Tarsal tunnel syndrome

Tarsal tunnel syndrome is a compressive neuropathy of the tibial nerve or its branches within the tarsal tunnel on the medial aspect of the ankle. It is a relatively uncommon condition that can lead to chronic pain, numbness, and functional impairment if not recognized early. Understanding the anatomy and clinical features is essential for proper diagnosis and management.

Anatomy of the Tarsal Tunnel

Location and Boundaries

The tarsal tunnel is located on the medial side of the ankle, posterior to the medial malleolus. It is a fibro-osseous canal formed by the flexor retinaculum, which stretches from the medial malleolus to the calcaneus, creating a protective covering over the underlying structures.

• Medial malleolus of the tibia
• Calcaneus bone
• Flexor retinaculum as the roof of the tunnel
• Floor formed by the talus and calcaneus

Contents of the Tarsal Tunnel

The tarsal tunnel contains several critical structures that pass from the leg into the foot. Compression of the tibial nerve or its branches within this tunnel can lead to the characteristic symptoms of tarsal tunnel syndrome.

• Tendons:
  • Tibialis posterior tendon
  • Flexor digitorum longus tendon
  • Flexor hallucis longus tendon
• Posterior tibial artery and veins
• Tibial nerve and its branches:
  • Medial plantar nerve
  • Lateral plantar nerve
  • Calcaneal branches

Pathophysiology

Tarsal tunnel syndrome occurs when the tibial nerve is compressed within the tarsal tunnel, leading to impaired nerve conduction and subsequent symptoms. The compression can result from both intrinsic and extrinsic factors affecting the tunnel space.

• Mechanical compression of the tibial nerve or its branches
• Inflammatory changes in surrounding tissues causing edema and nerve irritation
• Altered foot biomechanics, such as overpronation, increasing tension on the nerve
• Chronic compression leading to demyelination and axonal degeneration if left untreated

Etiology

The causes of tarsal tunnel syndrome can be classified into intrinsic, extrinsic, and systemic factors. Identifying the underlying cause is important for guiding appropriate treatment.

Intrinsic Causes

• Ganglion cysts within the tarsal tunnel
• Varicosities of the posterior tibial vein
• Lipomas or other soft tissue masses
• Tenosynovitis of the flexor tendons

Extrinsic Causes

• Trauma to the ankle, including fractures or sprains
• Post-surgical scarring or adhesions in the region
• Foot deformities such as pes planus or valgus hindfoot

Systemic Conditions

• Diabetes mellitus causing peripheral neuropathy and nerve susceptibility
• Inflammatory conditions such as rheumatoid arthritis
• Other metabolic or endocrine disorders that predispose to nerve entrapment

Clinical Presentation

Symptoms

Patients with tarsal tunnel syndrome typically present with a combination of sensory and motor symptoms that worsen with prolonged standing or walking. Early recognition of these symptoms is crucial for timely management.

• Pain along the medial ankle, plantar surface of the foot, or toes
• Paresthesia including numbness, tingling, or burning sensations
• Worsening symptoms at night or after activity
• Motor symptoms in severe cases, such as weakness or atrophy of the intrinsic foot muscles

Physical Examination

Careful examination of the ankle and foot can help confirm the diagnosis and rule out other conditions. Key findings often guide further diagnostic testing.

• Positive Tinel’s sign over the tarsal tunnel, producing tingling in the foot
• Assessment of muscle strength, particularly in the intrinsic foot muscles
• Sensory testing for light touch, pinprick, and vibration along the plantar surface
• Evaluation of foot posture, gait, and range of motion

Diagnostic Evaluation

Imaging Studies

Imaging helps identify structural causes of nerve compression and assess surrounding soft tissues.

• MRI to detect masses, tenosynovitis, or other soft tissue abnormalities
• Ultrasound for dynamic assessment of tendons and cysts

Electrodiagnostic Studies

Electrodiagnostic testing confirms nerve involvement and helps determine severity.

• Nerve conduction studies to assess tibial nerve latency and conduction velocity
• Electromyography (EMG) to evaluate muscle innervation and detect denervation changes

Differential Diagnosis

Several conditions can mimic tarsal tunnel syndrome, and these should be considered before confirming the diagnosis.

• Plantar fasciitis
• Peripheral neuropathy from diabetes or other causes
• Lumbar radiculopathy causing distal foot symptoms
• Other foot or ankle entrapment syndromes

Management

Conservative Treatment

Initial management of tarsal tunnel syndrome often focuses on non-surgical approaches aimed at relieving pressure on the tibial nerve and addressing contributing factors.

• Activity modification to reduce prolonged standing or repetitive stress
• Use of orthotic devices or supportive footwear to correct foot biomechanics
• Physical therapy including stretching of the calf, plantar fascia, and intrinsic foot muscles
• Medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) or agents for neuropathic pain

Interventional Treatments

For patients who do not respond to conservative measures, targeted interventions can provide symptom relief.

• Corticosteroid injections into the tarsal tunnel to reduce inflammation
• Botulinum toxin injections in select cases to decrease nerve irritability

Surgical Management

Surgery is indicated when conservative and interventional treatments fail or when there is a clear structural cause of nerve compression.

• Tarsal tunnel release procedure to decompress the tibial nerve
• Removal of space-occupying lesions such as ganglion cysts or lipomas
• Postoperative outcomes generally include pain relief and improved sensory function
• Potential complications include wound healing issues, infection, and persistent neuropathic symptoms

Prognosis

The prognosis of tarsal tunnel syndrome depends on the severity, duration of nerve compression, and the underlying cause. Early diagnosis and appropriate management are associated with better outcomes.

• Factors influencing recovery include age, comorbid conditions, and degree of nerve damage
• Conservative treatment often results in partial or complete symptom relief in mild cases
• Surgical intervention can provide significant improvement in severe or refractory cases
• Chronic compression may lead to permanent sensory deficits or muscle atrophy if not addressed promptly

Prevention

Preventive strategies for tarsal tunnel syndrome focus on minimizing risk factors and maintaining proper foot and ankle health. Early recognition of symptoms and proactive management can reduce the likelihood of chronic nerve compression.

• Wearing supportive and well-fitted footwear to reduce excessive foot pronation
• Using custom orthotics to correct biomechanical abnormalities
• Regular stretching and strengthening exercises for the foot and ankle
• Managing systemic conditions such as diabetes or inflammatory disorders
• Avoiding repetitive stress activities that place prolonged pressure on the medial ankle

References

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