Orthopaedic Surgery - Tarsal Tunnel Syndrome

Basics

Tarsal tunnel syndrome is an entrapment neuropathy involving the:

Tibial nerve

or one of its distal branches as the nerve passes through the:

Tarsal tunnel.

The neuropathy may result from:

Compression

or

Traction.

Anatomy

The proximal tarsal tunnel is a:

Fibro-osseous canal

located along the posteromedial aspect of the:

Ankle.

It represents a distal continuation of the:

Deep posterior compartment of the leg.

Contents of the Tarsal Tunnel

From anterior to posterior, the tunnel contains the:

Posterior tibial tendon

Flexor digitorum longus tendon

Posterior tibial artery and vein

Tibial nerve

and

Flexor hallucis longus tendon.

Floor of the Tunnel

The floor is formed by:

The medial talus

The sustentaculum tali

and

The medial wall of the calcaneus.

Roof of the Tunnel

The roof is formed by the:

Flexor retinaculum.

This structure may begin as far as approximately:

10 cm proximal to the medial malleolus.

Fibro-Osseous Compartments

The tendons and neurovascular bundle travel in relatively constrained:

Fibro-osseous compartments

connected to the:

Flexor retinaculum.

Because the tunnel is not easily expandable, even a modest increase in local volume can produce:

Nerve compression.

Tibial Nerve Branches

Within or near the tarsal tunnel, the tibial nerve gives rise to:

Medial calcaneal nerve

Medial plantar nerve

and

Lateral plantar nerve.

The exact branching anatomy is:

Variable.

Medial Calcaneal Nerve

The:

Medial calcaneal nerve

arises directly from the tibial nerve in approximately:

69–90% of individuals.

It may also originate from the:

Lateral plantar nerve.

Number of Calcaneal Branches

A single medial calcaneal branch is present in approximately:

79%

although multiple branches may occur.

Sensory Distribution

The medial calcaneal nerve supplies sensation to the:

Medial heel.

Because it may branch proximal to the site of compression, heel sensation can occasionally be:

Preserved

despite tarsal tunnel syndrome.

Medial and Lateral Plantar Nerves

The tibial nerve terminates as the:

Medial plantar nerve

and

Lateral plantar nerve.

In approximately:

93–96%

of individuals, this bifurcation occurs within the:

Tarsal tunnel.

In the remainder, the division occurs more proximally in the:

Leg.

Medial Plantar Nerve

The medial plantar nerve provides sensation to:

The plantar medial foot

Great toe

Second toe

Third toe

and the:

Medial side of the fourth toe.

Medial Plantar Motor Supply

It provides motor innervation to:

Abductor hallucis

Flexor digitorum brevis

Flexor hallucis brevis

and the:

First lumbrical.

Lateral Plantar Nerve

The lateral plantar nerve supplies sensation to:

The lateral side of the fourth toe

and

The fifth toe.

Lateral Plantar Motor Supply

It provides motor innervation to:

Quadratus plantae

Abductor digiti minimi

Flexor digiti minimi brevis

The lateral three lumbricals

Adductor hallucis

and

The interossei.

Most Commonly Involved Branch

The:

Lateral plantar nerve

is frequently involved in tarsal tunnel syndrome.

Distal Tarsal Tunnel

Distally, the medial and lateral plantar nerves pass through separate:

Fibrous tunnels

deep to the:

Abductor hallucis muscle.

These sites can also become points of:

Entrapment.

Medial Plantar Nerve Entrapment

The medial plantar nerve can become compressed between the:

Navicular

and

Abductor hallucis

or near the:

Knot of Henry.

First Branch of the Lateral Plantar Nerve

The first branch of the lateral plantar nerve may be compressed within the fascia of:

Abductor hallucis

as it courses toward the:

Abductor digiti minimi.

This may produce:

Chronic heel pain.

Pregnancy Considerations

Tarsal tunnel symptoms may develop during:

Pregnancy

because of:

Fluid retention

and increased local:

Tissue volume.

Management is usually:

Supportive

because symptoms often improve after:

Delivery.

Epidemiology

Tarsal tunnel syndrome can occur over a wide:

Age range.

Historical series have reported affected patients between approximately:

14 and 80 years.

Sex

It appears to be slightly more common in:

Women

than in men.

One historical review reported approximately:

56% female patients.

Incidence

The true incidence is:

Unknown.

Risk Factors

No single risk factor has been conclusively established.

Several occupations and repetitive activities have nevertheless been associated with:

Tibial nerve traction or compression.

Jogger’s Foot

Excessive:

Hindfoot valgus

may place traction on the tibial nerve during repetitive:

Running.

