Orthopaedic Surgery - Cubital Tunnel Syndrome

Basics

Cubital tunnel syndrome (CuTS) is an ulnar nerve entrapment neuropathy at the elbow caused by compression, traction, or both as the ulnar nerve passes through the cubital tunnel.

Patients typically experience pain, numbness, and paresthesias along the ulnar side of the forearm and hand. More advanced disease may produce weakness and wasting of muscles supplied by the ulnar nerve.

Synonym

Cubital tunnel syndrome is sometimes referred to as ulnar tunnel syndrome, although the term should be distinguished from compression of the ulnar nerve at Guyon canal in the wrist.

Epidemiology

Cubital tunnel syndrome is the second most common upper-extremity entrapment neuropathy, after carpal tunnel syndrome.

Men and women are affected at approximately similar rates, with reported incidences of about 25 per 100,000 person-years in men and 19 per 100,000 person-years in women.

Risk Factors

Important risk factors include diabetes mellitus and previous trauma around the elbow.

Degenerative changes, repetitive elbow flexion, local structural abnormalities, and prolonged external pressure may also contribute.

Etiology

Symptoms result from a combination of compression and traction on the ulnar nerve, particularly during elbow flexion.

Flexion decreases the volume of the cubital tunnel while simultaneously stretching the ulnar nerve around the medial epicondyle.

Potential Sites of Compression

The ulnar nerve may be compressed at several locations around the elbow.

These include the Arcade of Struthers, medial intermuscular septum, cubital tunnel proper, and the interval between the two heads of the flexor carpi ulnaris.

Cubital Tunnel Proper

The most common site of compression is the cubital tunnel itself, where the ulnar nerve passes behind the medial epicondyle and beneath Osborne’s ligament.

External and Structural Causes

Potential causes of compression include an enlarged medial head of the triceps, previous trauma, recurrent ulnar nerve subluxation, osteophytes from arthritis, ganglion cysts, and anomalous muscles such as an anconeus epitrochlearis.

Associated Conditions

Cubital tunnel syndrome may coexist with other compressive neuropathies, including carpal tunnel syndrome and thoracic outlet syndrome.

More than one site of nerve compression may therefore be present in the same patient.

Diagnosis

General Principles

The diagnosis is primarily clinical, based on the characteristic history and physical examination.

Nerve conduction studies can support the diagnosis, although false-negative electrodiagnostic studies may occur.

Signs and Symptoms

Patients commonly report a vague aching pain around the medial elbow that may extend into the ulnar aspect of the forearm, wrist, or hand.

Numbness and paresthesias commonly involve the ring and small fingers.

Sensory Symptoms

Altered sensation may occur in the ulnar distribution of the hand and sometimes the medial forearm.

Symptoms are often aggravated by prolonged elbow flexion, such as during sleep, driving, or telephone use.

Physical Examination

Sensory Examination

The examiner should identify sensory abnormalities in the ulnar nerve distribution but should also examine other dermatomes and peripheral nerves.

This is important for excluding cervical radiculopathy, additional peripheral nerve entrapment, or double-crush syndrome.

Dorsal Ulnar Hand Sensation

Numbness over the dorsal ulnar aspect of the hand suggests that ulnar nerve compression is proximal to Guyon canal because the dorsal sensory branch arises before the nerve enters the wrist canal.

Intrinsic Muscle Strength

Intrinsic hand strength should be assessed carefully.

Weakness may affect pinch, finger abduction and adduction, and other fine motor functions.

Froment Sign

The Froment test evaluates weakness of the adductor pollicis.

The patient grasps a piece of paper between the thumb and index finger while the examiner attempts to pull it away.

Positive Froment Sign

If the adductor pollicis is weak, the patient compensates by flexing the thumb interphalangeal joint using the flexor pollicis longus.

This compensatory thumb flexion constitutes a positive Froment sign.

Wartenberg Sign

A Wartenberg sign occurs when the small finger rests persistently in an abducted position.

