High Yield Overview
Chopart Injuries
Midtarsal Joint | Talonavicular and Calcaneocuboid
TN + CCJoints Involved
RareIncidence
MVACommon Mechanism
ORIFUsually Required
Chopart Injury Patterns
Medial
PatternTN dislocation. Navicular fracture.
TreatmentORIF TN
Lateral
PatternCC dislocation. Cuboid fracture.
TreatmentORIF CC
Combined
PatternBoth columns. High energy.
TreatmentORIF Both
Nutcracker
PatternCuboid compression (Lateral column shortening).
TreatmentORIF + Bone Graft
Critical Must-Knows
- Definition: Injury to the midtarsal (Chopart) joint - Talonavicular (TN) and Calcaneocuboid (CC).
- Importance: Critical for foot flexibility. Missed injury leads to painful arthrosis and flatfoot.
- Mechanism: High-energy (MVA, fall). Forced abduction or adduction of forefoot.
- Treatment: Anatomic reduction essential. ORIF usually required. May need fusion if arthritic.
- Nutcracker: Lateral column compression. Cuboid crushed. Bone graft to restore length.
Examiner's Pearls
- "Chopart joint is the 'transverse tarsal joint' - key for midfoot motion.
- "Talonavicular is the 'keystone' of the medial longitudinal arch.
- "Nutcracker fracture = Cuboid compression. Restore lateral column length.
- "Think of Chopart any time there is significant midfoot swelling/injury.
Clinical Imaging
Imaging Gallery
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Chopart Injury Pitfalls
Missed Injury
High Index of Suspicion. Midfoot injuries are often missed. Look for widening, subluxation on X-ray/CT.
Lateral Column Length
Nutcracker Cuboid. Crushed cuboid shortens lateral column. Must bone graft to restore length.
Compartment Syndrome
Foot Compartments. High-energy Chopart injuries can cause foot compartment syndrome. Monitor and release if needed.
Post-Traumatic Arthrosis
Common Outcome. Even with good reduction, arthrosis is common. May need fusion.
At a Glance: Chopart vs Lisfranc
| Feature | Chopart (Midtarsal) | Lisfranc (Tarsometatarsal) |
|---|---|---|
| Joints | TN + CC | TMT 1-5 |
| Location | Midfoot (Transverse Tarsal) | Midfoot (Forefoot base) |
| Keystone | Talonavicular | 2nd TMT |
| Function | Foot Flexibility/Adaptation | Rigid Lever for Push-off |
| Treatment | ORIF +/- Fusion | ORIF or Primary Fusion |
Mnemonic
TN-CCChopart Joint
T
Talonavicular
Medial column joint
N
Navicular
Keystone of arch
C
Calcaneocuboid
Lateral column joint
C
Cuboid
Nutcracker vulnerable
Memory Hook:Chopart = TN + CC.
Mnemonic
CRUNCHNutcracker Fracture
C
Cuboid
Cuboid bone
R
Reduced
Height reduced (Compression)
U
Underestimated
Often missed
N
Nutcracker
Crushed between bases
C
Column Length
Lateral column shortened
H
Height Restore
Bone graft to restore
Memory Hook:Nutcracker Cuboid.
Mnemonic
FLEXChopart Significance
F
Flexibility
Allows foot to adapt to terrain
L
Longitudinal Arch
TN is keystone of medial arch
E
Essential
Essential for gait
X
X-ray
Weight-bearing X-ray for stability
Memory Hook:Chopart = Foot Flexibility.
Overview and Epidemiology
Definition: Chopart joint (Midtarsal joint) injuries involve the Talonavicular (TN) and/or Calcaneocuboid (CC) joints. The Chopart joint is the boundary between the hindfoot and midfoot and is critical for foot flexibility.
Historical Note: Named after François Chopart (1743-1795), a French surgeon who described amputation through this joint.
Epidemiology:
- Rare: Less common than Lisfranc injuries.
- Mechanism: High-energy (MVA, motorcycle, fall from height). Occasionally low-energy (twisting).
- Pattern: Often associated with other foot injuries.
Anatomy and Pathophysiology
Anatomy:
- Talonavicular Joint: Ball-and-socket joint. Key for inversion/eversion. Keystone of medial longitudinal arch.
- Calcaneocuboid Joint: Saddle-shaped. Less mobile. Part of lateral column.
- Ligaments: Spring Ligament (plantar calcaneonavicular), Bifurcate ligament (calcaneonavicular + calcaneocuboid), Interosseous ligaments.
Biomechanics:
- Transverse Tarsal Joint: TN + CC together. Allows midfoot motion.
- Foot Flexibility: When subtalar joint is everted, TN and CC axes are parallel, allowing flexibility. When inverted, axes diverge, creating rigidity.
Injury Mechanism:
- Forced Abduction/Adduction: Forefoot forced laterally or medially on fixed hindfoot.
- Axial Load: Direct force through midfoot.
- Nutcracker: Forced plantarflexion compresses cuboid between 4th/5th metatarsals and calcaneus.
