A Pictorial Review of Ankle and Foot Coalitions Focused on Primary and Secondary Findings on Plain Films, CT, and MRI

Presentation Format: Educational poster presentation.

Purpose or Learning Objective: We present our experience at a large tertiary teaching hospital of the imaging of common and uncommon coalitions within the foot and ankle. We demonstrate their imaging features and their secondary effects on adjacent structures due to the altered biomechanics of the ankle.

Methods or Background: Several foot radiographs and subsequently computed tomography or magnetic resonance imaging are performed to search for the causes of foot pain in adolescents. In a significant number of these cases, symptoms are due to intra-articular or extra-articular congenital coalitions of the ankle or foot. A coalition is an abnormal congenital osseous, cartilaginous, or fibrous unification (or a combination of all three) of two or more bones. Clinical presentation of a coalition usually presents in the adolescent period, thought to be caused by progressive ossification of the bones. This condition subsequently leads to restricted range of motion, ankle or foot pain due to abnormal biomechanics/stresses, and unresolving ankle sprains. These abnormal biomechanics on the ankle and foot joint can cause long-term bony changes and early joint degenerative changes that make everyday physical activities difficult. This is a hindrance in this age group at a time when physical activity is performed at a high level.

Results or Findings: We demonstrate examples of common and uncommon coalitions of the subtalar joints, midfoot joints, and metatarsals. We focus on the findings of these changes on all imaging modalities, but also on their radiographic signs, such as the “talar beak” or the ball-and-socket appearance of the talocrural joint in cases of a subtalar coalition. The secondary features of coalitions also include potential tendon sprains and degenerative joint changes in chronic cases.

Conclusion: The complexity of the anatomy of the ankle and foot requires careful attention to identify congenital coalitions. We show how imaging is useful to identify the extent of a coalition and accompanying abnormalities to other structures. We also give examples of radiographic signs that can help identify coalitions. This aids early diagnosis, which is key, especially in the adolescent population for whom physical activity is an important aspect of daily life.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
03 June 2021