SUBTALAR DISLOCATIONS
Peritalar Injury | TN + TC Joints | Medial 80% | Urgent Reduction | AVN Risk
SUBTALAR DISLOCATION CLASSIFICATION
Critical Must-Knows
- Two joints involved: Talonavicular AND talocalcaneal (tibiotalar intact)
- Medial most common (85%): Foot inverted and adducted = 'acquired clubfoot'
- Urgent reduction: Skin tension causes necrosis within hours
- Associated fractures: CT after reduction - 40% have occult fractures
- AVN risk: Talus has tenuous blood supply - prolonged dislocation increases risk
Examiner's Pearls
- "Named by direction of FOOT relative to talus (medial = foot goes medial)
- "Medial dislocation = adducted/inverted = 'acquired clubfoot' appearance
- "Lateral dislocation = abducted/everted = 'acquired flatfoot' appearance
- "CT mandatory after reduction to detect associated fractures
- "Open dislocations have significantly worse outcomes
Exam Warning
Critical Exam Points - Subtalar Dislocations:
- JOINTS INVOLVED: Talonavicular + Talocalcaneal (NOT tibiotalar)
- MEDIAL IS MOST COMMON (85%): Foot displaced medial = acquired clubfoot appearance
- URGENT REDUCTION REQUIRED: Skin tension causes necrosis - reduce within hours
- CT AFTER REDUCTION: 40% have occult fractures - always scan after reduction
- REDUCTION TECHNIQUE: Knee flexed, traction, accentuate deformity then reverse
- OPEN INJURIES: Much worse prognosis - higher complication rates
At a Glance: Quick Decision Guide
| Feature | Medial Dislocation (85%) | Lateral Dislocation (15%) |
|---|---|---|
| Foot Position | Adducted and inverted | Abducted and everted |
| Appearance | Acquired clubfoot | Acquired flatfoot |
| Mechanism | Inversion force (most common) | Eversion force |
| Reduction Maneuver | Traction + EVERSION | Traction + INVERSION |
| Blocking Structure | Talar head on navicular/EHL | Talar head on cuboid/peroneal tendons |
| Open Injury Rate | Lower | Higher (worse prognosis) |
PERITALARPERITALAR - Key Features
Memory Hook:PERITALAR dislocations involve Paired joints, require Emergency reduction, and need CT to detect Associated fractures
MEDIALMEDIAL - Medial Dislocation Features
Memory Hook:MEDIAL is Most common and needs Eversion to reduce
Overview
Subtalar Dislocations - Peritalar Dislocations
Subtalar dislocations are rare but dramatic injuries characterized by simultaneous dislocation of the talonavicular and talocalcaneal joints while the tibiotalar joint remains intact. Also called "peritalar dislocations," they represent approximately 1% of all dislocations and require urgent reduction to prevent skin necrosis and long-term complications.
Epidemiology
Incidence:
- Rare injury - approximately 1% of all dislocations
- 1-2% of major joint dislocations
- Predominantly young males (70-80%)
- Usually high-energy mechanism
Mechanism:
- Motor vehicle accidents (40%)
- Falls from height (30%)
- Sports injuries (20%) - basketball, football
- Direct trauma (10%)
Age Distribution:
- Most common in 20-40 year age group
- Rare in children and elderly
- Associated with active lifestyle/sports
Anatomy and Pathophysiology
Subtalar Complex Anatomy
The Subtalar Complex
Joints Involved in Subtalar Dislocation:
- Talonavicular joint (ball and socket)
- Talocalcaneal joint (subtalar joint proper)
Joint NOT Involved:
- Tibiotalar joint - remains intact (talus stays in mortise)
This is why the injury is also called "peritalar dislocation" - the dislocation occurs AROUND the talus.
