Talipes Equinovarus

Etiology

TEV is a multifactorial disorder. Causes are structural and genetic. Historically, risk factors for TEV have been described to include maternal smoking, oligohydramnios, and a family history of TEV.[4] Multiple studies have linked maternal smoking to an increased risk of TEV.[3][5][6] A Norwegian study reports that other risk factors for TEV include a parental history of TEV and exposure to solvents.[3] A recent systematic review showed risk factors for TEV included paternal smoking, maternal smoking, maternal BMI >30, amniocentesis, family history, selective serotonin reuptake inhibitor (SSRI) exposure, gestational diabetes, nulliparity, and aboriginal Australian race.[7] However, studies have found no statistically significant increased risk for TEV associated with parental age, parental education level, oligohydramnios, parity, the season of birth, parental alcohol use, or maternal anxiety or depression.[3][4]

Many genetic studies have been performed looking for causes of TEV. No single genetic cause has been found. However, multiple genes have been associated with an increased risk of TEV. It has been proposed that homeobox A and D (HOXA and HOXD) genes, which are involved in apoptosis and muscle contraction, contribute some genetic risk of TEV.[8][9][10] Another recent study has shown there may be an association with the PITX1-TBX4 pathway as well, which is part of the limb development mechanism.[10]

Epidemiology

TEV has a variable penetrance within global populations. On the low end of the spectrum, the incidence in the Chinese population is 0.39 per 1000 live births, whereas, in native Hawaiian and Maori communities, the incidence is 7 per 1000 live births.[11] Estimates within populations of European descent and the United States are 1-2 per 1000 live births.[10][12] Multiple studies have shown a preference for males with a ratio of approximately 2:1. There is no significant difference across ethnicities.[4]

Pathophysiology

Lower limb development occurs due to interactions between the lateral plate mesoderm and outer ectoderm. Multiple signaling pathways exist as part of this development. The exact pathogenesis of the development of TEV has not been found to date. The lack of evidence may be due to variations in genetic codes associated with limb and muscle development, environmental exposure to smoking, and family history of TEV, among other potential risk factors. Ultimately, the characteristic finding of TEV is forefoot adduction, hindfoot varus, midfoot cavus, and hindfoot equinus.[7][10][11]

History and Physical

A thorough history should be taken, including prenatal and birth history, maternal medications, and any maternal risk factors, including smoking, alcohol, or drug use. There is an increased risk of TEV with maternal smoking. However, no association has been seen with alcohol use.[10] It is also essential to obtain family history as there is an increased risk for TEV with a family history positive for TEV.[13] One study has suggested solvent exposure as a possible risk factor as well. Thus, the mother should be asked if she had any personal or industrial exposure to solvents during pregnancy.[3]

On the physical exam of the newborn, the foot will assume a position of equinus and varus. Many times a prenatal ultrasound may indicate the possibility of TEV before the birth of the infant. The acronym CAVE (cavus, adduction, varus, equinus) is useful to recall the position of the affected foot. The midfoot arch is in cavus. The forefoot metatarsals are adducted, while the calcaneus is in varus and equinus.[2][14] Other findings on the physical exam include a small foot and calf, shortened tibia, and posterior and medial foot creases. A physical exam must be complete and inclusive of the whole body due to an increased incidence of associated disorders.[15] Of particular importance is the need to document leg length, skin creases, and calf circumference. Assessment of neurologic status should also be performed. The clinician must also assess the flexibility of the TEV deformity as this provides an idea of prognosis and potential for a non-operative correction.[15]

Evaluation

TEV is typically a clinical diagnosis. However, it is crucial to obtain appropriate imaging studies to assess the patient fully. Due to incomplete ossification in the newborn, the clinical utility of routine radiographs is questionable.[15] Anterior-posterior (AP) and lateral radiographs of the foot and tibia/fibula will aid in the assessment and management of TEV. Radiographic measurement should include the talocalcaneal angle, which will show parallelism in TEV.[15] Routine prenatal ultrasound may indicate a potential TEV deformity. However, this imaging modality is not 100 percent sensitive or specific to diagnose TEV, and clinical exam after birth is the most important clinical diagnostic evaluation. It has been suggested that there is a link between TEV and developmental dysplasia of the hip. However, recent studies have shown that routine imaging to screen the hips of a patient with TEV is not necessary.[16]

