Tarsal Coalition Resection - Calcaneonavicular and Talocalcaneal

Coalition Types and Distribution

Calcaneonavicular (CN) Bar - 45%

• Location: Sinus tarsi region, between anterior process of calcaneus and lateral navicular
• Anatomy: Usually middle 1/3 of potential CN articulation, 1-2cm wide anteroposterior
• Types: Osseous (bone bridge, easy to see), cartilaginous (harder to identify), fibrous (rare, rope-like)
• Access: Lateral approach (Ollier incision), superficial, easier exposure than TC

Talocalcaneal (TC) Bar - 45%

• Location: Most common at MIDDLE FACET (medial side of subtalar joint, sustentaculum tali)
• Less common: Posterior facet coalition (lateral, deeper)
• Anatomy: Flat fusion between talar body and sustentaculum tali (medially) or between talar body and calcaneal posterior facet (laterally)
• Types: Osseous most common (70%), cartilaginous (20%), fibrous (10%)
• Access: Medial approach for middle facet (posterior to PT), lateral sinus tarsi approach for posterior facet accessible laterally

Other Coalitions - 10%

• Talonavicular (rare, usually requires fusion not resection)
• Calcaneocuboid (very rare)
• Multiple coalitions (10-15% have >1 coalition, worse prognosis)

Pathophysiology of Rigid Flatfoot

Biomechanical Changes

1. Coalition restricts subtalar motion (normal 20-30° inversion/eversion → 0-10°)
2. Compensatory hindfoot valgus develops (eversion forces transmitted to midfoot)
3. Peroneal spasm occurs (peroneals contract to stabilize unstable hindfoot)
4. Talar head uncovering (medial talar prominence, "too many toes" sign)
5. Secondary changes: Talar beaking (25%, dorsal neck osteophyte), ball-and-socket ankle (5%, compensatory), midfoot arthritis (chronic cases)

Natural History

• Coalition present from birth (failure of mesenchymal segmentation)
• Remains cartilaginous/fibrous until adolescence
• Ossification occurs 8-16 years (CN earlier than TC)
• Symptoms begin as bar ossifies and becomes rigid
• 25% remain asymptomatic (incidental finding)
• Bilateral 50-60% (examine contralateral foot)

Surgical Anatomy - CN Bar

Layers (Lateral Sinus Tarsi)

1. Skin and subcutaneous tissue (sural nerve crosses here)
2. Intermediate dorsal cutaneous nerve (superficial peroneal branch)
3. Extensor digitorum brevis (EDB) muscle origin (lateral calcaneus)
4. CN bar (between anterior calcaneus and lateral navicular)
5. Sinus tarsi fat (interosseous talocalcaneal ligament deep)
6. Peroneal tendons (posterior)

Key Relationships

• EDB overlies bar (reflect superiorly for exposure and later use for interposition)
• Sinus tarsi contents: Fat, ligaments (interosseous, cervical), vessels
• Lateral tarsal artery (sinus tarsi) - branches of dorsalis pedis
• Peroneal tendons directly posterior (protect during retraction)

Surgical Anatomy - TC Bar

Medial Approach (Middle Facet)

Layers from superficial to deep:

1. Skin and subcutaneous tissue
2. Flexor retinaculum
3. Posterior tibialis tendon (MOST ANTERIOR, landmark)
4. Flexor digitorum longus tendon (middle)
5. Posterior tibial artery and veins (deep, between FDL and FHL)
6. Tibial nerve (deepest, posterior)
7. Flexor hallucis longus (MOST POSTERIOR)
8. Sustentaculum tali with TC bar

Mnemonic for Medial Structures: "Tom, Dick And Nervous Harry"

• Tom = Posterior Tibialis
• Dick = Flexor Digitorum longus
• And = Posterior tibial Artery
• Nervous = Tibial Nerve
• Harry = Flexor Hallucis longus

Lateral Approach (Posterior Facet)