Blood Supply to the Talus
Critical Vascular Anatomy:
- Posterior tibial artery: Main supply via artery of the tarsal canal
- Anterior tibial artery: Supplies talar neck and head dorsally
- Peroneal artery: Supplies via artery of the tarsal sinus
Why This Matters:
- 60% of talus is covered by articular cartilage (no periosteal vessels)
- Tenuous retrograde blood supply
- Prolonged dislocation can compromise vessels
- Risk of AVN, especially with delayed reduction
Vascular Anatomy Key Point
The talus has no muscle attachments and 60% articular cartilage coverage, making it dependent on intraosseous blood supply through the tarsal canal and sinus. Prolonged dislocation with stretched vessels significantly increases AVN risk.
Mechanism of Injury
Medial Dislocation (85%):
- High-energy inversion force
- Foot forced into plantarflexion and inversion
- Common scenarios: falls, MVA, sports (basketball - "basketball foot")
- Calcaneus, navicular, and forefoot displace medially under talus
Lateral Dislocation (15%):
- High-energy eversion force
- Foot forced into dorsiflexion and eversion
- Usually requires greater force than medial
- Higher association with open injuries and fractures
Understanding Direction
The dislocation is named by the direction of the FOOT relative to the talus:
- Medial dislocation: Foot goes MEDIAL = adducted, inverted = "acquired clubfoot"
- Lateral dislocation: Foot goes LATERAL = abducted, everted = "acquired flatfoot"
The talus remains in the ankle mortise in both types.
Structures That Can Block Reduction
Medial Dislocation (foot medial):
- Talar head buttonholes through extensor retinaculum
- EHL tendon may wrap around talar head
- Tibialis posterior tendon occasionally blocks
- Talonavicular capsule interposition
Lateral Dislocation (foot lateral):
- Peroneal tendons wrap around talar neck
- Talar head buttonholes through extensor retinaculum
- FHL tendon may block
- Posterior tibial tendon occasionally involved
BLOCKBLOCK - Structures Blocking Reduction
Memory Hook:If closed reduction BLOCKED, suspect soft tissue interposition - may need open reduction
Classification
Classification
Medial Subtalar Dislocation
Most Common Type (85%)
Mechanism:
- High-energy inversion force
- Plantarflexion and inversion
- Falls, MVA, sports (basketball)
Foot Position:
- Displaced MEDIALLY
- Adducted and inverted
- "Acquired clubfoot" appearance
Talar Head Prominence:
- Prominent DORSOLATERALLY
- Palpable and visible
- Skin tension over prominence
Reduction Technique:
- Knee flexed (relax gastrocnemius)
- Longitudinal traction
- Accentuate plantarflexion and inversion
- Then EVERT and dorsiflex to reduce
Blocking Structures:
- Extensor retinaculum (buttonholed)
- EHL tendon wrapping talar head
- Tibialis posterior tendon
- Talonavicular capsule
Prognosis:
- Better than lateral type
- 60-90% good-excellent outcomes (pure dislocation)
- Lower open injury rate
- Lower complication rate
Summary: Medial is most common, has better prognosis, and is easier to reduce.
Clinical Assessment
Initial Assessment
Presentation
Obvious Deformity:
-
Medial: Foot appears adducted and inverted ("acquired clubfoot")
- Talar head prominent DORSOLATERALLY
- Heel in varus
-
Lateral: Foot appears abducted and everted ("acquired flatfoot")
- Talar head prominent DORSOMEDIALLY
- Heel in valgus
Associated Features:
- Significant swelling
- Severe pain
- Unable to weight bear
- Skin tension - may be tented over talar head
- Open wounds (check carefully)
Skin Assessment - Critical
Skin Emergency
Skin tension over the talar head is an EMERGENCY
The prominent talar head causes extreme skin tension that can lead to:
- Necrosis within hours
- Full-thickness skin loss
- Open conversion of closed injury
- Infection risk
Immediate reduction is mandatory to relieve skin tension.
