Tarsal Tunnel Release (Posterior Tibial Nerve Decompression)

Primary Indications

Tarsal Tunnel Syndrome - Failed Conservative Management

Clinical Diagnosis Requirements:

• Burning, tingling, numbness plantar foot (medial plantar, lateral plantar, or calcaneal distribution)
• Symptoms worse with standing, walking, prolonged weight-bearing
• Nocturnal symptoms common (awakens patient from sleep)
• Relief with rest, elevation, shoe modification

Physical Examination Findings:

• Tinel's sign: Percussion tenderness posterior to medial malleolus with distal radiation
• Plantar percussion test: Dorsiflexion-eversion increases symptoms (stretches nerve)
• Valleix phenomenon: Percussion radiates distally along nerve distribution
• Two-point discrimination: May be diminished plantar foot if chronic
• Intrinsic muscle atrophy: Late finding if chronic severe compression

Electrodiagnostic Confirmation (Gold Standard):

• Motor NCS: Prolonged distal motor latencies medial/lateral plantar nerves (over 6.2ms abnormal)
• Sensory NCS: Reduced or absent sensory nerve action potentials plantar nerves
• EMG: Denervation potentials in abductor hallucis, flexor digitorum brevis if chronic (fibrillations, positive sharp waves)
• Comparison: Compare to contralateral side - asymmetry supports diagnosis

Conservative Management Failure

Required Conservative Trial (3-6 months):

1. NSAIDs: Anti-inflammatory medication for 6-8 weeks
2. Orthotics: Medial arch support, cushioned heel insert to reduce nerve tension
3. Activity modification: Avoid prolonged standing/walking
4. Corticosteroid injection: Single injection tarsal tunnel (controversial - may provide temporary relief)
5. Physical therapy: Nerve gliding exercises, ankle strengthening

Surgical Indications:

• Failure of 3-6 months conservative management
• Progressive motor weakness (intrinsic atrophy)
• Identifiable space-occupying lesion (ganglion, varicosities) on MRI
• Severe symptoms affecting quality of life, sleep, function

Relative Indications

• Acute tarsal tunnel syndrome: Traumatic onset with rapid symptom progression
• Space-occupying lesion: Ganglion cyst, varicosities, lipoma compressing nerve (even without failed conservative trial)
• Post-traumatic: Fracture malunion (calcaneus, pilon) causing secondary compression
• Iatrogenic: Post-surgical scarring from prior medial ankle surgery

Contraindications

Absolute:

• Peripheral neuropathy: Bilateral symptoms, systemic disease (diabetes, alcohol, B12 deficiency), normal EMG
• Active infection: Cellulitis, osteomyelitis medial ankle
• Severe vascular disease: Critical limb ischemia, non-healing wounds

Relative:

• Diabetes mellitus: Higher failure rate (50% vs 85% success), slower nerve recovery, wound healing concerns
• Bilateral symptoms: Suggests systemic neuropathy not isolated compression
• Normal EMG/NCS: Suggests alternative diagnosis (peripheral neuropathy, radiculopathy)
• Worker's compensation: Lower success rates, psychological factors
• Chronic symptoms (over 2 years): Irreversible nerve damage, lower success rate

Differential Diagnosis

Key Distinguishing Features

1. Peripheral Neuropathy:

   • Bilateral symmetric symptoms (vs unilateral tarsal tunnel)
   • Stocking-glove distribution (vs localized plantar)
   • Systemic disease: diabetes, alcohol, B12 deficiency, chemotherapy
   • Reduced ankle reflexes bilaterally
   • EMG: Diffuse demyelination, reduced amplitudes globally

2. L5-S1 Radiculopathy:

   • Back pain with radiation (vs isolated foot pain)
   • Dermatomal distribution (L5: dorsal foot/great toe, S1: lateral foot)
   • Positive straight leg raise
   • MRI lumbar spine: Disc herniation, foraminal stenosis

3. Plantar Fasciitis:

   • Heel pain (vs plantar foot numbness/tingling)
   • Morning stiffness, first-step pain (vs nocturnal symptoms)
   • Tenderness at plantar fascia origin (vs posterior malleolus)
   • No Tinel's sign, no neurologic symptoms