Classification
Main Classification
| Type | Injury | Key Feature |
|---|---|---|
| Medial Stress | TN Disruption | Navicular fracture, TN subluxation |
| Longitudinal | Combined | TN + CC disruption |
| Lateral Stress | CC Disruption | Cuboid fracture, CC subluxation |
| Plantar | Nutcracker | Cuboid compression |
| Crush | Comminuted | High-energy, multiple fragments |
Often combined patterns. High-energy.
Clinical Assessment
History:
- Mechanism: MVA? Fall? Twisting?
- Pain Location: Dorsal midfoot. Worse with walking.
Physical Examination:
- Swelling: Significant midfoot swelling.
- Tenderness: Over TN and/or CC joints.
- Deformity: May have visible abduction or adduction deformity.
- ROM: Painful midfoot motion.
- Neurovascular: Check pulses and sensation.
- Compartments: Monitor for foot compartment syndrome (especially with crush/high-energy).
Investigations
Imaging:
- X-ray (Foot - AP, Oblique, Lateral): Look for joint widening, subluxation, fractures.
- Weight-Bearing X-rays: If patient can tolerate. Better for subtle instability.
- CT Scan: Essential for surgical planning. Assess comminution, joint congruity.
- MRI: Rarely needed acutely. For ligamentous assessment if occult injury.
Key Findings:
- TN Gap: Widening or incongruity of Talonavicular joint.
- CC Subluxation: Malalignment of Calcaneocuboid joint.
- Cuboid Compression: Loss of cuboid height (Nutcracker).
- Lateral Column Shortening: Compare to contralateral.
Management Algorithm
📊 Management Algorithm
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Non-Operative (Rare)
Only for Truly Stable, Non-Displaced Injuries.
- Criteria: Anatomic alignment. No subluxation. Weight-bearing X-ray stable.
- Immobilization: NWB Cast/Boot 6-8 weeks.
- Transition: PWB then FWB as tolerated.
- Follow-up: Serial X-rays to confirm no displacement.
Most Chopart injuries need surgery.
Surgical Technique
Talonavicular ORIF
- Approach: Dorsomedial incision over TN joint.
- Reduction: Reduce TN joint. Joystick with K-wire in navicular.
- Fixation:
- Screws (3.5mm Cortical or Headless) across TN.
- Bridge plate if comminuted.
- Assess Spring Ligament: Repair if disrupted.
- Closure: Layered.
TN is the key joint - must be anatomic.
Complications
Complications
| Complication | Risk Factor | Management |
|---|---|---|
| Post-Traumatic Arthrosis | Cartilage damage | Fusion (TN and/or CC) |
| Malunion/Lateral Column Short | Inadequate reduction | Osteotomy / Lengthening |
| Compartment Syndrome | High-energy | Fasciotomy |
| Stiffness | Prolonged immobilization | Physiotherapy |
| Wound Complications | Swelling | Staged surgery if needed |
Postoperative Care
- NWB: 6-12 weeks (depending on fixation stability and healing).
- Cast/Boot: Initially NWB cast, then transition to boot.
- ROM: Gentle ROM when fixation secure.
- Weight-Bearing: Progress PWB to FWB at 8-12 weeks.
- Physiotherapy: After healing. Gait training. Strengthening.
Outcomes
- Good Reduction: Better long-term outcomes.
- Post-Traumatic Arthrosis: Common even with anatomic reduction. May need fusion.
- Lateral Column Length: Critical. Shortening leads to painful abductus.
Evidence Base
Chopart Joint Importance
Key Findings:
- Described the importance of TN joint for arch stability.
- TN is the 'keystone' of the medial longitudinal arch.
- Disruption leads to flatfoot.
Clinical Implication: Anatomic TN reduction is essential.
Limitation: Retrospective
Nutcracker Fracture
Key Findings:
- Described the 'Nutcracker' mechanism.
- Cuboid compressed between MT bases and calcaneus.
- Leads to lateral column shortening.
Clinical Implication: Must restore lateral column length with bone graft.
Limitation: Descriptive
Surgical Outcomes
Key Findings:
- Reviewed outcomes of midtarsal injuries.
- Anatomic reduction associated with better outcomes.
- High rate of arthrosis regardless.
Clinical Implication: Aim for anatomic reduction but counsel for arthrosis.
Limitation: Retrospective
Fusion for Arthrosis
Key Findings:
- TN and/or CC fusion effective for post-traumatic arthrosis.
- Good pain relief.
- Accept some loss of motion.
Clinical Implication: Fusion is a reliable salvage if arthrosis develops.
Limitation: Case series
Compartment Syndrome
Key Findings:
- Foot compartment syndrome common in crush/high-energy midfoot injuries.
- Release of all 9 compartments may be needed.
- Monitor closely.
Clinical Implication: Low threshold for fasciotomy in high-energy Chopart injuries.
Limitation: Descriptive
Viva Scenarios
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
The Midfoot Injury
EXAMINER
"What is your diagnosis and management plan?"