• Through sinus tarsi (same as CN bar approach)
• Deeper dissection laterally
• Access to posterior facet coalitions that extend laterally
• Higher risk of sural nerve injury (same field as CN)

Clinical Evaluation

History

• Age: 10-16 years typical (may present younger if osseous, older if fibrous)
• Symptoms: Hindfoot pain (sinus tarsi, medial arch), worse with activity/sports
• Duration: Usually insidious onset, may have acute presentation after trauma
• Previous treatment: Orthotics, activity modification, NSAIDs, physical therapy
• Bilateral symptoms: 50-60% bilateral (examine both feet)
• Family history: Autosomal dominant inheritance, incomplete penetrance

Physical Examination

• Gait: Rigid flatfoot, limited push-off, external rotation of limb
• Inspection: Pes planovalgus, talar head prominence medially, "too many toes" sign (view from behind)
• Palpation: Sinus tarsi tenderness (CN bar), sustentaculum tenderness (TC bar)
• Range of motion: Subtalar motion RESTRICTED (key finding), normal ankle dorsiflexion/plantarflexion
• Peroneal spasm: Attempted inversion causes peroneal contraction and pain
• Flexibility: Jack test (great toe dorsiflexion) - arch does NOT restore (rigid flatfoot)
• Hindfoot alignment: Valgus, assess correctibility (passive inversion)
• Neurovascular: Document intact, tibial nerve function

Peroneal Spastic Flatfoot

• Misnomer: Not true spasm, peroneals tight but not in spasm
• Mechanism: Peroneals contract to stabilize unstable valgus hindfoot
• Clinical: Tight peroneal tendons palpable, resistance to inversion
• Anteater nose sign: Elongated anterior calcaneus on lateral X-ray

Imaging Protocol

Plain Radiographs - First Line

1. Lateral view:

   • C-sign (70% sensitive for CN bar) = continuous C-shaped line from talar dome to inferior calcaneus
   • Talar beaking (25%) = dorsal talar neck osteophyte (abnormal biomechanics)
   • Anteater nose sign = elongated anterior calcaneus process
   • Flatfoot alignment: Reduced talocalcaneal angle (<20°, normal 35-50°)

2. AP view:

   • Ball-and-socket ankle (5% compensatory change)
   • Talar head uncovering
   • Assess for other coalitions

3. 45° oblique view:

   • Best view for CN bar (profiles sinus tarsi)
   • Bar appears as bony bridge or irregular contour

4. Harris axial (ski-jump) view:

   • Foot dorsiflexed, beam angled 45° from posterior
   • TC bar: ABSENT middle facet, sustentaculum blends with talus
   • 50% sensitive for TC bar

CT Scan - GOLD STANDARD

• Indications: Confirms diagnosis, surgical planning, defines bar size/type/location
• Protocol: Axial cuts with coronal and sagittal reformats, 1-2mm slices
• Information obtained:
  • Bar type: Osseous (bone window), cartilaginous (soft tissue window), fibrous (irregular gap)
  • Bar size: Measure percentage of joint involved (50% cutoff for resection vs fusion)
  • Bar location: Middle facet vs posterior facet (TC), medial vs lateral (CN)
  • Adjacent joints: Assess talonavicular, calcaneocuboid for arthritis
  • Other coalitions: Screen for multiple bars (10-15%)

MRI - Adjunctive

• Indications: Younger patients (cartilaginous bars), bone edema, soft tissue assessment
• Findings: Cartilaginous bar (T2 bright), bone marrow edema (activity), secondary changes
• Less useful than CT for surgical planning (bone detail inferior)

Bone Scan - Rarely Used

• Increased uptake at coalition site (non-specific)
• Useful if X-ray negative and CT uncertain (very rare scenario)

Decision Making: Resection vs Fusion

Favor RESECTION When

1. Age <16-18 years (growing skeleton)
2. Bar size <50% of joint surface (CT measurement critical)
3. Type: Cartilaginous > fibrous > osseous (better outcomes)
4. NO arthritis in adjacent joints (talonavicular, calcaneocuboid)
5. First-time surgery (not revision)
6. Isolated coalition (single CN or TC)
7. Motivated for rehabilitation (3-4 month recovery)

