Sinus Tarsi Approach to Calcaneus: Comprehensive Examination Guide

Introduction and Clinical Context

The sinus tarsi approach to the calcaneus is a minimally invasive alternative to the lateral extensile approach for surgical treatment of displaced intra-articular calcaneal fractures, utilizing a small (3-4cm) oblique incision centered over the sinus tarsi (anterolateral opening between talus and calcaneus) to access the anterolateral aspect of the posterior facet and lateral calcaneal wall, combined with percutaneous reduction techniques and fluoroscopy-guided fixation to achieve fracture reduction WITHOUT the extensive soft tissue dissection and full-thickness flap required by lateral extensile approach.

Historical Development and Surgical Evolution

The sinus tarsi approach was first described by Ebraheim et al (2000) for minimally invasive calcaneal fracture fixation and popularized by Weber et al (2008) and Yeo et al (2015) as alternative to lateral extensile approach. The technique emerged from recognition that lateral extensile approach wound complications (10-25% infection/dehiscence/necrosis) represent the SINGLE LARGEST barrier to successful calcaneal ORIF outcomes - even anatomic reduction yields poor results if wound complications occur (Folk 1999: 60% poor outcomes with wound complications vs 20% without).

The sinus tarsi approach addresses this limitation by MINIMIZING soft tissue dissection - small incision, no full-thickness flap elevation, no extensive periosteal stripping, reduced operative time (60-90 minutes vs 150-200 minutes lateral extensile). The trade-off is LIMITED direct visualization of posterior facet (only anterolateral aspect visible through sinus tarsi window) requiring INDIRECT reduction techniques (percutaneous Essex-Lopresti maneuver, percutaneous bone tamps, reduction tools placed through separate stab incisions, extensive fluoroscopy guidance).

Key principle: Sinus tarsi approach does NOT provide COMPLETE exposure - it is a minimally invasive technique relying on combination of (1) Limited direct visualization through sinus tarsi, (2) Indirect/percutaneous manipulation, (3) Fluoroscopy guidance for reduction assessment and hardware placement. Therefore, patient selection is CRITICAL - approach works well for simple fracture patterns (Sanders II-III with minimal comminution, 2-3 large fragments that can be manipulated with percutaneous tools) but is INADEQUATE for complex comminution (Sanders IV, central depression fractures requiring extensive fragment manipulation under direct vision).

Surgical Anatomy and Key Landmarks

Surface Anatomy and Planning

Sinus tarsi anatomy (KEY CONCEPT):

• Definition: Conical space on anterolateral hindfoot between talus (superiorly) and calcaneus (inferiorly)
• Location: Palpable depression anterior to lateral malleolus, lateral to extensor digitorum brevis muscle belly
• Contents (within sinus tarsi):
  • Talocalcaneal interosseous ligament (stabilizes subtalar joint)
  • Cervical ligament (lateral subtalar stabilizer)
  • Fat pad (filling space)
  • Arterial anastomosis (branches from dorsalis pedis and peroneal arteries)
• Boundaries:
  • Medial wall: Lateral process of talus (superior), sustentaculum tali (inferior)
  • Lateral opening: Space between talus and calcaneus (widens with subtalar joint distraction)
  • Floor: Anterolateral posterior facet of calcaneus (calcaneal articular surface)
  • Roof: Talar articular surface (corresponds to posterior facet)

Skin incision landmarks:

• Center of incision: Over sinus tarsi palpable depression (anterior to lateral malleolus 1-2cm, superior to calcaneocuboid joint)
• Length: 3-4cm oblique incision (oriented 45° from anterior-superior to posterior-inferior)
• Direction: Parallels peroneal tendons (avoids injury to tendons, nerves)

Palpable landmarks:

• Lateral malleolus: Superior posterior reference (incision anterior to malleolus 1-2cm)
• Calcaneocuboid joint: Palpable anteriorly (avoid extending incision anterior to joint - extensor digitorum brevis origin)
• Peroneal tendons: Palpable posterior to lateral malleolus (incision anterior to tendons - avoid injury)
• Sinus tarsi depression: Palpable with foot in neutral position (becomes more prominent with subtalar distraction)

Layer-by-Layer Anatomic Dissection

Layer 1 - Skin and Subcutaneous Tissue:

