopic (1 and 2 portal) carpal tunnel release are depicted. Precise location of the incisions is critical and depends on individual anatomy.

Click to see larger picture

 

 

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