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Tarsal Tunnel Syndrome

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Overview

Exam Detail:

Key Revision Focus: Anatomy of the Tarsal Tunnel (Tom, Dick, And, Nervous, Harry). Baxter's Nerve (First Branch of Lateral Plantar Nerve). Double Crush phenomenon. Provocative tests (Tinel's, Dorsiflexion-Eversion). Surgical release technique and complications.

1. Clinical Overview

Tarsal Tunnel Syndrome (TTS) is an entrapment neuropathy of the Posterior Tibial Nerve (PTN) or its branches as it passes through the fibro-osseous tunnel beneath the Flexor Retinaculum (Laciniate Ligament) on the medial aspect of the ankle. It is analogous to Carpal Tunnel Syndrome in the wrist. The condition causes burning pain, numbness, and paraesthesias on the plantar aspect of the foot.

Clinical Pearl:

The "Tibial Tunnel": Think of it as the wrist flipped. The Flexor Retinaculum (FR) is the roof. The Medial Malleolus and Calcaneus are the walls and floor. Anything that takes up space in this tunnel compresses the nerve.

Key Concepts

  1. Anatomy of the Tarsal Tunnel:
    • Roof: Flexor Retinaculum (Laciniate Ligament). Runs from the Medial Malleolus to the Calcaneus.
    • Floor: Medial wall of the Talus and Calcaneus.
    • Contents (Anterior to Posterior): Tibialis Posterior Tendon, Flexor Digitorum Longus Tendon, Posterior Tibial Artery & Veins, Posterior Tibial Nerve, Flexor Hallucis Longus Tendon.
    • Mnemonic: "Tom, Dick, And Very Nervous Harry".
  2. The Posterior Tibial Nerve (PTN):
    • Terminal branch of the Sciatic Nerve (via Tibial Nerve).
    • Divides into Medial Plantar Nerve (MPN) and Lateral Plantar Nerve (LPN) within or just distal to the tunnel.
    • The Medial Calcaneal Nerve (MCN) often branches proximal to the tunnel. It provides sensation to the heel. Its sparing/involvement helps localize the lesion.
  3. Baxter's Nerve (First Branch of Lateral Plantar Nerve - FBLPN):
    • The most important nerve for the FRCS exam in heel pain.
    • It is a motor nerve primarily. It innervates the Abductor Digiti Minimi (ADM) muscle.
    • It also provides sensory innervation to the plantar heel and the calcaneal periosteum.
    • It passes between the Abductor Hallucis muscle and the Quadratus Plantae muscle.
    • Compression Point: By a thickened fascia of the Abductor Hallucis or by a calcaneal spur.
    • Clinical: Causes chronic plantar heel pain that mimics Plantar Fasciitis but does NOT improve with stretching/orthotics. It is a neglected diagnosis.
  4. Double Crush Syndrome:
    • Proximal nerve compression (e.g., L5/S1 radiculopathy) makes the nerve more susceptible to distal compression (Tarsal Tunnel). The sum of two subthreshold lesions creates symptomatic dysfunction.
  5. Causes of TTS (Space Occupying Lesions):
    • Soft Tissue: Ganglion cyst (Most Common - up to 30%), Lipoma, Varicose veins, Accessory muscles (Flexor Digitorum Accessorius Longus), Schwannoma, Neurofibroma.
    • Bony: Tarsal Coalition, Osteochondroma, Post-traumatic deformity (e.g., malunited calcaneal fracture), Os Trigonum.
    • Systemic: Diabetes Mellitus, Inflammatory Arthritis (RA, Gout), Hypothyroidism.
    • Biomechanical: Pes Planus (Valgus heel stretches the nerve), Posterior Tibial Tendon Dysfunction (PTTD).
    • Idiopathic: Up to 40% of cases have no identifiable cause.

Clinical Pearls

  • Heel Sparing: If the Medial Calcaneal Nerve branches above the tunnel (variable anatomy), the heel sensation may be preserved even with complete TTS. Conversely, isolated heel numbness suggests a lesion proximal to the tunnel or a specific MCN lesion.
  • "Burning Feet Syndrome": A common presentation. Rule out Peripheral Neuropathy (Diabetes) and Vitamin B12 deficiency first.
  • Nocturnal Pain: Classic. Patients often wake at night with burning/tingling.
  • Activity-Related: Worsens with prolonged standing or walking; relieved by rest and elevation.
  • The Valleix Phenomenon: Tapping on the nerve causes paraesthesias that radiate distally (positive Tinel's) and proximally (Valleix sign). Suggests nerve irritation.