This presentation has sometimes been termed:

Jogger’s foot.

Repetitive Squatting

Activities requiring repeated:

Squatting

or

Crouching

may increase pressure within the tarsal tunnel.

Historical examples include:

Race jockeys.

Pathophysiology

Tarsal tunnel syndrome develops when the tibial nerve or one of its branches is subjected to:

Compression

Traction

or both.

Restricted Tunnel Volume

Because the tarsal tunnel has relatively rigid boundaries, increases in local tissue volume may raise:

Intratunnel pressure.

Sensory Dysfunction

Sensory symptoms are thought to result partly from:

Nerve ischemia

and impaired:

Axonal conduction.

Motor Dysfunction

Late motor deficits may result from more prolonged:

Direct nerve compression

and axonal injury.

Chronic Traction

Repetitive traction can lead to:

Epineurial fibrosis

and decreased:

Nerve mobility.

This may make the nerve more susceptible to additional:

Compression or injury.

Etiology

A specific cause can be identified in approximately:

60–80% of patients.

Causes can broadly be grouped into:

Trauma

Space-occupying lesions

and

Foot or hindfoot deformity.

Common Causes

Historical series have reported approximate frequencies of:

Trauma – 17%

Varicosities – 13%

Hindfoot varus – 11%

Fibrosis – 9%

and

Hindfoot valgus – 8%.

Space-Occupying Lesions

Other causes include:

Ganglion cyst

Lipoma

Neurilemmoma

Inflammatory synovitis

Pigmented villonodular synovitis

Tarsal coalition

and

Accessory musculature.

Diagnosis

Tarsal tunnel syndrome is commonly:

Missed or misdiagnosed

because symptoms can be:

Variable

and

Poorly localized.

Signs and Symptoms

The typical presentation is an:

Insidious or intermittent onset

of neuropathic:

Pain

Burning

Paresthesia

or

Numbness.

Distribution of Symptoms

Symptoms depend on which branch of the tibial nerve is:

Affected.

They may involve the:

Plantar foot

Heel

or

Toes.

Valleix Phenomenon

Pain or paresthesia may radiate proximally up the:

Medial leg

along the course of the tibial nerve.

This is known as the:

Valleix phenomenon.

Historical series have reported it in approximately:

One-third of patients with severe compression.

Distal Radiation

Symptoms may also radiate distally along the distribution of the:

Medial or lateral plantar nerves.

Activity-Related Symptoms

Pain typically worsens with:

Prolonged standing

Walking

or

Activity.

Night Pain

Some patients report substantial:

Night pain.

Venous congestion or prolonged nerve irritation may contribute.

Factors That Relieve Symptoms

Symptoms may improve with:

Rest

Loose footwear

and

Elevation.

Physical Examination

A complete examination of the:

Foot and ankle

should be performed.

Foot Alignment

Assess the patient for:

Hindfoot valgus

or

Hindfoot varus.

Alignment abnormalities may increase:

Traction

or

Compression

on the tibial nerve.

Provocative Positioning

Forced:

Dorsiflexion

Inversion

or

Eversion

may reproduce symptoms by stretching or narrowing the:

Tarsal tunnel.

Palpation

Palpate the tarsal tunnel and the course of the tibial nerve for:

Tenderness

Swelling

or evidence of a:

Mass.

Tinel Sign

Percussion over the:

Tibial nerve

may reproduce distal:

Paresthesia.

A positive Tinel sign supports a diagnosis of:

Tibial nerve irritation.

Cuff Test

A pneumatic cuff may be used to produce temporary:

Venous congestion.

Engorgement of varicosities can reproduce symptoms when venous structures are contributing to:

Compression.

This test is used infrequently in modern practice.

Compression Test

Direct pressure over the:

Tarsal tunnel

for approximately:

60 seconds

may reproduce the patient’s:

Neuropathic symptoms.

Sensory Examination

Examine sensation over the territories of the:

Medial calcaneal

Medial plantar

and

Lateral plantar nerves.

Heel Sensation

The medial calcaneal nerve is often:

Spared

because it may branch proximal to the site of:

Compression.

Two-Point Discrimination

Reduced:

Two-point discrimination

may be an early finding of:

Sensory dysfunction.

Motor Examination

Motor deficits are usually:

Late findings.

Intrinsic Weakness

Weakness of the intrinsic muscles can be difficult to:

Detect clinically.

Toe Plantarflexion

Rarely, weakness of:

Toe plantarflexion

may be evident.

Muscle Atrophy

Late disease may produce atrophy of:

Abductor hallucis

or

Abductor digiti minimi.

Laboratory Tests

Routine laboratory tests do not diagnose:

Tarsal tunnel syndrome.

