Lateral Oblique Incision | Sural Nerve Protection | Posterior Facet Exposure
Surgical Imaging
The sural nerve runs in the subcutaneous tissue posterior to the peroneal tendons. It must be identified and protected before any deep dissection. Injury causes lateral foot numbness and painful neuroma. Use gentle retraction and avoid tight vessel loops.
The peroneus longus and brevis lie immediately anterior to the incision. They are retracted either plantarward or dorsally to expose the sinus tarsi. Over-retraction can cause tendon subluxation or neurapraxia of the superficial peroneal nerve branches.
The extensor digitorum brevis originates from the sinus tarsi and anterior calcaneus. It is elevated subperiosteally from lateral to medial to expose the sinus tarsi and posterior facet. The muscle is reflected dorsally and held with stay sutures or self-retaining retractors.
The posterior facet of the subtalar joint slopes from posterolateral to anteromedial. The sinus tarsi lies anterior to the posterior facet. Full exposure requires removal of the fat pad and capsule incision parallel to the joint line.
The extensile lateral approach adds a vertical limb along the posterior calcaneus. It increases risk of wound necrosis at the corner, sural nerve injury, and peroneal tendon exposure. Reserved for displaced intra-articular calcaneal fractures.
For triple arthrodesis, the sinus tarsi approach is combined with a medial approach to the talonavicular and subtalar joints. The medial approach protects the posterior tibial tendon and neurovascular bundle while allowing access to the middle and anterior facets.
At a Glance
The sinus tarsi approach (also called the Ollier oblique approach) provides direct lateral access to the subtalar (talocalcaneal) joint, particularly the posterior facet, sinus tarsi, and middle/anterior facets. It is the workhorse approach for subtalar arthrodesis, tarsal coalition resection, and selected calcaneal fracture work. The classic oblique Ollier incision runs from the tip of the lateral malleolus toward the base of the fourth metatarsal, centered over the sinus tarsi. The key interval lies between the peroneal tendons (retracted plantarward) and the extensor digitorum brevis (elevated dorsally). The sural nerve is the primary structure at risk and must be identified in the subcutaneous plane posterior to the peroneals before any deeper work. The approach exposes the posterior facet for joint preparation in arthrodesis and allows access to the sinus tarsi contents for coalition excision or OCD lesion treatment. It does not provide medial column access; a separate medial incision is required for triple arthrodesis.
SINUSTARSISINUS TARSI - Surgical Steps
Hook:SINUS TARSI approach - protect sural nerve and expose the posterior facet!
SURALSUR AL NERVE - Protection Principles
Hook:The sural nerve is the most important structure at risk - keep it protected!
EDB SAFEEDB ELEVATION - Key Points
Hook:EDB elevation safely exposes the entire subtalar joint complex!
Indications and Approach Selection
Primary Indications:
- Subtalar arthrodesis (isolated talocalcaneal fusion)
- Tarsal coalition resection (calcaneonavicular or talocalcaneal bars)
- Calcaneal fracture ORIF (selected Sanders II/III via sinus tarsi or extensile lateral)
- Osteochondral lesions of the talar posterior facet or subtalar joint
- Subtalar joint debridement or loose body removal
- Triple arthrodesis (combined with medial approach)
Why This Approach is Chosen:
The sinus tarsi approach provides direct visualization of the posterior facet of the subtalar joint and the sinus tarsi contents without violating the peroneal tendon sheath. It allows excellent preparation of the joint surfaces for arthrodesis and resection of coalitions. The extensile lateral modification provides wider exposure for displaced calcaneal fractures at the cost of increased wound complications.
