Background

Clubfoot can be classified as either of the following:

• Postural or positional - Technically, these are not true clubfeet
• Fixed or rigid - These are either flexible (ie, correctable without surgery) or resistant (ie, requiring surgical release, though this is not entirely true according to the Ponseti experience ^{[1, 2, 3]} )

The Pirani, Goldner, Di Miglio, Hospital for Joint Diseases (HJD), and Walker classifications have been published, but no classification system is universally used.^{[4, 5, 6]}

In the past, clubfoot surgery was performed in a way that did not differentiate severity. The same procedure was performed for all patients. Bensahel proposed a more individualized approach (ie, addressing only the structures that are required are released), in which the surgery is tailored to the deformity. For example, if the forefoot is well corrected and externally rotated, if there is no cavus, but if there is still significant equinus, a posterior approach alone should suffice (see Treatment).^[7]

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Anatomy

Factors related to bone anatomy include the following:

• Tibia - Slight shortening is possible
• Fibula - Shortening is common
• Talus - In equinus in the ankle mortise, with the body of the talus being in external rotation, the body of the talus is extruded anterolaterally and is uncovered and can be palpated; the neck of the talus is medially deviated and plantarflexed; all relations of the talus to the surrounding bones are abnormal
• Os calcis - Medial rotation and an equinus and adduction deformity are present
• Navicular - The navicular is medially subluxated over the talar head
• Cuboid - The cuboid is medially subluxated over the calcaneal head
• Forefoot - The forefoot is adducted and supinated; severe cases also have cavus with a dropped first metatarsal

Factors related to muscle anatomy include the following:

• Atrophy of the leg muscles, especially in the peroneal group, is seen in clubfeet
• The number of fibers in the muscles is normal, but the fibers are smaller
• The triceps surae, tibialis posterior, flexor digitorum longus (FDL), and flexor hallucis longus (FHL) are contracted
• The calf is smaller and remains so throughout life, even after successful long-lasting correction of the feet

Thickening of the tendon sheaths frequently is present, especially of the tibialis posterior and peroneal sheaths. Contractures of the posterior ankle capsule, subtalar capsule, and talonavicular and calcaneocuboid joint capsules commonly are seen. Contractures are seen in the calcaneofibular, talofibular, (ankle) deltoid, long and short plantar, spring, and bifurcate ligaments. The plantar fascial contracture contributes to the cavus, as does contracture of fascial planes in the foot.

Pathophysiology

Various theories of the pathogenesis of clubfeet have been advanced, including the following:

• Arrest of fetal development in the fibular stage
• Defective cartilaginous anlage of the talus
• Neurogenic factors
• Retracting fibrosis
• Anomalous tendon insertions
• Seasonal variations

With respect to neurogenic factors, histochemical abnormalities have been found in posteromedial and peroneal muscle groups of patients with clubfeet. This is postulated to be due to innervation changes in intrauterine life secondary to a neurologic event, such as a stroke leading to mild hemiparesis or paraparesis. This is further supported by a 35% incidence of varus and equinovarus deformity in spina bifida.

Retracting fibrosis (or myofibrosis) may occur secondary to increased fibrous tissue in muscles and ligaments. In fetal and cadaveric studies, Ponseti also found the collagen in all of the ligamentous and tendinous structures (except the Achilles [calcaneal] tendon), and it was very loosely crimped and could be stretched. The Achilles tendon, on the other hand, was made up of tightly crimped collagen and was resistant to stretching. Zimny et al found myoblasts in medial fascia on electron microscopy and postulated that they cause medial contracture.^{[1, 2, 8]}

Inclan proposed that anomalous tendon insertions result in clubfeet.^[9] However, other studies have not supported this proposal. It is more likely that the distorted clubfoot anatomy can make it appear that tendon insertions are anomalous.

Robertson noted seasonal variations to be a factor in his epidemiologic studies in developing countries.^[10] This coincided with a similar variation in the incidence of poliomyelitis in the children in the community. Clubfoot was therefore proposed to be a sequela of a prenatal poliolike condition. This theory is further supported by motor neuron changes in the anterior horn in the spinal cord of these babies.

Etiology

The true etiology of congenital clubfoot is unknown. Most infants who have clubfoot have no identifiable genetic, syndromal, or extrinsic cause.^[11]

Extrinsic associations include teratogenic agents (eg, sodium aminopterin), oligohydramnios, and congenital constriction rings. Genetic associations include mendelian inheritance (eg, diastrophic dwarfism; autosomal recessive pattern of clubfoot inheritance).

