TARSAL TUNNEL SYNDROME
Posterior Tibial Nerve Compression | Flexor Retinaculum | Medial Ankle
Severity Classification
Critical Must-Knows
- Posterior Tibial Nerve Branches: Medial plantar (abductor hallucis), lateral plantar (intrinsics), medial calcaneal (heel sensation)
- Tinel Sign: Most reliable clinical test - tap posterior to medial malleolus
- Space-Occupying Lesions: 20-30% have identifiable cause (ganglion, lipoma, varicosities)
- Double Crush: Exclude proximal nerve compression (L4-S2 radiculopathy)
- Surgical Release: Must decompress entire tunnel including abductor hallucis fascia
Examiner's Pearls
- "Burning plantar pain worse at night = classic presentation
- "Always examine for intrinsic muscle weakness (toe spread)
- "MRI before surgery to identify space-occupying lesions
- "Incomplete release = recurrence - extend distally through abductor tunnel
Clinical Imaging
Imaging Gallery
Critical TTS Exam Points
Anatomical Course
Posterior tibial nerve posterior to medial malleolus. Passes beneath flexor retinaculum with posterior tibial artery and tendons (Tom, Dick, And Very Nervous Harry).
Branch Sequence
Medial calcaneal first, then bifurcation. Medial plantar (larger, sensory dominant), lateral plantar (motor dominant). All may be affected.
Examination
Tinel most reliable. Dorsiflexion-eversion stress test positive in 80%. Check intrinsic muscle power and sensation.
Surgical Pearls
Complete release essential. Must decompress flexor retinaculum AND abductor hallucis origin. Identify and protect all branches.
Quick Decision Guide
| Presentation | Investigations | Treatment | Key Pearl |
|---|---|---|---|
| Intermittent burning, positive Tinel | NCS baseline | Orthotics, activity modification | Trial 3 months conservative treatment |
| Constant symptoms, sensory loss | MRI to exclude lesion | Corticosteroid injection trial | Injection confirms diagnosis if relief |
| Motor weakness, intrinsic wasting | Urgent MRI and NCS | Surgical decompression | Complete release including distally |
TOM, DICK And Very Nervous HARRYTarsal Tunnel Contents
Memory Hook:Anterior to posterior order - Tom, Dick And Very Nervous Harry. The NERVE is vulnerable between the vessels and FHL!
MLCPTN Terminal Branches
Memory Hook:MLC = Medial, Lateral, Calcaneal - the three branches you must identify and decompress!
SPACECauses of Tarsal Tunnel Syndrome
Memory Hook:SPACE = Something is taking up SPACE in the tunnel! Look for mass lesions.
Overview and Epidemiology
Why TTS Matters
TTS is the lower limb analogue of carpal tunnel syndrome but is much less common. Understanding the anatomy and terminal branches is essential for exam and surgical planning.
Tarsal Tunnel Syndrome is compression of the posterior tibial nerve or its terminal branches beneath the flexor retinaculum on the medial aspect of the ankle.
Demographics
- Female predominance: 2:1 ratio
- Peak age: 40-60 years
- Bilateral: 25% of cases
- Associated conditions: Pes planus, diabetes, RA
Less common than carpal tunnel syndrome but important to recognise.
Risk Factors
- Trauma: Ankle fractures, sprains (most common)
- Pes planus: Increased nerve tension
- Space-occupying lesions: Ganglion, lipoma
- Systemic: Diabetes, hypothyroidism, RA
20-30% have identifiable mass lesion causing compression.
Anatomy and Pathophysiology
Tarsal Tunnel Anatomy
The tarsal tunnel is a fibro-osseous tunnel on the medial ankle. The ROOF is the flexor retinaculum (laciniate ligament) extending from medial malleolus to calcaneus. The FLOOR is the medial talus, sustentaculum tali, and medial calcaneus.
