Peer Reviewed

Photoclinic

Congenital Vertical Talus

Authors:
Tolulope F. Obafemi, BS; Sam N. Russo, MD; Elizabeth Becker, MD; and Lynnette J. Mazur, MD, MPH
Department of Pediatrics, McGovern Medical School at UT Health, Houston, Texas

Citation:
Obafemi TF, Russo SN, Becker E, Mazur LJ. Congenital vertical talus [published online August 12, 2019]. Consultant360.

 

A full-term boy was born by spontaneous vaginal delivery to a 37-year-old gravida 3, para 3 mother. His birth weight, length, and head circumference were 2885 g (16th percentile), 49 cm (32nd percentile), and 32 cm (third percentile), respectively.

At birth, physical examination findings were unremarkable except for an undescended left testicle and an everted, flat left foot (Figures 1 and 2). The right foot was normal in appearance, but crepitus was felt and heard in both feet. There was no evidence of flexion contractures, other joint abnormalities, or an underlying neuromuscular disease. The family history was negative for similarly affected individuals. The neonate passed screening tests for heart and hearing defects. Radiographs of the left ankle showed vertical orientation of the talus (Figure 3).

Figure 1
Figure 1. Lateral view demonstrating distinct dorsiflexion of the left midfoot and forefoot with hindfoot equinovarus.

Fig 2
Figure 2. Anterior view demonstrating distinct dorsiflexion of the left midfoot and forefoot with hindfoot equinovarus.

Fig 3
Figure 3. Lateral plantar flexion radiograph demonstrating abnormal vertical orientation of the talus..

Discussion. Congenital vertical talus (CVT), also known as rocker-bottom foot or congenital convex pes valgus, occurs in 1 in 10,000 infants, is bilateral in 50% of cases, and has a 1-to-1 male-to-female ratio.1,2 It is characterized by a rigid irreducible dorsolateral dislocation of the talonavicular joint, in which the talus becomes vertically aligned.1,2 In addition to the dislocation, soft tissue contractures commonly occur in the Achilles and extensor digitorum longus tendons.1,2

The differential diagnosis of CVT includes oblique talus, calcaneovalgus, pes planus (flat foot), and talipes equinovarus (clubfoot) (Table 1).3,4 Differentiation can be achieved via thorough physical examination and imaging, the interpretation of which will determine whether surgical correction is required. Magnetic resonance imaging can be useful to rule out an underlying neurological disorder.5

Table 1. Differential Diagnoses of Congenital Vertical Talus

Congenital Deformity

Examination Findings

Radiography Findings

Congenital vertical talus

Rigid hindfoot equinovalgus and dorsiflexed and abducted forefoot—“rocker-bottom deformity”

Vertically positioned talus and irreducible dorsolateral dislocation of talonavicular joint; talus plantarflexion

Oblique talus

Comparable findings to congenital vertical talus

Oblique talus, talonavicular subluxation, talonavicular joint can be reduced with forced plantarflexion

Calcaneovalgus

Hindfoot in excessive dorsiflexion, dorsum often touches distal leg, flexible deformity, plantar flexion normal

Can appear normal, first metatarsal aligned with talus, nondislocated talonavicular joint

Talipes equinovarus

Shortened tibia, hindfoot in equinovarus, forefoot adduction, variable rigidity

Talocalcaneal angle <25°, metatarsal base convergence

Pes planus

Collapse of longitudinal foot arch, hindfoot valgus, forefoot abduction

Normal heel, parallel metatarsals, talonavicular joint sag, increased talocalcaneal angle

Approximately half of CVT cases have associated neuromuscular or chromosomal abnormalities; the other half are idiopathic or nonsyndromic (Table 2).6

Table 2. Clinical Associations of Congenital Vertical Talus

Central nervous system

Myelomeningocele, spina bifida, spinal muscular atrophy, caudal regression syndrome, hydrocephalus

Chromosomal abnormalities

Trisomy 13, trisomy 18, trisomy 21

Genetic syndromes

Prune-belly syndrome, Costello syndrome, De Barsy syndrome, Rasmussen syndrome

Muscular abnormalities

Distal arthrogryposis, multiple pterygium syndrome, neurofibromatosis

Single-gene defects

HOXD10, GDF5 (CDMP1)

In isolated CVT, a positive family history occurs in 12% to 20% of patients.7 In families with an autosomal dominant inheritance pattern, incomplete penetrance has been detected.7 Although the etiology of the disease unknown, it is likely multifactorial. One study of a family with complete penetrance of CVT found a single missense mutation in HOXD10 in each family member, while another study in patients with sporadic CVT did not show HOX mutations.8,9 Another study linked a GDF5 (formerly CDMP1) mutation to deformities in the hands and feet, including a child with isolated CVT.10 Genetic testing for children with multiple anomalies is recommended by the American Academy of Pediatrics.11 Testing with chromosomal microarray analysis has a higher diagnostic yield (15%-20%) than conventional G-banding karyotype analysis (3%).12,13 However, because our patient had an isolated deformity, no genetic testing was deemed necessary.

If left untreated, CVT may result in painful calluses, skin breakdown, foot pain that affects the child’s gait, and difficulty in finding proper footwear.14 Treatment options include casting and surgical correction.7 Traditionally, children up to the age of 3 years are offered 1- or 2-stage open reduction of the talonavicular joint via release of tendons and ligaments of the foot.7 When performed between 9 and 12 months of age, the long-term prognosis is improved. After the age of 3 years, a more permanent deformity persists; these children are usually treated with open reduction and arthrodesis.7

Complications after surgical procedures include degenerative arthritis and avascular necrosis of the talus in adulthood.7 To mitigate surgical complications, a minimally invasive method—the Dobbs method—has been proposed, involving serial casting followed by a percutaneous Achilles tenotomy and limited open reduction of the talonavicular joint.7,15 This method is similar to the Ponseti method for correction of clubfoot with serial casting.7,15 For CVT, approximately 4 to 6 casts are needed. Casts are changed weekly to achieve adequate talonavicular reduction prior to percutaneous surgery.7,15  Following the operation, a dynamic shoe-bar cast is worn 23 hours a day for the first 3 months of life and then 12 to 14 hours a day (naps and nighttime) for 2 more years.7 Stretching exercises with every diaper change also improve outcomes.7

Our patient’s parents opted for serial casting of the foot, and the boy was referred to orthopedics specialists.

References
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