4. Medial Ankle Sprain:

   • Acute trauma history (vs insidious onset)
   • Deltoid ligament tenderness (vs nerve percussion tenderness)
   • No paresthesias, no Tinel's sign
   • MRI: Deltoid ligament injury, no nerve compression

Tarsal Tunnel Anatomy

Boundaries

Fibro-Osseous Canal - posterior to medial malleolus:

• Floor (deep): Medial malleolus, posterior talus, sustentaculum tali, medial calcaneus
• Roof (superficial): Flexor retinaculum (laciniate ligament)
  • Origin: Medial malleolus (anterior attachment)
  • Insertion: Calcaneus medial tubercle (posterior attachment)
  • Two layers: Superficial and deep - both must be released

Contents (Anterior to Posterior)

Tom Dick ANd Very Nervous Harry:

1. Tibialis Posterior Tendon (Most anterior):

   • Largest tendon, inserts navicular tuberosity
   • No critical relationship to nerve

2. Flexor Digitorum Longus Tendon:

   • Inserts distal phalanges 2-5
   • Posterior to TP, anterior to vessels

3. Posterior Tibial Artery:

   • Immediately anterior to nerve
   • Bifurcates into medial/lateral plantar arteries
   • Injury causes hematoma

4. Posterior Tibial Vein (Usually two venae comitantes):

   • Can be varicose (20% - cause of compression)
   • Requires ligation if varicose

5. Tibial Nerve (Posterior Tibial Nerve):

   • KEY STRUCTURE - target of surgery
   • Second-most posterior in tunnel
   • Thick white cord, longitudinal striations

6. Flexor Hallucis Longus Tendon (Most posterior):

   • Inserts distal phalanx hallux
   • Posterior to nerve, against floor

Posterior Tibial Nerve Course and Branches

Proximal Course:

• Enters tarsal tunnel 8cm proximal to medial malleolus
• Runs between FDL and FHL tendons
• Posterior to vessels, anterior to FHL

Trifurcation (at or distal to tarsal tunnel):

• Medial Calcaneal Nerve (first branch, proximal to bifurcation):

  • Multiple branches common (2-4 branches)
  • Supplies sensation medial heel
  • Can be compressed by flexor retinaculum
  • Injury causes painful heel

• Medial Plantar Nerve (larger, anterior):

  • Supplies sensation medial 3.5 toes (hallux, 2nd, 3rd, medial 4th)
  • Motor: Abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, first lumbrical
  • Runs deep to abductor hallucis muscle (site of distal compression)
  • Most commonly symptomatic branch

• Lateral Plantar Nerve (smaller, posterior):

  • Supplies sensation lateral 1.5 toes (lateral 4th, 5th toes)
  • Motor: Remaining intrinsics (interossei, lateral lumbricals, adductor hallucis)
  • Runs deep toward lateral plantar foot
  • Can have secondary compression at lateral plantar tunnel

Abductor Hallucis Muscle - Critical Structure

Anatomy:

• Origin: Medial tubercle of calcaneus, medial plantar fascia
• Insertion: Medial base proximal phalanx hallux
• Innervation: Medial plantar nerve (motor branch)

Surgical Significance:

• Origin creates fibrous arch over medial plantar nerve
• Distal tarsal tunnel syndrome: Compression of medial plantar nerve under abductor
• Release of abductor origin is CRITICAL - most commonly missed step
• Incomplete release causes persistent symptoms (30% of failures)

Superficial Anatomy (Avoid Injury)

Great Saphenous Vein:

• Runs anterior to incision line
• 1-2cm anterior to medial malleolus
• Preserve if possible (cosmetic, possible future CABG conduit)

Saphenous Nerve:

• Accompanies saphenous vein (variable relationship)
• Supplies sensation medial ankle, medial foot
• Injury causes numbness, painful neuroma
• Stay 1-2cm posterior to malleolus to avoid

Patient Positioning and Setup

Positioning

• Supine on operating table
• Bump under ipsilateral hip (rolled towel) - internally rotates leg, improves medial ankle access
• Foot off end of table - allows ankle manipulation, checks nerve excursion
• Thigh tourniquet - hemostasis, clear visualization (inflate 250-300 mmHg)
• Loupe magnification (2.5x - 3.5x) - recommended for nerve visualization, prevents injury

