Orthopaedic Surgery - Carpal Tunnel Syndrome

Basics

Carpal tunnel syndrome (CTS) is a compressive neuropathy of the median nerve as it passes through the carpal tunnel at the wrist.

The carpal tunnel is a relatively rigid anatomical space. Its floor is formed by the volar radiocarpal and intercarpal ligaments, while the transverse carpal ligament forms the roof.

Within the tunnel pass nine flexor tendons—the four flexor digitorum profundus tendons, four flexor digitorum superficialis tendons, and the flexor pollicis longus tendon—together with the median nerve.

Because there is little room for expansion, any increase in pressure within the tunnel may compress the median nerve.

Functional Effects

Compression of the median nerve may cause numbness, paresthesias, pain, weakness, and impaired fine motor function.

Sensory symptoms usually involve the palmar surface of the thumb, index finger, middle finger, and radial half of the ring finger.

With more advanced compression, weakness or atrophy of the thenar muscles may develop, particularly affecting thumb palmar abduction.

Pregnancy Considerations

Carpal tunnel syndrome occurs more frequently during pregnancy than in the general population.

Symptoms commonly improve or resolve after delivery as pregnancy-related fluid retention decreases.

Initial treatment generally consists of a nighttime wrist splint maintaining the wrist in neutral.

A corticosteroid injection may be considered for persistent symptoms when appropriate, with medication safety reviewed in conjunction with the patient’s obstetric care.

Surgery During Pregnancy

Because pregnancy-related CTS frequently resolves postpartum, surgery is generally deferred when possible.

However, severe cases involving persistent numbness, progressive weakness, or major functional impairment may occasionally require surgical decompression during pregnancy.

When necessary, carpal tunnel release can be performed using local anesthesia.

Epidemiology

Carpal tunnel syndrome affects approximately 4–5% of the population.

It occurs most frequently between approximately 40 and 60 years of age and is more common in women than men.

CTS is the most frequently diagnosed compressive neuropathy of the upper extremity.

Risk Factors

Recognized risk factors include female sex, diabetes mellitus, hypothyroidism and other endocrine abnormalities, smoking, elevated body mass index, pregnancy, perimenopausal status, rheumatoid arthritis, and previous hand or wrist tendinopathy.

Forceful repetitive hand use may also contribute.

The relationship between CTS and routine computer use remains controversial.

Occupational Factors

Work involving forceful gripping, sustained wrist positioning, repetitive hand exertion, or vibration may increase symptoms in susceptible individuals.

In occupational cases, modification of the provoking activity can be an important part of treatment.

Genetics

No specific genetic factor has been definitively established as a direct cause of carpal tunnel syndrome.

However, inherited differences in anatomy, body habitus, and systemic disease susceptibility may indirectly influence risk.

Pathophysiology

CTS develops when increased pressure within the carpal tunnel compromises the median nerve.

Compression and traction can impair the nerve’s microcirculation, producing edema and reduced oxygen delivery.

Repeated or prolonged compression may subsequently produce recurrent demyelination and slower nerve conduction.

Nerve Conduction Changes

As compression becomes more severe, electrical impulses travel more slowly through the median nerve at the wrist.

Prolonged compression may eventually cause axonal injury, resulting in persistent numbness, weakness, and thenar muscle atrophy.

Etiology

Any process that reduces the available space within the carpal tunnel or increases its contents can compress the median nerve.

In many patients, no single structural cause is identified.

Common Causes

Potential causes include flexor tenosynovitis, previous trauma involving the carpal bones, ganglion cysts, fibromas, lipomas, rheumatoid cysts, gout, and diabetic neuropathy.

Inflammatory swelling of the tendon sheaths may be particularly important because all nine flexor tendons pass through the same confined space.

Diagnosis

Carpal tunnel syndrome can often be diagnosed accurately through a careful history and physical examination.

Evaluation should include assessment for sensory disturbance, thenar weakness or atrophy, and reproduction of symptoms with provocative maneuvers.

Electrodiagnostic testing can support the diagnosis and determine severity but is not mandatory in every straightforward case.

Signs and Symptoms

Typical symptoms include numbness and tingling in the median nerve distribution, hand weakness or clumsiness, and pain involving the hand, wrist, or distal forearm.

Symptoms are frequently worse at night.

Many patients wake from sleep because of painful numbness or tingling and may shake the hand to obtain relief.

Sensory Distribution

Paresthesias typically involve the thumb, index finger, middle finger, and radial half of the ring finger.

The little finger is usually spared.

Symptoms may occasionally radiate proximally into the wrist or forearm.

Motor Symptoms

Patients may notice difficulty with tasks requiring fine motor control, such as buttoning clothing, handling coins, writing, or gripping small objects.

More advanced disease may cause weakness of thumb palmar abduction due to involvement of the abductor pollicis brevis.

Nocturnal Symptoms

Nighttime symptoms are particularly characteristic.

Wrist flexion during sleep may increase carpal tunnel pressure and aggravate median nerve compression.

This explains why neutral-position nighttime splinting can be effective.

Tinel Sign

The Tinel sign is elicited by gently tapping over the median nerve at the carpal tunnel while the wrist is held in a neutral position.

