Congenital Vertical Talus 

Congenital vertical talus (CVT) is an uncommon disorder of the foot, manifested as a rigid rocker-bottom flatfoot. Its characteristic radiographic feature is a dorsal dislocation of the navicular on the talus. If left untreated, CVT results in a painful and rigid flatfoot with weak push-off power. CVT has been referred to in the literature by several synonyms, including congenital convex pes valgus.^[1]

Recent studies

Thometz et al reported on the MRI pathoanatomy of CVT. They found significant pathology at the level of the subtalar joint. Based on this, they recommended that methods to ensure realignment of the calcaneus under the talus may be a crucial component of deformity correction and to prevent recurrence of deformity.^[2]

Merrill et al published an investigation on skeletal muscle abnormalities and genetic factors related to vertical talus. They found that abnormal skeletal muscle biopsies from the abductor hallucis muscle were common but it was unclear whether this was primary or secondary to the joint deformity.^[3]

Closed treatment, consisting of manipulation and casting, was the earliest form of treatment. Limited surgery was sometimes additionally employed.

Lamy and Weissman recommended excision of the talus, while Eyre-Brook advocated excising the navicular.^{[4, 5]} Today, neither of these techniques is accepted as a definitive treatment.

Several authors, beginning with Osmond-Clarke, Herndon and Heyman, and Coleman and associates, described staged, 2-incision reconstructive surgery.^{[6, 7, 8]} The first stage of the Coleman procedure consisted of lengthening the extensor digitorum longus (EDL), extensor hallucis longus (EHL), and tibialis anterior, with capsulotomies of the talonavicular and calcaneocuboid joints and release of the talocalcaneal interosseous ligament. The second stage consisted of tendo-Achilles lengthening (TAL) and a posterior capsulotomy of the ankle and subtalar joints.

After noting a high incidence of complications with the 2-stage technique, Ogata and colleagues recommended a single-stage procedure with a medial approach.^[9] Kodros and Dias published results they derived using a single-stage approach with a Cincinnati incision.^[10]

Seimon described a single-stage dorsal approach in which the EHL and peroneus tertius were tenotomized and the talonavicular joint was opened.^[11] The talonavicular joint was reduced and held with a Kirschner (K) wire. The Achilles tendon was lengthened percutaneously. Stricker and Rosen published their experience with this technique, as did Mazzocca and associates; both groups noted excellent results with few complications.^{[12, 13]}

The trend toward less surgery for CVT continued with Dobbs and colleagues, who published their technique of casting; percutaneous K-wire pinning of the talonavicular joint; and percutaneous heel-cord tenotomy.^[14] No patients had extensive soft-tissue releases, although some required lengthening of the anterior tibialis or the peroneus brevis tendon. Casting without pinning of the talonavicular joint was associated with recurrence of deformity.

Saini et al reported on their surgical experience with 20 cases of CVT using a dorsal approach. According to the authors, talonavicular reduction was achieved in all 20 feet, and postoperative talocalcaneal and talo-first metatarsal angles were significantly improved. The results were retained at 4-year follow-up.^[15]

Bhaskar described a surgical technique used for idiopathic CVT in 4 feet, similar to the Ponseti technique for clubfoot except that the forces applied were in reverse direction. In the author's experience, the 4 feet were treated by serial manipulation and casting, tendoachilles tenotomy, and percutaneous pinning of the talonavicular joint. To correct the forefoot deformity, according to the author, 4 to 6 plaster cast applications were required. Once the talus and navicular were aligned, percutaneous fixation of the talo-navicular joint with a Kirschner wire and percutaneous tendoachilles tenotomy under anesthesia were performed, followed by application of a cast with the foot in slight dorsiflexion. Following treatment, the mean talocalcaneal angle decreased from 70º to 31º, and the mean talar axis first metatarsal base angle (TAMBA) decreased from 60º to 10.5º.^[16]

Congenital vertical talus (CVT) is defined by an irreducible and rigid dorsal dislocation of the navicular on the talus. If the navicular is reducible on the lateral maximum plantarflexion radiograph, it is deemed an oblique talus, which is better treated with tendo-Achilles lengthening (TAL) and orthotics.

Frequency

Congenital vertical talus (CVT) is an uncommon disorder. Jacobsen and Crawford reported only 273 cases.^[17] Some have estimated the incidence of CVT to be one tenth that of congenital clubfoot.

The etiology is unknown, but congenital vertical talus (CVT) frequently is associated with a wide variety of neuromuscular disorders. Ogata and associates proposed a CVT classification system that divides patients into 3 groups: idiopathic, genetic/syndromic, and neuromuscular.^[9]

Vertical talus is a heterogeneous birth defect resulting from many diverse etiologies. Based on skeletal muscle biopsies, the most common findings in patients with idiopathic vertical talus were abnormal variations in muscle fiber size and type I muscle fiber smallness. These findings were not specific, but they are common in congenital myopathies and distal arthrogryposis. It is unclear whether the biospy findings are primary or secondary to the joint deformity.^[3]

The hallmark of the deformity is an irreducible and rigid dorsal dislocation of the navicular on the talus. Seimon hypothesized that a contracture of the tendo-Achilles posteriorly creates equinus of the calcaneus, with increased verticality of the talus, while contracture of the extensor digitorum longus (EDL) (and sometimes the extensor hallucis longus [EHL] and tibialis anterior) pulls the navicular onto the dorsum of the navicular.^[11]

Clinically, congenital vertical talus (CVT) presents as a rigid flatfoot with a rocker-bottom appearance of the foot. The calcaneus is in fixed equinus, and the Achilles tendon is very tight. The hindfoot is in valgus, while the head of the talus is found medially in the sole, creating the rocker-bottom appearance. The forefoot is abducted and dorsiflexed.

The foot is stiff. In ambulatory children, calluses can develop under the head of the talus, which is very prominent along the plantar-medial foot.

Associated genetic syndromes must be excluded; therefore, a consultation with a pediatric geneticist may be indicated.

Surgery is indicated when the talonavicular joint is found, after a trial of serial casting, to be unreducible. Although most patients require surgical intervention, serial casting with the foot in plantarflexion may occasionally be successful. More importantly, serial casting helps to stretch out the contracted dorsal skin, tendons, and joint capsules, which should be helpful at the time of surgery. Lateral radiographs of the foot in maximal plantarflexion can reveal if the navicular is reducible.

A rigid, irreducible talonavicular dislocation is the hallmark of congenital vertical talus. Contractures of the tendo-Achilles posteriorly and the extensor digitorum longus (EDL) and dorsal talonavicular capsule anteriorly are common. In feet with greater involvement or in older children, more contractures and deformity are present (eg, contractures of the tibialis anterior and extensor hallucis longus (EHL) anteriorly, peroneus tertius and inferior retinaculum of the ankle anterolaterally, peroneus brevis and longus laterally with the calcaneofibular ligament, and the tibiotalar joint posteriorly).

Coleman divided CVT into 2 types: type 1 was associated with a calcaneocuboid dislocation, and type 2 was not. This distinction is important clinically because the type 1 deformity is stiffer and particular attention must be paid to releasing the calcaneocuboid joint.^[6]

If the talonavicular joint is reducible on the lateral maximum plantarflexion view radiograph, surgery is probably not needed. In these cases, TAL and orthotics, such as a University of California Berkeley Laboratory (UCBL) orthosis, may be effective.