Contraindications:
- Active infection over the lateral hindfoot
- Severe scarring from previous lateral incisions (consider alternative)
- Isolated medial pathology requiring medial approach only
- Patient factors precluding non-weight bearing (compliance issues)
Alternative Approaches:
- Medial approach to subtalar joint: For isolated middle facet coalition or medial talocalcaneal pathology
- Posterior approach: For posterior subtalar joint access in selected cases
- Arthroscopic subtalar arthrodesis: Minimally invasive option with limited visualization
- Lateral extensile approach: For complex calcaneal fractures requiring broad exposure
Overview
Sinus Tarsi Approach provides direct lateral access to the subtalar joint, sinus tarsi, and posterior facet of the talocalcaneal articulation. The classic Ollier oblique incision exploits the interval between the peroneal tendons and extensor digitorum brevis.
Key Characteristics:
- Oblique incision from lateral malleolus tip toward fourth metatarsal base
- Sural nerve protection in subcutaneous plane
- EDB elevation exposes sinus tarsi contents
- Excellent for posterior facet preparation in arthrodesis
- Extensile lateral variant for calcaneal ORIF
Why This Approach Matters:
- Subtalar arthrodesis is a common salvage procedure for arthritis, coalition, and deformity
- Tarsal coalition resection prevents progressive flatfoot deformity in adolescents
- Calcaneal fractures require precise posterior facet reduction to avoid subtalar arthritis
- Sinus tarsi approach minimizes soft tissue disruption compared with extensile lateral
Exam Relevance:
- High-yield surgical approach for foot and ankle operative surgery station
- Sural nerve protection and EDB elevation are classic examiner questions
- Must know when to combine with medial approach for triple fusion
Anatomy
Bony Anatomy:
The subtalar joint comprises three articulations between the talus and calcaneus: the posterior facet (largest, load-bearing), the middle facet (sustentaculum tali), and the anterior facet (continuous with talonavicular in some descriptions). The sinus tarsi is a conical space between the talar neck and calcaneal anterior process, containing fat, the cervical ligament, the interosseous talocalcaneal ligament, and proprioceptive nerve endings. The posterior facet is oriented with a posterolateral to anteromedial slope of approximately 30-40 degrees.
Muscular Layers:
|| Layer | Muscle | Nerve Supply | Action | ||-------|--------|--------------|--------| || Superficial subcutaneous | Sural nerve branches | Sural nerve | Sensation lateral foot | || Lateral compartment | Peroneus longus and brevis | Superficial peroneal | Eversion and plantarflexion | || Dorsal | Extensor digitorum brevis | Deep peroneal | Toe extension (lateral four toes) | || Deep | Interosseous muscles and ligaments | Various | Subtalar stability |
Neurovascular Anatomy:
|| Structure | Location | Clinical Significance | ||-----------|----------|----------------------| || Sural nerve | Subcutaneous, posterior to peroneal tendons | MOST IMPORTANT - injury causes lateral foot numbness and neuroma pain | || Superficial peroneal nerve | Anterior to incision, dorsal branches | Sensory to dorsum of foot; at risk with extensile exposure | || Peroneal tendons | Immediately anterior to incision | Must be protected and retracted; sheath should not be violated | || Lateral calcaneal artery | Runs with sural nerve | May require ligation; contributes to lateral flap perfusion | || Peroneal artery perforators | Deep to EDB | Supply the lateral calcaneal skin flap in extensile approaches |
Ligamentous Anatomy:
The sinus tarsi contains the cervical ligament (runs from talar neck to calcaneal anterior process) and the interosseous talocalcaneal ligament (deep in the tarsal canal). These structures are divided during subtalar arthrodesis preparation. The bifurcate ligament and spring ligament are more medial and not accessed from this approach.
Internervous Plane
Deep Internervous Plane:
- Between: Peroneal tendons (superficial peroneal nerve) laterally/plantarward and Extensor digitorum brevis (deep peroneal nerve) medially/dorsally
- Clinical relevance: This intermuscular interval allows access to the sinus tarsi and subtalar joint without denervating either muscle group. The plane is developed after subcutaneous dissection and sural nerve protection.
Superficial Dissection:
There is no true internervous plane superficially. The incision passes through subcutaneous fat where the sural nerve and lateral calcaneal artery branches are encountered. The fascia over the peroneal tendons and EDB is incised in line with the skin incision.
