Tarsal coalition is a congenital disability where two or more tarsal bones in the foot are joined together abnormally. This joint connection may consist of bone, cartilage, or fibrous tissue, which limits the foot’s natural range of motion and flexibility, resulting in discomfort and stiffness, a failure of division during embryonic growth between weeks 6 and 8 of gestation that causes tarsal coalition.
With a low frequency of 1%, the tarsal coalition is a rare cause of painful feet, while many individuals show no symptoms. Asymptomatic patients may remain undiagnosed; however, some individuals present later in adulthood, which can lower their quality of life. This combination of tissues is identified as cartilaginous, fibrous, and bony based on the types of tissues involved. Radiography, computed tomography (CT), and magnetic resonance imaging (MRI) are used in the diagnosis of tarsal coalitions.
A 49-year-old male patient complained of some pain in the right ankle and midfoot that occurred during a normal walk. The patient reported no history of trauma, joint illness, or other serious conditions. The first radiograph of the ankle joint recorded a bony growth linked with the cuboid bone and calcaneum at the medial portion of the mid-to-posterior foot. A tarsal coalition is an improper union or connection between two bones that results in a lack of motion in the afflicted joint, causing generalized pain in the midfoot or hindfoot.
The disorder usually appears in childhood or early adolescence, but it is more common in men. Inadequate segmentation during development is the pathophysiology of tarsal coalition, which leads to improper bone-to-bone connection and a lack of normal joint formation. There are three types of imaging available for diagnosing tarsal coalitions, including radiography, CT, or MRI. If radiographs are not conclusive, physicians prefer CT. There is only one case record of the calcaneum and cuboid forming a coalition, which is reported as very rare. It arises more frequently in combination with other foot abnormalities rather than as a single condition.
The radiographic appearance of tarsal coalition is dependent on the tissue crossing between bones in the case of osseous coalition. In fibrous coalitions, the bony interface is uneven, and joint space loss occurs. In the early stages of the condition, conservative treatment is recommended. On the other hand, surgical excision provides superior results and stops the joint from degenerating later if conservative treatment fails.
While understanding radiographs, CT, and MRI images, knowledge of the normal anatomy of the foot, especially the hindfoot, as well as the various histological subtypes of the tarsal coalition, is important. It also helps to determine the cause of rigid, painful flatfoot in certain situations that other factors cannot explain.
Reference: Shah M, Khalid N, Nazeer R, Akhtar S. An unusual cause of painful foot: calcaneocuboid synostosis. medtigo J Med. 2025;3(2):e3062324. doi:10.63096/medtigo3062324