• 3-4cm oblique skin incision centered over sinus tarsi
• Incise through subcutaneous tissue
• Identify and protect intermediate dorsal cutaneous nerve (branch of superficial peroneal nerve):
  • Runs superficially on anterolateral foot (provides sensation to dorsum of foot)
  • May cross incision site (identify, retract, or accept division - causes limited dorsal foot numbness)

Layer 2 - Extensor Digitorum Brevis (EDB) Muscle:

• EDB muscle belly overlies sinus tarsi (origin from anterolateral calcaneus, specifically calcaneal sulcus just anterior to sinus tarsi)
• Retraction technique:
  • Identify EDB muscle belly (reddish muscle overlying sinus tarsi)
  • Retract EDB ANTERIORLY and INFERIORLY (exposes sinus tarsi space posteriorly)
  • Gentle retraction (excessive traction risks muscle injury, peroneal nerve branch injury - EDB innervated by deep peroneal nerve lateral branch)
  • Self-retaining retractor (small Weitlaner or Gelpi) holds EDB anteriorly

Layer 3 - Sinus Tarsi Contents:

• Sinus tarsi fat pad: Adipose tissue filling sinus tarsi space (remove to expose deeper structures)
• Talocalcaneal interosseous ligament: Thick ligament spanning talus to calcaneus within sinus tarsi (may need to partially release for exposure)
• Cervical ligament: Lateral subtalar ligament (lateral to interosseous ligament, may need release)
• Exposure technique:
  • Remove fat pad with sharp dissection (rongeur, scissors)
  • Partially incise talocalcaneal interosseous ligament if needed (improves visibility of posterior facet)
  • DO NOT completely destabilize subtalar joint (preserve some ligamentous structures for stability)

Layer 4 - Posterior Facet Exposure:

• Visualization: Through sinus tarsi window, ANTEROLATERAL aspect of posterior facet visible
  • Can see: Lateral 30-40% of posterior facet articular surface
  • CANNOT see: Posteromedial aspect (blocked by talus), medial sustentaculum region, posterior tuberosity
• Fracture exposure:
  • Remove fracture hematoma from visible articular surface
  • Assess fracture lines visible through sinus tarsi (typically see primary depression of lateral posterior facet)

Neurovascular Anatomy and Relationships

Intermediate Dorsal Cutaneous Nerve:

• Origin: Superficial peroneal nerve (common peroneal nerve branch)
• Course: Pierces deep fascia 10-15cm proximal to ankle, runs subcutaneously across anterolateral ankle/foot
• Innervation: Sensation to dorsum of foot (between great toe and 2nd toe dorsally, and 4th/5th toes laterally)
• Injury risk: 5-10% (nerve may cross incision site)
• Injury consequence: Numbness dorsal foot (NOT functionally limiting, less bothersome than sural nerve injury in lateral extensile approach)

Deep Peroneal Nerve (lateral branch to EDB):

• Course: Deep peroneal nerve gives off lateral branch to EDB muscle belly (near EDB origin on calcaneus)
• Injury risk: Low (less than 1%) if EDB retracted gently (excessive traction risks nerve stretch injury)
• Injury consequence: EDB denervation (loss of toe extension at MTP joints 2-5 - subtle deficit, most patients unaware)

Peroneal Tendons:

• Location: Posterior to incision (run behind lateral malleolus in retrofibular groove, turn anteriorly inferior to lateral malleolus)
• Protection: Incision anterior to tendons (does NOT violate peroneal tendon sheath), tendons NOT at risk if incision properly placed

Sinus Tarsi Arterial Anastomosis:

• Components: Branches from dorsalis pedis artery (medially) and peroneal artery (laterally) anastomose within sinus tarsi
• Clinical significance: These vessels ligate/cauterize during dissection (collateral circulation adequate, no ischemic complications)

Indications and Contraindications

Primary Indications (Evidence-Based, SELECTIVE)

IDEAL Indications (Sanders II-III Simple Patterns):

1. Sanders type II fractures (2-part posterior facet, 1 fracture line):
   • Single fracture line in CORONAL plane (allows lateral manipulation to reduce depression)
   • Minimal comminution (2 large fragments - can reduce with percutaneous tools)
   • Displaced greater than 2mm articular step-off or Böhler angle less than 20°
2. Sanders type III fractures (3-part posterior facet, 2 fracture lines) with LIMITED comminution:
   • Primary fracture lines in CORONAL/SAGITTAL planes (simple geometric pattern)
   • 2-3 large fragments (amenable to percutaneous manipulation + fluoroscopy guidance)
   • Avoid if central depression with small comminuted pieces (cannot manipulate indirectly)
3. High wound-risk patients (Sanders II-III appropriate patterns):
   • Smokers (sinus tarsi approach wound complications 3-5% vs 30-40% lateral extensile in smokers)
   • Diabetics (wound complications 5-8% vs 20-30% lateral extensile)
   • Elderly with thin skin/poor vascularity
   • Obesity (larger soft tissue envelope - wound healing concerns)
   • Previous surgery/scarring lateral hindfoot

