Resposta ao Caso 2

Tarsal coalition

Tarsal coalition is an abnormal connection between two tarsal bones of the feet. Tarsal coalition is seen in nearly 1% of the population and most often seen between the calcaneus and navicular (calcaneonavicular) or the talus and calcaneus (talocalcaneal). The union can be bony, fibrous or cartilaginous and is a result of abnormal development. As the child matures, the abnormal union can ossify and create abnormal stress on the foot. As a result, children will often experience a loss of mobility and foot pain that presents during the adolescent period. More than half of cases will be bilateral.

 

Radiologic Overview of the Diagnosis:

Radiographs: Talonavicular coalition is difficult to visualize on radiographs, as in this case, and is suggested by secondary findings such as "talar beaking", irregular joint margins, and degenerative change at other joints. Visualization of the talonavicular joint on the lateral view excludes coalition. CT is usually performed to make the diagnosis.

 

Calcaneonavicular coalition is usually easily demonstrated on radiographs. The abnormal connection between the calcaneous and navicular is best demonstrated on the oblique view. The lateral view can demonstrate an elongated anterosuperior calcaneous which extends towards the navicular and termed "anteater’s nose."

 

CT: CT is often used to make the final diagnosis of coalition following radiographic evaluation. Coronal and axial images are usually obtained. CT will demonstrate bony bridging at the respective joints or narrowed irregular margins of the joint in the case of fibrous and cartilaginous coalitions.

 

Key points:

• Coalition often presents in adolescence with foot stiffness and pain.
• Coalition is difficult to see directly on radiographs and often suggested by secondary signs
• CT is often performed to make the final diagnosis.