They may help identify systemic causes of:

Peripheral neuropathy.

Diabetes and Systemic Disease

Testing may be appropriate when evaluating for:

Diabetes mellitus

Vitamin deficiency

Thyroid disease

or other systemic:

Neuropathies.

Imaging

Weight-Bearing Radiographs

Routine weight-bearing foot and ankle radiographs help assess:

Alignment

Bony deformity

Exostosis

and

Tarsal coalition.

MRI

MRI is useful when evaluating for:

Space-occupying lesions

or other structural causes of:

Nerve compression.

MRI Findings

MRI can identify:

Ganglion cysts

Tumors

Varicosities

Accessory muscles

and inflammatory:

Soft-tissue abnormalities.

Diagnostic Yield

One historical study identified a potential causative abnormality on MRI in approximately:

88% of symptomatic feet.

Pediatric Considerations

In children, MRI is especially valuable because nerve compression may occasionally result from:

Neoplastic or other mass lesions.

Electrodiagnostic Studies

Electrodiagnostic testing may help evaluate:

Tibial nerve dysfunction

and identify more generalized:

Peripheral neuropathy.

Motor Latency

Isolated motor latency testing has relatively:

Low sensitivity.

Sensory Action Potentials

Sensory action potentials are among the more sensitive:

Electrodiagnostic measurements.

Historical data have reported sensitivity around:

90.5%

but with a modest:

False-positive rate.

Mixed Nerve Conduction Studies

Mixed motor-sensory conduction studies may demonstrate abnormalities with relatively good:

Specificity.

Historical series have reported abnormalities in approximately:

85.7% of cases.

Limitations of Electrodiagnostic Testing

Normal electrodiagnostic studies do not completely exclude:

Tarsal tunnel syndrome.

Findings must be interpreted together with:

History

Physical examination

and

Imaging.

Proximal Nerve Compression

Evaluation should also consider more proximal causes such as:

Lumbar radiculopathy

or a:

Double-crush phenomenon.

Pathological Findings

Surgical exploration may reveal:

Focal nerve swelling

Fibrosis

Scarring

or an identifiable:

Compressive lesion.

Differential Diagnosis

Important differential diagnoses include:

Diabetic peripheral neuropathy

Peripheral neuritis

Peripheral vascular disease

Morton neuroma

Metatarsalgia

Subtalar arthritis

Posterior tibial tendon dysfunction

Plantar fasciitis

Complex regional pain syndrome

Proximal tibial nerve or sciatic nerve compression

and

Lumbar radiculopathy.

Plantar Fasciitis

Plantar fasciitis usually produces:

Mechanical plantar heel pain

rather than burning or paresthetic:

Neuropathic symptoms.

Lumbar Radiculopathy

Lumbar nerve-root compression may mimic distal tibial nerve symptoms.

A complete neurologic examination should therefore include assessment for:

Proximal neurologic disease.

Treatment

Initial treatment is generally:

Nonoperative.

Exceptions include:

Acute severe nerve compression

or an identified:

Space-occupying lesion

that requires removal.

General Measures

Conservative treatment may include:

Activity modification

Rest

Temporary immobilization

Orthotics

Anti-inflammatory medication

Neuropathic pain medication

Physical therapy

Compression stockings

and

Weight reduction when appropriate.

Immobilization

A boot or brace may temporarily decrease:

Nerve irritation

by reducing repetitive:

Ankle and hindfoot motion.

Orthotics

Orthotic devices may help correct:

Hindfoot valgus

or other alignment abnormalities that increase:

Tibial nerve tension.

NSAIDs

NSAIDs may reduce:

Associated inflammatory pain

although they do not directly reverse:

Nerve compression.

Corticosteroid Injection

A carefully placed corticosteroid injection may sometimes reduce local:

Inflammation

or

Synovitis.

Injections should be performed cautiously because of the proximity of the:

Tibial nerve and vascular structures.

Neuropathic Pain Medication

Medications used for neuropathic symptoms may include selected:

Tricyclic antidepressants

or

Antiepileptic agents.

Nerve Blocks

Diagnostic or therapeutic:

Nerve blocks

may occasionally be used in selected patients.

Physical Therapy

Therapy may include:

Neural mobilization

Desensitization

Stretching

and correction of:

Biomechanical abnormalities.

Compression Stockings

When symptoms are related to:

Venous congestion

or

Varicosities

compression stockings may help reduce:

Local swelling.

Weight Management

Weight reduction may decrease repetitive:

Mechanical loading

and pressure around the:

Tarsal tunnel.

Surgery

Surgical decompression may be considered when:

Conservative treatment fails

or when a clear structural cause is identified.