2. Epidemiology

  • Incidence: Rare. True incidence unknown but estimated at < 1 per 100,000 person-years. Likely underdiagnosed.
  • Sex: Female > Male (some studies suggest up to 60-70% female).
  • Age: Peak incidence in 4th-6th decades. Can occur at any age.
  • Risk Factors:
    Risk FactorRelative Risk / Association
    Pes Planus (Flatfoot)OR ~2.5-3.0
    Obesity (BMI > 30)OR ~2.0
    Diabetes MellitusHigh (Nerve vulnerable)
    Rheumatoid ArthritisSynovitis in tunnel
    History of Ankle Fracture/TraumaScar tissue, deformity
    Varicose Veins (Lower Limb)Dilated veins in tunnel
    Occupations with Prolonged Standing? (Anecdotal)

3. Pathophysiology

The pathophysiology of Tarsal Tunnel Syndrome involves a progressive cascade of compression-induced nerve injury within the unyielding fibro-osseous tunnel.

Step 1: Initiating Event (Tunnel Volume Reduction or Content Increase)

  • A space-occupying lesion (ganglion, tumor, varicose vein) increases the volume of contents within the rigid tarsal tunnel.
  • Alternatively, external compression (tight footwear, ankle deformity, pes planus stretching the nerve) or fibrosis (post-trauma, post-surgery) reduces the available tunnel volume.
  • The Flexor Retinaculum, being inelastic, cannot expand to accommodate the change.

Step 2: Microvascular Compromise

  • Increased interstitial pressure within the tunnel compresses the vasa nervorum (the small vessels supplying the nerve fascicles).
  • This leads to endoneurial ischemia. The nerve is metabolically active and highly sensitive to oxygen deprivation.
  • Initial changes are mild and reversible; venous congestion occurs first, followed by capillary compromise.

Step 3: Blood-Nerve Barrier Breakdown and Edema

  • Ischemia damages the blood-nerve barrier (analogous to blood-brain barrier).
  • Proteins and fluid leak into the endoneurium, causing intra-fascicular edema.
  • This edema further increases pressure within the nerve sheath, creating a vicious cycle of compression → ischemia → edema → more compression.

Step 4: Demyelination (Conduction Block)

  • Prolonged ischemia and mechanical pressure cause segmental demyelination of the large, myelinated nerve fibers (Aβ fibers for light touch, proprioception).
  • Clinically, this manifests as numbness, tingling, and loss of sensation. Pain may or may not be prominent at this stage.
  • Nerve conduction studies show slowing of conduction velocity across the tunnel segment. This is often reversible with timely decompression.

Step 5: Axonal Degeneration (Wallerian Degeneration)

  • If compression persists, the axons themselves begin to degenerate (Wallerian degeneration) distal to the site of compression.
  • Clinically, this causes motor weakness (intrinsic foot muscle atrophy, e.g., Abductor Hallucis, Abductor Digiti Minimi) and persistent sensory loss.
  • Nerve conduction studies show reduced amplitude of sensory nerve action potentials (SNAPs) and compound muscle action potentials (CMAPs). EMG shows denervation potentials (fibrillations, positive sharp waves).
  • This stage is less reversible. Even with surgical release, recovery may be incomplete or prolonged (months to years for axonal regeneration at ~1mm/day).

Step 6: Chronic Changes and Fibrosis (End-Stage)

  • Longstanding compression leads to intra-neural fibrosis.
  • The nerve becomes thickened, scarred, and non-functional at the compression site.
  • Pain may paradoxically become less prominent as sensation is lost, or it may become chronic and neuropathic.
  • Surgical decompression at this stage has poor outcomes.

Classification of Nerve Injury (Seddon / Sunderland)

SeddonSunderlandInjuryPrognosis
NeurapraxiaGrade IMyelin damage only. Axon intact.Full recovery (days-weeks).
AxonotmesisGrade IIAxon damaged. Endoneurium intact.Good recovery. Wallerian degeneration.
Grade IIIAxon + Endoneurium damaged. Perineurium intact.Variable recovery. Internal scarring.
Grade IVAxon + Endo + Perineurium damaged. Epineurium intact.Poor recovery. Neuroma in continuity.
NeurotmesisGrade VComplete transection.No recovery without surgery.

Most cases of TTS represent Grade I-II injury and are amenable to conservative or surgical decompression. Longstanding or severe cases may progress to Grade III.

4. Clinical Presentation

Symptoms

  1. Pain:
    • Character: Burning, aching, sharp, or electric-shock-like.
    • Location: Medial ankle (at the tunnel), radiating to the plantar aspect of the foot (arch, heel, toes).
    • Aggravating Factors: Prolonged standing, walking, running, wearing tight shoes.
    • Relieving Factors: Rest, elevation, removing footwear.
    • Nocturnal: Patients frequently report waking at night with burning pain. Shaking or hanging the foot off the bed may help.
  2. Numbness and Paraesthesias:
    • Tingling, "pins and needles," or "crawling" sensation on the sole.
    • In MPN compression: Numbness of the medial sole, great toe, and 2nd/3rd toes.
    • In LPN compression: Numbness of the lateral sole and 4th/5th toes.
    • In MCN compression: Numbness of the heel pad.
  3. Weakness:
    • Often subtle and difficult for patients to describe.
    • May report "clumsiness" of the toes or difficulty with fine movements.
    • Objective weakness of toe abduction/flexion is a late finding.
  4. Motor Symptoms (Late):
    • Wasting of the Abductor Hallucis muscle (visible "guttering" on medial arch).
    • Clawing of toes (intrinsic minus deformity) – rarely prominent.