Neurovascular Examination
Pre-Reduction Assessment:
- Dorsalis pedis pulse (may be displaced)
- Posterior tibial pulse
- Capillary refill
- Sensory examination (if patient can cooperate)
- Superficial peroneal (dorsum of foot)
- Deep peroneal (first web space)
- Tibial nerve (plantar foot)
- Sural nerve (lateral foot)
Document Before AND After Reduction:
- Changes in vascular status
- Sensory changes
- Motor function once pain controlled
Associated Injuries to Assess
Local:
- Open wounds (check carefully between toes)
- Associated fractures (malleoli, talus, calcaneus, navicular, cuboid)
- Ankle mortise integrity
- Skin condition
Systemic:
- High-energy mechanism - assess for polytrauma
- Spine injuries
- Other extremity injuries
- Head injury
Investigations
Imaging Protocol
Pre-Reduction X-rays
Required Views:
- AP foot
- Lateral foot
- AP ankle
- Lateral ankle
What to Assess:
- Confirm subtalar dislocation (TN and TC disrupted)
- Confirm tibiotalar joint intact
- Identify obvious fractures
- Determine direction of dislocation
Don't Delay Reduction for Perfect X-rays: If skin is compromised, reduce emergently based on clinical findings and whatever imaging is immediately available.
Post-Reduction Imaging
X-rays:
- Confirm congruent reduction of TN and TC joints
- Check ankle mortise alignment
- Assess any fractures now visible after reduction
CT Scan - MANDATORY:
CT After Reduction
Always get CT after successful reduction of a subtalar dislocation:
- 40% of subtalar dislocations have associated fractures
- Many are occult on plain X-rays
- May change management if large fragments present
- Identifies loose bodies
- Assesses congruency of reduction
CT Assessment:
- Talar dome and neck fractures
- Posterior process fractures
- Calcaneal fractures (sustentaculum, anterior process)
- Navicular fractures
- Cuboid fractures
- Loose bodies
- Reduction congruency
MRI (Rarely Indicated Acutely)
Potential Indications:
- Suspected chondral injury
- Soft tissue interposition preventing reduction
- Late presentation with concerns for AVN
- Usually delayed investigation
Management
Management Algorithm
Initial Emergency Department Management
Immediate Assessment:
- Neurovascular examination and documentation
- Skin assessment - tented skin is emergency
- Check for open wounds
- Pain control
Imaging:
- AP and lateral foot X-rays
- AP and lateral ankle X-rays
- Do NOT delay reduction if skin compromised
- Imaging confirms diagnosis and direction
Priority:
- Skin tension over talar head = URGENT reduction
- Can occur within hours of injury
- Risk of skin necrosis and full-thickness loss
- May convert closed to open injury
Setup:
- Patient supine
- Procedural sedation or regional anesthesia
- Assistant for counter-traction
- Fluoroscopy helpful but not mandatory
Key Point: Skin tension is the primary driver of urgency.
Surgical Technique
Surgical Approaches for Open Reduction
Indications for Open Reduction
Absolute Indications:
- Irreducible closed reduction (soft tissue interposition)
- Open dislocation requiring debridement
- Large displaced fracture-dislocation requiring fixation
Relative Indications:
- Failed closed reduction under GA with complete muscle relaxation
- Associated fractures requiring ORIF
- Persistent instability after closed reduction (rare)
Success Rates:
- 80-90% of subtalar dislocations reduce with closed technique
- 10-20% require open reduction
- Most failures due to soft tissue interposition
Note: Most subtalar dislocations can be successfully reduced with proper technique and adequate analgesia/muscle relaxation.
