Etiology, Pathoanatomy, Basic Ponseti Technique, and Ponseti in Older Patients

Fig. 34.1

(a) An ambulatory child with untreated clubfoot. (b)Walking on the lateral border of the foot can lead to excessive shoe wear and skin breakdown. (Photo courtesy of J. Norgrove Penny)

Clubfoot can be classified as idiopathic, postural, syndromic, or neurologic. The etiology of idiopathic clubfoot is debated, but the weight of evidence suggests a genetic etiology, though the inheritance pattern is unclear. A postural clubfoot is due to intrauterine positioning and either resolves spontaneously or is easily treated by gentle manipulation or several casts. Syndromic clubfoot is seen in association with a variety of conditions including arthrogryposis multiplex congenital, early amniotic rupture sequence/constriction band syndrome, and skeletal dysplasias, while the neurologic type is due to conditions such as myelomeningocele. Clubfoot associated with syndromic and neuromuscular conditions tends to be more rigid and difficult to treat compared with idiopathic clubfoot.

Pathoanatomy

The pathoanatomy of clubfoot primarily involves abnormalities in the talocalcaneonavicular complex with the calcaneus and navicular rotating around the talus. Both intraosseous (morphologic) and interosseous (alignment) abnormalities are accompanied by soft tissue contractures. Alignment abnormalities are illustrated in the model in (Fig. 34.2a, b). Clinical findings include (1) midfoot cavus, (2) forefoot adductus, (3) hindfoot varus, and (4) hindfoot equinus (CAVE) (Fig. 34.2c).

../images/270913_2_En_34_Chapter/270913_2_En_34_Fig2_HTML.png — Fig. 34.2

Clubfoot is a hindfoot deformity involving malalignment between the talus, calcaneus, and navicular. (*Congenital Clubfoot, Fundamentals of Treatment* by Ponseti () Fig. 34.9a p. 18. By permission of Oxford University Press). (a, b) Osseous components of the deformity are illustrated on this model. (c) Clinical components of the deformity include cavus (midfoot), adductus (midfoot), varus (hindfoot), and equinus (hindfoot)

The talus in clubfoot is smaller than normal, with medial and plantar deviation of the head and neck. The anteromedial surface of the head articulates with the navicular, while the anterolateral surface is uncovered. Paradoxically, the talus is externally rotated within the ankle mortise. The calcaneus is adducted and inverted under the talus with dysplastic facets, while the sustentaculum tali is underdeveloped. The navicular is flattened and medially displaced relative to the talar head and in severe cases articulates with the medial malleolus. The cuboid is medially displaced and inverted relative to the talus, with obliquity at the calcaneocuboid joint in which the medial corner of the joint is proximal to the lateral. At the ankle joint, the tibia articulates only with the most posterior part of the talus, and in severe deformities the posterior tuberosity of the calcaneus may touch the posterior surface of the tibia.

Soft tissue contractures accompany these abnormalities in bony morphology and alignment. The musculotendinous units of the deep posterior compartment (tibialis posterior, flexor digitorum longus, and flexor hallucis longus) are contracted, while the muscles and tendons of the anterior and lateral compartments (tibialis anterior, peroneus longus, and brevis) are elongated. The heel cord is thickened and contracted and is inserted slightly medially on the calcaneus. Multiple soft issue contractures are observed including the deep plantar muscles of the foot, the abductor hallucis, and the posterior tibiotalar, talofibular, calcaneofibular, deltoid, and spring ligaments.

Basic Ponseti Technique

The aim of clubfoot treatment is to obtain a functional, pain-free, plantigrade foot with adequate mobility. The available evidence suggests that while clubfeet treated by both the Ponseti method and extensive soft tissue releases have limited range of motion, reduced strength, and residual deformities, feet treated by the Ponseti method have greater strength and range of motion, fewer degenerative changes, less need for additional surgical procedures, and better functional outcomes. The method is now practiced to some extent in more than 100 countries.

The Ponseti method of serial casting with percutaneous tendoachilles tenotomy is described as extra-articular and “minimally invasive” rather than nonsurgical. Long-term bracing is essential to maintain the correction. Treatment is ideally started shortly after birth. Evidence from programs encompassing all ranges of economic development suggests that task shifting or sharing can be employed as non-orthopedic or even nonmedical caregivers can be trained to apply the casts.