RELATIVE Indications:

1. Bilateral calcaneal fractures - consider sinus tarsi approach for one side (minimizes bilateral wound morbidity)
2. Patient preference for minimally invasive approach (after counseling on limitations vs lateral extensile)

Contraindications

ABSOLUTE Contraindications (Use Lateral Extensile Instead):

1. Sanders type IV fractures (severe comminution, 4+ fracture lines):
   • Small comminuted fragments cannot be manipulated percutaneously (require direct visualization/manipulation fragment-by-fragment)
   • Central depression fracture patterns (multiple small depressed fragments)
2. Significant tuberosity displacement requiring direct realignment/fixation:
   • Varus/valgus tuberosity deformity (no access to tuberosity through sinus tarsi)
   • Tuberosity separate fragment needing anatomic reduction
3. Medial wall comminution or sustentaculum fracture:
   • Loss of reduction reference (sustentaculum usually intact serves as medial template - if fractured, cannot reliably reduce lateral fragments)
4. Fracture requiring direct posterior facet visualization:
   • Surgeon unfamiliar with indirect reduction techniques (requires experience/training)
   • Complex fracture anatomy not amenable to fluoroscopy-based reduction

RELATIVE Contraindications:

1. Active infection (cellulitis, open fracture with contamination) - same as lateral extensile
2. Severe PVD (ABI less than 0.7) - healing unlikely regardless of approach (favor nonoperative)
3. Fracture age greater than 3 weeks - early callus formation makes indirect reduction difficult (consider lateral extensile for direct manipulation or nonoperative management)

Preoperative Planning and Patient Positioning

Preoperative Assessment

Clinical Examination (Same as Lateral Extensile):

• Soft tissue assessment:
  • Wrinkle sign (skin wrinkles with ankle motion - indicates edema resolved, safe to proceed)
  • Fracture blisters (clear vs hemorrhagic), skin quality
• Neurovascular examination: Pulses, compartment assessment
• Heel position: Varus/valgus, widening

Radiographic Planning (CRITICAL for Patient Selection):

• CT scan (MANDATORY):
  • Sanders classification (coronal CT posterior facet):
    • Sanders I: Non-displaced (less than 2mm) - nonoperative
    • Sanders II: 2-part (1 fracture line) - IDEAL for sinus tarsi if simple pattern
    • Sanders III: 3-part (2 fracture lines) - CONSIDER sinus tarsi if limited comminution
    • Sanders IV: 4+ parts (3+ fracture lines) - AVOID sinus tarsi (use lateral extensile)
  • Assess fracture complexity:
    • Count fragments (2-3 large fragments = suitable, 4+ small fragments = unsuitable)
    • Fracture line orientation (coronal/sagittal = favorable for lateral manipulation, oblique/transverse = unfavorable)
    • Central depression vs lateral depression (lateral depression easier to reduce through sinus tarsi)
  • Sustentaculum integrity: Confirm sustentaculum intact (medial reference for reduction)

Surgical Planning:

• Decision: Sinus Tarsi vs Lateral Extensile?
  • Sinus tarsi: Sanders II-III, 2-3 large fragments, minimal comminution, intact sustentaculum, high wound risk patient
  • Lateral extensile: Sanders III-IV, complex comminution, small fragments, tuberosity displacement, medial wall injury, low-risk patient

Patient Positioning

LATERAL DECUBITUS position (SAME as lateral extensile):

• Patient lateral, injured side up, ankle neutral
• Bean bag or lateral positioners for stability
• Bolsters support leg (allows access to anterolateral foot)
• Tourniquet: Optional (many surgeons prefer tourniquet down for minimally invasive approach - less ischemia time concern due to shorter procedure)

Step-by-Step Surgical Technique

Step 1: Positioning and Skin Incision

Technique:

