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previously visited CALCANEONAVICULAR COALITION
Contributed by: Faculty and residents Children's Hospital, Radiologist, Children's Health System, Birmingham, Alabama., USA.
Patient: 10 year old male
History: bilateral foot pain.
Images:[small]larger

Fig. 1: AP radiograph: Right foot

Fig. 2: Oblique Radiograph: Right foot

Fig. 3: Ap Radiograph: Left foot

Fig. 4: Oblique radiograph: Left foot

Fig. 5: Sagital CT: Left foot

Fig. 6: Sagital CT: Right foot
Findings: Figures 1-4: Radiographs of the feet showing irregular, sclerotic calcaneonavicular joint surfaces with joint narrowing.

Figures 5 & 6: Sagital CT of the feet showing bilateral abnormal processes of the lateral border of the navicular and anterior, superior border of the calcaneous consistent with bilateral calcaneonavicular tarsal coalition of a fibrous/cartilaginous nature.
Diagnosis: Calcaneonavicular Coalition
Discussion: A tarsal coalition is defined as an abnormal union of two or more bones in the mid and/or hindfoot.  The union may be bony (synostosis), cartilaginous (synchondrosis), or fibrous (syndesmosis), and may be the result of a congenital abnormality, trauma, infection, or surgery.

The classification of tarsal coalitions is based on the bones affected. The 2 most common types are calcaneonavicular and talocalcaneal coalition, which together equal ~90% of all cases.  The incidence rate is reported at ~1%; however, the rate may be higher because many patients are asymptomatic. There is a slight predominance of males affected.   Approximately 50% of cases are bilateral, more often these are cases of calcaneonavicular coalition.
 
Patients most commonly present during the 2nd decade of life, once ossification of the coalition occurs, with pain due to restrictions in motion following vigorous activity or strain.  Physical examination can reveal pes planus, with heel valgus, flattening of the medial longitudinal arch, and pronation of the midfoot. Peroneal spasms are occasionally present with inversion of the foot causing significant pain.

Evaluation of a patient with suspected coalition should begin with plain films, inlcuding oblique, AP, and lateral weight-bearing views of the feet.  Most calcaneonavicular coalitions can be seen with plain radiographs; however, talocalcaneal coalitions may be difficult to identify with these studies.  CT or MRI is advantageous for evaluation of complicated cases of tarsal coalition and for preop planning. MRI is particularly useful in depicting nonosseous fibrous and cartilaginous coalitions.

Calcaneonavicular coalition:
Best viewed on a 45° internal oblique radiograph.
Bridge extends from the anterolateral process of the calcaneus to the dorsolateral margin of the navicular bone.
Solid, bony bridge present if an osseous coalition is present.
In fibrous and cartilaginous coalitions, irregularity and narrowing of bone interfaces may occur in addition to sclerosis.

Talocalcaneal coalition:
Difficult to visualize using the 3 standard radiographic projections.
Often involves the middle facet at the talar-sustentaculum tali junction. Less frequently, the anterior and posterior facets are involved.
Harris-Beath (axial) views of the hindfoot are useful for visualizing the posterior and middle facets.
Talar beak - occurs because of limitations of the subtalar joint motion.
C sign - formed by the prominence at the inferior border of the sustentaculum tali and by the medial outline of the talar dome. Seen on lateral projections.
References: Wang, E. Tarsal Coalition. eMedicine. 2008.

Wheeless, C. Calcaneonavicular Coalition. Wheeless' Textbook of Orthopedics.
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Additional Details:

Case Number: 18628372Last Updated: 10-30-2008
Anatomy: Skeletal System   Pathology: Congenital
Modality: CT, Conventional RadiographAccess Level: Readable by all users
Keywords: coalition

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