The Chopart joint, also known as the midtarsal or transverse tarsal joint, is a complex articulation in the foot that separates the hindfoot from the midfoot. Injuries to this area, which can range from a mild sprain to a severe fracture-dislocation, often result from significant trauma and require precise diagnosis. Because of its location and function, an injury here can deeply affect the foot’s ability to move and bear weight.
Structure and Function of the Chopart Joint
The Chopart joint is not a single joint but a functional unit composed of two distinct articulations that work together. These are the talonavicular joint and the calcaneocuboid joint, which together form an S-shaped joint line across the foot. The joint involves four primary bones: the talus and calcaneus in the hindfoot, and the navicular and cuboid in the midfoot.
The articulation of the talus with the navicular creates a flexible connection, while the calcaneus and cuboid form a more rigid segment. This structure allows the foot to perform movements like inversion and eversion. The Chopart joint also acts as a critical transition zone, allowing the hindfoot to pivot while the forefoot remains stable. On heel inversion during walking, this joint complex locks, which stabilizes the midfoot to prepare for the powerful push-off phase of gait.
Common Ways Injuries Occur
Chopart joint injuries are typically classified based on the amount of force involved, often resulting from high-energy mechanisms. Severe fracture-dislocations frequently occur in scenarios like motor vehicle accidents, significant falls from a height, or crush injuries.
Less severe injuries, such as sprains or avulsion fractures, can result from low-energy trauma, often involving a severe twisting motion. A common mechanism is an indirect force applied to a foot that is plantar-flexed, combined with a sudden, forceful inversion or eversion. These forces can cause a rotational injury or swivel dislocation, where the midfoot twists beneath the hindfoot.
Identifying a Chopart Injury
A Chopart injury is characterized by immediate and severe pain in the midfoot, accompanied by rapid and significant swelling. The person is typically unable to bear any weight on the injured foot. In cases of severe dislocation, a noticeable foot deformity may be present, and a large bruise may appear on the sole of the foot.
Initial diagnosis relies on standard X-rays, which may show disruption of the S-shaped joint line, or evidence of fractures or dislocations. However, the diagnosis is missed in a significant number of cases because the injury can spontaneously reduce, masking the full extent of the damage. A Computed Tomography (CT) scan is commonly recommended to fully assess the extent of osseous injury, including subtle fractures and the degree of joint displacement. Magnetic Resonance Imaging (MRI) is often used to visualize soft tissue damage, such as ligament tears and bone bruising, which is crucial for determining the overall stability of the joint.
Treatment and Long-Term Outlook
Management of a Chopart joint injury depends heavily on its severity. Minor sprains without displacement may be managed non-surgically with rest, ice, compression, and elevation, followed by a period of immobilization. This conservative treatment allows the ligaments to heal before a gradual transition to weight-bearing and physical therapy.
Most fracture-dislocations require surgical intervention, typically Open Reduction and Internal Fixation (ORIF). The goal of this surgery is to restore the anatomical alignment of the joint surfaces. Surgeons use plates, screws, or pins to stabilize the bones and joints. Achieving an accurate reduction is considered the factor most associated with a favorable long-term result.
Recovery involves a long period of non-weight-bearing immobilization, followed by extensive rehabilitation that can last many months. The long-term prognosis often involves functional restrictions, and a high percentage of patients show radiographic signs of post-traumatic arthritis in follow-up studies. Purely ligamentous dislocations, where no bone fragments are present to hold the alignment, often carry a worse prognosis than fracture-dislocations that can be anatomically fixed. Chronic pain and stiffness in the midfoot are common complications, even after successful surgical repair.