Treatment / Management

Treatment of TEV is typically non-operative in the majority of cases. Before the 1990s, most orthopedists managing a patient with TEV used the method described by Hiram Kite. However, Ignacio Ponseti developed a new way of non-operative management, which became widely popular in the 1990s. The success of the Ponseti method has been reported at greater than 90 percent in multiple studies. The Ponseti process involves serial manipulation and casting of the affected limb(s). The molding should not be forceful or painful. The clinician spends about one minute manipulating the foot before casting. The affected limb is cast with weekly cast changes. Initially, the cast is placed with the forefoot supinated. The goal is to align the forefoot and hindfoot with the first metatarsal dorsiflexion. Subsequent casts are placed with gradual forefoot abduction around the talar head. Casting will also bring the calcaneus into valgus or eversion. Typically, after 3-4 casts, the only remaining deformity will be equinus, which is addressed by casting in gradual dorsiflexion. Scher states that percutaneous Achilles tenotomy is required in 80%-90% of cases to correct equinus.[17] Once the deformity has been fixed with casting, the child is then placed into a foot abduction orthosis. In the orthosis, feet are placed shoulder-width apart, in 10 degrees of dorsiflexion and 70 degrees of external rotation. If only 1 foot is being treated, the foot is set in 45 degrees external rotation. Initially, the orthosis is worn for 23 hours per day for 3-4 months, then worn during naps and at night until approximately age 3 to 5.[17](B3)

Surgical management for TEV consists of anterior tibialis tendon transfer, midfoot osteotomies, distal tibial hemiepiphysiodesis, posterior ankle, and subtalar release. These are typically utilized after relapse or failure of non-surgical management. Weakness in eversion with inversion while dorsiflexing the foot can be seen after non-operative management. Weakness is typically managed with an anterior tibialis tendon transfer. Before anterior tibialis tendon transfer, the foot must have recovery of the initial correction. The foot must be able to evert to at least neutral passively. For children greater than 2.5 years of age, the anterior tibialis tendon is transferred from its insertion on the base of the first metatarsal to the lateral cuneiform. The transfer changes its action from dorsiflexion and inversion to dorsiflexion and eversion.[18] Midfoot osteotomies are used for correction of persistent or recurrent forefoot adduction despite casting. Osteotomies are done in children aged 4-9 years old and involve a closing wedge osteotomy over the cuboid and an opening wedge osteotomy through the cuneiforms.[18] Distal tibial hemiepiphysiodesis can be used in patients with recurrent equinus. However, it is not a well-proven method to correct equinus.[19] Posterior ankle and subtalar capsulotomy is also used to correct residual equinus but can be associated with ankle stiffness.[18](B2)

Differential Diagnosis

TEV has a classic appearance, and it is unlikely to be confused with any other diagnosis. However, it is essential to rule out a correctable deformity. Correctable deformities that have the appearance of TEV may be postural and often will self-correct with time. Thus, when planning treatment, one must differentiate between correctable and non-correctable TEV.

Prognosis

The prognosis for TEV is excellent. The vast majority of TEV can be corrected utilizing the Ponseti method of manipulation and sequential casting, followed by foot abduction orthosis. For cases with relapse or incomplete correction, a variety of surgical methods exist that can assist in the correction of the deformity. Multiple studies reports >90% success with the use of the Ponseti method for TEV correction.[17]

Complications

Complications that may occur with TEV include loss of mobility, disability, and decreased quality of life. Treatment complications can include typical cast complications, including skin breakdown, and nerve injury related to pressure over superficial nerves. These are mitigated by the frequent cast changes utilized with the Ponseti method. Weakness in eversion with inversion while dorsiflexing the foot can be seen after non-operative management. Weakness is typically managed with an anterior tibialis tendon transfer. Rocker-bottom foot deformity can also occur, typically this happens as a result of trying to correct the equinus deformity before the adduction and varus deformities.[15] Surgical complications include those related to anesthesia risks, as well as typical surgical risks of pain, infection, wound complications, and blood loss. Complications and failures with surgical care are reported at 13%-50%.[17] One study reported 2% of their patients had serious bleeding complications following percutaneous Achilles tenotomy, most often related to inadvertent injury to the peroneal artery.[20] The greatest complication risk is the recurrence of TEV despite treatment. Reoccurrence typically occurs with the Ponseti method due to poor compliance with orthosis use at home.[17][20]