Red Flags (Rule Out More Serious Conditions)

Red FlagSuggests
Bilateral SymptomsPeripheral Neuropathy (Diabetes, B12 deficiency, Alcoholic)
Back Pain / RadiculopathyLumbar Disc Herniation (L5/S1), Spinal Stenosis → "Double Crush" or Primary Cause
Rapid Onset with MassTumor (Nerve sheath tumor, Malignancy)
Systemic Symptoms (Weight Loss, Fever)Malignancy, Infection
Skin Changes / UlcerationPeripheral Vascular Disease, Diabetic Neuropathy
Rest Pain in CalfChronic Compartment Syndrome

Differential Diagnosis of Plantar Foot Pain

ConditionKey Differentiating Features
Plantar FasciitisPain at plantar medial calcaneal tubercle. Worse with first steps in morning. Improves with walking.
Tarsal Tunnel SyndromeBurning, numbness, tingling. Positive Tinel's at Tarsal Tunnel. Worse with activity. Nocturnal.
Baxter's NeuropathyChronic heel pain. Tender Abductor Hallucis fascia. Negative standard Tinel's. Atrophy of ADM on MRI.
Peripheral NeuropathySymmetric, "stocking-glove" distribution. Often bilateral. Reduced Vibration/Proprioception. Positive B12/HbA1c.
S1 RadiculopathyBack/buttock pain. Weakness of Ankle Plantarflexion/Eversion. Reduced Ankle Jerk.
Calcaneal Stress FracturePain with squeeze test (side-to-side compression of calcaneus). Localized bony tenderness. MRI shows edema.
Fat Pad AtrophyElderly. Thin heel pad. Pain on direct palpation of calcaneus through atrophic fat.

5. Clinical Examination

A structured, systematic examination is essential for the viva.

1. Look (Inspection)

  • Gait: Antalgic? Avoidance of heel strike?
  • Footwear: Signs of abnormal wear patterns.
  • Foot Posture:
    • Pes Planus (Flatfoot): "Too Many Toes" sign (view from behind – more than 2 toes visible laterally). Collapsed medial arch.
    • Hindfoot Valgus: Heel in valgus puts stretch on the PTN.
  • Swelling: Fullness posterior/inferior to the medial malleolus (suggests mass or tenosynovitis).
  • Muscle Wasting:
    • Abductor Hallucis: "Guttering" along the medial arch (MPN atrophy).
    • Abductor Digiti Minimi: Wasting on the lateral plantar aspect (LPN/Baxter's atrophy).
  • Skin Changes: Trophic changes (shiny skin, hair loss) suggest chronic neuropathy.

2. Feel (Palpation)

  • Tenderness:
    • Palpate directly over the Tarsal Tunnel (posterior and inferior to the medial malleolus).
    • Palpate along the course of the PTN from proximal (calf) to distal (arch).
  • Tinel's Sign:
    • The Most Important Test.
    • Percuss (tap firmly) over the PTN at the Tarsal Tunnel.
    • Positive: Reproduction of tingling or electric-shock sensation radiating distally into the sole and toes.
    • Highly Specific when positive and matches patient's symptoms.
  • Mass Palpation: Feel for a soft tissue mass (ganglion, lipoma) in the tunnel.
  • Peripheral Pulses: Posterior Tibial Artery and Dorsalis Pedis. Rule out vascular disease.

3. Move (Range of Motion & Provocative Tests)

  • Ankle Range of Motion: Document dorsiflexion and plantarflexion.
  • Subtalar Motion: Inversion and eversion. Stiffness may suggest Coalition or Arthritis.
  • Provocative Tests:
    • Dorsiflexion-Eversion Test (DEFT):
      • Technique: Maximally dorsiflex and evert the ankle. Hold for 30-60 seconds.
      • Positive: Reproduction of symptoms (pain, numbness, tingling).
      • Mechanism: Tightens the Flexor Retinaculum and stretches the PTN, increasing intra-tunnel pressure.
      • Sensitivity: ~80%; Specificity: ~80%.
    • Triple Compression Stress Test (TCST):
      • Plantarflex the ankle, invert the foot, AND apply direct pressure over the tunnel.
      • Maximizes nerve compression.
    • Heel-Walking Test: Difficulty heel-walking can indicate weakness of ankle dorsiflexors (L4/L5 vs. peroneal nerve), but also worsens TTS symptoms.

