Subtalar Arthrodesis

Standard views:

• AP, lateral, oblique foot (weight-bearing)
• AP mortise and lateral ankle (weight-bearing)
• Hindfoot alignment view (Saltzman view)

Findings to assess:

• Joint space narrowing (posterior facet most common)
• Subchondral sclerosis and cyst formation
• Osteophyte formation
• Heel alignment (varus/valgus)
• Calcaneal pitch and Bohler's angle
• Adjacent joint arthritis (ankle, talonavicular, calcaneocuboid)
• Previous fracture pattern and malunion

Plain radiographs are essential baseline but may underestimate arthritis severity.

Indications: All patients being considered for subtalar arthrodesis.

Protocol: Fine-cut CT (1mm slices) of hindfoot with coronal, sagittal, and axial reconstructions.

Value:

• Accurately quantifies posterior facet arthritis
• Evaluates middle and anterior facets (often normal on radiographs)
• Assesses bone quality and presence of cysts
• Identifies tarsal coalition anatomy
• Measures exact heel alignment in multiple planes
• Surgical approach planning (bone defects, screw trajectory)
• Detects occult ankle or midfoot arthritis

CT is the gold standard for subtalar arthrodesis planning and is obtained in virtually all cases.

Indications:

• Rule out avascular necrosis of talus (affects fusion strategy)
• Assess soft tissue pathology (tendons, ligaments)
• Evaluate bone marrow edema pattern
• Differentiate arthritis from other causes of pain
• Occult fracture or stress injury

Findings: Cartilage loss, bone marrow edema, AVN, tendon tears, ligament injury.

Limitations: More expensive, not essential for most cases, CT superior for bony detail.

Indications:

• Multiple potential pain sources
• Previous failed fusion or surgery
• Diagnostic uncertainty despite standard imaging

Value: Combines anatomic (CT) and metabolic (SPECT) information to precisely localize active pathology. Expensive but can be invaluable in complex cases.

Goal: Reduce inflammation and pain

Interventions:

• Activity restriction (avoid impact, prolonged standing)
• NSAIDs for 2-4 weeks (if no contraindications)
• Ice application after activity
• Gentle ROM exercises for ankle (maintain motion)
• Patient education about condition

Goal: Optimize foot mechanics and reduce subtalar stress

Interventions:

• Custom foot orthoses with medial or lateral posting
• Rocker-bottom shoe modifications
• Ankle-foot orthosis (AFO) for severe cases
• Lace-up ankle brace for additional support
• Heel cushions for shock absorption

Goal: Provide temporary symptom relief and diagnostic information

Protocol:

• Fluoroscopy-guided subtalar joint injection
• Corticosteroid (40mg triamcinolone or equivalent) plus local anesthetic
• May repeat once at 3-month interval
• Document pain relief percentage and duration

Success: 30-50% achieve lasting relief (over 6 months) with 1-2 injections.

Decision point: Determine if conservative management has failed

Criteria for surgical consideration:

• Persistent pain limiting function despite 6-12 months conservative care
• Failed injection therapy (relief under 6 weeks)
• Progressive deformity
• Inability to work or perform desired activities
• Patient motivated for surgical intervention and prolonged recovery

Approximately 50-60% of patients ultimately require surgery after failed conservative care.

Intra-articular calcaneal fracture (Sanders Type III-IV most common). Primary injury includes posterior facet disruption, heel widening, varus/valgus malalignment.

Shoe modifications, orthotics, activity modification, NSAIDs, intra-articular steroid injections. Conservative management successful in 40-50% of cases.

Pain with weight-bearing, hindfoot stiffness, difficulty on uneven ground, peroneal impingement from heel widening. Failed conservative management indicates surgery.

Lateral decubitus position (most common) or supine with bump under ipsilateral hip.

• Operative side up if lateral
• Hip and knee flexed to relax Achilles tension
• Beanbag or supports for stability
• Opposite leg well-padded

Critical pressure points:

• Axillary roll under dependent axilla (check radial pulse)
• Pillow between knees
• Padding of dependent fibular head (common peroneal nerve)
• Heel protection with foam padding

Thigh tourniquet application:

• Well-padded high on thigh
• Inflate to 100mmHg above systolic (typically 250-300mmHg)
• Limit tourniquet time to under 120 minutes
• Consider exsanguination with Esmarch bandage

Surgical field preparation:

• Circumferential prep to mid-calf
• Foot free to allow manipulation
• C-arm positioned for AP, lateral, and Broden views
• Confirm fluoroscopy images before draping complete

Landmarks: Oblique incision from tip of fibula toward base of 4th metatarsal, centered over sinus tarsi (approximately 4-5cm length).

Technique: Incise skin and subcutaneous tissue sharply. Identify and protect superficial peroneal nerve branches (usually superior) and sural nerve (usually inferior to incision).

Extensor digitorum brevis (EDB): Identify muscle belly arising from calcaneus at sinus tarsi opening. Reflect superiorly or partially detach from origin for exposure.

Sinus tarsi fat: Excise fat pad within sinus tarsi to visualize interosseous talocalcaneal ligament.

Ligament excision: Remove interosseous and cervical ligaments to fully expose posterior facet of subtalar joint.

Capsulotomy: Incise capsule circumferentially around posterior facet. Use periosteal elevator to complete exposure of entire joint surface.

Visualization check: Should see entire posterior facet on both talus and calcaneus. Use retractors to maintain exposure.

Fluoroscopy: Confirm adequate exposure with AP and lateral images showing clear joint space.