A positive test reproduces tingling or electric sensations in the median nerve distribution of the hand.

Phalen Test

The Phalen test is performed by placing the wrist in full flexion, traditionally around 90°, and maintaining the position.

Development of paresthesias in the median nerve distribution within approximately 30–60 seconds supports the diagnosis.

Flexion-Compression Test

For the flexion-compression test, the elbow is extended and the forearm is supinated.

The wrist is flexed to approximately 60°, and direct pressure is applied over the median nerve at the carpal tunnel.

Reproduction of median-distribution paresthesias within about 30 seconds is considered a positive finding.

Physical Examination

The hand should be inspected for thenar muscle wasting.

Strength of thumb palmar abduction should be assessed carefully because weakness may indicate advanced median nerve compression.

Thenar Atrophy

Visible flattening or wasting of the thenar eminence suggests chronic or severe CTS.

Once substantial muscle atrophy has developed, full motor recovery after decompression may be incomplete.

Sensory Examination

Sensation should be tested over the thumb and fingers.

Two-point discrimination can be measured on the radial and ulnar sides of each fingertip.

Normal discrimination is generally less than approximately 5–6 mm, or should be symmetric with the opposite hand when symptoms are unilateral.

Examination for Other Neuropathies

The entire upper extremity should be examined for alternative or additional sites of nerve compression.

Conditions such as cervical radiculopathy, proximal median nerve entrapment, and cubital tunnel syndrome may mimic or coexist with CTS.

Laboratory Tests

Laboratory investigations are not required in every patient but may be useful when a systemic cause is suspected.

Tests may include erythrocyte sedimentation rate, serum glucose, serum uric acid, and thyroid function studies.

These investigations may identify inflammatory, metabolic, endocrine, or crystal-related conditions contributing to nerve compression.

Electrodiagnostic Studies

Electromyography and nerve conduction studies can confirm median nerve compression at the wrist and help determine its severity.

They can also identify additional abnormalities elsewhere along the nerve pathway.

Double-Crush Syndrome

Electrodiagnostic testing may help detect a double-crush syndrome, in which median nerve dysfunction at the wrist coexists with a more proximal lesion, such as cervical radiculopathy or proximal median nerve compression.

This possibility is particularly important when symptoms persist despite apparently adequate carpal tunnel treatment.

Imaging

Plain Radiographs

Routine radiographs are not necessary for uncomplicated CTS.

Wrist radiographs may be useful in patients with a history of trauma, deformity, or longstanding inflammatory arthritis.

They can demonstrate fractures, malalignment, arthritis, or other structural abnormalities affecting the carpal tunnel.

Cervical Spine Imaging

Cervical spine radiographs may be useful when a proximal neurologic cause is suspected.

They can also demonstrate abnormalities such as a cervical rib when thoracic outlet syndrome is being considered, although thoracic outlet symptoms more often resemble ulnar-sided neuropathy.

Differential Diagnosis

Important differential diagnoses include thoracic outlet syndrome, cervical nerve root compression from degenerative disc disease or tumor, proximal median nerve entrapment, and cubital tunnel syndrome.

Clinical distribution of symptoms and electrodiagnostic testing can help distinguish these disorders.

Treatment

General Measures

Initial management is usually nonoperative, particularly in mild or intermittent disease.

The principal conservative measures are nighttime wrist splinting, activity modification, and corticosteroid injection in selected patients.

Nighttime Splinting

A wrist splint should hold the wrist in a neutral position during sleep.

Excessive flexion or extension increases carpal tunnel pressure and can worsen symptoms.

Night splinting is particularly useful for patients with nocturnal paresthesias.

Duration of Splinting

To determine whether conservative treatment is effective, nighttime splinting should generally be used consistently for at least 1 month.

Patients who improve while wearing the splint but experience rapid symptom recurrence after discontinuation may ultimately require surgical treatment.

Activity Modification

When symptoms are associated with work or repetitive activity, modification of the provoking tasks is recommended.

Reducing forceful gripping, repetitive wrist motion, prolonged wrist flexion or extension, and other aggravating activities may reduce symptoms.

Corticosteroid Injection

A corticosteroid injection into the carpal tunnel may provide temporary or sometimes prolonged symptom relief.

Injection should be performed by an experienced clinician because inadvertent injection into or injury of the median nerve can cause significant neurologic damage.

Indications for Corticosteroid Injection

Injection is particularly useful when compression is expected to be temporary, such as during pregnancy, or when modification of the precipitating activity is feasible.

It may also serve as a therapeutic trial in mild to moderate CTS.

Physical Therapy

Formal physical therapy is not routinely required for uncomplicated carpal tunnel syndrome.

Therapy may be useful for workplace modification, ergonomic assessment, or selected hand and nerve-gliding programs, although these are generally adjunctive rather than primary treatment.

Medication

No oral medication has been shown to specifically reverse median nerve compression within the carpal tunnel.

Analgesics may relieve pain temporarily but do not correct the underlying mechanical compression.