1. Patient lateral decubitus, injured side up, ankle neutral
2. Palpate sinus tarsi (depression anterior to lateral malleolus, lateral to EDB)
3. Mark incision: 3-4cm oblique incision centered over sinus tarsi
   • Orientation: 45° anterior-superior to posterior-inferior (parallels peroneal tendons)
   • Avoid extending anterior to calcaneocuboid joint (EDB origin)
4. Incise skin and subcutaneous tissue:
   • Sharp dissection through skin
   • Identify intermediate dorsal cutaneous nerve if visible (retract or accept division)

Step 2: Exposure of Sinus Tarsi

Technique:

1. Identify EDB muscle belly (overlies sinus tarsi, reddish muscle)
2. Retract EDB anteriorly and inferiorly:
   • Use small Weitlaner or Gelpi retractor (self-retaining)
   • Gentle retraction (avoid excessive force on muscle/nerve)
   • Exposes sinus tarsi space posteriorly
3. Clear sinus tarsi contents:
   • Remove fat pad: Rongeur or sharp dissection (exposes deeper structures)
   • Partially release talocalcaneal interosseous ligament (if needed for exposure):
     • Use knife or scissors to incise ligament fibers (improves visibility of posterior facet)
     • DO NOT completely destabilize (preserve some ligament for subtalar stability)
   • Identify posterior facet articular surface: ANTEROLATERAL aspect visible through sinus tarsi window
4. Assess fracture:
   • Visualize depressed lateral posterior facet fragments through sinus tarsi
   • Remove fracture hematoma from visible articular surface

Step 3: Percutaneous Fracture Reduction (CRITICAL STEP)

Reduction Sequence (Essex-Lopresti + Percutaneous Manipulation):

1. Essex-Lopresti maneuver (percutaneous traction on tuberosity):
   • Make small stab incision (5mm) posterior to heel (directly posterior over tuberosity)
   • Insert Steinmann pin or Schanz screw (4.0mm) through tuberosity fragment under fluoroscopy guidance (lateral view)
   • Apply traction POSTERIORLY and INFERIORLY (pull tuberosity distally)
   • Disimpacts posterior facet (lifts depressed fragments)
   • Check lateral fluoroscopy: Böhler angle should improve toward 25-40°
2. Percutaneous elevation of depressed posterior facet:
   • Technique: Transcalcaneal approach through plantar surface
     • Make small stab incision (5mm) on PLANTAR heel (inferior surface of calcaneus, medial to weight-bearing area)
     • Insert bone tamp or curved periosteal elevator through plantar incision
     • Advance tamp superiorly through calcaneus (UNDER fluoroscopy guidance)
     • Engage UNDERSIDE of depressed posterior facet fragment (from inferior)
     • Gently lever tamp to ELEVATE depressed fragment superiorly
   • Fluoroscopy assessment:
     • AP view: Assess medial-lateral position (ensure fragments align with sustentaculum)
     • Lateral view: Assess Böhler angle restoration (target 25-40°)
     • Broden views (oblique 10-40° cephalad): Assess posterior facet articular congruity (less than 2mm step-off goal)
3. Direct visualization through sinus tarsi:
   • Once reduction achieved with percutaneous tools, inspect VISIBLE portion of posterior facet through sinus tarsi
   • Palpate articular surface with probe (should feel flush, no step-off)
   • Limited visualization (only anterolateral 30-40% visible) - rely on fluoroscopy for medial/posterior assessment
4. Adjust reduction if needed:
   • Reposition tamp/Steinmann pin, repeat elevation
   • May require multiple attempts to achieve anatomic reduction (fluoroscopy guidance essential)

Step 4: Fixation

Technique:

1. Maintain reduction with temporary K-wires:
   • Percutaneous K-wires (2.0mm) through lateral calcaneal wall into reduced posterior facet fragments
   • Place under fluoroscopy guidance (avoid intra-articular penetration)
   • 2-3 K-wires typically needed to stabilize reduction
2. Definitive fixation options:
   • Option A: Small plate via sinus tarsi incision (most common):
     • Small calcaneal plate (3-4 hole, low-profile) positioned on anterolateral wall
     • Insert through sinus tarsi incision (extends incision slightly if needed - total 5-6cm)
     • Screws (3.5mm) placed through plate into calcaneal body
     • Provides stable fixation for most Sanders II-III patterns
   • Option B: Percutaneous screws only (no plate):
     • Large lag screws (4.0-4.5mm cannulated) placed percutaneously from lateral wall into calcaneal body
     • Achieve interfragmentary compression across fracture lines
     • Used for simple 2-part fractures (Sanders II)
   • Option C: Combined plate + percutaneous screws:
     • Plate via sinus tarsi for lateral wall support
     • Additional percutaneous lag screws for interfragmentary compression (posterior or plantar-to-dorsal)
3. Fluoroscopy confirmation:
   • AP, lateral, Broden views: Check Böhler angle restored (25-40°), articular congruity (less than 2mm step-off), hardware position
   • Ensure no intra-articular screw penetration (subtalar joint)
   • Heel width normalized (axial view)

