Chopart Injuries

The topic repeatedly calls the talonavicular (TN) joint the "keystone" and notes that fusion may be needed, but the most examinable consequence — that the TN joint is the keystone of hindfoot motion, not just the medial arch — is worth developing, because it governs salvage decisions after a Chopart injury.

Motion is coupled through the TN joint. Subtalar (hindfoot) inversion/eversion is transmitted forward through the transverse tarsal (Chopart) joint, and the TN joint is its dominant component. As the anatomy section notes, with the heel everted the TN and CC axes are parallel (a flexible foot) and with the heel inverted they diverge (a rigid foot for push-off) — and the TN joint is the pivot of that mechanism.

Why this matters for fusion (the key point). 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. By contrast, an isolated calcaneocuboid or isolated subtalar fusion preserves much more motion. So when post-traumatic arthrosis forces fusion after a Chopart injury, fusing the TN keystone is the most motion-costly option and must be counselled, whereas 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.)

"Restore lateral column length" is the recurring goal of nutcracker repair throughout this topic, and a viva will ask how you actually assess it — so the method is worth setting out.

Why it 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/midfoot arthrosis. Restoring length is therefore the central operative goal.

How to assess it:

• Compare with the contralateral (uninjured) foot. 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 (calcaneus–cuboid–4th/5th metatarsals) should form a smooth, continuous line; loss of cuboid length and a forefoot that deviates laterally (abductus) signal shortening. Look for loss of cuboid height on the lateral/oblique view.
• Intra-operatively. Use fluoroscopic comparison with the normal side, and directly measure 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.

The take-home: do not simply fix the cuboid — measure and restore its length against the other foot, because residual lateral column shortening leaves a fixed forefoot abductus and a poor result.

• 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.

• 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.

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.