Favor FUSION When

1. Large bar >50% of joint surface
2. Degenerative changes present (subtalar, talonavicular arthritis)
3. Failed prior resection (recurrence, persistent symptoms)
4. Older patient >18-20 years (less adaptive potential)
5. Severe rigid flatfoot with significant arthritis
6. Multiple coalitions (complex anatomy)
7. Patient preference (faster return, definitive)

Controversy Areas

• Some surgeons advocate primary fusion for TC bars >30% (higher failure resection)
• Role of adjunctive osteotomy: At time of resection vs staged later
• Age cutoff: Some operate on adults <25 if no arthritis

Surgical Planning Checklist

• CT scan reviewed: Bar type, size, location confirmed
• Adjacent joints assessed: No arthritis on CT
• Hindfoot alignment measured: Plan for adjunctive osteotomy if severe valgus
• Bilateral assessment: Check contralateral foot clinically and radiographically
• Interposition material planned: EDB (CN), fat/wax (TC)
• Consent includes: Nerve injury, recurrence, need for fusion, osteotomy
• Equipment: Image intensifier, osteotomes (10-15mm), retractors, loupe magnification

Setup and Positioning

Patient Position - CN Bar

• Supine on operating table
• Bump/sandbag under ipsilateral hip (internal rotation of limb for lateral access)
• Knee flexed 30-45° (relaxes gastrocnemius, easier foot positioning)
• Foot/ankle prepped free (able to manipulate for assessment)
• Thigh or calf tourniquet (250-300mmHg)

Patient Position - TC Bar

• Supine for medial approach (middle facet)
• Lateral decubitus for lateral approach (posterior facet accessible laterally)
• Beanbag and axillary roll if lateral
• Same tourniquet and prep principles

Equipment

• Image intensifier (essential, sterile drape)
• Loupe magnification (2.5-3.5x for nerve identification)
• Osteotomes: 10mm, 15mm straight and curved
• Deep retractors: Small Hohmann, bent Homan
• Rongeurs, curettes for bar removal
• Bipolar cautery (hemostasis)

CN Bar Resection - Step by Step

1. Ollier Incision

Landmarks: Lateral malleolus tip, navicular tuberosity, sinus tarsi (depression anterior to lateral malleolus)

Incision: Oblique skin incision from lateral malleolus tip toward navicular tuberosity, centered over sinus tarsi. Length 5-6cm. Curve gently following skin creases.

Pearls:

• Mark incision with skin marker before inflation tourniquet (blanched skin harder to landmark)
• Palpate sinus tarsi depression as guide
• Image intensifier can confirm bar location if uncertain

2. Deep Dissection to CN Bar

Subcutaneous Layer: Blunt dissection with spreaders. Identify and protect sural nerve (most common), intermediate dorsal cutaneous nerve branches.

EDB Muscle: Muscle belly originates from lateral calcaneus, overlies CN bar. Palpate muscle-bone interface.

Options for EDB:

1. Reflect superiorly (preferred - preserves muscle for later interposition)
2. Split along fibers (if reflection difficult)
3. Partial detachment from calcaneus origin (rarely needed)

Bar Exposure: Use periosteal elevator to clear soft tissue from bar surface. Define all margins (superior, inferior, anterior, posterior). Palpate abnormal bony bridge between calcaneus and navicular.