The sinus tarsi approach is an intermuscular rather than strictly internervous dissection. The peroneal tendons are retracted as a unit without violating their sheath. The EDB is elevated from its calcaneal origin rather than split. This preserves innervation while providing excellent exposure. In the extensile lateral modification, the plane is extended posteriorly and the sural nerve is formally mobilized with the posterior flap to protect it during the vertical limb dissection.
Structures at Risk in Each Layer:
|| Layer | Structure | Protection Strategy | ||-------|-----------|-------------------| || Subcutaneous | Sural nerve | Identify early, gentle vessel loop retraction, no metal on nerve | || Subcutaneous | Lateral calcaneal artery | Ligate if bleeding; preserve when possible for flap perfusion | || Deep fascial | Peroneal tendons | Protect sheath, retract as a unit, avoid over-retraction | || Deep muscular | EDB muscle belly | Elevate subperiosteally, use stay sutures, avoid crushing | || Articular | Posterior facet cartilage | Protect during joint preparation, avoid iatrogenic damage | || Deep | Interosseous ligament | Divide deliberately during arthrodesis, not inadvertently |
Positioning and Patient Setup
Position: Supine with Bump under Ipsilateral Hip
Pre-positioning Checklist:
- Confirm patient can tolerate supine position with hip bump
- Radiolucent table confirmed for fluoroscopy
- Tourniquet applied high on thigh (optional but recommended)
- Foot positioned at end of table for easy access
- C-arm positioned for lateral, Broden, and axial heel views
Positioning Details:
- Supine position with sandbag or bump under ipsilateral hip to internally rotate the foot
- Knee slightly flexed over a bolster to relax the gastrocnemius
- Foot plantigrade or slightly plantarflexed for sinus tarsi exposure
- Tourniquet inflated to 250-300 mmHg after exsanguination
- Fluoroscopy verified for AP, lateral, Broden (oblique subtalar), and axial heel views
Prolonged tourniquet time (greater than 120 minutes) increases risk of nerve palsy and muscle damage. Document tourniquet time. Ensure adequate padding of all bony prominences and avoid excessive internal rotation of the hip which can cause femoral nerve stretch.
Alternative Positioning:
- Lateral decubitus with affected side up for combined medial and lateral approaches
- Prone rarely used for sinus tarsi approach but may be considered for posterior subtalar work
- Beach chair position with leg holder for arthroscopic assistance if planned
Surface Anatomy and Landmarks
Key Bony Landmarks:
- Lateral malleolus tip - starting point of oblique incision
- Sinus tarsi - palpable depression anterior and inferior to lateral malleolus
- Anterior process of calcaneus - palpable prominence distal to sinus tarsi
- Base of fourth and fifth metatarsals - end point reference for incision
- Peroneal tubercle - palpable on lateral calcaneus, marks peroneal tendon course
Key Soft Tissue Landmarks:
- Sural nerve - often palpable or visible with transillumination posterior to peroneal tendons
- Peroneal tendons - palpable and visible behind lateral malleolus, course anteriorly over calcaneus
- Extensor digitorum brevis - muscle belly palpable anterior to sinus tarsi
- Lateral calcaneal skin - assess for previous scars, ulcers, or compromised quality
Incision Planning:
- Oblique Ollier incision: starts 1cm distal to lateral malleolus tip, runs obliquely toward base of fourth metatarsal
- Length typically 3-5cm centered over sinus tarsi
- Stays anterior to sural nerve distribution
- For extensile lateral: add vertical limb along posterior calcaneal border, creating an L-shape with the corner at the peroneal tubercle level
Surgical Technique
Patient Positioning:
Supine with ipsilateral hip bump to internally rotate the limb. Knee slightly flexed. Tourniquet applied. Fluoroscopy positioned for lateral, Broden, and axial views. Prep and drape the entire foot and ankle to the knee.