Complications
Acute Complications
Skin Necrosis
Most Urgent Acute Complication:
- Occurs with prolonged dislocation
- Skin tented over talar head
- Can develop within 6-12 hours
- Full-thickness skin loss possible
- May convert closed to open injury
- Prevention: Urgent reduction
Neurovascular Injury
Incidence: 5-10% of cases
Nerve Injuries:
- Superficial peroneal nerve (most common)
- Deep peroneal nerve
- Tibial nerve
- Usually neurapraxia from stretch
- Most recover with time
Vascular Injuries:
- Dorsalis pedis artery injury rare
- Posterior tibial artery injury rare
- Compartment syndrome (very rare)
Inability to Reduce
Failed Closed Reduction (10-20%):
- Soft tissue interposition
- Buttonholed extensor retinaculum
- EHL tendon (medial dislocation)
- Peroneal tendons (lateral dislocation)
- Requires open reduction
Compartment Syndrome
Very Rare but Possible:
- High-energy injuries
- Associated fractures
- Prolonged dislocation
- Monitor closely first 48 hours
- High index of suspicion needed
Chronic Complications
Post-Traumatic Arthritis
Most Common Long-Term Complication:
Incidence by Injury Type:
- Pure closed medial: 30-40%
- Fracture-dislocation: 50-70%
- Open or lateral: 60-80%
Time Course:
- May take 5-10 years to develop
- Progressive symptoms
- Joint space narrowing on X-ray
- Subtalar crepitus and pain
Management:
- Activity modification
- Orthotics and supportive footwear
- NSAIDs for pain
- Corticosteroid injections
- Subtalar fusion if severe (good pain relief, further stiffness)
Prognosis:
- Fusion provides reliable pain relief
- Further loss of inversion/eversion
- Often well-tolerated
Avascular Necrosis (AVN)
Incidence:
- Pure dislocation: 5-10%
- Fracture-dislocation: 15-20%
- Open injury: 20-30%
- Higher with delayed reduction
Risk Factors:
- Delayed reduction (over 6 hours)
- High-energy mechanism
- Associated talar neck fracture
- Open injury
- Need for open reduction
Presentation:
- Initially asymptomatic
- Pain develops as collapse occurs
- Progressive deformity
- Eventually arthritis
Detection:
- Hawkins sign at 6-8 weeks (subchondral lucency = good blood supply)
- Absence of Hawkins sign concerning for AVN
- MRI most sensitive for early detection
- X-ray changes later (sclerosis, collapse)
Management:
- Protected weight bearing if detected early
- Core decompression rarely beneficial
- Usually progresses to fusion if symptomatic
- May require talonavicular or triple fusion
Subtalar Stiffness
Universal Complication:
Expected Loss of Motion:
- 50-70% loss of subtalar motion typical
- Inversion more affected than eversion
- Often well-compensated by ankle and midfoot
- Stiffness may protect against arthritis pain
Functional Impact:
- Walking on flat ground usually normal
- Difficulty on uneven terrain
- Difficulty on slopes/inclines
- May need orthotic support
Treatment:
- Aggressive physical therapy for ROM
- Orthotic devices for support
- Ankle-foot orthosis if severe
- Most patients adapt well
Chronic Pain
Incidence: 10-40% depending on injury severity
Sources:
- Post-traumatic arthritis
- Subtalar stiffness
- Nerve injury (neuroma, dysesthesia)
- Complex regional pain syndrome (rare)
Management:
- Multimodal pain management
- Physical therapy
- Psychological support
- Orthotics
- Surgical options if structural cause
Malunion/Nonunion (with Associated Fractures)
Talar Fracture Malunion:
- Alters hindfoot alignment
- Accelerates arthritis
- May need osteotomy or fusion
Nonunion:
- Rare with adequate immobilization
- May occur with talar neck fractures
- Usually requires surgical fixation
Prevention of Complications
Early Reduction
Single Most Important Factor:
- Reduces skin necrosis risk
- Reduces AVN risk
- Improves overall outcomes
- Target: Reduction within 6 hours
CT Scanning
Detects Occult Fractures:
- Changes management in 20% of cases
- Allows appropriate fixation
- Prevents displacement during healing