This reflects weakness of the intrinsic muscles responsible for finger adduction.

Muscle Wasting

The hand should be inspected for intrinsic muscle atrophy.

Wasting is often especially visible in the first dorsal interosseous muscle and along the hypothenar region.

Tinel Sign

Tapping over the ulnar nerve at the cubital tunnel may reproduce tingling or electric sensations into the ring and small fingers.

This constitutes a positive Tinel sign at the elbow.

Elbow Flexion Test

The elbow is held in maximal flexion for approximately 1 minute, usually with the wrist maintained neutral or slightly extended.

Reproduction of ulnar-sided numbness or paresthesias supports the diagnosis.

Keeping the wrist neutral helps avoid provoking coexisting carpal tunnel syndrome.

Scratch Collapse Test

The scratch collapse test has been described as an additional provocative maneuver.

The patient resists shoulder internal rotation while the examiner lightly scratches the skin over the suspected compression site.

Transient loss of resistance has been described in association with compressive neuropathy, although this maneuver should be interpreted together with the rest of the examination.

Ulnar Nerve Subluxation

The ulnar nerve should be palpated while the elbow moves from extension into flexion.

Subluxation or dislocation of the nerve over the medial epicondyle may affect surgical planning and can favor anterior transposition in selected patients.

Imaging and Diagnostic Testing

Plain Radiographs

Elbow radiographs may be obtained when there is concern for a bony cause of compression, previous trauma, deformity, or osteoarthritis.

Radiographs are not required in every uncomplicated case.

Nerve Conduction Studies

Nerve conduction velocity studies may demonstrate slowing of ulnar nerve conduction across the elbow.

The above-elbow and below-elbow conduction velocities are compared.

Electrodiagnostic Criteria

Findings supporting cubital tunnel syndrome include a conduction velocity drop of more than approximately 10 m/s across the elbow or an absolute conduction velocity of less than approximately 50 m/s across the involved segment.

Electrodiagnostic findings should be correlated with clinical symptoms.

Pathological Findings

During surgical decompression, one or more specific areas of nerve constriction may be visible.

All potential sites of compression should be inspected to ensure complete release.

Differential Diagnosis

Cervical Radiculopathy

Compression of the C8 or T1 cervical nerve roots can produce hand numbness, weakness, and intrinsic muscle dysfunction similar to CuTS.

A cervical examination is therefore important when symptoms are atypical.

Thoracic Outlet Syndrome

Thoracic outlet syndrome may produce ulnar-sided paresthesias and upper-extremity discomfort.

The distribution and associated vascular or proximal neurologic findings can help distinguish it from isolated cubital tunnel syndrome.

Guyon Canal Syndrome

Ulnar nerve compression at Guyon canal in the wrist can produce sensory and motor abnormalities in the ulnar hand.

Preserved dorsal ulnar hand sensation favors compression at the wrist rather than the elbow.

Carpal Tunnel Syndrome

Carpal tunnel syndrome affects the median nerve rather than the ulnar nerve but may coexist with CuTS.

The sensory distribution and provocative examination findings help distinguish the two.

Neurologic Disorders

Systemic neurologic conditions such as Guillain–Barré syndrome and amyotrophic lateral sclerosis can produce weakness or sensory changes that mimic peripheral entrapment neuropathy.

Medial Epicondylitis

Medial epicondylitis causes pain over the medial elbow but does not usually produce ulnar nerve sensory loss or intrinsic muscle weakness unless associated CuTS is also present.

Ulnohumeral Osteoarthritis

Degenerative arthritis of the elbow can cause medial elbow pain and osteophyte formation.

Large osteophytes may also contribute directly to ulnar nerve compression.

Treatment

General Measures

Initial treatment is usually nonoperative in patients with mild or moderate symptoms and no progressive motor deficit.

The primary goals are to reduce nerve compression and minimize prolonged elbow flexion.

