Chopart Injuries

The Chopart, or midtarsal, joint is the talonavicular (TN) and calcaneocuboid (CC) joints taken together, and a Chopart injury involves either or both. The joint is the boundary between the hindfoot and the midfoot. It is critical for foot flexibility: it lets the foot adapt to terrain and is essential for gait.

It is named after François Chopart (1743-1795), a French surgeon who described amputation through this joint.

Epidemiology. Chopart injuries are rare, less common than Lisfranc injuries, and often associated with other foot injuries. The mechanism is high-energy (a motor vehicle or motorcycle accident, a fall from height), and occasionally a low-energy twist.

Chopart versus Lisfranc. The two midfoot joints differ in where they sit, which joint is the keystone, and what the joint does for the foot.

The two joints. The talonavicular joint is a ball-and-socket joint, key for inversion and eversion, and the keystone of the medial longitudinal arch. The calcaneocuboid joint is saddle-shaped and less mobile, and it belongs to the lateral column.

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Ligaments. The named restraints:

• Spring ligament (plantar calcaneonavicular)
• Bifurcate ligament, with calcaneonavicular and calcaneocuboid limbs
• Interosseous ligaments

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Biomechanics. Together the TN and CC joints form the transverse tarsal joint, which allows midfoot motion. When the subtalar joint is everted, the TN and CC axes are parallel and the foot is flexible. When it is inverted, the axes diverge and the foot becomes rigid for push-off.

How the joint is injured. The injuring forces:

• Forced abduction or adduction: the forefoot is driven laterally or medially on a fixed hindfoot
• Axial load: direct force through the midfoot
• Nutcracker: forced plantarflexion compresses the cuboid between the 4th/5th metatarsal bases and the calcaneus

Motion is coupled through the TN joint. Subtalar inversion and eversion are transmitted forward through the transverse tarsal joint, and the TN joint is its dominant component. It is the pivot of the parallel-and-divergent axis mechanism described above.

Why this matters for fusion. Because TN and subtalar motion are obligatorily linked, isolated talonavicular arthrodesis abolishes roughly 90 percent of subtalar motion and most midtarsal motion, functionally close to a triple fusion. An isolated calcaneocuboid or isolated subtalar fusion preserves much more motion.

Counselling before fusion. When post-traumatic arthrosis forces fusion after a Chopart injury, fusing the TN keystone is the most motion-costly option and stiffens essentially the whole hindfoot, and the patient must be told so. The lateral-column (CC) joint tolerates fusion with comparatively little functional loss. General fusion technique sits in the triple-arthrodesis and subtalar-arthrodesis topics, and TN degenerative disease in the talonavicular-arthritis topic.

Main and Jowett (1975). The name is two surgeons, not the adjective. Main and Jowett described 71 midtarsal injuries and grouped them by the direction of the deforming force, which is why the type names are directions rather than bones. The classification tells you where the force went, and therefore what else to look for, not which bone is broken.

Reading the types. Medial and longitudinal types are the commonest, and crush injuries have the worst outcome. Combined patterns are frequent, so read the type as the dominant mechanism rather than an exclusive category. A force large enough to disrupt the midtarsal joint has usually done something else to the foot as well.

The nutcracker fracture. A compression fracture of the cuboid, produced by the plantarflexion mechanism above, and often missed. The crushed cuboid shortens the lateral column, and if length is not restored the result is an abductus deformity.

Suspicion. Midfoot injuries are often missed, so keep a high index of suspicion.

History. Establish the mechanism: a motor vehicle accident, a fall or a twist. The pain is over the dorsal midfoot and worse with walking.

Examination. Look for:

• Significant midfoot swelling
• Tenderness over the TN and/or CC joints
• Deformity: there may be visible abduction or adduction
• Painful midfoot motion
• Neurovascular status: pulses and sensation

Compartments. High-energy Chopart injuries can cause foot compartment syndrome, especially after a crush. Monitor the foot compartments and release them if needed.

The imaging sequence. Each study answers a different question:

1. Foot radiographs (AP, oblique, lateral): joint widening, subluxation, fractures
2. Weight-bearing radiographs, if the patient can tolerate them: better for subtle instability
3. CT: essential for surgical planning, to assess comminution and joint congruity
4. MRI: rarely needed acutely; for ligamentous assessment when the injury is occult

What to look for. On radiographs and CT:

• TN gap: widening or incongruity of the talonavicular joint
• CC subluxation: malalignment of the calcaneocuboid joint
• Cuboid compression (nutcracker) and lateral column shortening, assessed as in the next section

CT defines the injury. The plain film can understate a mixed injury, and overlapping bones can hide a combined pattern that CT defines. CT then determines both approaches and the fixation sequence.

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The occult injury. A small avulsion may be the only sign on the radiographs, and the first visible avulsion is a search sign rather than the whole diagnosis. Ongoing focal symptoms after apparently normal films require cross-sectional imaging.

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Why length matters. The lateral column (calcaneus, cuboid, 4th/5th metatarsals) must keep its length for a balanced foot. Shortening, typically from a crushed nutcracker cuboid, pulls the forefoot into a fixed abductus, overloads the lateral border, and drives painful gait and calcaneocuboid and midfoot arthrosis.