- Improves long-term outcomes
Adequate Immobilization
Prevents Redislocation:
- 4-6 weeks immobilization typical
- Non-weight bearing essential
- Progressive loading protocol
- Serial X-rays to monitor
Aggressive Rehabilitation
Optimizes Function:
- ROM exercises after immobilization
- Strengthening program
- Proprioception training
- Return to activity protocol
Postoperative Care
Rehabilitation Protocol
Phase 1: Protection (0-6 Weeks)
Weeks 0-2:
- Below-knee backslab or cast
- Strictly non-weight bearing
- Crutches or knee scooter
- Elevation and ice
- DVT prophylaxis (rivaroxaban or enoxaparin)
- Monitor for compartment syndrome (first 48h)
Weeks 2-6:
- Transition to CAM boot or short leg cast
- Continue non-weight bearing
- Begin ankle ROM exercises (if tibiotalar stable)
- Gentle active dorsiflexion/plantarflexion
- Do NOT invert/evert (protect subtalar healing)
X-ray Schedule:
- Post-reduction (immediate)
- 2 weeks
- 6 weeks
CT Scan:
- MANDATORY after reduction to detect occult fractures
- Usually performed within 24-48 hours of reduction
Phase 2: Progressive Loading (6-12 Weeks)
Weeks 6-8:
- X-rays to confirm healing
- Begin partial weight bearing in CAM boot (25-50%)
- Progressive increase based on pain
- Continue ankle ROM
- Begin gentle subtalar ROM
Weeks 8-12:
- Progress to full weight bearing
- Wean from CAM boot to supportive shoe
- Physical therapy 2-3x per week
- Focus on proprioception and balance
- Strengthening exercises
Phase 3: Return to Function (3-6 Months)
Months 3-4:
- Full weight bearing in regular shoes
- Progress strengthening
- Sport-specific training if applicable
- Continue balance and proprioception work
Months 4-6:
- Return to sports/full activity
- May have persistent subtalar stiffness
- Monitor for signs of post-traumatic arthritis
Monitoring for Complications
Avascular Necrosis (AVN):
- Hawkins sign on X-ray at 6-8 weeks (subchondral lucency = good blood supply)
- Absence of Hawkins sign may indicate AVN
- MRI if high clinical suspicion
- Peak incidence 12-24 months post-injury
Post-Traumatic Arthritis:
- May not manifest for years
- Serial X-rays if symptomatic
- Consider subtalar fusion if symptomatic arthritis develops
Subtalar Stiffness:
- Universal to some degree
- Often well-tolerated
- Physical therapy for ROM
- May protect against arthritis pain
Long-Term Follow-Up
Schedule:
- 6 weeks, 12 weeks, 6 months, 12 months
- Then as needed if symptomatic
What to Assess:
- Pain levels
- ROM (especially subtalar inversion/eversion)
- Gait pattern
- Return to work/sport
- X-ray changes (arthritis, AVN)
Outcomes and Prognosis
Prognostic Factors
Factors Associated with Better Outcomes
Patient Factors:
- Younger age (under 40 years)
- Higher activity level pre-injury
- Non-smoker
- Healthy BMI
Injury Factors:
- Medial dislocation (vs lateral)
- Closed injury (vs open)
- Pure dislocation (no associated fractures)
- Early reduction (within 6 hours)
- Successful closed reduction (vs open)
Factors Associated with Worse Outcomes
Injury Factors:
- Lateral dislocation (much worse than medial)
- Open injury (infection, AVN, arthritis rates all higher)
- Associated fractures (fracture-dislocation)
- Delayed reduction (over 12 hours)
- Need for open reduction
- High-energy mechanism
Expected Outcomes by Injury Type
Pure Closed Medial Dislocation
Best Prognosis Group
Good-Excellent Outcomes: 60-90%
- Most return to work
- Many return to sport (may be delayed)
- Subtalar stiffness common but often asymptomatic
Complications:
- Post-traumatic arthritis: 30-40%
- AVN: 5-10%
- Persistent stiffness: Common (often well-tolerated)
- Chronic pain: 10-20%
Return to Activity:
- Sedentary work: 2-3 months
- Manual labor: 4-6 months
- Contact sports: 6-9 months
- May never regain full subtalar motion
Fracture-Dislocation (Closed)
Moderate Prognosis
Good-Excellent Outcomes: 40-60%
Complications:
- Post-traumatic arthritis: 50-70%