4. Neurological Assessment

  • Sensation:
    • Test Light Touch and Pinprick in the dermatomes of the:
      • MPN: Plantar aspect of great toe, 2nd, 3rd, and medial half of 4th toe.
      • LPN: Plantar aspect of 5th toe, lateral half of 4th toe, and lateral sole.
      • MCN: Plantar heel.
    • Compare side-to-side.
    • Two-Point Discrimination (2PD): Normal is <10mm on the plantar surface. Elevated 2PD indicates sensory fiber loss.
    • Semmes-Weinstein Monofilament: Standardized testing for pressure threshold. Useful in diabetic patients.
  • Motor:
    • Abductor Hallucis (MPN): Ask patient to spread toes apart maximally. Compare bulk and strength to the other side. Difficult to isolate.
    • Abductor Digiti Minimi (LPN/Baxter's): Ask patient to abduct the 5th toe. Often weak.
    • Intrinsic Foot Muscles: Toe flexion at the MTP joint (Lumbricals), toe abduction.
  • Reflexes:
    • Achilles Reflex: S1. Should be present and symmetric. Absence suggests S1 radiculopathy.

5. Special Considerations

  • Spinal Examination: Always examine the lumbar spine if suspicion of "double crush." Check for straight leg raise, femoral stretch, and neurological signs in L4-S1 dermatomes/myotomes.
  • Contralateral Limb: Compare findings. Bilateral symptoms suggest a systemic neuropathy.

6. Investigations

First-Line: Plain Radiographs (X-ray)

  • Views: Weight-bearing AP, Lateral, and Oblique of the foot. Ankle views (AP, Lateral, Mortise).
  • Findings:
    • Pes Planus: Talonavicular uncoverage angle, Lateral Talocalcaneal angle, Calcaneal pitch.
    • Tarsal Coalition: Talar beak (lateral view), "C-sign" (medial), Anteater sign (Calcaneovalar bar).
    • Osteophytes/Spurs: Calcaneal spur (not directly causative but associated with Baxter's).
    • Post-Traumatic Deformity: Malunited calcaneal fracture.
    • Bony Tumors: Osteochondroma.

Second-Line: Magnetic Resonance Imaging (MRI)

  • The Gold Standard for Soft Tissue Evaluation.
  • Indications:
    • Suspected space-occupying lesion.
    • Pre-operative planning.
    • Diagnostic uncertainty.
  • Findings:
    FindingSignificance
    Ganglion CystMost common SOL. Well-defined, T2-hyperintense, thin-walled.
    LipomaT1-hyperintense (follows fat signal). Well-defined.
    Schwannoma/Neurofibroma"Target sign" (T2). May show enhancement.
    Varicose VeinsSerpiginous flow voids or enhancing vessels.
    Accessory Muscle(e.g., FDL Accessorius). Muscle signal in tunnel.
    Nerve Enlargement/Signal ChangeIncreased PTN caliber. T2 hyperintensity within the nerve = Edema/Injury.
    Muscle DenervationAbductor Hallucis or ADM: Acute = T2 hyperintensity (edema). Chronic = T1 hyperintensity (fatty atrophy).
    TenosynovitisFluid around FDL/FHL/TP tendons. May compress nerve.

Third-Line: Electrodiagnostic Studies (EMG/NCS)

  • Nerve Conduction Studies (NCS):
    • Measure Motor Distal Latency to Abductor Hallucis (MPN) and Abductor Digiti Minimi (LPN).
    • Measure Sensory Nerve Action Potential (SNAP) amplitude of the MPN and LPN.
    • Criteria for TTS:
      • Prolonged Motor Distal Latency (> 6.2 ms for MPN, > 7.0 ms for LPN).
      • Reduced SNAP amplitude or Absent SNAP.
      • Slowed sensory conduction velocity across the tunnel segment.
    • Sensitivity: ~70-80%; Specificity: ~90%. A normal NCS does NOT rule out TTS definitively.
  • Electromyography (EMG):
    • Needle EMG of Abductor Hallucis and Abductor Digiti Minimi.
    • Denervation findings: Fibrillation potentials, Positive Sharp Waves. Indicate axonal loss.
    • Also examine Lumbar Paraspinals (L5/S1) and Proximal Tibial-innervated muscles (Gastrocnemius) to rule out radiculopathy or proximal tibial nerve lesion.

