Discussion in 'Spot Diagnosis' started by neo_star, Dec 25, 2012.
What's the condition and which radiological sign is being demonstrated by the arrows ?
Hint: The sign is named after this animal's nose / snout and it eats a very very small creature.
Another Hint: A 10-year-old boy with recurrent ankle sprains and painful flat feet should be evaluated for what possible diagnosis?
I will give the ans in a couple of days and elaborate on the topic ( a little bit ).
Ans: Tarsal coalition and to be more specific - Calcaneo-Navicular coalition.
Fusion of various tarsal bones via fibrous or bony bridges can result in a stiff foot that inverts with difficulty. When inversion of the foot is done during an examination, tenderness occurs on the lateral aspect of the foot, and peroneal tendons become very prominent. Thus, the condition is also referred to as "peroneal spastic flat foot." Unless the condition is very severe and warrants surgery, corrective shoes are usually adequate treatment. Other possible causes of a rigid flat foot include rheumatoid arthritis, septic arthritis, posttraumatic arthritis, neuromuscular conditions, and congenital vertical talus.
The specific sign for this condition is called "Ant-eater Nose sign" and is called so because of the resemblance of the osseous bar between the talus and the calcaneus to the Ant-eater's nose.
Tarsal coalition is a congenital malformation of the foot, thought to be the result of embryonic failure of tarsal segmentation and resulting in abnormal osseous, cartilaginous, or ﬁbrous communication between bones within the hindfoot or mid-foot or between bones of the two areas.
Prevalence is estimated at 1%–2% of the population; however, it may be higher, because many patients are asymptomatic. Tarsal coalition is inherited as an isolated autosomal dominant trait with variable penetrance and may occur in association with other anomalies. Bilateral coalitions are seen in 40%–68% of affected patients.
Symptomatic patients usually present in late childhood or adolescence with restricted subtalar movement and painful, rigid, ﬂatfoot deformity with contracture of the peroneal tendons (peroneal spasticﬂatfoot).
The most common of these tarsal conditions is calcaneonavicular coalition, followed by middle facet talocalcaneal coalition. Patients with calcaneonavicular coalition typically become symptomatic between 8 and 12 years of age, when the cartilaginous calcaneonavicular bar undergoes ossiﬁcation. This coalition
is best demonstrated on a 45Â° internal oblique radiograph of the foot.
Secondary signs are present on the lateralfoot or ankle radiograph, including theanteater nose sign and hypoplasia of the talus . Computed tomography
and magnetic resonance imaging aregenerally not necessary to make the diagnosis of calcaneonavicular coalition, however they may be useful for excluding a coexistent talocalcaneal coalition, which is difﬁcult to diagnose on radiographs.
Treatment of symptomatic calcaneonavicular coalition without tarsal joint degenerative change often requires surgical excision of the calcaneonavicular bar, with interposition ofthe extensor digitorum brevis muscle. Between 77% and 90% of patients have good or excellent results, with treatment failures attributed totalonavicular or subtalar joint arthritis, incomplete excision, or recurrence of the coalition. Patients with tarsal joint degenerative change are best treated with triple arthrodesis.
In conclusion, calcaneonavicular tarsal coalition is a cause of foot pain and deformity that can be identiﬁed on alateral radiograph of the foot or ankle on the basis of the presence of the ant-eater nose sign.
ref - Radiology: Volume 245: Number 2—November 2007
Credit to bb100 for solving the challenge.
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