Tarsal Tunnel Boundaries:
- Roof: Flexor retinaculum (laciniate ligament)
- Floor: Medial surface of talus, sustentaculum tali, medial calcaneus
- Anterior: Medial malleolus
- Posterior: Medial calcaneal tuberosity
Contents (Anterior to Posterior - Tom, Dick And Very Nervous Harry):
- Tibialis posterior tendon
- Flexor digitorum longus tendon
- Posterior tibial artery and veins
- Posterior tibial nerve
- Flexor hallucis longus tendon
Posterior Tibial Nerve Branches:
- Medial calcaneal nerve: First branch, sensory to medial heel
- Medial plantar nerve: Larger terminal branch, sensory to medial 3.5 toes, motor to abductor hallucis, FHB, FDB, first lumbrical
- Lateral plantar nerve: Smaller terminal branch, motor to intrinsics, sensory to lateral 1.5 toes
Pathophysiology:
- Increased pressure within the tarsal tunnel (greater than 30 mmHg)
- Venous congestion and nerve ischaemia
- Demyelination (reversible in early stages)
- Axonal damage (irreversible - motor weakness, atrophy)
- Fibrosis and adhesions (chronic cases)
Aetiology and Classification
Aetiological Classification
| Category | Examples | Frequency |
|---|---|---|
| Post-traumatic | Ankle fractures, sprains, dislocation | Most common |
| Space-occupying lesions | Ganglion, lipoma, neurilemoma, varicosities | 20-30% |
| Biomechanical | Pes planus, hindfoot valgus, tarsal coalition | Common |
| Systemic | Diabetes, hypothyroidism, RA, amyloidosis | Variable |
| Idiopathic | No identifiable cause | 30-40% |
Always investigate for underlying cause - MRI before surgery.
Clinical Assessment
History
- Burning pain: Plantar foot and toes
- Nocturnal symptoms: Worse at night, wake from sleep
- Aggravating factors: Prolonged standing, walking
- Radiation: Along medial arch to toes
- Associated: Weakness of toe flexion
Burning plantar pain worse at night is virtually diagnostic.
Examination
- Tinel sign: Tap posterior to medial malleolus
- Dorsiflexion-eversion test: Positive in 80%
- Two-point discrimination: Greater than 6mm abnormal
- Intrinsic muscle testing: Toe spread, FHB power
- Hindfoot alignment: Check for pes planus
Always compare to contralateral side.
Provocative Tests:
Clinical Tests for TTS
| Test | Technique | Sensitivity | Specificity |
|---|---|---|---|
| Tinel sign | Tap posterior to medial malleolus | 58% | 92% |
| Dorsiflexion-eversion | Hold 30 seconds, reproduces symptoms | 81% | 85% |
| Direct compression | 30 seconds over tunnel | 50% | 90% |
| Triple compression | DF + eversion + compression | 85% | 88% |
Differential Diagnosis
Consider: Plantar fasciitis (different location), Morton neuroma (forefoot), L5-S1 radiculopathy (check back), peripheral neuropathy (bilateral, diabetics), Baxter neuropathy (first branch LPN).
Investigations
Nerve Conduction Studies
Gold standard for confirmation but false negative rate 30-50%.
| Parameter | Normal | Abnormal |
|---|---|---|
| Medial plantar DML | Less than 4.4 ms | Greater than 4.4 ms |
| Lateral plantar DML | Less than 4.6 ms | Greater than 4.6 ms |
| SNAP amplitude | Greater than 5 mcV | Reduced or absent |
EMG findings in motor involvement:
- Fibrillation potentials in intrinsics
- Positive sharp waves
- Reduced recruitment
NCS may be normal in 30-50% of clinical TTS.
Management
Non-Operative Management
First-line treatment for 3-6 months.
Activity Modification:
- Avoid prolonged standing
- Limit high-impact activities
- Comfortable, supportive footwear
Orthotics:
- Medial arch support for pes planus
- Heel cushioning
- Custom orthotics if required
Medications:
- NSAIDs for pain relief
- Gabapentin for neuropathic pain
- Topical capsaicin
Physical Therapy:
- Nerve gliding exercises
- Stretching programme
- Strengthening
Success rate 40-50% with conservative treatment.