Surgical Approach

Medial approach along posterior tibial nerve course:

• Proximal extent: 8cm proximal to medial malleolus
• Distal extent: Navicular tuberosity
• Total incision: 12-15cm

Incision Planning

Curvilinear incision:

• Start 8cm proximal to medial malleolus (proximal extent)
• Curve 1-2cm posterior to medial malleolus apex (avoid saphenous structures)
• Extend distally to navicular tuberosity
• Gentle curve, avoid sharp angles (vascular compromise)

Operative Steps - Detailed Technique

Step 1: Skin Incision and Superficial Dissection

Incision:

• Sharply incise skin with #15 blade
• Full-thickness incision to subcutaneous tissue
• Curve 1-2cm posterior to medial malleolus

Superficial Dissection:

• Identify and preserve great saphenous vein (anterior to incision)
• Identify and preserve saphenous nerve (variable, usually with vein)
• Ligate small perforating veins with 3-0 absorbable ties
• Create skin flaps anteriorly and posteriorly
• Full-thickness flaps including subcutaneous tissue

Step 2: Flexor Retinaculum Identification

Flexor Retinaculum (Laciniate Ligament):

• Strong fibrous band from medial malleolus to calcaneus
• Forms roof of tarsal tunnel
• Appears as taut, glistening white band
• Two layers: Superficial and deep - both require release

Identify Underlying Structures:

• Palpate structures deep to retinaculum
• Anterior: Tendons (TP, FDL)
• Middle: Neurovascular bundle (pulsation)
• Posterior: FHL tendon

Step 3: Proximal Retinaculum Release

Begin Proximally (8cm above malleolus):

• Safer anatomy proximally - less crowded
• Make small longitudinal incision in retinaculum
• Carefully identify posterior tibial nerve beneath
• Nerve identification: Thick white cord, longitudinal striations, between vessels (anterior) and FHL (posterior)

Progressive Release:

• Use Metzenbaum scissors parallel to nerve
• Divide retinaculum longitudinally, full thickness
• Protect underlying nerve and vessels
• Advance distally along nerve course
• Release superficial AND deep layers

Adequacy Check:

• Released nerve should "bulge" or "mushroom" out
• No constricting bands remaining
• Visible gap in retinaculum

Step 4: Distal Retinaculum Release and Nerve Trifurcation

Extend Release Distally:

• Continue release past medial malleolus
• Follow nerve to trifurcation level (at or distal to malleolus)
• Release retinaculum over all three branches

Identify Three Branches:

1. Medial Calcaneal Nerve (proximal, to heel):

   • Branches proximal to bifurcation
   • Often multiple (2-4 branches)
   • Preserve during release

2. Medial Plantar Nerve (larger, anterior):

   • Larger branch, runs anteriorly
   • Passes deep to abductor hallucis (requires separate release)

3. Lateral Plantar Nerve (smaller, posterior):

   • Smaller branch, runs posterolaterally
   • Deeper course toward lateral plantar foot

Distal Extent:

• Release to navicular tuberosity distally
• Ensure medial plantar nerve completely decompressed to this level

Step 5: Abductor Hallucis Release - CRITICAL STEP

Abductor Hallucis Anatomy:

• Origin: Medial tubercle calcaneus, medial plantar fascia
• Creates fibrous arch over medial plantar nerve
• Distal tarsal tunnel syndrome - compression of medial plantar nerve

Release Technique:

1. Identify abductor muscle belly (medial plantar foot)
2. Trace to origin at calcaneus
3. Sharply release origin from calcaneus using electrocautery or scalpel
4. Release attachment to medial plantar fascia
5. Elevate muscle anteriorly to expose medial plantar nerve
6. Ensure nerve completely free, no tethering

Adequacy Assessment:

• Visualize medial plantar nerve along entire course under abductor
• No compressing fibrous bands
• Nerve mobile with gentle traction

Step 6: External Neurolysis

Inspect Entire Nerve Course:

• Proximal to distal visualization
• Look for extrinsic compression (scar, lesions)
• Look for intrinsic pathology (neuroma, hourglass deformity)

