A calcaneonavicular coalition is an abnormal bridge between the calcaneus and the navicular bone. It is the commonest tarsal coalition, usually becomes painful between ages 8 and 12 as the bridge ossifies, and is best seen on a 45-degree oblique X-ray of the foot as the 'anteater nose' sign. Resection with fat or muscle interposition relieves pain in the large majority.
The child is typically 8 to 12 years old and complains of aching along the outer side of the midfoot, worse after sport or on uneven ground. Parents often report recurrent ankle sprains and a foot that looks flat and feels rigid. Examination shows limited subtalar motion and tenderness over the sinus tarsi.
A 45-degree internal oblique radiograph shows the bar directly; on the lateral view the elongated anterior process of the calcaneus produces the anteater nose sign. CT defines the size and orientation of the bar and rules out a second coalition; MRI is used when the bridge is fibrous or cartilaginous and therefore invisible on plain films.
Treatment starts with a period of immobilisation in a boot or cast for four to six weeks, activity modification and an orthosis. When pain returns, resection of the bar with interposition of the extensor digitorum brevis muscle or fat graft prevents regrowth. Results are excellent in the growing child with preserved joint surfaces; concurrent hindfoot valgus is corrected at the same operation when it is marked.
It is the appearance on a lateral foot X-ray of an elongated anterior process of the calcaneus reaching toward the navicular, resembling an anteater's snout. It is a reliable indirect sign of a calcaneonavicular coalition.
No. Many children settle with immobilisation and orthoses and never need an operation. Surgery is offered when pain returns after non-operative treatment and limits normal activity.
Dr. Mutasem Aldhoon is a leading Pediatric Orthopedic Consultant specializing in complex lower extremity deformities. With extensive experience in advanced joint-sparing and reconstructive techniques, he is the trusted authority for severe pediatric flatfoot and neurological foot reconstructions.
