Vertical Talus

► [Rocker-bottom foot deformity]

Congenital vertical talus is a rare foot deformity characterized by two fixed deformities, equinus of the hindfoot with a vertical talus and dislocation of the talonavicular joint with dorsiflexion of the forefoot at the midtarsal level (Badelon et al. 1984). When the heel is held in marked equinus and the forefoot everted a convex plantar surface of the foot results, which is the reason for the designation 'rocker-bottom deformity.' The deformity may go unrecognized at birth owing to its deceptive resemblance to congenital flexible flatfoot, a benign condition requiring no treatment in the majority of cases (Sullivan 1999). The key clinical element in the differential diagnosis is loss of motion at the subtalar joint in congenital vertical talus, which is unambiguous proof of a fixed deformity (Greenberg 1981). In fact, the talus is locked in plantar flexion by the navicular bone, which is displaced dorsally between the cuneiform and the neck of the talus. On clinical palpation, the head of the talus can be perceived as a hard mass under the sole of the foot. The diagnosis is facilitated by radiographic demonstration of the vertical orientation of the talus with talonavicular joint dislocation and equinus deformity of the calcaneus (Salo et al. 1992). In addition, radiography rules out other causes

Congenital Vertical Talus

Fig. 7.9. Chromosome 4p trisomy syndrome in a male newborn. Note bilateral vertical talus with rocker-bottom foot deformity. The talar axis is oriented vertically, and the calcaneus is in marked equinus (plantar flexion). The forefoot is everted, contributing to the convex deformity of the plantar foot. The navicular bone is not yet ossified, but its cartilaginous nucleus is likely to be displaced dorsally, putting it in close proximity to the talar neck

Fig. 7.9. Chromosome 4p trisomy syndrome in a male newborn. Note bilateral vertical talus with rocker-bottom foot deformity. The talar axis is oriented vertically, and the calcaneus is in marked equinus (plantar flexion). The forefoot is everted, contributing to the convex deformity of the plantar foot. The navicular bone is not yet ossified, but its cartilaginous nucleus is likely to be displaced dorsally, putting it in close proximity to the talar neck

Congenital Vertical Talus
Fig. 7.10. Freeman-Sheldon syndrome in a 16-year-old patient (also seen in Part 2, Fig. 47.5 a, b). Note abnormal plantar flexion of the talus, with dorsal subluxation of the navicular bone. The calcaneus is in mild equinus, and the forefoot is dorsally flexed

of rigid flatfoot that can simulate vertical talus, in particular tarsal coalition (Hefti and Brunner 1999). Although direct X-ray visualization of the unossified navicular bone is lacking in infants, altered articular relationships at the midtarsal level can be inferred from dorsal migration of the ossified cuneiforms. Early recognition of congenital vertical talus is mandatory, since prompt surgical treatment yields satisfactory results whereas delayed or inadequate treatment is associated with persistent deformity and significant complications, including avascular necrosis of the body of the talus, premature osteoarthritis, pain, and gait disturbances (Napiontek 1995; Duncan and Fixsen 1999; Mazzocca et al. 2001; Zorer et al. 2002). Current treatment strategies include one-stage open reduction of the talonavicular dislocation combined with posterior release and subtalar arthrodesis to correct for and maintain the equinus deformity of the hindfoot (Wirth et al. 1994; Ogata et al. 1979).

Congenital vertical talus can occur as an isolated condition or as part of a malformation syndrome (Fig. 7.9) or generalized disorder, notably arthrogryposis and myelomeningocele (Hamanishi 1984; West-cott et al. 1992; Specht 1975).

Vertical transmission for the isolated form of congenital vertical talus (rocker-bottom foot, OMIM 192950) has been reported in a Honduran family (Stern et al. 1989). Nine members of the family over three generations were affected in all. There was incomplete penetrance in one woman with two affected children. Unilateral and bilateral involvement was seen, ranging widely in severity. On the basis of these observations, it was suggested that isolated congenital vertical talus might be inherited as an autosomal dominant trait with variable expression and incomplete penetrance. An affected mother and son were described in another kindred (Hamanishi 1984). Congenital vertical talus occurs in association with bilateral symmetrical subtotal atresia of the external auditory canal in Rasmussen syndrome (OMIM 133705) (Rasmussen et al. 1979). When fully expressed, the syndrome features increased interocular distance, epicanthal folds, congenital exotropia, convergent strabismus, low-set nasal bridge, abnormal external ears with hypoplastic lobes and overfolded helices, dysplastic dental enamel, short 5th fingers, abnormal thumb position, pyloric stenosis, congenital hip dislocation, and umbilical hernia (Julia et al. 2002). Digitotalar dysmorphism (OMIM 126050) is a syndromic association of flexion of fingers with ulnar deviation and bilateral vertical talus (Sallis and Beighton 1972; Stevenson et al. 1975). Moderate short stature may be an additional finding (Dhaliwal and Myers 1985). There is a close similarity between this disorder and distal arthrogryposis type I (OMIM 108120), an autosomal dominant condition with variable expression, which is characterized by a distinct positioning of the hands (tightly clenched fists,with thumb adduction and medially overlapping fingers at birth, followed by striking ulnar deviation of fingers and camp-todactyly in adulthood) and bilateral foot deformities (calcaneovalgus, equinovarus, or a combination of the two). Contractures at other joints, especially the hips, knees, and shoulders, are variably associated (Hall et al. 1982). Similarities in the limb phenotype (flexion and ulnar deviation of fingers in the hands, and talipes equinovarus or vertical talus in the feet) are also recognized in Freeman-Sheldon syndrome (whistling face syndrome, OMIM 193700) (Fig. 7.10), which can in fact be regarded as a form of distal arthrogryposis type I (Bamshad et al. 1996) associated with a characteristic facial morphology (small mouth giving a

'whistling' appearance, deep-sunken eyes with hypertelorism, and retraction of the alae nasi). The idea of a link between distal arthrogryposis type I and the Freeman-Sheldon syndrome is further supported by the occurrence of both disorders in the same pedigree (Klemp and Hall 1995) as well as by the existence of intermediate forms (Krakowiak et al. 1998).

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