Night Splinting

A nighttime elbow splint, brace, or soft wrap can be used to prevent excessive flexion during sleep.

Keeping the elbow from flexing beyond approximately 50° may reduce nocturnal symptoms.

Activity Modification

Patients should avoid prolonged elbow flexion and repetitive activities that provoke symptoms.

Direct pressure over the cubital tunnel, such as leaning the medial elbow on a desk or armrest, should also be minimized.

Duration of Conservative Treatment

A trial of nonoperative treatment for approximately 1–3 months is reasonable in patients without severe weakness or progressive neurologic impairment.

Surgery

Indications

Surgery should be considered when symptoms persist despite appropriate conservative care, when numbness is worsening, or when weakness of ulnar-innervated muscles is present.

Progressive muscle wasting is a particularly important indication for surgical evaluation.

Surgical Options

Operative techniques include in situ decompression, anterior ulnar nerve transposition, and medial epicondylectomy.

The optimal procedure depends on nerve stability, anatomy, previous surgery, and the specific site of compression.

In Situ Decompression

Simple decompression releases constricting structures while leaving the ulnar nerve in its native position.

The procedure can be performed through an open or endoscopic approach.

Anterior Transposition

Anterior transposition relocates the ulnar nerve from behind the medial epicondyle to a position anterior to it.

The nerve may be placed subcutaneously, intramuscularly, or submuscularly.

Indications for Transposition

After decompression, the nerve is examined dynamically.

If it is unstable, subluxates, or dislocates over the medial epicondyle, anterior transposition may be performed.

Medial Epicondylectomy

Medial epicondylectomy removes part of the medial epicondyle to reduce tension and compression on the ulnar nerve.

Care must be taken to protect the medial collateral ligament of the elbow.

Medial Antebrachial Cutaneous Nerve

Branches of the medial antebrachial cutaneous nerve cross the operative field during medial elbow surgery.

These branches should be carefully identified and protected because injury can produce painful neuroma or numbness.

Follow-Up

Nonoperative Prognosis

In patients with mild cubital tunnel syndrome, nonoperative management has historically produced excellent results in approximately 58% of cases, excluding many post-traumatic neuropathies.

Surgical Prognosis

Surgical treatment produces good to excellent outcomes in approximately 70–90% of patients.

The degree of recovery depends partly on the severity and duration of preoperative nerve dysfunction.

Decompression Versus Transposition

In the absence of ulnar nerve instability or hypermobility, outcomes after simple decompression are generally comparable with those following anterior transposition.

This allows a less extensive procedure in appropriately selected patients.

Recovery of Weakness

Sensory symptoms may improve earlier than motor weakness.

When severe intrinsic muscle atrophy has been present for a prolonged period, complete strength recovery may not occur even after adequate decompression.

Complications

Postoperative Nerve Irritation

Persistent or new nerve irritation may occur after surgery.

Scar formation, incomplete decompression, nerve instability, or iatrogenic injury may contribute.

Complex Regional Pain Syndrome

Complex regional pain syndrome, historically termed reflex sympathetic dystrophy, may rarely occur after surgery and can produce disproportionate pain, stiffness, and autonomic changes.

Untreated Severe Neuropathy

Progressive untreated ulnar neuropathy can lead to intrinsic muscle atrophy, persistent sensory loss, and clawing of the ring and small fingers.

Ulnar Clawing

Loss of intrinsic muscle function allows imbalance between the extrinsic flexors and extensors.

This can produce hyperextension at the metacarpophalangeal joints and flexion at the interphalangeal joints of the ring and small fingers.

Joint Contractures

Longstanding muscle imbalance and clawing can eventually produce fixed joint contractures.

Early treatment of progressive motor dysfunction may reduce this risk.

Patient Monitoring

Follow-up examinations should document motor strength, sensory function, intrinsic muscle bulk, provocative findings, and progression or improvement of symptoms.

Patients treated surgically should also be monitored for wound problems, recurrent nerve instability, persistent compression, and recovery of hand function.