Surgical Technique
Complete Tarsal Tunnel Release
Indications:
- Failed conservative treatment (3-6 months)
- Space-occupying lesion
- Progressive motor deficit
- Intractable symptoms
Patient Positioning:
- Supine with leg externally rotated
- Thigh tourniquet
- Foot at end of table
Incision:
- Curvilinear incision posterior to medial malleolus
- Extend distally along abductor hallucis
- Length 6-8 cm for adequate exposure
Superficial Dissection:
- Identify and protect posterior tibial vessels
- Incise flexor retinaculum completely
- Identify main PTN trunk
Deep Dissection:
- Trace nerve proximally and distally
- Identify and release all three branches
- Release medial calcaneal nerve
- Continue release through abductor hallucis tunnel
- Excise any mass lesions
Closure:
- Leave retinaculum open
- Close subcutaneous tissue and skin
- Bulky dressing
Critical Points:
- Must release distally through abductor tunnel
- Identify and protect all branches
- Excise mass lesions completely
- Neurolysis if fibrosis present
These principles ensure complete decompression and optimal outcomes.
Complications
Surgical Complications
- Recurrence: 10-20% (incomplete release)
- Wound complications: Delayed healing, infection
- Nerve injury: Damage to branches
- Scar tethering: Nerve adhesions
- Persistent symptoms: Incomplete decompression
Most complications from inadequate release.
Prevention
- Complete release: Include abductor tunnel
- Meticulous technique: Identify all branches
- MRI preoperatively: Plan for mass lesions
- Gentle handling: Minimise nerve trauma
- Early mobilisation: Reduce adhesions
Attention to detail prevents recurrence.
Postoperative Problems
| Complication | Incidence | Prevention | Management |
|---|---|---|---|
| Incomplete release | 10-20% | Full exposure distally | Revision surgery |
| Wound dehiscence | 5% | Careful closure, offload | Wound care, possible grafting |
| Persistent symptoms | 15-30% | Proper patient selection | NCS, consider revision |
| CRPS | 2-5% | Early mobilisation | Pain management, therapy |
Postoperative Care and Rehabilitation
Immediate Postoperative:
- Bulky dressing and posterior splint
- Elevation above heart level
- Non-weight bearing 2 weeks
Weeks 0-2:
- Rest, ice, elevation
- Ankle pumps
- Wound check at 2 weeks
Weeks 2-6:
- Transition to weight-bearing as tolerated
- Gentle range of motion
- Scar massage once healed
Weeks 6-12:
- Progressive strengthening
- Return to normal footwear
- Gradual return to activity
Expected Recovery:
- Burning pain relief: 2-4 weeks
- Sensory improvement: 3-6 months
- Motor recovery: 6-12 months (if present)
- Full recovery: 6-12 months
Outcomes and Prognosis
Prognostic Factors:
Predictors of Outcome
| Good Prognosis | Poor Prognosis |
|---|---|
| Identifiable cause (mass lesion) | Idiopathic TTS |
| Short duration of symptoms | Chronic symptoms over 12 months |
| Positive response to injection | Failed injection |
| Sensory symptoms only | Motor deficit present |
| Normal EMG | Denervation on EMG |
Evidence Base
Tarsal Tunnel Release Outcomes
- Retrospective review of 60 patients with surgical release
- 85% good/excellent results at mean 30-month follow-up
- Better outcomes in patients with identifiable mass lesion (over 90%)
- Idiopathic cases had only 50% good/excellent results
Electrodiagnostic Studies in TTS
- NCS sensitivity 40-60% for tarsal tunnel syndrome
- False negative rate significant (30-50%)
- Clinical diagnosis remains primary diagnostic tool
- NCS supportive but not exclusionary - proceed with clinical TTS
MRI in Tarsal Tunnel Syndrome
- MRI identified space-occupying lesions in 33% of patients
- Preoperative MRI changed surgical planning significantly
- Ganglions and lipomas most common lesions identified
- Recommends routine MRI before surgical decompression
Surgical Outcomes Meta-Analysis
- Meta-analysis of 8 studies with 314 patients
- Overall success rate 60-85% at medium-term follow-up
- Complete decompression including distal release essential
- Recurrence rate 10-20% primarily from incomplete release
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
A 45-year-old woman presents with burning pain in the sole of her foot
"How would you assess this patient?"