It is preferable to have the child relaxed by feeding immediately prior to and during casting. With the patient supine in the mother’s lap, the person manipulating the foot stabilizes the leg at or above the malleoli without touching the calcaneus. There are two common hand positions (Fig. 34.3). In the first, the index finger puts pressure on the lateral side of the talar head, while the tip of the thumb elevates the first ray and abducts the forefoot. In the second hand position, the thumb puts pressure on the lateral side of the talar head while the index finger dorsiflexes the first ray and abducts the foot. Because the navicular is medially displaced with its tuberosity almost in contact with the medial malleolus, one can feel the prominent lateral part of the talar head as the first bony prominence, just anterolateral to the lateral malleolus. An assistant is helpful in stabilizing the foot and upper thigh.

../images/270913_2_En_34_Chapter/270913_2_En_34_Fig3_HTML.jpg — Fig. 34.3

Two different ways to hold the foot while applying the cast. The diaper should always be removed when applying the plaster to ensure that the cast will extend up to the groin

The talus serves as a fixed fulcrum, while the malalignment is corrected by rotating the hindfoot bones around the talus (Fig. 34.4a). In the initial cast, the first metatarsal is dorsiflexed to correct the cavus (Fig. 34.4b). This supinates the forepart of the foot and aligns the forefoot with the hindfoot, which remains in varus. Progressive abduction of the foot is used to simultaneously correct adductus and varus (Fig. 34.4c, d). The foot should never be pronated as this increases the cavus and locks the calcaneus in varus. Once full abduction is achieved, the ankle equinus is corrected, usually by a percutaneous tenotomy. Long leg casts are used in all stages of casting (Fig. 34.5).

../images/270913_2_En_34_Chapter/270913_2_En_34_Fig4_HTML.png — Fig. 34.4

(a) The talus must be fixed in space during manipulation and casting. (b) The first metatarsal is elevated to correct the midfoot cavus, and the (c) forefoot is abducted while maintaining pressure on the talus. (d) Abduction simultaneously corrects adduction and varus, note the eversion of the calcaneus and the correction from varus to valgus

../images/270913_2_En_34_Chapter/270913_2_En_34_Fig5_HTML.png — Fig. 34.5

(a) Long leg casts are applied with the foot (b) progressively abducted. Once full abduction is achieved, equinus is treated by casting or tendoachilles tenotomy. (Reprinted with permission from Ponseti ())

During the next several casts, care is taken to keep pressure on the lateral talar head during manipulation and casting; otherwise the talus will rotate laterally as the foot is abducted, pushing the lateral malleolus posteriorly, resulting in spurious correction. The foot is maintained in mild plantar flexion during this initial series of casts, leaving correction of equinus until later castings.

Initially, a below-knee cast is applied. After molding is completed, the cast is extended above the knee to the groin. Short leg casts do not hold the calcaneus abducted, allowing the foot to slip within the cast. The cast should be removed at the time of cast change and not the night prior. Dr. Ponseti believed the gains in contracture resolution achieved by the cast could be partially lost, adding more total time to the casting. Soaking and unwrapping the plaster by the parent is more child-friendly than using a cast saw or cast knife (Fig. 34.6). The parents are taught to keep the plaster dry and clean and to examine the toes for any pallor or discoloration that might indicate the cast is too tight.

../images/270913_2_En_34_Chapter/270913_2_En_34_Fig6_HTML.jpg — Fig. 34.6

The cast can be removed by first soaking in warm water and then gently unrolling the wet plaster

The goal of casting is 70° abduction—usually requiring three to six casts. Once this is achieved and the heel is in valgus, the residual equinus is addressed. Attempts to correct the equinus before heel varus and forefoot supination are corrected will result in a rocker-bottom deformity. Avoid external rotation of the tibial axis, which can achieve spurious correction by pushing the lateral malleolus posteriorly.

A tenotomy of the tendoachilles is required to correct residual equinus (ankle dorsiflexion <10°) in approximately 90% of patients once the other components of the deformity are corrected (Fig. 34.7). The tenotomy can be performed under local in the outpatient clinic in infants, but walking aged patients may require ketamine or general anesthesia. The ankle is dorsiflexed by the assistant with the knee in extension, making the tendon taut so it is easily palpated. The scalpel blade is introduced approximately 1 cm above the calcaneal insertion and directed from medial to lateral. The blade is turned 90° to lie horizontally on the anterior surface of the tendon, making the tenotomy from inside to out. A sudden pop is felt along with an increase in dorsiflexion. A dressing and compression bandage are applied, and the child is immediately handed to the mother for feeding. Once the child becomes pacified and the bleeding stops, a toe-to-groin cast is applied with the foot in maximum dorsiflexion (usually 15° or more but never normal) and 60° abduction. This cast is worn for 3 weeks, after which an abduction orthosis is applied.