Step 5: Closure

Technique:

1. Remove temporary K-wires (once definitive fixation complete)
2. Replace EDB muscle over sinus tarsi (falls back into position when retractor removed)
3. Subcutaneous closure: 3-0 absorbable sutures (Vicryl or Monocryl)
4. Skin closure:
   • Simple interrupted or subcuticular sutures (3-0 or 4-0 nylon/monocryl)
   • Small incision heals quickly (lower wound tension vs lateral extensile)
5. Dressing: Bulky compressive dressing, posterior splint
6. Post-operative protocol (SAME as lateral extensile):
   • Strict elevation, NWB 6-8 weeks, advance to partial then full weight-bearing by 12 weeks
   • ROM exercises (ankle and subtalar) starting week 2-3 to prevent stiffness

Complications and Management

Intraoperative Complications

1. Inadequate Reduction (Most Common - 5-15% incidence)

Recognition:

• Fluoroscopy shows persistent articular step-off greater than 2mm (Broden views)
• Böhler angle not restored to 25-40° range (lateral view)
• Heel width not normalized (axial view)

Management:

• Intraoperative: Repeat percutaneous reduction maneuvers (reposition tamp, adjust Steinmann pin traction, attempt multiple angles)
• If unable to achieve adequate reduction after 2-3 attempts:
  • Option 1: Convert to lateral extensile approach (extend sinus tarsi incision into full L-shaped lateral extensile incision - allows direct visualization/manipulation)
    • Appropriate if fracture more complex than pre-op imaging suggested (Sanders III with more comminution than appreciated)
    • Accept higher wound risk to achieve anatomic reduction (inadequate reduction = poor outcomes regardless of approach)
  • Option 2: Accept suboptimal reduction (if step-off 2-4mm, consider acceptable in high-risk wound patient)
    • Rare - most surgeons prefer conversion to lateral extensile over accepting malreduction
• Post-operative (if malreduction recognized post-op within 2-3 weeks):
  • Consider revision ORIF via lateral extensile approach (if patient accepts wound risk and reduction critically inadequate)
  • OR accept malreduction, plan for subtalar fusion IF symptomatic arthritis develops (treat arthritis when/if occurs rather than reoperate acutely)

Prevention:

• Careful pre-operative CT assessment (exclude complex comminution patterns not suitable for sinus tarsi)
• Low threshold to convert to lateral extensile intraoperatively (do NOT persist with sinus tarsi if reduction not achievable - inadequate reduction worse than wound risk)
• Extensive fluoroscopy use (multiple views - AP, lateral, Broden, axial - to confirm reduction before fixation)

2. Intra-articular Hardware Placement (3-5% incidence)

Recognition:

• Fluoroscopy shows screw penetration into subtalar joint
• Post-operative: Pain with subtalar motion, stiffness

Management:

• Intraoperative: Remove screw, redirect (ensure screw does NOT violate joint)
• Post-operative (if recognized post-op): Return to OR for screw removal/revision (intra-articular hardware causes rapid cartilage damage)

Prevention:

• Fluoroscopy confirmation BEFORE tightening screws (multiple views including Broden to visualize subtalar joint)
• Use of guide wires (drill guide wire first, check position with fluoroscopy, then overdrill/tap/screw)

3. Neurovascular Injury (Rare, less than 1%)

Recognition:

• Intermediate dorsal cutaneous nerve injury: Dorsal foot numbness (seen immediately post-op)
• Dorsalis pedis artery injury: Loss of DP pulse (rare - artery not in direct surgical field)

Management:

• Nerve injury: Usually transient neuropraxia, recovers 6-12 months (counsel patient)
• Arterial injury: Vascular surgery consultation if pulse absent post-operatively (rare complication)

Early Postoperative Complications (0-6 weeks)

1. Wound Complications (3-5% incidence - PRIMARY ADVANTAGE over lateral extensile 10-25%)

Types:

• Superficial dehiscence (2-3%)
• Superficial infection (1-2%)
• Deep infection (rare, less than 1%)

Management (SAME as lateral extensile):

• Superficial: Local wound care, oral antibiotics if cellulitis
• Deep: Return to OR for irrigation/debridement, IV antibiotics, hardware removal if infected and fracture not healed

2. Loss of Reduction (5-8% incidence)

Recognition:

• Serial X-rays show fracture displacement (Böhler angle loss, posterior facet step-off recurrence)
• Usually early post-op (first 2-4 weeks before healing)

Mechanism:

• Inadequate initial fixation (percutaneous screws insufficient stability)
• Early weight-bearing (patient non-compliance)
• Severe osteoporosis (hardware loosening)

Management:

• Early (less than 3 weeks): Consider revision ORIF (may convert to lateral extensile for direct fixation, augment with plate)
• Late (greater than 3 weeks): Observe, plan subtalar fusion if symptomatic arthritis develops (revision difficult once early healing started)

Late Postoperative Complications (6+ months)

1. Subtalar Arthritis (40-50% long-term - SAME as lateral extensile)

Recognition and Management: IDENTICAL to lateral extensile approach

• Conservative: NSAIDs, activity modification, AFO, corticosteroid injections
• Surgical: Subtalar arthrodesis (90-95% pain relief, 85-90% fusion rate)

Key point: Subtalar arthritis rate similar between sinus tarsi and lateral extensile approaches (Weber 2008: 48% vs 45%, p = 0.79) - suggests arthritis driven by INITIAL INJURY severity rather than surgical technique/approach

2. Hardware Irritation (5-10% incidence)

Recognition:

• Palpable/prominent hardware through sinus tarsi incision (small plate or screw heads)
• Pain with shoe wear

Management:

• Observation if asymptomatic
• Hardware removal after fracture union (12-18 months)
• Lower rate than lateral extensile (smaller incision, less prominent hardware)

3. Malunion (if inadequate reduction at index procedure)

Recognition:

• Persistent heel widening, varus/valgus deformity
• Radiographic malunion (Böhler angle less than 20°, articular step-off greater than 2mm)

Management:

• Usually managed with subtalar fusion (corrective osteotomy rarely indicated for calcaneal malunion)
• Prevention better than treatment - ensure adequate reduction at index procedure OR convert to lateral extensile if reduction inadequate

Comparison with Lateral Extensile Approach

Pearls, Pitfalls, and Expert Tips

Surgical Pearls (What Separates Good from Great)

Pearl 1: Patient selection is 80% of success

• Sinus tarsi approach works ONLY for appropriate fracture patterns (Sanders II-III, 2-3 large fragments, minimal comminution)
• Meticulous pre-operative CT assessment (count fragments, assess fracture line orientation)
• Low threshold to convert to lateral extensile if reduction inadequate (better to have wound risk with anatomic reduction than inadequate reduction with low wound risk)

Pearl 2: Percutaneous Essex-Lopresti maneuver is foundation

• Posterior Steinmann pin/Schanz screw through tuberosity provides longitudinal traction
• Disimpacts posterior facet (lifts depressed fragments superiorly)
• Creates "space" for elevation - makes percutaneous tamp elevation easier

Pearl 3: Plantar bone tamp from inferior is KEY technique

• Insert tamp through plantar incision (medial heel, avoid weight-bearing area)
• Advance tamp superiorly through calcaneus under fluoroscopy guidance
• Engage UNDERSIDE of depressed fragment, lever superiorly
• Multiple angles/attempts often needed (patient, persistent technique - not quick operation)

Pearl 4: Fluoroscopy is your "eyes" - use extensively

• AP, lateral, Broden (oblique 10-40°), axial views - ALL needed for complete assessment
• Broden views critical for posterior facet articular congruity (only way to assess medial/posterior facet through sinus tarsi approach)
• Do NOT proceed to fixation until fluoroscopy confirms adequate reduction (less than 2mm step-off, Böhler 25-40°)

Pearl 5: Direct visualization through sinus tarsi confirms fluoroscopy

• Use probe to palpate visible articular surface (should feel flush, no step-off)
• Inspect with loupe/headlight (magnification helps assess subtle step-off)
• If palpable step-off despite "adequate" fluoroscopy - adjust reduction (tactile feedback more reliable than fluoroscopy alone)