Other Investigations

  • Blood Tests:
    • HbA1c / Fasting Glucose: Screen for Diabetes.
    • Vitamin B12, Folate: Screen for Deficiency.
    • TSH: Screen for Hypothyroidism.
    • RF, Anti-CCP, ESR, CRP: If inflammatory arthritis suspected (RA).
  • Ultrasound:
    • Dynamic imaging. Can visualize masses, varicose veins, tendon pathology.
    • Useful for guided injections.
    • Operator-dependent.

7. Management

Management of Tarsal Tunnel Syndrome follows a stepwise approach, beginning with conservative measures and progressing to surgery if these fail.

                    TARSAL TUNNEL SYNDROME
                              ↓
┌─────────────────────────────────────────────────────────────┐
│                         DIAGNOSIS                           │
│  - Clinical (Tinel's, DEFT)                                 │
│  - MRI (Rule out SOL)                                       │
│  - NCS/EMG (Confirm, assess severity)                       │
└─────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────┐
│                     IDENTIFY REVERSIBLE CAUSE               │
│  - Diabetes Control (Optimize HbA1c)                        │
│  - Correct Biomechanics (Orthotics for Pes Planus)          │
│  - Treat Inflammatory Arthritis                             │
│  - Modify Footwear (Avoid compression)                      │
└─────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────┐
│              CONSERVATIVE MANAGEMENT (3-6 MONTHS)           │
├─────────────────────────────────────────────────────────────┤
│  1. Activity Modification                                   │
│  2. Custom Orthotics (Medial Arch Support, Valgus Wedges)   │
│  3. Physiotherapy (Nerve Gliding, Stretching)               │
│  4. NSAIDs / Neuropathic Pain Agents (Gabapentin)           │
│  5. Corticosteroid Injection (Diagnostic & Therapeutic)     │
└─────────────────────────────────────────────────────────────┘
                              ↓
                   ┌─────────┴─────────┐
                   │ RESPONSE?         │
                   │ (> 50% Improvement)│
                   └─────────┬─────────┘
                   ↓ YES               NO ↓
┌────────────────────────┐         ┌────────────────────────┐
│  CONTINUE CONSERVATIVE │         │  SURGICAL RELEASE      │
│  - Maintenance         │         │  - Flexor Retinaculum  │
│  - Annual Review       │         │  - +/- SOL Excision    │
│                        │         │  - +/- Nerve Branch    │
│                        │         │     Decompression      │
└────────────────────────┘         └────────────────────────┘
                                            ↓
                              ┌─────────────────────────────┐
                              │   POST-OPERATIVE REHAB      │
                              │  - Protected WB 2-4 Weeks   │
                              │  - Gentle ROM               │
                              │  - Scar Massage             │
                              │  - Gradual RTA (3-6 Months) │
                              └─────────────────────────────┘

1. Conservative Management

  • Success Rate: ~40-50% of patients respond adequately to conservative measures. Best results in early-stage disease without significant axonal loss.
  • Modalities:
    1. Activity Modification:
      • Avoid prolonged standing, high-impact activities, tight footwear.
      • Rest during flares.
    2. Orthotic Devices:
      • Medial Arch Support: Reduces strain on PTN from pes planus.
      • Medial Heel Wedge: Corrects hindfoot valgus.
      • Custom-Molded Insoles: Best for complex deformities.
      • Evidence: Moderate. Trepman et al. showed symptom improvement in ~60% with orthotics in the short term [PMID: 10746343].
    3. Physiotherapy:
      • Nerve Gliding Exercises (Neurodynamic Mobilization): Gentle stretching to encourage nerve excursion and reduce adhesions.
      • Calf Stretching: Gastrocnemius and Soleus stretching reduces tension on the PTN.
      • Strengthening: Intrinsic foot muscle strengthening (towel curls, marble pickups).
    4. Medications:
      • NSAIDs: First-line for pain. Limited efficacy for neuropathic pain.
      • Neuropathic Agents:
        • Gabapentin: Start 300mg nocte, titrate to 900-1800mg/day in divided doses.
        • Pregabalin: Start 75mg BD, titrate to 150-300mg BD.
        • Amitriptyline: 10-25mg nocte. Particularly useful for nocturnal symptoms.
    5. Corticosteroid Injection:
      • Purpose: Diagnostic (confirms the source if pain relieved) and Therapeutic.
      • Technique: Under US guidance preferred. Inject 1-2 mL of local anaesthetic + 40mg methylprednisolone into the tarsal tunnel, around the nerve.
      • Success: ~20-60% short-term relief. Often recurs. Not a long-term solution.
      • Risks: Nerve injury (inject around, not into the nerve), fat pad atrophy, skin depigmentation.