- AVN: 15-20%
- Persistent pain: 30-40%
Outcome Depends On:
- Size and location of fracture
- Quality of reduction
- Successful fixation if needed
Lateral or Open Dislocations
Poor Prognosis
Good-Excellent Outcomes: 20-40%
Complications:
- Post-traumatic arthritis: 60-80%
- AVN: 20-30%
- Infection (open injuries): 10-30%
- Chronic pain: 40-60%
- Need for salvage procedure: 20-40%
Salvage Procedures:
- Subtalar fusion (most common)
- Triple arthrodesis
- Below-knee amputation (severe cases)
Functional Outcomes
Subtalar Motion
Normal Subtalar Motion:
- Inversion: 20-30 degrees
- Eversion: 10-20 degrees
After Subtalar Dislocation:
- Expect 50-70% loss of motion
- Inversion more affected than eversion
- Often well-compensated by ankle and midfoot
- Stiffness may protect against arthritis pain
Activities of Daily Living
Most Patients:
- Normal walking on flat ground
- Difficulty on uneven terrain
- Difficulty with slopes/stairs
- May need orthotic support
Return to Sport
Low Impact (walking, cycling): 3-4 months typical Moderate Impact (running): 6-9 months typical High Impact (basketball, football): 9-12 months typical Elite Athletes: May not return to pre-injury level
Evidence Base
Key Studies and Evidence
Long-Term Outcomes of Subtalar Dislocation
- Follow-up of 39 subtalar dislocations at mean 8.8 years. 70% good-excellent outcomes overall. Medial dislocations had better outcomes than lateral. Open injuries and associated fractures were negative prognostic factors. Post-traumatic arthritis was the most common complication.
- Key point: 70% good-excellent outcomes overall, but lateral and open injuries fare worse
Role of CT in Subtalar Dislocation
- Study demonstrating that 40% of subtalar dislocations have associated fractures not visible on plain X-rays. CT scan after reduction changed management in 20% of cases by identifying fractures requiring fixation or loose bodies requiring removal.
- Key point: CT is mandatory after reduction - 40% have occult fractures
Classification and Treatment
- Classic paper on subtalar dislocations defining the classification system by direction of dislocation. Established medial as most common (85%), described reduction techniques, and identified prognostic factors. Emphasized urgency of reduction for skin viability.
- Key point: Medial 85%, lateral 15% - urgent reduction essential for skin
Open Subtalar Dislocations
- Series of open subtalar dislocations demonstrating significantly worse outcomes compared to closed injuries. Higher rates of infection, AVN, and post-traumatic arthritis. Recommended aggressive debridement and early soft tissue coverage.
Factors Affecting Outcome
- Analysis of factors affecting outcome after subtalar dislocation. Identified associated fractures, lateral direction, and open wounds as negative prognostic factors. Emphasized importance of anatomic reduction and early mobilization after adequate healing.
Summary of Evidence
Level IV Evidence Dominates:
- Most studies are case series and retrospective reviews
- No randomized controlled trials exist
- Injury is too rare for prospective trials
Consistent Findings Across Studies:
- Medial dislocation is most common (80-85%)
- CT detects occult fractures in 40% of cases
- Open and lateral dislocations have worse outcomes
- Early reduction is critical for skin viability
- Post-traumatic arthritis is most common long-term complication
Knowledge Gaps:
- Optimal immobilization duration not well-defined
- Role of K-wire stabilization unclear
- Rehabilitation protocols not standardized
- Long-term functional outcome studies needed
Viva Scenarios
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
"A 25-year-old basketball player presents after a fall landing on an inverted foot. The foot is markedly deformed with an adducted and inverted position. The skin is tented over a prominent bony structure dorsolaterally. How would you manage this?"