3. CN Bar Resection

Osteotome Technique:

1. Start with 10-15mm straight osteotome
2. Begin at SUPERIOR margin of bar (easier to control)
3. Work from superior to inferior, removing bar in coronal plane
4. Remove in ONE PIECE if possible (confirms complete resection)
5. If large, remove in multiple pieces (ensure all fragments removed)

Resection Endpoints:

• Normal bone visible on BOTH calcaneus and navicular sides
• Gap created 1-1.5cm width minimum
• Smooth edges (rongeur sharp points to prevent impingement)
• Subtalar motion improves (test intraoperatively - should gain inversion/eversion)

Image Intensifier Confirmation:

• AP view: Gap between calcaneus and navicular visible
• Lateral view: C-sign resolved, clear sinus tarsi
• Oblique view: No residual bar fragments

Common Errors:

• Incomplete resection (most common cause of recurrence) - must see normal bone both sides
• Excessive resection entering talonavicular or calcaneocuboid joint
• Fracture of navicular (thin bone, gentle technique in young patients)
• Leaving sharp bony edges (cause impingement pain)

4. EDB Muscle Interposition

Technique:

1. Take EDB muscle belly (already reflected)
2. Fold/roll muscle into resection gap
3. Should fill gap completely (1-1.5cm)
4. Suture muscle to periosteum on BOTH sides (calcaneus and navicular)
5. Use 2-0 or 3-0 absorbable suture (Vicryl)
6. Multiple sutures to secure position (3-4 sutures)

Alternatives if EDB inadequate:

• Fat graft from sinus tarsi or subcutaneous tissue
• Split abductor digiti minimi muscle
• Bone wax (simple but non-biological)
• Synthetic materials (historical, rarely used now)

5. Wound Closure - CN Bar

• Irrigate copiously (pulse lavage, 3L normal saline)
• Tourniquet down, achieve hemostasis (bipolar cautery)
• Reapproximate EDB if not fully used for interposition
• Close deep fascia: 2-0 or 3-0 absorbable
• Subcutaneous: 3-0 or 4-0 absorbable (buried)
• Skin: 4-0 nylon interrupted or running subcuticular 4-0 absorbable
• Sterile dressing, soft padding
• Below-knee cast or walking boot (neutral position, slight inversion)

TC Bar Resection - Medial Approach (Middle Facet)

6. Medial Incision

Landmarks: Medial malleolus, sustentaculum tali (1cm inferior to malleolus), posterior tibialis tendon (palpate with foot inversion)

Incision: Longitudinal 4-5cm, centered 2cm posterior and inferior to medial malleolus tip. Parallels course of posterior tibialis tendon.

Pearls:

• Keep 2cm posterior to avoid injury to saphenous vein/nerve (anterior)
• Incision directly over PT tendon course
• Can extend proximally or distally as needed for exposure

7. Deep Dissection - Medial

Subcutaneous Layer: Identify and protect saphenous vein and nerve if encountered (usually anterior). Deepen to flexor retinaculum.

Flexor Retinaculum: Identify and incise sharply (superficial and deep layers)

Tendon Identification (Mnemonic: Tom, Dick And Nervous Harry):

1. Posterior Tibialis (MOST ANTERIOR, largest, flat)
2. Flexor Digitorum Longus (middle, round, tendons to 4 toes)
3. Posterior Tibial Artery and Veins (pulsatile, deep)
4. Tibial Nerve (deepest, posterior, yellow, large)
5. Flexor Hallucis Longus (MOST POSTERIOR, deep, muscular in tunnel)

Retraction:

• PT retracted ANTERIORLY (with blunt retractor)
• FDL and FHL retracted POSTERIORLY
• Neurovascular bundle protected deep and posterior (deep retractor)

8. TC Bar Identification

Sustentaculum Tali Palpation: Bony shelf projecting medially from calcaneus, 1cm inferior to medial malleolus. Normally should be separate from talus with middle facet gap.

Bar Features: Flat bony/cartilaginous fusion between sustentaculum (calcaneus) and talar body medially. No clear facet joint line. May be 1-2cm wide mediolaterally, 1-2cm anteroposterior.

Image Intensifier: AP and lateral views to confirm bar location. Harris axial view if available (shows middle facet clearly).

