The chopart joint refers to the articulation of the hindfoot and the midfoot. It is characterized by the talonavicular joint and calcaneocuboid joint. The term ‘chopart’ refers to French surgeon Francois Chopart (1743-1795), who performed amputations through this joint in cases of necrosis of the forefoot. The joint primarily allows for inversion and eversion of the foot relative to the ankle.
Injuries to the Chopart joint, often termed Chopart Complex Injuries (CCI) are rare and poorly described in the literature. The incidence is estimated at about 3.6 per 100,000 person years. The average age of a CCI is 37 and about 40% of them are missed or misdiagnosed on initial evaluation. Similar to lisfranc injuries, CCIs can be thought of as a spectrum of disease from soft tissue injuries to complex fracture-dislocations depending on the etiology. About 10-25% are purely ligamentous, with the rest involving fracture dislocations.
Loosely, there are two major etiologies. High energy mechanisms such as a motor vehicle crash or fall from height can lead to fracture-dislocations. Low energy mechanisms involve a twisting force on a plantarflexed foot. Low energy mechanisms can also lead to avulsion fractures. Crush injuries have also been described and are more likely to have significant neurovascular compromise. Associated conditions include cuboid, calcaneus and navicular fractures. CCIs are often misdiagnosed as lateral ankle sprain due to the high likelihood of spontaneous reduction.
Patients typically can describe a violent mechanism of injury. They will have pain, swelling and trouble bearing weight. Deformity may be present, especially in the acute setting. Prominent plantar ecchymosis is often present due to the rupture of strong plantar ligaments. There is also tenderness along the chopart joint. There are no well described special tests for CCIs.
Standard radiographs of the foot and ankle are often insufficient to make the diagnosis. The cyma line, a “lazy S-shape” of the talonavicular and calcaneocuboid joints, can be disrupted. CT is useful for evaluating osseous injuries including fractures and dislocations. MRI is more valuable for osseous contusions and evaluating the degree of soft tissue involvement. The Zwipp classification is most commonly used and is based upon the affected ligaments and bones.
Management depends on the degree of CCI. A conservative approach can be used on isolated ligamentous injuries, bone contusions, extra-articular avulsion fractures and potentially some non-displaced intra-articular injuries. Individuals should be placed in a short leg cast for 6-8 weeks and transition to a lace up ankle brace for another 4-6 weeks. Weight bearing is typically toe touch initially which can be progressed at around 6-8 weeks. Physical therapy begins when the patient comes out of the cast. Surgical indications include displaced intra-articular fractures, dislocations, intra-articular impaction fractures and other complex injury patterns.
There are no clear rehabilitation or return to play guidelines for athletes. The prognosis is not well described in the literature. One study by Van Drop et al found that a delayed diagnosis did not lead to worse outcomes among 9 patients. Post traumatic pes planus is described in some cases. Other sequelae likely includes post traumatic OA, chronic pain and inability to return to sport