Immediate Assessment:
- Neurovascular examination and documentation
- Assessment of skin viability - tented skin is emergency
- Rapid assessment for open wounds
- Brief history of mechanism
Imaging:
- Quick X-rays if skin allows (AP and lateral foot/ankle)
- Do NOT delay reduction for imaging if skin compromised
- Confirm subtalar dislocation (TN and TC disrupted, tibiotalar intact)
Reduction:
- Procedural sedation in ED
- Flex knee to relax gastrocnemius
- Apply longitudinal traction
- Accentuate deformity (increase inversion momentarily)
- While maintaining traction, EVERT and dorsiflex the foot
- Direct pressure on talar head may assist
- Expect audible/palpable "clunk"
Post-Reduction:
- Confirm reduction with X-rays
- CT scan mandatory - 40% have occult fractures
- Below-knee backslab
- Non-weight bearing 2-4 weeks
- Total immobilization 4-6 weeks
Prognosis:
For a closed medial dislocation reduced promptly, expect 60-90% good-excellent outcome. Subtalar stiffness is common but often asymptomatic. Post-traumatic arthritis may develop over years.
"You are unable to reduce a subtalar dislocation despite adequate sedation. What would you do next?"
Causes of Failed Reduction:
- Soft tissue interposition (tendons, capsule)
- Buttonholed extensor retinaculum
- Fracture fragments blocking
- Inadequate analgesia/muscle relaxation
Next Steps:
- Ensure adequate muscle relaxation - consider general anesthesia
- If skin compromised, proceed urgently to OR
- Attempt reduction under GA with complete paralysis
- If still fails, proceed to open reduction
Open Reduction:
- Approach depends on dislocation direction
- Medial dislocation: anteromedial approach
- Lateral dislocation: anterolateral approach
- Identify blocking structure (usually tendon)
- Release/retract blocking tissue
- Reduce under direct vision
- Repair soft tissues
- Address any associated fractures
Post-Operative Care:
Same protocol as closed reduction - splint, non-weight bearing, CT scan if not already done, progression to CAM boot at 2-4 weeks.
"Post-reduction CT of a subtalar dislocation shows a talar neck fracture involving 30% of the joint surface. How does this change your management?"
Significance of Finding:
- This is now a fracture-dislocation (worse prognosis)
- 30% articular involvement is significant
- Talar neck fractures have high AVN risk (Hawkins classification applies)
- Combined injury has 40-60% good outcomes (vs 60-90% pure dislocation)
Management Changes:
- Surgical fixation likely needed for talar neck fracture
- Timing depends on soft tissue status
- ORIF via anteromedial or dual approach
- Screws from anterior to posterior typically
- Restore talar neck length and alignment
Post-Operative Protocol:
- Non-weight bearing extended (8-12 weeks typically)
- Serial X-rays to monitor for AVN (Hawkins sign at 6-8 weeks)
- MRI if concern for AVN
- Protect until union confirmed
Prognosis Discussion:
- AVN risk: 15-20% (higher than pure dislocation)
- Post-traumatic arthritis: 50-70%
- May require fusion if symptomatic arthritis develops
- Counsel patient regarding guarded prognosis
MCQ Practice Points
High-Yield Exam Facts
Definition and Classification
Q: What defines a subtalar dislocation? A: Simultaneous dislocation of the Talonavicular and Talocalcaneal joints, while the Tibiotalar joint remains intact.
Q: Which type is most common? A: Medial (85%) - caused by inversion (basketball foot), foot displaced medially ("acquired clubfoot").
Emergency Management
Q: Why is skin tension an emergency? A: Tented skin over the talar head can necrose within hours. Immediate reduction is mandatory before imaging if skin is compromised.
Q: What is the reduction maneuver? A: Knee flexed (relax gastroc), Traction, Accentuate Deformity, then Reverse Deformity. Medial needs Eversion; Lateral needs Inversion.