Cytogenetic abnormalities (eg, congenital talipes equinovarus [CTEV]) can be seen in syndromes involving chromosomal deletion. It has been proposed that idiopathic CTEV in otherwise healthy infants is the result of a multifactorial system of inheritance.^[12] Evidence for this is as follows:

• Incidence in the general population is 1 per 1000 live births
• Incidence in first-degree relations is approximately 2%
• Incidence in second-degree relations is approximately 0.6%
• If one monozygotic twin has a CTEV, the second twin has only a 32% chance of having a CTEV

Epidemiology

The incidence of clubfoot is approximately 1 case per 1000 live births in the United States. The incidence differs among ethnicities. For example, it is close to 75 cases per 1000 live births in the Polynesian islands, particularly in Tonga.

The male-to-female ratio is 2:1. Bilateral involvement is found in 30-50% of cases. There is a 10% chance of a subsequent child being affected if the parents already have a child with a clubfoot.

Parker et al pooled data from several birth defects surveillance programs (6139 cases of clubfoot) to better estimate the prevalence of clubfoot and investigate its risk factors.^[11] The overall prevalence of clubfoot was 1.29 per 1,000 livebirths, with 1.38 among non-Hispanic whites, 1.30 among Hispanics, and 1.14 among non-Hispanic blacks or African Americans. Maternal age, parity, education, and marital status were significantly associated with clubfoot, along with maternal smoking and diabetes.

Prognosis

Approximately 50% of clubfeet in newborns can be corrected nonoperatively. Ponseti has reported an 89% success rate using his technique (including an Achilles tenotomy); others have reported success rates of 10-35%. One study analyzed the correction progression of patients with idiopathic clubfeet after the Ponseti technique.^[13] The data indicated that successive castings resulted in reduced cavus and medial crease with a gradual correction of midfoot rotation, adduction, and heel varus. Interestingly, heel equinus improved concurrent with midfoot variables and also with final casting.

Most series report 75-90% satisfactory results of operative treatment (appearance and function of the foot). The amount of motion in the joints of the foot and ankle correlates with the degree of patient satisfaction.^{[14, 15, 16]}

Satisfactory results were obtained in 81% of cases, and the range of ankle movement was a major factor in determining the functional result, which again was influenced by the degree of talar dome flattening (suggesting that the primary bone deformity present at birth dictates the eventual result of treatment). In all, 44% of patients had no dorsiflexion beyond neutral, and 38% of patients required further surgery (nearly two thirds of these were bony procedures).

Recurrence rates of deformity were reported at around 25%, with a range of 10-50%. Menelaus reported a 38% recurrence rate.^{[17, 18]}

The best results were obtained with children older than 3-4 months with a foot large enough to allow the procedure to be performed without compromise (longer than 8 cm, as specified by Simons^{[19, 20]} ). The age at operation is directly related to the result. Less-than-satisfactory results may be associated with overcorrection, which occurs in approximately 15% of cases.

Previous surgery seems to have a deleterious effect on the result.

Steinman et al compared the Ponseti and French functional methods for idiopathic clubfeet (265 feet [176 patients] by the Ponseti method; 119 feet [80 patients] by the French functional method).^[21] The study showed that although there was a trend toward improved results with the Ponseti method, the difference was not significant. Parents chose the Ponseti method twice as often as the French functional method. Initial correction rates were 94.4% for the Ponseti method and 95% for the French functional method.

Relapses occurred in 37% of the Ponseti-method feet, and in a third of these cases, further nonoperative treatment was successful; however, surgical treatment was necessary for the other two thirds.^[21] Relapses occurred in 29% of the feet treated by the French functional method; surgical intervention was necessary in all those cases. At the latest follow-up, outcomes with the Ponseti method were good in 72% of cases, fair in 12%, and poor in 16%. For the French functional method, outcomes were good in 67%,fair in17%,and poor in 16%.

Parada et al reviewed the safety of general anesthesia in infants who underwent percutaneous tendoachilles tenotomy. The procedure was performed in 137 patients (182 tenotomies). Of the tenotomies, 92 were unilateral and 45 bilateral. No complications related to anesthesia were identified, and nearly all patients were discharged on the day of surgery.^[22]

Pavone et al achieved good/excellent outcomes in 96% of the 82 patients with 114 congenital clubfeet treated with the Ponseti method from 2004 through 2010, with follow-up through 2011.^[23]

A two-institution review by Miller et al found that strict adherence to the Ponseti method in nonoperative treatment of isolated clubfoot was associated with improved outcome in the form of a reduced risk of subsequent unplanned surgical intervention.^[24]

Clinical Presentation