9. TC Bar Resection - Medial

Osteotome Technique:

1. Use straight or CURVED osteotome (10-15mm)
2. Direction: Medial to lateral, parallel to posterior facet
3. Work systematically removing bar
4. Goal: Separate sustentaculum from talus, create mobile middle facet gap
5. Remove 1-1.5cm of bone to ensure complete resection

Resection Endpoints:

• Sustentaculum tali separate from talus
• Normal bone contours visible on both sides
• Subtalar motion restored (test inversion/eversion intraoperatively)
• Gap 1cm minimum width

Key Challenge: Deeper exposure than CN bar, harder to visualize. Use headlight, retractors, image intensifier frequently.

Common Errors:

• Incomplete resection (cannot see gap, motion not restored)
• Fracture of sustentaculum (thin bone, gentle technique)
• Injury to posterior tibial artery (deep in field)
• Excessive lateral resection entering posterior facet

10. Interposition - TC Bar

Options:

1. Fat graft (most common): Harvest from heel pad or subcutaneous tissue (1-2cm³)
2. Bone wax: Pack into gap (simple, effective but non-biological)
3. Muscle flap: Split flexor digitorum brevis or abductor hallucis (complex)

Technique:

• Fill gap with fat graft or pack with bone wax
• Suture fat graft to surrounding tissues (2-0 Vicryl)
• Ensure material fills gap completely and stays in position

11. Closure - TC Bar

• Irrigate thoroughly
• Tourniquet down, hemostasis
• Repair flexor retinaculum (2-0 absorbable) - restores pulley for PT
• Subcutaneous and skin closure as CN bar
• Below-knee cast or walking boot

Adjunctive Procedures

Calcaneal Osteotomy

Indications: TC bar with severe rigid hindfoot valgus that does NOT correct with bar resection alone (assess intraoperatively)

Options:

1. Medializing calcaneal osteotomy (Koutsogiannis): Shifts calcaneal tuberosity medially (corrects valgus)
2. Lateral column lengthening: Evans osteotomy (lengthens lateral column, corrects valgus and abduction)

Timing:

• Concurrent with TC resection (one surgery) OR
• Staged (resection first, reassess at 6 months, osteotomy later if needed)

Technique (Medializing Osteotomy):

1. Lateral incision over calcaneus
2. Osteotomy posterior to posterior facet (oblique or transverse)
3. Shift tuberosity 5-10mm medially
4. Fix with 1-2 screws (partially threaded or cannulated)

Postoperative: Non-weight-bearing 6 weeks if osteotomy performed

Immediate Postoperative (0-2 Weeks)

Immobilization:

• Below-knee cast or walking boot
• Hindfoot position: Neutral ankle, slight inversion (corrects flatfoot tendency)
• Keep elevated for 48-72 hours (reduce swelling)

Weight-Bearing:

• Resection ONLY (no osteotomy): Touch weight-bearing or weight-bearing as tolerated (per surgeon preference)
• Resection + Osteotomy: NON-weight-bearing 6 weeks

Pain Management:

• Multimodal analgesia (paracetamol, ibuprofen)
• Short course opioids if needed (3-5 days)
• Ice, elevation

Wound Care:

• Dressing change 2-3 days post-op (inspect wound)
• Suture removal 10-14 days (earlier if concerns)
• Monitor for infection, dehiscence

Early Rehabilitation (2-6 Weeks)

Mobilization:

• Remove cast at 2-4 weeks (soft tissue healing complete)
• Transition to walking boot or supportive shoe
• Begin ROM exercises

Range of Motion Exercises (Start 2-4 weeks):

• Subtalar inversion/eversion (key motion to restore)
• Ankle dorsiflexion/plantarflexion
• Toe curls, toe spreads
• Goal: Restore subtalar motion (10-20° inversion/eversion minimum)

Weight-Bearing Progression:

• If resection only: Full weight-bearing in boot 2-4 weeks
• If osteotomy: Non-weight-bearing 6 weeks, then progressive weight-bearing in boot weeks 6-10

Physical Therapy:

• Start 3-4 weeks
• Focus: ROM, reduce stiffness, prevent adhesions
• Gentle subtalar mobilizations

Intermediate Phase (6-12 Weeks)