Surface Landmarks:
Mark the tip of the lateral malleolus, the sinus tarsi depression, and the base of the fourth metatarsal. Palpate the peroneal tendons and mark their course. Identify the sural nerve with gentle palpation or transillumination if visible.
Incision:
Make a 3-5cm oblique incision from 1cm distal to the lateral malleolus tip, directed toward the base of the fourth metatarsal, centered over the sinus tarsi. For extensile exposure, add a vertical limb posteriorly along the calcaneus.
Structures at Risk
THE most important structure at risk. Runs in subcutaneous tissue posterior to peroneal tendons. Injury causes lateral foot numbness, dysesthesia, and painful neuroma formation. Prevention: identify early before deep dissection, gentle vessel loop retraction, no metal retractors directly on nerve, avoid tight kinking.
The peroneus longus and brevis lie in their sheath immediately anterior to the incision. Over-retraction can cause subluxation, tenosynovitis, or rupture. Prevention: protect the sheath, retract as a unit, avoid excessive force, ensure smooth gliding after closure.
The EDB muscle is elevated from its origin. Crushing or excessive retraction can cause muscle necrosis or denervation. Prevention: subperiosteal elevation, stay sutures or gentle retractors, avoid bipolar cautery directly on muscle.
Runs with the sural nerve in the subcutaneous plane. May require ligation during extensile approaches. Contributes to lateral calcaneal skin flap perfusion. Prevention: preserve when possible, ligate cleanly if bleeding, avoid thermal injury.
At risk during joint preparation and reduction. Iatrogenic damage leads to persistent pain and arthritis. Prevention: careful technique, protect with retractors or K-wires, avoid overzealous debridement, confirm with fluoroscopy.
Dorsal sensory branches may be encountered with extensile or proximal exposure. Injury causes dorsal foot numbness. Prevention: identify and protect during proximal extension, avoid tight retraction, document sensation pre-operatively.
Sural Nerve Injury Management:
- If nerve identified as damaged intra-operatively: primary repair if clean transection, otherwise bury proximal end in muscle to prevent neuroma
- If neurapraxia suspected: observe, document, follow up closely
- Post-operative painful neuroma: desensitization, local steroid injection, surgical excision and burial if refractory
Extensile Modifications and Combined Approaches
Proximal Extension:
- Extend incision proximally along the posterior border of the fibula
- Allows access to the lateral ankle joint and peroneal tendons
- Sural nerve becomes more superficial proximally - increased risk
- Useful for combined ankle and subtalar pathology
Distal Extension:
- Extend toward the base of the fourth metatarsal or add a dorsal limb
- Provides access to the talonavicular joint for triple arthrodesis
- May require separate medial incision for complete triple fusion
- Useful for combined subtalar and midfoot procedures
Extensile Lateral (L-shaped) Approach:
- Indication: displaced intra-articular calcaneal fractures (Sanders II-IV)
- Technique: oblique limb as standard sinus tarsi, add vertical limb along posterior calcaneal border
- The corner of the L must be handled carefully to avoid wound edge necrosis
- Sural nerve is formally mobilized with the posterior skin flap
- Peroneal tendons are exposed and protected throughout
- Higher risk of wound complications (10-20%) compared with limited sinus tarsi approach
Combined Medial Approach for Triple Arthrodesis:
- For triple arthrodesis, the sinus tarsi approach is combined with a medial utility incision
- Medial approach exposes the talonavicular joint, middle facet, and sustentaculum
- Protects the posterior tibial tendon and neurovascular bundle
- Allows complete joint preparation of all three joints (subtalar, talonavicular, calcaneocuboid)
- Fixation typically includes 2-3 screws across subtalar joint and additional screws or staples for TN and CC joints
Complications
Intra-operative Complications:
|| Complication | Prevention | Management | ||--------------|------------|------------| || Sural nerve injury | Identify early, gentle retraction, no metal retractors | Primary repair if transected, bury proximal end if neuroma risk | || Peroneal tendon subluxation | Protect sheath, retract as unit, avoid over-retraction | Reduce and repair retinaculum, immobilize in eversion | || EDB muscle damage | Subperiosteal elevation, gentle retractors | Allow to fall back, loose approximation, avoid necrosis | || Intra-articular damage | Protect cartilage, careful instrumentation | Document, consider microfracture or grafting if focal | || Inadequate exposure | Extend incision or add medial approach | Do not force exposure through limited window |
Post-operative Complications:
|| Complication | Incidence | Prevention | Treatment | ||--------------|-----------|------------|-----------| || Sural neuroma | 5-10% | Careful nerve handling | Desensitization, injection, surgical excision and burial | || Wound necrosis (extensile) | 10-20% | Careful flap handling, no tension closure | Local wound care, delayed closure, flap coverage if severe | || Peroneal tendinitis | 5-8% | Protect sheath, smooth gliding post-op | NSAIDs, physiotherapy, rarely reoperation | || Subtalar nonunion | 5-15% | Good joint preparation, stable fixation, bone graft | Revision arthrodesis with autograft | || Infection | 2-5% | Antibiotics, soft tissue care | Irrigation and debridement, antibiotics, possible hardware removal | || Persistent pain | 10-20% | Accurate diagnosis, realistic expectations | Pain management, consider revision or other salvage |
Sural nerve injury or neuroma formation occurs in approximately 5-15% of lateral hindfoot approaches depending on the series. Most patients tolerate lateral foot numbness well, but painful neuromas can be debilitating. Careful identification and protection reduces permanent symptomatic injury to less than 5% in experienced hands.
Post-operative Care
Immediate Post-operative:
- Neurovascular check documenting lateral foot sensation (sural nerve function)
- Wound inspection
- Posterior splint or short leg cast with ankle in neutral
- Elevate limb above heart level for 48-72 hours
- DVT prophylaxis per protocol
Weight Bearing Protocol:
- Non-weight bearing for 6-12 weeks depending on procedure (arthrodesis vs ORIF)
- Progression based on radiographic healing and surgeon preference
- Crutches or walker required until full weight bearing
Range of Motion:
- For arthrodesis: no ROM exercises until union confirmed
- For ORIF or coalition resection: early gentle ROM as pain allows once wound healed
- Goal: maintain ankle and midfoot motion to compensate for lost subtalar motion
Follow-up Schedule:
- 2 weeks: Wound check, suture/staple removal, cast change
- 6 weeks: Radiographs (lateral, Broden, axial), assess healing
- 12 weeks: Radiographs, confirm union, progress to full WB if appropriate
- 6 months: Clinical and radiographic review, functional assessment
- 1 year: Final review, discuss long-term expectations
DVT Prophylaxis:
- LMWH or aspirin per institutional protocol
- Duration: Until mobile (minimum 2 weeks, often 6-12 weeks for arthrodesis)
Evidence Base
Implant Choice and Outcomes of the Sinus Tarsi Approach for Displaced Intra-articular Calcaneal Fractures
Modified sinus tarsi approach with a variable-angle locking anterolateral plate for Sanders type II and III calcaneal fractures
Increased Lateral Calcaneal Body and Subtalar Joint Visualization Utilizing a Modified Sinus Tarsi Approach
Complication and Revision Rate in Complex Intraarticular Calcaneal Fractures: Extended Lateral vs Sinus Tarsi Approach
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 45-year-old labourer with post-traumatic subtalar arthritis after a calcaneal fracture presents for surgical consideration. CT confirms isolated subtalar joint arthritis with preserved talonavicular and calcaneocuboid joints. Describe your surgical approach.”
“A 14-year-old with a symptomatic calcaneonavicular tarsal coalition fails conservative management. Describe the surgical approach for coalition resection.”
“A 35-year-old with a displaced Sanders III calcaneal fracture presents 10 days after injury with significant lateral swelling but intact skin wrinkles posteriorly. How would you decide between sinus tarsi and extensile lateral approach?”