Common Pitfalls (and How to Avoid Them)

Pitfall 1: Using sinus tarsi for Sanders IV (severe comminution)

• Problem: Cannot achieve adequate reduction with percutaneous techniques (small comminuted fragments require fragment-by-fragment manipulation under direct vision)
• Solution: Pre-operative CT assessment - if Sanders IV or central depression with small fragments, use lateral extensile approach from start (do NOT attempt sinus tarsi)
• Recovery: If attempted sinus tarsi and inadequate reduction - convert to lateral extensile intraoperatively (extend incision into L-shaped lateral extensile incision)

Pitfall 2: Accepting suboptimal reduction

• Problem: "Close enough" mentality with step-off 2-4mm because wound complications low (but functional outcomes correlate with reduction quality - persistent step-off greater than 2mm = subtalar arthritis)
• Solution: LOW threshold to convert to lateral extensile if reduction not achievable after 2-3 attempts (anatomic reduction priority over wound risk - inadequate reduction guarantees poor outcome)
• Prevention: If reduction challenging, consider converting early (easier to extend fresh incision than reopen/extend after closure)

Pitfall 3: Inadequate fluoroscopy assessment

• Problem: Relying on AP/lateral views only (miss subtle articular step-off visible on Broden views) - leads to unrecognized malreduction
• Solution: MANDATORY Broden views (10°, 20°, 30°, 40° cephalad oblique) - visualize posterior facet articular surface (confirms less than 2mm step-off)
• Fluoroscopy time: Accept higher fluoroscopy exposure (mean 75-145 seconds - Yeo 2015) as necessary for adequate assessment via indirect approach

Pitfall 4: Attempting sinus tarsi approach without adequate training

• Problem: Steep learning curve (Yeo 2015: first 20-25 cases higher malreduction rate 12% vs 4% late) - inexperienced surgeon risks inadequate reduction
• Solution: Mentored cases or cadaver training before independent practice (consider lateral extensile for complex fractures until proficiency with sinus tarsi developed)
• Alternative: Use lateral extensile approach until comfortable with indirect reduction techniques (no shame in choosing familiar technique with proven outcomes over unfamiliar minimally invasive technique)

Pitfall 5: Not counseling patient on limitations

• Problem: Patient expects "minimally invasive = better outcome" (but outcomes SAME as lateral extensile for appropriate fractures, and sinus tarsi has higher malreduction risk if fracture not suitable)
• Solution: Explain: (1) Sinus tarsi advantage is WOUND SAFETY (3-5% complications vs 10-25%), (2) Functional outcomes SAME if appropriate fracture pattern, (3) If fracture too complex, lateral extensile may be needed (cannot guarantee sinus tarsi at start)

Expert Tips (From High-Volume Surgeons)

Tip 1: Use subtalar distraction to improve sinus tarsi visualization

• Apply axial traction on foot with ankle distraction (pulls talus away from calcaneus)
• Widens sinus tarsi opening (improves visibility of posterior facet)
• Can use laminar spreader placed in sinus tarsi (gently distract talus from calcaneus)

Tip 2: Combine with mini-open lateral incision if needed

• If lateral wall collapse severe (cannot reduce through sinus tarsi alone), add small (2-3cm) lateral incision over lateral wall
• Push lateral wall fragments medially through lateral incision (restores heel width)
• Still minimally invasive (total incision length 5-7cm vs 12-15cm lateral extensile), lower wound risk

Tip 3: Consider bone graft through sinus tarsi

• If large metaphyseal void after reduction, fill with bone graft (autograft or allograft bone chips)
• Insert through sinus tarsi incision (pack into void under fluoroscopy guidance)
• Improves structural support, may reduce loss of reduction risk

Tip 4: Protect plantar nerves during plantar bone tamp

• Plantar incision for bone tamp should be MEDIAL heel (avoid lateral plantar nerve distribution)
• Medial calcaneal branch of tibial nerve at risk (provides heel sensation)
• Stay close to bone during tamp advancement (subperiosteal), avoid excessive soft tissue dissection

Tip 5: Consider sinus tarsi approach for one side in bilateral fractures

• If patient has bilateral calcaneal fractures, mix approaches (sinus tarsi one side, lateral extensile other side)
• Minimizes bilateral wound morbidity (at least one side has low complication risk)
• Prioritize sinus tarsi for side with simpler fracture pattern (Sanders II vs III) or dominant extremity (minimize wound risk on critical side)