Strengthening (Start 6-8 weeks):

• Peroneal strengthening (critical - often weak/spastic pre-op)
  • Resistance band eversion exercises
  • Single leg balance (proprioception)
  • Heel raises (tibialis posterior, gastrocnemius)
• Intrinsic foot strengthening (toe curls, marble pickup)
• Progressive resistance

Proprioception:

• Single leg stance (eyes open then closed)
• Wobble board exercises
• Balance progressions

Orthotic Support:

• Custom orthotic recommended for 6-12 months
• Features: Medial arch support, heel cup (controls valgus)
• Transition to prefabricated orthotic later

Activity Progression:

• Low-impact activities week 8-10 (swimming, cycling)
• Impact activities week 10-12 (jogging, light sports)

Return to Sport (3-4 Months)

Criteria:

• Pain-free weight-bearing
• Subtalar ROM 80% of contralateral side
• Strength 85% of contralateral (isokinetic testing or functional)
• Single leg hop test >90%
• Sport-specific drills completed

Progressive Return:

• Month 3: Light jogging, sport-specific drills
• Month 4: Full training, non-contact sports
• Month 4-5: Return to full contact sports (if criteria met)

Long-Term:

• Continue orthotic support (many need long-term)
• Annual X-rays years 1-3 (assess for recurrence, degenerative changes)
• Monitor contralateral foot (50% bilateral, may become symptomatic later)

Follow-Up Schedule

• 2 weeks: Wound check, suture removal
• 6 weeks: X-rays (assess healing, no recurrence), clinical exam (ROM, strength)
• 3 months: X-rays, functional assessment, clear for sport if criteria met
• 6 months: Clinical check, X-rays
• 1 year: Final follow-up, X-rays, document outcome

Red Flags Requiring Earlier Review:

• Increasing pain (infection, CRPS, recurrence)
• Wound dehiscence or drainage
• Numbness/tingling (nerve injury)
• Loss of subtalar motion (adhesions, recurrence)
• Severe persistent flatfoot (incomplete correction, need osteotomy)

Complications - Detailed Management

Outcomes and Evidence

Success Rates:

• CN Bar Resection: 70-90% good to excellent results
• TC Bar Resection: 60-80% good to excellent results (lower than CN due to complexity)
• Recurrence: 10-20% overall (higher without interposition: 40-50%)
• Progression to Fusion: 5-10% within 5 years

Prognostic Factors for Success:

Favorable:

• Bar size <30% of joint surface (best predictor)
• Age <16 years
• Cartilaginous > osseous bars
• CN > TC location
• No degenerative changes
• Good interposition technique
• Adequate rehabilitation

Unfavorable:

• Bar size >50% of joint
• Age >18 years
• Severe rigid flatfoot
• Adjacent joint arthritis
• Incomplete resection
• Multiple coalitions
• Poor rehabilitation compliance

Evidence Summary:

1. Interposition Material (Kumar et al. 2007, J Pediatr Orthop): EDB muscle vs fat vs bone wax for CN bars - no significant difference in recurrence (12% vs 15% vs 14%), all superior to no interposition (45%)

2. TC Bar Outcomes (Cohen et al. 2018, Foot Ankle Int): 67% good/excellent at 5 years. Predictors of failure: >40% joint involvement, age >16, degenerative changes

3. Adjunctive Osteotomy (Mubarak et al. 2009, JBJS): TC resection + calcaneal osteotomy vs resection alone - 85% vs 65% good outcomes in severe flatfoot group

4. Long-Term Follow-Up (Docquier et al. 2019, JBJS): Mean 15 year follow-up CN resections - 75% good outcomes, 12% required fusion. Recurrence occurred within 3 years in all cases

Australian Context:

• MBS item 50336: Excision tarsal coalition ($500-800 rebate)
• Private hospital costs: $5,000-8,000 total
• Public hospital: No cost to patient (category 2-3, wait 3-12 months)
• AOANJRR: No specific data (not joint replacement)