External Neurolysis (Standard):

• Release scar tissue, adhesions around nerve
• Gentle technique using tenotomy scissors
• Free nerve from surrounding structures
• Nerve should be mobile, glide freely

Internal Neurolysis (Controversial):

• Opening epineurium, fascicular decompression
• Only if localized hourglass constriction or neuroma
• Risks: More scarring, nerve injury, worse outcomes
• I do NOT routinely perform - only external neurolysis

Step 7: Space-Occupying Lesion Management

Common Lesions (20-30% of cases):

1. Ganglion Cyst (Most common):

   • From subtalar or talonavicular joint
   • Excise completely, trace to joint origin
   • Ligate stalk with 2-0 absorbable suture
   • Prevents recurrence

2. Varicosities (Dilated posterior tibial veins):

   • Common in 20% of cases
   • Ligate proximal and distal with 3-0 absorbable ties
   • Excise dilated segment
   • Hemostasis critical

3. Accessory Muscle (FDL or FHL):

   • Accessory muscle belly compressing nerve
   • Excise muscle belly
   • Preserve tendons

4. Lipoma:

   • Soft tissue mass
   • Excise completely
   • Send for pathology

Technique:

• Identify lesion compressing nerve
• Excise with careful technique (protect nerve)
• Send all tissue for pathology
• Ensure no residual compression

Step 8: Dynamic Assessment - Nerve Excursion

Range of Motion Testing:

• Put ankle through full ROM:
  • Dorsiflexion/plantarflexion
  • Inversion/eversion
• Nerve should glide smoothly, no tethering
• Dorsiflexion-eversion = maximum nerve tension
• Nerve should accommodate without excessive stretch

Adequacy Confirmation:

• Nerve "mushrooms" out of released retinaculum
• Visible gap in retinaculum (complete division)
• No constricting bands with ankle motion
• All three branches mobile

If Tethering Present:

• Identify source (incomplete release, scar, lesion)
• Release additional structures
• Reassess until nerve glides freely

Step 9: Hemostasis and Drain Placement

Hemostasis:

• Deflate tourniquet - identify all bleeding
• Bipolar cautery for small vessels (safer near nerve)
• Ligate larger vessels with 3-0 absorbable ties
• Avoid cautery directly on or near nerve
• Irrigation with normal saline

Drain Placement (Recommended):

• 10-French round drain deep to skin, superficial to nerve
• Exit through separate stab incision inferiorly
• Prevents hematoma (causes scarring, compression, poor outcomes)
• Remove at 24-48 hours when output less than 30mL/24hr

Step 10: Wound Closure

Deep Layer:

• Reapproximate subcutaneous tissue with 3-0 absorbable interrupted sutures
• Retinaculum: Controversy exists
  • Some surgeons leave open
  • Some loosely approximate
  • I loosely approximate to prevent bowstringing but avoid compression
  • Alternative: Z-lengthening retinaculum if closing
• Do NOT close tightly - will re-compress nerve

Skin:

• 4-0 nylon interrupted vertical mattress sutures
• OR 4-0 absorbable subcuticular running suture
• Sterile dressing, soft padding

Immobilization:

• Below-knee backslab in neutral ankle position
• 2 weeks for immobilization, edema control, wound protection
• Non-weight-bearing

Immediate Postoperative Period (Day 0-2)

In Hospital:

• Elevate leg above heart level (reduce edema)
• Ice application (20 minutes every 2-3 hours)
• Neurovascular checks every 4 hours (capillary refill, sensation, movement)
• Pain control: Multimodal (paracetamol, NSAIDs, opioids if needed)
• Below-knee backslab immobilization

Drain Management:

• Monitor output every 8 hours
• Remove when output less than 30mL/24 hours (typically 24-48 hours)
• Remove drain before discharge if output minimal

Discharge (Usually day 1-2):

• Backslab immobilization
• Non-weight-bearing with crutches
• Elevate when sitting/lying
• Follow-up week 2 for suture removal

Week 2-6: Early Mobilization

Week 2 Appointment:

• Remove backslab and sutures
• Wound assessment
• Remove remaining drain if present
• Transition to CAM boot or ankle brace
• Begin gentle active ankle/toe ROM exercises