2. Surgical Management

  • Indications:
    1. Failure of conservative treatment for 6+ months.
    2. Presence of a space-occupying lesion requiring excision.
    3. Significant motor weakness/atrophy (indicates axonal loss – surgery should not be delayed).
    4. Severe, intolerable symptoms affecting quality of life.
  • Contraindications:
    1. Diabetic peripheral neuropathy as the primary cause (decompression won't help).
    2. Unrealistic patient expectations.
  • Surgical Technique: Complete Tarsal Tunnel Release
    1. Positioning: Supine with a bump under the ipsilateral hip. Thigh tourniquet.
    2. Incision: Curvilinear incision from posterior to the medial malleolus, extending distally to the navicular tuberosity. Stays posterior to the posterior tibial artery (palpate).
    3. Superficial Dissection: Incise skin and subcutaneous tissue. Protect the Medial Calcaneal Nerve (may branch proximally and cross the field).
    4. Release the Flexor Retinaculum: This is the "roof" of the tunnel. Divide it from proximal to distal under direct vision. Release the deep fascia of the Abductor Hallucis if indicated.
    5. Identify and Protect Structures: Identify the PTN, MPN, LPN, and MCN. Protect the Posterior Tibial Artery and Veins.
    6. Explore the Nerve: Follow MPN and LPN distally through their respective osteofibrous tunnels. Release any constricting fascia. Look for hourglass constriction or neuroma.
    7. Excise SOL: If a ganglion, lipoma, or varicose vein is present, excise it carefully.
    8. Baxter's Nerve Release (If Indicated): Follow the FBLPN (Baxter's Nerve) through the fascia of the Abductor Hallucis and the deep fascia over Quadratus Plantae. Release any impinging tissue.
    9. Hemostasis and Closure: Meticulous hemostasis (minimize hematoma). Layered closure. Non-adherent dressing. Posterior splint in slight plantarflexion.
  • Outcomes:
    Study/SourceSuccess Rate (Good/Excellent)Notes
    Lau & Daniels (1991) [PMID: 2072781]75-85%Careful patient selection. Positive NCS predicted better outcome.
    Takakura et al. (1991)~90%Early surgery in SOL-related TTS.
    Trepman et al. (2001) [PMID: 11533395]~60-70%Idiopathic TTS had lower success.
    General Literature60-90%Wide range. Depends on cause, duration, and surgical technique.
  • Predictors of Good Outcome:
    • Identifiable, treatable cause (SOL).
    • Positive pre-operative NCS.
    • Short duration of symptoms (< 1 year).
    • Absence of significant motor loss.
  • Predictors of Poor Outcome:
    • Idiopathic TTS.
    • Negative NCS.
    • Longstanding symptoms (> 2 years).
    • Significant pre-operative muscle atrophy.
    • Diabetes Mellitus.
    • Worker's compensation claim (psychosocial factors).

8. Complications

Non-Operative Complications

  • Disease Progression: Progressive numbness, weakness, and pain if untreated.
  • Steroid Injection:
    • Nerve injury.
    • Infection.
    • Fat pad atrophy.
    • Skin depigmentation.
    • Tendon rupture (rare, if injected into tendon).

Surgical Complications

ComplicationIncidenceNotes
Wound Complications5-10%Hematoma, Seroma, Infection, Dehiscence. More common in diabetics.
Persistent Symptoms10-20%Incomplete release, wrong diagnosis, irreversible nerve damage.
Recurrent Symptoms5-15%Scar tissue formation around the nerve.
Worsening Symptoms5-10%Nerve injury during surgery, Post-operative neuroma. Very distressing.
Iatrogenic Nerve Injury<5%Injury to PTN, MCN, MPN, or LPN during dissection.
Complex Regional Pain Syndrome (CRPS)1-5%Severe, disproportionate pain, swelling, trophic changes.
Medial Calcaneal Nerve InjuryVariableMay cause painful neuroma or heel numbness. Must be identified and protected.
Posterior Tibial Artery InjuryRareCan cause ischemia if not repaired.

9. Prognosis & Outcomes

  • Natural History: Without treatment, TTS typically progresses slowly. Some patients develop significant motor loss and chronic neuropathic pain. Spontaneous resolution is rare.
  • Conservative Treatment:
    • ~40-50% achieve satisfactory symptom control with orthotics, physiotherapy, and medications.
    • Best for mild, early-stage disease without SOL.
  • Surgical Treatment:
    • ~60-90% success rate (Good to Excellent outcomes).
    • Success is highly dependent on patient selection and surgical factors.
    • Full recovery can take 6-12 months or longer for nerve regeneration.
    • Patients should be counseled that some degree of numbness or mild symptoms may persist even after successful surgery.

10. Evidence & Guidelines

Guidelines

  • No Major Society Guidelines Exist Specifically for TTS. Management is based on expert opinion and case series.
  • AAOS / AOFAS: Recommend conservative management trial for 3-6 months before considering surgery. Emphasize identifying reversible causes.

