Fact-sheet: Tarsal coalition
Updated on 04/03/2016 at 9:41 PM
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Definition
Abnormal fusion between 2 or more tarsal bones
-The bridge between the bones involved in these synostoses can be: fibrous=syndesmosis
cartilaginous=synchondrosis
osseous=synostosis
Most often congenital (genetic abnormality transmitted in an autosomal dominant pattern),
otherwise acquired (joint involvement of degenerative, inflammatory, infectious origin or related to a static disorder of the foot)
-1% of the population, sex ratio=1
-Often discovered during the 2nd or 3rd decades
-The bony bridge is initially fibrous or cartilaginous in children -->diagnostic delay
-Calcaneonavicular or talocalcaneal synostoses in 90% of cases
-Bilateral in 50% of cases
Clinical features
-Most often asymptomatic -
Ankle pain or instability -
Recurrent sprains
Complications: increased risk of tarsal fractures
Radiography
Frontal, lateral, and external oblique radiographs -
Decrease or disappearance of the physiological space between the tarsal bones involved -
Sclerosis and irregularity of the bone surfaces
Calcaneonavicular synostosis: -
Bony bridge or decreased space between the superomedial angle of the anterior process of the calcaneus and the inferolateral border of the navicular -
Hypoplasia of the talar head -
Anteater nose sign: appearance of an excessively long anterior process of the calcaneus
CT
Complete synostosis: bony bridge between tarsal bones with continuous cortex and cancellous bone
Incomplete synostosis: non union, irregular and sclerotic margins
MRI
T2 fat-sat or STIR weighting to look for edema-like abnormality
Analysis of the nature of the synostotic bridge:
- osseous: continuity of marrow signal
- fibrous: intermediate signal
- cartilaginous: high T2 signal, sometimes close to that of synovial fluid
Management
-Therapeutic abstention if asymptomatic
-Conservative treatment as first-line: cessation of sports activities, immobilization, anti-inflammatory drugs or even corticosteroid injections, physical therapy
-In case of failure, surgical treatment (tarsal arthrodesis)