Progressive Weight-Bearing:

• Week 2-3: Touch-down weight-bearing in boot
• Week 3-4: Partial weight-bearing (50%)
• Week 4-6: Progress to full weight-bearing as tolerated

Exercises:

• Gentle active ankle ROM (dorsiflexion, plantarflexion)
• Toe flexion/extension
• Intrinsic muscle activation (toe spreads, gripping)
• NO passive stretching (nerve irritation)

Week 6-12: Strengthening

Week 6:

• Wean from CAM boot to supportive shoe
• Full weight-bearing
• Begin proprioception exercises (balance board, single-leg stance)
• Gentle resistance exercises (theraband)

Strengthening Protocol:

• Ankle plantar flexion (calf raises)
• Ankle dorsiflexion (resistance band)
• Inversion/eversion strengthening
• Intrinsic foot strengthening (towel curls, marble pickup)

Activity Progression:

• Walking program - gradually increase distance
• Avoid high-impact activities (running, jumping)
• Supportive footwear with arch support

Month 3-6: Return to Activity

Return to Normal Activities:

• Most activities as tolerated
• Athletic activities if appropriate
• Monitor for symptom recurrence

Nerve Recovery Timeline:

• Symptoms may initially worsen (surgical trauma, nerve manipulation)
• Gradual improvement over 3-6 months
• Sensory recovery before motor recovery
• Positive Tinel's migrates distally as nerve recovers (good sign)
• Full recovery may take 12 months

Follow-Up Schedule

• Week 2: Suture removal, wound check
• Week 6: Progress assessment, wean boot
• Month 3: Symptom assessment, functional evaluation
• Month 6: Repeat EMG/NCS if no improvement
• Year 1: Final outcome assessment

Red Flags - When to Contact Surgeon

• Increasing pain, redness, drainage (infection)
• Numbness/weakness worse than preoperatively
• Fever, chills
• Wound dehiscence
• No symptom improvement by 6 months

Intraoperative Complications

Nerve Injury

Posterior Tibial Nerve Laceration:

• Incidence: Rare (less than 1%) but devastating
• Recognition: Nerve transected, gap visible
• Management:
  • Immediate repair if clean laceration
  • Tension-free primary neurorrhaphy with 8-0 or 9-0 nylon
  • Nerve graft if gap (sural nerve)
  • Immobilize 4 weeks post-repair
• Prevention: Loupe magnification, identify nerve before cutting, scissors parallel to nerve

Branch Injury (Medial plantar, lateral plantar, calcaneal):

• Recognition: Branch transected during release
• Management: Repair if possible, document if not repairable
• Prevention: Careful identification of all branches before dissection

Vascular Injury

Posterior Tibial Artery Injury:

• Incidence: 2-5%
• Recognition: Pulsatile bleeding, hematoma formation
• Management:
  • Direct pressure
  • Bipolar cautery or ligation with 3-0 absorbable ties
  • Usually can ligate - collateral flow adequate
  • Check distal perfusion (capillary refill, pulse)
• Prevention: Careful retinaculum division, identify vessels before cutting

Varicosity Injury:

• Recognition: Venous bleeding, oozing
• Management: Ligate proximal and distal, excise segment
• Prevention: Control varicosities before excision

Early Postoperative Complications (0-6 weeks)

Hematoma

• Incidence: 5-10% without drain, less than 2% with drain
• Recognition: Increasing pain, swelling, tense wound, drainage
• Management:
  • Small: Observation, elevation, ice
  • Large/expanding: Return to OR for evacuation, hemostasis, re-drain
  • Hematoma causes scarring - evacuate early if significant
• Prevention: Meticulous hemostasis, drain placement, immobilization, elevation

Wound Complications

Infection:

• Incidence: 2-3%
• Recognition: Erythema, warmth, purulent drainage, fever
• Management:
  • Superficial: Oral antibiotics (cephalexin 500mg QID)
  • Deep: IV antibiotics, surgical debridement if abscess
  • Culture-directed antibiotics
• Prevention: Sterile technique, prophylactic antibiotics, atraumatic tissue handling

Dehiscence:

• Incidence: 2-5% (thin skin over medial malleolus)
• Recognition: Wound edges separated, exposed deep tissue
• Management:
  • Small: Local wound care, allow secondary healing
  • Large: Return to OR for re-closure, possible flap coverage
• Prevention: Careful skin handling, avoid tension, immobilization

Skin Necrosis:

• Incidence: Rare (less than 2%)
• Recognition: Black eschar, non-viable skin edges
• Management: Debridement, local wound care, possible skin graft
• Prevention: Full-thickness skin flaps, avoid excessive retraction, protect vascular supply

Saphenous Nerve Injury

• Incidence: 5% (often unrecognized)
• Recognition: Numbness medial ankle/foot, dysesthesia
• Management:
  • Observation if neuropraxia
  • Painful neuroma: Neuroma excision, nerve burial
  • Desensitization therapy
• Prevention: Incision 1-2cm posterior to malleolus, identify and preserve nerve

Late Postoperative Complications (After 6 weeks)

Incomplete Decompression - Failed Surgery

• Incidence: 10-30% (most common cause of poor outcome)
• Recognition: Persistent symptoms identical to preoperative, positive Tinel's
• Causes:
  • Incomplete flexor retinaculum release (missed deep layer)
  • Incomplete abductor hallucis release (most common)
  • Missed lateral plantar tunnel compression
  • Unrecognized space-occupying lesion
• Management:
  • Confirm with repeat EMG/NCS
  • MRI to assess release completeness
  • Revision surgery: Wide release, neurolysis, scar excision
• Prevention: Complete release (proximal to distal, abductor origin), dynamic assessment

Persistent Symptoms - Wrong Diagnosis

• Incidence: 10-30%
• Recognition: No improvement post-surgery, bilateral symptoms
• Causes:
  • Peripheral neuropathy (diabetes, alcohol, B12 deficiency)
  • L5-S1 radiculopathy
  • Double-crush syndrome (cervical and tarsal compression)
  • Functional/psychological
• Management:
  • Neurologic consultation
  • EMG/NCS full leg, cervical spine MRI
  • Treat underlying condition (B12 supplementation, diabetic control)
  • Revision unlikely to help if wrong diagnosis
• Prevention: Thorough preoperative workup, EMG confirmation, exclude systemic neuropathy

Scar Formation and Recurrent Compression

• Incidence: 5-15%
• Recognition: Initial improvement then symptom recurrence at 3-12 months
• Causes: Perineural scarring, hematoma organizing, aggressive internal neurolysis
• Management:
  • MRI: Scar tissue around nerve
  • Revision: External neurolysis, scar excision, nerve wrap (vein, fat, synthetic)
  • Nerve wrapping prevents recurrent scarring
• Prevention: Atraumatic technique, avoid excessive internal neurolysis, drain placement, gentle tissue handling

Calcaneal Nerve Injury - Painful Heel

• Incidence: 2-5%
• Recognition: Heel pain, numbness medial heel
• Causes: Calcaneal branch injury during proximal release
• Management:
  • Observation (often improves over 6-12 months)
  • Desensitization therapy
  • Painful neuroma: Neuroma excision, nerve burial
• Prevention: Identify and preserve calcaneal branches during release (multiple branches common)

Complex Regional Pain Syndrome (CRPS)

• Incidence: Rare (less than 2%)
• Recognition: Severe pain out of proportion, allodynia, temperature/color changes, edema
• Management:
  • Early recognition critical
  • Physical/occupational therapy (desensitization, ROM)
  • Pain management (gabapentin, pregabalin)
  • Sympathetic blocks
  • Rare: Spinal cord stimulation
• Prevention: Gentle surgical technique, early mobilization, pain control

Recurrence

• Incidence: 5-15%
• Recognition: Symptom recurrence after initial improvement
• Causes:
  • Scar tissue formation
  • Recurrent ganglion cyst
  • Progression of systemic neuropathy
  • Incomplete initial release
• Management:
  • Repeat EMG/NCS, MRI
  • Conservative trial (injection, therapy)
  • Revision surgery if clear mechanical compression
• Prevention: Complete initial release, lesion excision with stalk ligation, treat underlying conditions