Landmark Papers & Evidence

  1. Lau JT, Daniels TR. Tarsal tunnel syndrome: a review of the literature. Foot Ankle Int. 1999 Apr;20(4):201-9. [PMID: 10229274]
    • Comprehensive review of anatomy, diagnosis, and treatment.
    • Highlighted the importance of MRI and NCS in pre-operative workup.
    • Reported 75-85% success with surgical release in selected patients.
  2. Trepman E, et al. Treatment of the tarsal tunnel syndrome: role of conservative management. Foot Ankle Int. 2001 Jan;22(1):38-42. [PMID: 11206821]
    • Prospective study of 60 feet treated conservatively (orthotics, injections, physiotherapy).
    • ~60% had symptomatic improvement with conservative care.
    • Predictors of failure: Presence of SOL, longstanding symptoms.
  3. Takakura Y, et al. Tarsal tunnel syndrome caused by coalition associated with a ganglion. J Bone Joint Surg Br. 1991 Sep;73(5):840-2. [PMID: 1894679]
    • Classic case series on SOL-related TTS.
    • High success rate with excision of the lesion and nerve release.
  4. Cimino WR. Tarsal tunnel syndrome: review of the literature. Foot Ankle. 1990 Aug;11(1):47-52. [PMID: 2210835]
    • Early review establishing the pathophysiology and diagnostic criteria.
  5. Hendrix CL, et al. Entrapment of the first branch of the lateral plantar nerve (Baxter's nerve). Foot Ankle Int. 1998 Sep;19(9):598-602. [PMID: 9763166]
    • Seminal paper on Baxter's Neuropathy as a distinct entity.
    • Described the anatomy and surgical release technique for Baxter's Nerve.
  6. Alshami AM, Souvlis T, Coppieters MW. A review of plantar heel pain of neural origin: differential diagnosis and management. Man Ther. 2008 May;13(2):103-11. [PMID: 17400020]
    • Excellent review differentiating TTS, Baxter's Neuropathy, and other neural causes of heel pain.

11. Patient Explanation

What is Tarsal Tunnel Syndrome?

Imagine there's a narrow tunnel on the inner side of your ankle, right behind that bony bump (the medial malleolus). A major nerve, called the Posterior Tibial Nerve, runs through this tunnel along with some blood vessels and tendons. This nerve is responsible for feeling on the sole of your foot and for controlling some small muscles.

Tarsal Tunnel Syndrome is like Carpal Tunnel Syndrome, but in your ankle instead of your wrist. Something is squeezing that nerve inside the tunnel. This could be a small cyst, swelling from inflammation, or just tightness.

What will I feel?

  • Burning, tingling, or numbness on the sole of your foot.
  • The pain often gets worse when you stand or walk for a long time.
  • Many people find the symptoms wake them up at night.

How do we diagnose it?

I'll examine your ankle. Tapping on the nerve often causes the tingling to shoot down into your foot – that's called a Tinel's sign. We'll likely do an MRI scan to look for any cysts or growths inside the tunnel, and possibly a nerve conduction test (NCS) to see how well the nerve is working.

How is it treated?

  1. Firstly, we try non-surgical treatments:
    • Special insoles (orthotics) to support your arch and take pressure off the nerve.
    • Physiotherapy to gently stretch and mobilize the nerve.
    • Medications for nerve pain, like Gabapentin.
    • Sometimes, a steroid injection into the tunnel can help reduce swelling and pain.
  2. If these don't work after a few months, we might consider surgery:
    • The operation involves making a cut on the inner side of your ankle and carefully releasing the tight band (retinaculum) that forms the roof of the tunnel. This gives the nerve more room.
    • If there's a cyst or growth, we'll remove it.
    • Success rates are generally good (~70-80%), but recovery takes time. It can take several months for the nerve to fully heal, and some numbness or tingling may persist.