EXCEPTIONAL ANSWER
**Chopart Joint Injury with Nutcracker Cuboid.**
1. **Diagnosis**:
- TN widening = TN disruption.
- Cuboid compression = Nutcracker fracture.
- Combined Chopart injury (Medial + Lateral columns).
2. **Immediate**:
- Splint. Elevate. Monitor compartments.
- CT Scan for surgical planning.
3. **Surgical Plan**:
- *TN*: Open reduction. Screw or plate fixation.
- *Nutcracker*: Open reduction. Bone graft to restore lateral column length. Plate fixation.
4. **Post-op**: NWB 8-12 weeks. Serial X-rays.
5. **Prognosis**: Risk of post-traumatic arthrosis. May need fusion if pain persists.
KEY POINTS TO SCORE
Chopart = TN + CC
Nutcracker = Cuboid compression
ORIF both columns
Bone graft for Nutcracker
COMMON TRAPS
✗Missing lateral column shortening
✗Not bone grafting the cuboid
LIKELY FOLLOW-UPS
"What is the mechanism of Nutcracker?"
"What is the long-term prognosis?"
VIVA SCENARIOStandard
The Difference
EXAMINER
"Explain the key differences."
EXCEPTIONAL ANSWER
**Chopart vs Lisfranc.**
**Chopart (Midtarsal):**
- *Joints*: Talonavicular (TN) + Calcaneocuboid (CC).
- *Location*: Transverse tarsal joint (boundary hindfoot/midfoot).
- *Function*: Foot flexibility. Adaptation to terrain.
- *Keystone*: Talonavicular.
- *Treatment*: ORIF. May fuse if arthrosis.
**Lisfranc (Tarsometatarsal):**
- *Joints*: TMT 1-5 (Cuneiform/Cuboid to Metatarsals).
- *Location*: Base of metatarsals.
- *Function*: Rigid lever for push-off. Stability.
- *Keystone*: 2nd TMT (Lisfranc ligament).
- *Treatment*: ORIF or Primary Fusion (especially medial column).
**Summary**: Chopart is more proximal (Transverse Tarsal). Lisfranc is at MT bases.
KEY POINTS TO SCORE
Chopart: TN + CC
Lisfranc: TMT joints
Chopart = Flexibility
Lisfranc = Stability
COMMON TRAPS
✗Confusing the two
✗Not knowing the anatomy
LIKELY FOLLOW-UPS
"What is the keystone of each?"
"What is the Lisfranc ligament?"
VIVA SCENARIOStandard
Nutcracker Mechanism
EXAMINER
"Explain the Nutcracker mechanism."
EXCEPTIONAL ANSWER
**Nutcracker Fracture Mechanism.**
1. **Position**: Foot is plantarflexed and abducted.
2. **Force**: Longitudinal axial load (e.g., fall, MVA).
3. **Compression**: The cuboid is 'nutcracked' between:
- *Distally*: Bases of 4th and 5th metatarsals.
- *Proximally*: Anterior process of calcaneus.
4. **Result**: Cuboid is compressed. Loses height. Lateral column shortens.
5. **Consequence**: Forefoot abduction deformity. Painful gait.
**Treatment**: ORIF with bone graft to restore lateral column length.
KEY POINTS TO SCORE
Cuboid compressed between MT bases and calcaneus
Lateral column shortens
Bone graft to restore length
COMMON TRAPS
✗Not recognizing on X-ray
✗Not bone grafting
LIKELY FOLLOW-UPS
"What graft do you use?"
"How do you assess lateral column length?"
MCQ Practice Points
Chopart Joints
Q: Which joints make up the Chopart (Midtarsal) joint? A: Talonavicular (TN) and Calcaneocuboid (CC).
Keystone
Q: What is the keystone of the medial longitudinal arch? A: The Talonavicular joint.
Nutcracker
Q: What is a Nutcracker fracture? A: Compression fracture of the cuboid, 'nutcracked' between the bases of the 4th/5th metatarsals and the calcaneus.
Nutcracker Treatment
Q: What is the treatment for Nutcracker fracture? A: ORIF with bone graft to restore lateral column length.
Chopart Function
Q: What is the function of the Chopart joint? A: Allows foot flexibility and adaptation to uneven terrain.
Australian Context
- Trauma Centers: Complex midfoot injuries managed at major trauma centers.
- CT Access: CT is standard for surgical planning.
- Sports Context: Midfoot injuries seen in football (tackles), equestrian (stirrup injuries).
High-Yield Exam Summary
Anatomy
- •Chopart: TN + CC
- •TN: Ball-Socket
- •CC: Saddle
- •Keystone: TN
Nutcracker
- •Cuboid compressed
- •Between MT bases + Calc
- •Lateral column short
- •Bone graft to restore
Treatment
- •ORIF standard
- •Anatomic reduction
- •NWB 8-12 weeks
- •Fusion for arthrosis
Pitfalls
- •Missed injury
- •Compartment syndrome
- •Lateral column length
- •Post-traumatic arthrosis