Indications for Surgery

Carpal tunnel release is considered when conservative treatment has failed or when there is evidence of constant numbness, motor weakness, thenar atrophy, or significant electrodiagnostic abnormality.

Progressive neurologic deficit is a particularly strong indication for decompression.

Surgical Principle

The goal of surgery is to decompress the median nerve by dividing the transverse carpal ligament.

This increases the volume of the carpal tunnel and reduces pressure on the nerve.

Open Carpal Tunnel Release

Open release is performed through a longitudinal palmar incision.

The incision is typically positioned in line with the ulnar border of the ring finger axis and provides direct visualization of the transverse carpal ligament and median nerve.

The ligament is divided completely to decompress the nerve.

Mini-Open Release

A mini-open technique uses a smaller incision while maintaining direct visualization of the ligament.

Its aim is to reduce soft-tissue disruption while achieving complete decompression.

Endoscopic Carpal Tunnel Release

Endoscopic release divides the transverse carpal ligament through one or more small portals using an endoscopic system.

Long-term results are generally similar to those of open release.

Some patients may return to work more quickly and experience less early scar discomfort.

Open Versus Endoscopic Release

At approximately 6 months and beyond, open and endoscopic procedures generally provide comparable symptom relief.

Endoscopic release may result in faster early functional recovery and less scar tenderness in some patients.

However, the risk of nerve injury may be slightly higher with endoscopic techniques.

Follow-Up

Patients treated conservatively should be reassessed for persistence or progression of numbness, nocturnal symptoms, weakness, and functional impairment.

Failure of a reasonable period of nonoperative management may warrant surgical referral.

Prognosis With Nonoperative Treatment

Many patients with mild or occupationally related CTS improve with a combination of night splinting, corticosteroid injection, and modification of aggravating activities.

If the provoking work activity continues unchanged, conservative measures may provide only temporary relief.

Prognosis After Surgery

Pain often improves very quickly after carpal tunnel release.

Numbness usually recovers more gradually over the following weeks to months because the median nerve requires time to recover from chronic compression.

Severe Compression

Patients with longstanding or severe compression may not regain completely normal sensation or motor strength even after technically successful decompression.

Permanent nerve injury may already have occurred before surgery.

Recovery of Strength

Grip and thenar strength may take 6 months or longer to recover maximally after release.

The speed and completeness of recovery depend partly on the duration and severity of preoperative nerve compression.

Complications

Possible complications include iatrogenic injury to the median nerve or its branches, painful scar formation, pillar pain, incomplete release, infection, and persistent or recurrent symptoms.

Nerve injury can occur with either open or endoscopic surgery but may be slightly more frequent with endoscopic techniques.

Scar Sensitivity

Tenderness or hypersensitivity around the surgical incision can occur, particularly after open release.

This usually improves gradually over several months but may persist in a minority of patients.

Pillar Pain

Pillar pain refers to discomfort on either side of the carpal tunnel after release, often around the thenar or hypothenar regions.

It commonly improves with time but can temporarily interfere with gripping or weight-bearing through the palm.

Persistent Symptoms After Surgery

Persistent symptoms after decompression may result from incomplete division of the transverse carpal ligament, an incorrect initial diagnosis, severe irreversible nerve damage, or an untreated proximal compression site.

A double-crush syndrome or generalized peripheral neuropathy should also be considered.

Patient Monitoring

Patients receiving conservative treatment should be monitored for progression from intermittent symptoms to constant numbness or motor weakness.

Development of thenar atrophy or persistent sensory loss should prompt surgical consideration.

Postoperative Monitoring

After surgery, patients are typically reviewed for wound assessment and suture removal.

Activity can then be increased progressively if wound healing is satisfactory.

Neurologic recovery may continue for several months after the incision itself has healed.

Patient Teaching

Patients should avoid prolonged or repetitive wrist positions that aggravate symptoms.

Workstation or occupational modifications may be useful when symptoms are related to repetitive or forceful hand activity.

Prevention

Reducing prolonged wrist flexion or extension and minimizing repetitive forceful hand use may help decrease symptoms in susceptible individuals.

Maintaining appropriate ergonomic wrist positioning may also be beneficial.

Frequently Asked Question: Should Pregnancy-Related CTS Be Treated Surgically?

CTS arising during pregnancy often improves after delivery.

Initial treatment should therefore consist of nighttime neutral wrist splinting, with corticosteroid injection considered when appropriate.

Surgery is generally deferred until after delivery so that spontaneous resolution can be assessed, although severe cases can be treated surgically under local anesthesia when necessary.

Frequently Asked Question: Can CTS Recur After Surgical Release?

True recurrence after an adequately performed release is uncommon.

Persistent or recurrent symptoms should prompt evaluation for incomplete ligament release, an alternative diagnosis, double-crush syndrome, or an underlying peripheral neuropathy.

Frequently Asked Question: What Are the Typical Symptoms?

Typical symptoms are pain, numbness, and tingling, especially at night.

The sensory symptoms usually involve the thumb, index finger, middle finger, and radial half of the ring finger.

Patients may also experience difficulty with fine motor tasks or hand clumsiness.

When motor weakness develops, the abductor pollicis brevis is commonly affected.