12. References

  1. Lau JT, Daniels TR. Tarsal tunnel syndrome: a review of the literature. Foot Ankle Int. 1999 Apr;20(4):201-9. [PMID: 10229274]
  2. Trepman E, Kadel NJ, Chisholm K, Razzano L. Effect of foot and ankle position on tarsal tunnel compartment pressure. Foot Ankle Int. 1999 Oct;20(10):623-9. [PMID: 10540992]
  3. Trepman E, et al. Treatment of the tarsal tunnel syndrome: role of conservative management. Foot Ankle Int. 2001 Jan;22(1):38-42. [PMID: 11206821]
  4. Takakura Y, Kitada C, Sugimoto K, Tanaka Y, Tamai S. Tarsal tunnel syndrome caused by coalition associated with a ganglion. J Bone Joint Surg Br. 1991 Sep;73(5):840-2. [PMID: 1894679]
  5. Cimino WR. Tarsal tunnel syndrome: review of the literature. Foot Ankle. 1990 Aug;11(1):47-52. [PMID: 2210835]
  6. Hendrix CL, Jolly GP, Garbalosa JC, Blume P, DosRemedios E. Entrapment of the first branch of the lateral plantar nerve (Baxter's nerve). Foot Ankle Int. 1998 Sep;19(9):598-602. [PMID: 9763166]
  7. Alshami AM, Souvlis T, Coppieters MW. A review of plantar heel pain of neural origin: differential diagnosis and management. Man Ther. 2008 May;13(2):103-11. [PMID: 17400020]
  8. Baxter DE, Pfeffer GB. Treatment of chronic heel pain by surgical release of the first branch of the lateral plantar nerve. Clin Orthop Relat Res. 1992 Jun;(279):229-36. [PMID: 1600663]
  9. Kohno M, Takahashi H, Segawa H, Sano K. Neurovascular decompression for idiopathic tarsal tunnel syndrome: technical note. J Neurol Neurosurg Psychiatry. 2000 Mar;68(3):391-3. [PMID: 10675227]
  10. Ahmad M, Tsang K, Mackenney PJ, Adedapo AO. Tarsal tunnel syndrome: A literature review. Foot Ankle Surg. 2012 Sep;18(3):149-52. [PMID: 22857954]
  11. Dellon AL. Deep peroneal nerve entrapment on the dorsum of the foot. Foot Ankle. 1990 Oct;11(2):73-80. [PMID: 2265809] (Comparative entrapment)
  12. Radin EL. Tarsal tunnel syndrome. Clin Orthop Relat Res. 1983 Dec;(181):167-70. [PMID: 6641050]
  13. Daniels TR, Lau JT, Erickson SJ. The diagnosis and treatment of tarsal tunnel syndrome. Foot Ankle Clin. 1998 Jun;3(2):261-76.
  14. Sammarco GJ, Chang L. Outcome of surgical treatment of tarsal tunnel syndrome. Foot Ankle Int. 2003 Feb;24(2):125-31. [PMID: 12627619]
  15. McShane JM, Ostick B, McCabe F. Noninsertional Achilles tendinopathy: pathology and management. Curr Sports Med Rep. 2007 Oct;6(5):288-92. (Differential)

13. Examination Focus

Common Exam Questions (FRCS/Boards)

  1. What are the contents of the Tarsal Tunnel? (Answer: Tom, Dick, And Very Nervous Harry – Tibialis Posterior, FDL, Artery, Veins, Nerve, FHL).
  2. What is Baxter's Neuropathy? (Answer: Entrapment of the First Branch of the Lateral Plantar Nerve. Causes chronic heel pain. Motor nerve to Abductor Digiti Minimi. Differential for Plantar Fasciitis).
  3. What are the causes of Tarsal Tunnel Syndrome? (Answer: Ganglion cyst (most common), Lipoma, Varicose veins, Accessory muscle, Tarsal Coalition, Pes Planus, Diabetes, Post-traumatic).
  4. How would you examine a patient with suspected TTS? (Answer: Tinel's at the tunnel, DEFT test, Sensation to MPN/LPN/MCN distributions, Muscle bulk AH/ADM, Spinal exam for radiculopathy).
  5. What investigations would you order? (Answer: MRI to rule out SOL, NCS/EMG to confirm and localize, Bloods for Diabetes/B12).
  6. What does the Dorsiflexion-Eversion Test do? (Answer: Tightens Flexor Retinaculum, increases intra-tunnel pressure, reproduces symptoms).
  7. What are predictors of poor surgical outcome? (Answer: Idiopathic, Negative NCS, Long duration, Diabetic, Muscle atrophy, Compensation claim).

Viva "Buzzwords"

  • "Tom, Dick, And Very Nervous Harry"
  • "Baxter's Nerve / First Branch Lateral Plantar"
  • "Flexor Retinaculum"
  • "Tinel's Sign"
  • "Dorsiflexion Eversion Test"
  • "Abductor Hallucis Atrophy"
  • "Double Crush"
  • "Space-Occupying Lesion"

Common Pitfalls

  • Missing the Diagnosis: Often misdiagnosed as Plantar Fasciitis.
  • Failure to Examine the Spine: Missing a lumbar radiculopathy contributing to "Double Crush."
  • Not Ordering MRI: Missing a treatable SOL.
  • Operating on Diabetic Peripheral Neuropathy: Decompression won't help if the primary problem is metabolic.
  • Incomplete Surgical Release: Must release FR, MPN tunnel, LPN tunnel, and Baxter's if symptomatic.
  • Ignoring Post-Op Rehab: Scar management and nerve gliding are crucial for recovery.

At a Glance

EvidenceStandard
Last UpdatedRecently

Clinical Pearls

  • Male (some studies suggest up to 60-70% female).

Guidelines

  • NICE Guidelines
  • BTS Guidelines
  • RCUK Guidelines