The operative goal. Restoring length is therefore the central goal of nutcracker repair. Do not simply fix the cuboid: measure and restore its length against the other foot, because residual shortening leaves a fixed forefoot abductus and a poor result.

How to assess it.

• Contralateral comparison: side-by-side standing AP and lateral radiographs are the most practical reference for the patient's own normal length
• Radiographic alignment: on the AP view the lateral column should form a smooth, continuous line, and loss of cuboid length with a forefoot that deviates laterally (abductus) signals shortening; look for loss of cuboid height on the lateral or oblique view
• Intra-operatively: fluoroscopic comparison with the normal side, and direct measurement of restored length after elevating the impacted articular surface; a lamina spreader, distractor or temporary external fixator regains and holds length before grafting and plate fixation

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Most Chopart injuries need surgery. Non-operative treatment is rare and reserved for truly stable, non-displaced injuries. For the rest, anatomic reduction is essential.

Non-operative. The criteria for it:

• Anatomic alignment
• No subluxation
• Stable on a weight-bearing radiograph

The foot is immobilised non-weight-bearing in a cast or boot for 6-8 weeks, then progressed from partial to full weight-bearing as tolerated. Serial radiographs confirm that nothing displaces.

Operative. ORIF is the standard. The indications:

• Displaced or subluxated TN or CC joint
• Nutcracker (cuboid compression)
• Combined or high-energy injuries

The surgical goals, in order:

1. Anatomic reduction of the TN and CC joints
2. Restoration of lateral column length (bone graft for the nutcracker)
3. Stable fixation: screws, plates, bridge plating

Open or closed reduction. Richter's series (Evidence Base) found open reduction better than closed, especially in fracture-dislocations, and supports closed reduction only for pure dislocations that reduce anatomically.

Talonavicular ORIF. TN is the key joint, and its reduction must be anatomic.

1. Approach: dorsomedial incision over the TN joint
2. Reduction: reduce the TN joint, using a K-wire in the navicular as a joystick
3. Fixation: screws (3.5mm cortical or headless) across the TN joint, or a bridge plate if comminuted
4. Spring ligament: assess it and repair if disrupted
5. Closure: layered

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Nutcracker cuboid repair. The aim is to restore lateral column length and so prevent abductus.

1. Approach: lateral incision over the cuboid
2. Assess: the degree of compression, and measure lateral column length
3. Reduction: elevate the articular surface with a bone tamp
4. Bone graft: fill the defect with structural graft (iliac crest, allograft or femoral head)
5. Fixation: plate with or without screws to hold length
6. External fixator: may be needed to maintain length

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After ORIF the foot is kept non-weight-bearing for 6-12 weeks, then moved to protected weight-bearing.

Reduction drives the result. Good reduction gives better long-term outcomes. Post-traumatic arthrosis is common even after anatomic reduction, and it is the main reason for secondary fusion.

What to tell the patient. The modern series report median AOFAS midfoot scores of 64-76, with quality of life below reference populations after high-energy injuries.

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Global epidemiology

• Chopart injuries are rare, accounting for roughly 0.2 percent of all dislocations; midfoot fracture-dislocations are around five to ten times less common than Lisfranc injuries.
• Most series report a male predominance with a peak in young to middle-aged adults; high-energy mechanisms (road traffic, fall from height, crush) dominate, though a low-energy "twisting" subset exists in athletes.
• Up to a quarter present as combined Chopart-Lisfranc patterns, which carry the worst functional scores.

Side-by-side guidance

Registry and evidence notes

• No dedicated national registry tracks Chopart injuries (they are not implant-arthroplasty procedures); the evidence base is single-centre series and small cohorts, so guidance is consensus- and principle-driven rather than registry-derived.

High- vs limited-resource practice variation

• Well-resourced settings: routine CT, dedicated foot-and-ankle plating systems, cuboid-specific plates, and staged soft-tissue management.
• Limited-resource settings: reliance on plain radiographs and intra-operative fluoroscopy, K-wire and external-fixator constructs to hold column length, and a lower threshold for primary fusion when implants or follow-up are constrained.

• Primary fusion vs ORIF: For severely comminuted, non-reconstructable Chopart joints (especially the talonavicular keystone), the threshold for primary arthrodesis versus attempted reconstruction is debated; no randomised data exist.
• Spanning (bridge) plate vs internal fixation: Whether to span the midtarsal joint with a temporary bridge plate or external fixator versus rigid internal fixation, and when to remove spanning hardware, remains practice-dependent.
• Nutcracker graft choice: Structural autograft (iliac crest), allograft, and synthetic wedges are all used to restore lateral column length; comparative outcome data are lacking.
• Closed reduction in pure dislocations: Richter's data support closed reduction only when truly anatomic; the durability of this approach versus routine open confirmation is uncertain.
• Weight-bearing protocol: Optimal duration of non-weight-bearing (6 vs 12 weeks) and timing of hardware removal are not standardised.