Indications for Surgery

Typical indications include:

Persistent symptoms after approximately 3–6 months of nonoperative treatment

Acute tarsal tunnel syndrome

or

Space-occupying lesion.

Surgical Approach

A curved:

Posteromedial incision

is made along the course of the:

Tibial nerve.

Flexor Retinaculum Release

The entire:

Flexor retinaculum

should be released to decompress the proximal:

Tarsal tunnel.

Distal Decompression

The:

Medial plantar

and

Lateral plantar nerves

should also be released distally as they pass beneath the:

Abductor hallucis.

Space-Occupying Lesions

Any responsible lesion such as a:

Ganglion

Tumor

or other mass should be:

Excised or treated.

Associated Pathology

Underlying abnormalities such as:

Posterior tibial tendon dysfunction

or

Tarsal coalition

may also require treatment.

Scar Prevention

Surgical dissection should be minimized when possible because excessive tissue disruption may increase:

Postoperative scar formation

around the:

Nerve.

Follow-Up

Postoperative care usually begins with:

Protected non-weight-bearing.

Initial Immobilization

A splint is maintained until the incision heals, generally for approximately:

2–3 weeks.

Weight-Bearing Progression

After wound healing, patients gradually begin:

Weight bearing

and

Range-of-motion exercises.

Swelling Control

Elevation, compression, and other swelling-control measures may help reduce postoperative:

Edema.

Prognosis

Outcomes are generally more favorable when:

The patient is younger

Symptoms have been present for a shorter duration

and a specific:

Compressive lesion

can be identified.

Timing of Surgery

Results tend to be better when decompression is performed before development of:

Motor weakness

or

Muscle atrophy.

Surgical Outcomes

Historical reviews have reported improvement or resolution of symptoms in approximately:

90% of selected patients.

However, longer-term studies using stricter outcome criteria have reported:

Less predictable results

and deterioration of benefit in some:

Patients.

Complications

The principal adverse outcome is:

Persistent or recurrent symptoms after decompression.

Failed Tarsal Tunnel Release

Important causes of failed surgery include:

Incorrect initial diagnosis

Incomplete surgical release

Adhesive neuritis

Intraneural damage

and

Untreated proximal or additional nerve compression.

Incorrect Diagnosis

Symptoms may persist when the true problem is:

Lumbar radiculopathy

Peripheral neuropathy

or another:

Foot disorder.

Incomplete Release

Failure to release the full length of the:

Flexor retinaculum

or distal plantar nerve tunnels may leave residual:

Compression.

Adhesive Neuritis

Postoperative scar formation around the nerve may produce:

Adhesive neuritis

with recurrent:

Pain and paresthesia.

Intraneural Damage

Chronic systemic neuropathy or direct nerve injury may produce irreversible:

Intraneural damage.

Double-Crush Phenomenon

Symptoms may persist if both:

Distal tibial nerve compression

and a more proximal lesion such as:

Lumbar radiculopathy

are present.

Evaluation After Failed Release

The surgical scar and extent of the previous incision should be examined carefully because an incision that is too short may suggest:

Incomplete decompression.

Electrodiagnostic Testing After Failed Surgery

Electrodiagnostic studies are generally less useful for determining the cause of:

Failed tarsal tunnel release.

Revision Surgery

Revision decompression may be considered in selected patients with:

Incomplete release

or

Adhesive neuritis.

Barrier Procedures

In cases of extensive scar formation, the nerve may be wrapped with:

Vein

or

Synthetic biologic material

to reduce recurrent:

Adhesion formation.

Revision Prognosis

Outcomes after:

Revision surgery

are generally less favorable than after successful:

Primary decompression.

Patient Monitoring

Patients should be followed for changes in:

Pain

Paresthesia

Sensation

Intrinsic muscle strength

and

Functional walking tolerance.

Key Principle

Tarsal tunnel syndrome is an entrapment neuropathy of the tibial nerve or its distal branches within the fibro-osseous tunnel along the medial ankle.

Symptoms typically include:

Burning pain, paresthesia, numbness, and activity-related plantar foot discomfort, sometimes with a positive:

Tinel sign.

Evaluation should identify potential causes such as:

Trauma, varicosities, hindfoot deformity, fibrosis, ganglion cyst, tumor, tarsal coalition, or accessory muscle.

Initial treatment is usually:

Nonoperative, using activity modification, orthotics, medication, physical therapy, and treatment of contributing deformity or swelling.

Surgical decompression is considered for:

Persistent symptoms, acute compression, or a defined space-occupying lesion, and should include release of the:

Flexor retinaculum and distal medial and lateral plantar nerve tunnels.