NCS shows prolonged distal latency. MRI shows a ganglion in the tarsal tunnel
"What is your management plan?"
Patient presents 6 months post tarsal tunnel release with recurrent symptoms
"How would you approach this?"
MCQ Practice Points
Anatomy Question
Q: What is the order of structures in the tarsal tunnel from anterior to posterior? A: Tom, Dick And Very Nervous Harry - Tibialis posterior, Flexor Digitorum longus, Artery (posterior tibial), Vein, Nerve (posterior tibial), Flexor Hallucis longus. The posterior tibial nerve lies between the vessels anteriorly and FHL posteriorly.
Clinical Test
Q: A patient has burning pain in the plantar foot. Which test is most sensitive for tarsal tunnel syndrome? A: Dorsiflexion-eversion stress test has highest sensitivity (81%) and specificity (85%). Hold position for 30 seconds to reproduce symptoms. Tinel sign is more specific (92%) but less sensitive (58%).
Surgical Technique
Q: What is the most common cause of recurrence after tarsal tunnel release? A: Incomplete release, particularly failure to decompress distally through the abductor hallucis tunnel. Complete release must include the flexor retinaculum proximally and extend through the abductor hallucis fascia distally to fully decompress the medial and lateral plantar nerves.
Prognostic Factor
Q: Which patient with tarsal tunnel syndrome is most likely to have a good surgical outcome? A: Patient with space-occupying lesion (ganglion, lipoma) has approximately 90% success rate. Idiopathic cases have only 50% success. Other good prognostic factors include short duration of symptoms, sensory only symptoms, and positive response to diagnostic injection.
Nerve Branches
Q: Which branch of the posterior tibial nerve branches first within the tarsal tunnel? A: Medial calcaneal nerve branches first (proximal in the tunnel), providing sensory innervation to the medial heel. The nerve then bifurcates into medial plantar (larger, sensory dominant) and lateral plantar (motor dominant) branches more distally.
Australian Context
Tarsal tunnel syndrome management in Australia follows standard orthopaedic practice. Conservative management with orthotics and physiotherapy is typically the first-line approach, with surgical decompression reserved for refractory cases or those with identifiable space-occupying lesions. Australian centres report outcomes consistent with international literature, with success rates of 60-85% for surgical decompression.
Documentation of pre-operative symptoms, informed consent regarding realistic expectations (noting that success rates vary with aetiology), and appropriate perioperative management including VTE prophylaxis are important considerations. Patients with systemic conditions such as diabetes or rheumatoid arthritis may have less predictable outcomes and warrant careful counselling.
Tarsal Tunnel Syndrome Exam Cheat Sheet
High-Yield Exam Summary
Anatomy
- •Tom, Dick And Very Nervous Harry = contents anterior to posterior
- •Three terminal branches: medial calcaneal (first), medial plantar, lateral plantar
- •Flexor retinaculum = roof, carpal bones = floor
Clinical Features
- •Burning plantar pain worse at night
- •Tinel positive posterior to medial malleolus
- •Dorsiflexion-eversion test most sensitive
- •Intrinsic weakness = advanced disease
Investigations
- •NCS: prolonged distal motor latency (less than 4.4ms MPN)
- •MRI: essential to identify mass lesions (20-30% have one)
- •NCS false negative rate 30-50%
Treatment Algorithm
- •Conservative 3-6 months: orthotics, activity modification, medications
- •Injection: diagnostic and therapeutic, 50-60% temporary relief
- •Surgery if failed conservative or progressive motor deficit
Surgical Pearls
- •Curvilinear incision posterior to medial malleolus
- •Complete release of flexor retinaculum
- •MUST extend through abductor hallucis tunnel distally
- •Identify and protect all three branches
Outcomes
- •60-85% overall success
- •90% success with mass lesion
- •50% success idiopathic
- •Recurrence 10-20% (incomplete release)