Congenital Vertical Talus

Etiology

The exact etiology of congenital vertical talus is still debatable.[3] More than 50% of the cases are idiopathic, and the remaining are mainly associated with genetic or neuromuscular conditions. Congenital vertical talus can manifest itself in either systemic or isolated forms.[1] In rare instances, it can be associated with a nonsyndromic condition.[3] 

Commonly associated conditions include Marfan syndrome, De Barsy Syndrome, chromosomal abnormalities of 13,15,18,30,31, Multiple pterygium syndrome, Cri du chat syndrome, and muscle abnormalities like ischiocalcaneal band, spinal abnormalities, migration anomalies, and fetal brain abnormalities.[2][5] 

Other possible etiologies are increased intrauterine pressure, muscle imbalance, intrauterine growth retardation, and arrest in fetal development or the rotational development of the foot.[4]

Epidemiology

The estimated prevalence of congenital vertical talus is 1 in 10,000 live births, which qualifies it as a rare condition and contributes to it being difficult to diagnose in a newborn child.[4]

Pathophysiology

Congenital vertical talus is a condition of the foot in which there is plantar flexion of the talus and equinus of the calcaneum bone.[1] There is associated talonavicular dislocation, which is rigid and irreducible. It results in the prominence of the talar head over the medial aspect, and the appearance of rocker bottom on the sole of the foot is seen.[3] 

The valgus and equinus deformity in congenital vertical talus occur mainly due to the contracture of the subtalar joint capsule, tendon Achilles tendon, and involvement of primarily the posterolateral part of the ankle.[3]

The dorsiflexion and abduction at the forefoot and midfoot occur due to the contracture of the peroneus tertius, extensor digitorum longus, tibialis anterior, extensor hallucis longus tendon, extensor hallucis brevis, and dorsal part of the talonavicular capsule.[4] The anterior subluxation of the peroneus longus and tibialis posterior tendon results in dorsiflexion of the ankle joint.[1][2] 

All of this results in hypoplasia of the navicular bone, abnormal shape of the talus, and dorsolateral dislocation of the calcaneocuboid joint.[4]

History and Physical

Whenever a child is suspected of having a congenital vertical talus, a detailed history must be taken from the guardian, including prepartum, intrapartum, and postpartum.[3] It is usually characterized by valgus and equinus at the hindfoot, abduction at the forefoot, and forefoot dorsiflexion at the midtarsal joint.[1] 

Due to the vertical positioning of the talus and weakening of the spring ligament, a convexity over the plantar aspect of the foot develops, which ultimately results in a rocker-bottom appearance.[2] Deep creases can be easily noticed over the dorsolateral aspect of the foot. The talar head can be palpated as a bony prominence over the medial and plantar aspect of the midfoot.

If this condition is left untreated, it may increase the rigidity and development of the adaptive changes in the tarsal bones. When a child starts weight-bearing, callosities develop around the talar head along the medial border of the foot.[4] The forefoot abduction and its rigidity restrict the heel from touching the ground. In all patients with congenital vertical talus, a thorough examination of the neuroaxis should be done to rule out any associated abnormalities.[6]

Evaluation

Anteroposterior and lateral roentgenogram in the neutral position of the foot should be done for infants and standing views for weight-bearing children.[2] Sometimes the diagnosis of congenital vertical talus at birth is challenging due to the lack of ossification of multiple bones in the foot.[3] 

The metatarsals, calcaneus, tibia, and talus are usually ossified at the time of birth. The ossification of the cuboid bone occurs in the first month of life, whereas the ossification of the cuneiforms and the navicular bone usually happens around the ages of 2 and 3 years, respectively.[4] 

As most cases of congenital vertical talus are presented in the newborn period, the relationship of the ossified talus and calcaneum relative to the tibia and the relationship of the metatarsals with regard to the hindfoot becomes important while evaluating the radiographs.

Classical radiological findings are increased in talocalcaneal angle. The long axis of the talus lies vertically and looks parallel on the lateral roentgenogram with the longitudinal axis of the tibia. To establish the diagnosis of vertical talus, forced dorsiflexion, and plantar flexion, roentgenograms are required, which is also helpful in opting out of the diagnosis of calcaneovalgus and oblique talus.[2] 

On lateral views of the roentgenogram, forced dorsiflexion shows decreased tibiocalcaneal angle and malalignment of the long axis of the talus bone with respect to the navicular bone, whereas forced plantar flexion shows malalignment of the long axis of the talus with respect to the first metatarsal.