Complete denudation: Use osteotomes, curettes, and rongeurs to remove ALL cartilage and subchondral bone from both talus and calcaneus facets.

Exposure: Must visualize bleeding cancellous bone on all surfaces. Denude posterior, middle, and anterior facets completely.

Bone surface: Use small osteotome or power burr to "feather" subchondral bone, creating irregular surface for better bone contact.

Fish-scaling: Create multiple small drill holes (2-3mm drill bit) across both surfaces to enhance bleeding bone and biological environment.

For in-situ fusion: Minimal bone removal, preserve bone stock, aim for maximal contact.

For realignment fusion: Remove wedge of bone from appropriate location (laterally for valgus, medially for varus) to achieve neutral alignment. May require structural graft to maintain height and prevent over-correction.

Alignment goals:

• Heel in 0-5° valgus (physiologic alignment)
• Restore calcaneal pitch and Bohler's angle
• Maximize bone contact area
• Confirm with fluoroscopy AP and lateral views

K-wire placement: Hold reduction with 2-3 K-wires (1.6-2.0mm) placed from posterior calcaneus into talar body/neck.

Trajectory: Wires in divergent pattern (one aimed laterally, one medially) for rotational control. Confirm position with AP and lateral fluoroscopy before proceeding.

Location: 1-2cm posterior to posterior facet, on lateral calcaneus, approximately at level of angle of Gissane.

Cortex preparation: Use awl or drill to penetrate lateral cortex. Starting point is critical - too anterior risks posterior facet, too posterior gives poor screw trajectory.

Trajectory: Aim from posterolateral calcaneus toward talar neck, staying lateral.

Drilling: Use 3.2mm drill over guidewire, drill to desired length (typically 60-80mm). Measure, tap if using fully threaded screw.

Insertion: Insert 6.5mm or 7.0mm partially threaded cannulated screw. Tighten to compress joint (watch for over-compression causing gapping).

Trajectory: Divergent from first screw, aim from posterolateral calcaneus toward medial talar neck.

Technique: Same drilling and measurement technique. Insert second large screw to complete fixation.

Compression: Both screws provide compression across fusion site. Fluoroscopy confirms good position, no joint gapping.

Imaging: AP, lateral, and Broden views to confirm screw position within bone, no intra-articular penetration, satisfactory compression.

Stability: Manually stress the fusion site to confirm rigid fixation. Should have NO motion at fusion site.

Release tourniquet and achieve meticulous hemostasis with electrocautery. Identify and cauterize any bleeding vessels. Consider 10 minutes of tourniquet-down observation.

Drain: Generally NOT required for standard isolated fusion.

Consider drain if: Extensive dissection, significant bone grafting, bleeding tendency, or prolonged tourniquet time. Use 10Fr round Blake drain, remove at 24-48 hours.

Capsule/fascia: Close deep layers with absorbable suture (2-0 Vicryl). Repair EDB to anatomic position if detached. Ensure no dead space.

Subcutaneous: Close with 3-0 Vicryl in interrupted or running fashion.

Skin: Use 3-0 or 4-0 nylon in interrupted vertical mattress or simple interrupted pattern. Alternatively, running subcuticular 4-0 Monocryl.

Dressing: Apply sterile dressing over incision. Consider negative pressure dressing if high-risk wound.

Splint: Apply well-padded posterior splint with foot in neutral dorsiflexion and heel in 0-5° valgus alignment. Ensure splint does not cause pressure on incision.

Hospital care:

• Posterior splint maintained
• Elevation above heart level
• Ice application (20 min on/off cycles)
• DVT prophylaxis (mechanical and chemical per protocol)
• Pain management (multimodal analgesia)
• Strict non-weight-bearing with crutches or walker

Wound check:

• Remove splint and inspect incision
• Suture removal if non-absorbable used
• Apply short leg non-weight-bearing cast or removable boot
• Continue strict non-weight-bearing
• Radiographs (AP, lateral, oblique) to assess alignment

First radiographic assessment:

• AP, lateral, oblique radiographs
• Look for early bridging bone, no lucency around screws
• If early fusion signs: transition to weight-bearing as tolerated in boot
• If no fusion signs: continue non-weight-bearing for 6 more weeks
• Begin ankle and toe range of motion exercises

Primary fusion endpoint:

• Radiographs to confirm fusion (bridging bone on 3 views)
• CT scan if radiographs equivocal
• If fused: progress to full weight-bearing in supportive shoe
• If not fused: continue protected weight-bearing, repeat imaging at 16 weeks
• Begin proprioception and strengthening exercises

Progressive rehabilitation:

• Full weight-bearing in regular shoes
• Physical therapy for gait training and strengthening
• Gradual return to work (light duty at 3-4 months, heavy at 6 months)
• Low-impact activities (swimming, cycling) at 4 months
• Impact activities (running, jumping) not before 6 months

Surveillance:

• Annual radiographs for first 2 years
• Monitor for adjacent joint symptoms
• Functional outcome scores (AOFAS, SF-36)
• Return to pre-injury activity level in 75% of patients

Strict non-weight-bearing for 8 weeks (vs 6 weeks standard). Cast immobilization preferred over boot. Consider bone stimulator (ultrasound or electrical).

Radiographs PLUS CT scan to assess fusion. Progress to partial weight-bearing only if CT shows early bridging. Otherwise continue non-weight-bearing.

Repeat CT at 12 weeks. Allow protected weight-bearing only with confirmed fusion. Use supportive boot for additional 4-6 weeks after starting weight-bearing.

Delayed return to full activity by 6-8 weeks compared to standard protocol. More intensive PT for muscle atrophy from prolonged immobilization.