Imaging Protocol
Q: What is the critical imaging step after reduction? A: CT Scan is MANDATORY. 40% of cases have occult fractures not visible on X-ray, which may change management.
Complications and Prognosis
Q: What is the most common long-term complication? A: Post-traumatic arthritis (30-40% in pure dislocations, higher in fracture-dislocations).
Q: Which factors predict a worse outcome? A: Lateral dislocation, Open injury, Associated fractures, and Delayed reduction.
Exam Traps
Q: What structure commonly blocks reduction in medial dislocations? A: The Extensor Retinaculum (buttonholing) or the EHL tendon.
Q: How do you distinguish Subtalar from Total Talar dislocation? A: In Subtalar, the Tibiotalar joint is intact. In Total Talar, the talus is dislocated from the tibia as well (extruded).
Australian Context
Australian Context
Epidemiology in Australia
Subtalar dislocations are rare injuries in the Australian trauma system, accounting for approximately 1% of major joint dislocations. Most occur in the younger, active population (ages 20-40 years) through motor vehicle accidents, sporting injuries (particularly Australian Rules Football, rugby, and basketball), and workplace injuries in manual labor occupations.
The injury is more common in males (70-80%) and is typically seen in major trauma centers rather than regional hospitals due to the high-energy mechanisms often involved.
Emergency Department Management
Initial management follows standard protocols:
- Triage as Category 2 (emergency) if skin threatened
- Procedural sedation with propofol or ketamine commonly used
- Regional anesthesia (ankle block) less common for reduction
- Most emergency departments attempt closed reduction
- Transfer to orthopedic theater if failed reduction
Imaging protocols:
- Plain X-rays performed in ED
- CT scan typically performed within 24 hours post-reduction
- Most major trauma centers have 24-hour CT access
Surgical Management
Open reductions are typically performed by orthopedic foot and ankle specialists or trauma surgeons. Most major hospitals have on-call orthopedic coverage capable of managing these injuries.
Rehabilitation usually involves public hospital physiotherapy services or private physiotherapy depending on patient insurance status. CAM boots and crutches are provided through hospital orthotic services.
Return to Work and Compensation
Many patients are covered under workers' compensation schemes if injury occurred at work. Return to work timelines vary significantly based on occupation type, with manual laborers requiring longer periods off work (4-6 months) compared to sedentary workers (2-3 months).
Patients involved in motor vehicle accidents may have Transport Accident Commission (Victoria) or equivalent state-based compensation coverage for ongoing treatment and rehabilitation costs.
Preventive Strategies
Australian workplace health and safety regulations mandate appropriate footwear and fall prevention strategies in high-risk occupations. Sports medicine organizations promote ankle proprioception training and appropriate footwear for field sports to reduce inversion/eversion injuries.
Subtalar Dislocations - Exam Quick Reference
High-Yield Exam Summary
DEFINITION
- •Dislocation of BOTH talonavicular AND talocalcaneal joints
- •Tibiotalar joint remains INTACT
- •Also called 'peritalar dislocation'
- •Named by direction of FOOT relative to talus
TYPES
- •MEDIAL (85%): Foot medial = acquired clubfoot
- •LATERAL (15%): Foot lateral = acquired flatfoot
- •Anterior and posterior are rare
- •Medial has better prognosis than lateral
EMERGENCY
- •Tented skin = URGENT reduction needed
- •Skin necrosis within hours if unreduced
- •Do NOT delay for imaging if skin compromised
- •Document neurovascular status before and after
REDUCTION TECHNIQUE
- •Flex knee (relax gastrocnemius)
- •Longitudinal traction
- •ACCENTUATE deformity first
- •REVERSE: Medial = evert; Lateral = invert
CT MANDATORY
- •40% have occult fractures on CT
- •Plain X-rays miss many injuries
- •CT changes management in 20%
- •Always scan after successful reduction