Treatment / Management

The primary aim of managing congenital vertical talus is to resume the normal functioning of the foot by achieving the correct anatomical alignment between the talus, calcaneum, and navicular bone. Non-invasive conservative management options include manipulation followed by serial casting.[4] 

In cases of congenital vertical talus role of early casting is sporadic with unpredicted mixed outcomes, unlike in congenital talipes equino varus, where early casting is associated with successful outcomes.[7] In cases where conservative treatment fails, surgical intervention is necessary, which can be performed either in a single or multiple stages.[8] Many surgeons initially go for conservative treatment in the form of serial casting until the talonavicular joint is reduced and then plan for minimal surgical procedures.[9] (B2)

The preferable age group for surgical management is below two years.[6][7] Various surgeries are described in the literature for managing congenital vertical talus. The type of surgery mainly depends on the severity of the deformity, the age of the patient, and the surgeon's preference.(B2)

Children below the age of 2 years are usually managed by open reduction of the talonavicular joint, which can be performed using either single-stage or two-stage surgery. If a two-stage surgery is being performed, the first stage usually includes the reduction of the talonavicular joint and lengthening of the extensor tendons, the tibialis anterior tendon. The second stage of surgery includes the lengthening of the peroneal tendons and correction of the equinus contracture through the lengthening of an Achilles tendon and release of the posterior ankle and subtalar soft tissues.[6][9] (B2)

However, nowadays, most surgeons prefer a single-stage procedure due to fewer complications like avascular necrosis of the talus bone. There are basically three main components to the one-stage procedure. The initial first step is to achieve the reduction of the talonavicular joint. The second step is to lengthen the peroneals and toe extensors. The final third step is to correct the equinus contracture of the ankle by lengthening the Achilles tendon and releasing the subtalar and ankle joint capsules.[6][7](B2)

Differential Diagnosis

Congenital vertical talus needs to be differentiated from various other deformities of the foot like congenital talipes equinovarus, calcaneovalgus foot, and posterior medial bowing of the tibia. In congenital vertical talus, displacement of the talonavicular joint is directed medially and downward, whereas, in congenital vertical talus, it is directed laterally and upward. In cases of calcaneovalgus foot, a gap that is palpated between the neck of the talus and navicular bone dorsally occurs primarily due to the forefoot dorsiflexion at the midtarsal joints, vanishes on doing plantar flexion.[3][4]

Staging

Coleman proposed that anatomical classification is widely used, subdividing the congenital vertical talus into two types. Type 1 deformity includes dorsal rigid dislocation of the talonavicular joint. Type II deformity includes the features of type 1 along with subluxation or dislocation of the calcaneocuboid joint. One of the milder forms of congenital vertical talus includes oblique talus, which is primarily diagnosed based on clinical and radiographic workup.[1] 

This form shows a similar clinical picture as seen in the vertical talus, but the deformities are less rigid here. While performing the plantar flexion in such patients, the navicular bone will reduce, whereas, in patients with vertical talus, the navicular bone is rigidly dislocated.[3]

Ogata and Schoenecker classify it into three groups. Group 1 is idiopathic vertical talus without any associated diagnoses. Group 2 is a vertical talus patient with associated congenital anomalies but no neurological deficit. Group 3 is a vertical talus patient with an associated neurological disorder.[10]

Hamanishi divides the vertical talus into five groups based on its association with: (1) spinal anomalies or neural tube defects, (2) neuromuscular conditions, (3) malformation anomalies, (4) chromosomal aberrations, and (5) idiopathic.[10]

Prognosis

The prognosis of the condition varies, and it mainly depends on what age group the condition has been diagnosed with and what was the staging at the time of diagnosis.

Complications

If congenital vertical talus is left untreated, it will result in multiple bony deformities with a rocker-bottom appearance. It also results in callosities formation and difficulty in wearing shoes. Other complications are mainly due to associated disorders or surgery related if needed.