Metatarsus Adductus

This 1-year-old boy has a mild, flexible metatarsus adductus deformity of the right foot. The left foot is normal.

Metatarsus adductus, one of the most common childhood foot deformities, describes a medial deviation (adduction) of the forefoot.¹ The lateral border of the foot is convex and the base of the fifth metatarsal has increased prominence. The medial aspect of the foot is concave. There may be a slight separation between the great and second toe.

Metatarsus adductus occurs in 1 per 1000 live births, affects boys and girls equally, and is bilateral in approximately 50% of affected children. The condition is believed to be secondary to normal in utero positioning.¹ It is more common in firstborn children because of the greater molding effect of the primigravid uterus and abdominal wall. The hips are typically flexed, abducted, and externally rotated while the knees are flexed and the lower legs are inwardly rotated. This allows the medial border of both feet to wrap around the posterolateral aspect of the thighs-which is thought to produce forefoot adduction.

Physical examination. Metatarsus adductus is usually diagnosed at or shortly after birth. The condition has been classified into 3 categories, based on forefoot flexibility.¹

• Type I deformity (as seen in this case): the forefoot is flexible and corrects past neutral both actively and passively.

• Type II deformity: there is partial flexibility in the forefoot, which corrects passively past neutral but actively only to neutral.

• Type III deformity: the forefoot is rigid and does not correct to neutral, even with passive stretching.

These categories provide a useful way to assess deformity. The range of motion of the ankle, hindfoot, and midfoot is normal in all 3 types.

Radiographic evaluation. AP and lateral weight-bearing radiographs or simulated weight-bearing radiographs are necessary in any child with rigid metatarsus adductus. These images can distinguish a more severe skewfoot deformity from metatarsus adductus. However, radiographs in children with flexible metatarsus adductus are usually of no value because they do not demonstrate flexibility of the forefoot. In metatarsus adductus, the alignment of the hindfoot and midfoot is normal, but there is medial deviation of the forefoot (metatarsals).

Management. Metatarsus adductus tends to resolve spontaneously by 3 years of age. Children with types I and II metatarsus adductus need only observation²; occasionally, a corrective shoe or commercial orthosis can hasten correction.

A type III deformity is best managed by manipulation and serial casting.^1,3 For best results, this should be performed before an infant reaches 8 months of age. The forefoot is manipulated into the correct position while the hindfoot is supported in the neutral position and a short leg cast is applied. The cast is changed at 1- to 2-week intervals until complete correction has been achieved. Most feet will correct in 6 to 8 weeks. After casting, the foot is maintained in a corrective shoe or an orthosis until the child is walking well. Dynamic adduction of the great toe (sometimes called a “searching” great toe) may be observed after satisfactory correction, but this will resolve within 1 to 2 years.

Children with metatarsus adductus rarely require surgical correction.² It is a relatively benign deformity that has been shown to produce minimal disability as an adult. However, if a significant forefoot adduction is present in a child up to 6 years of age, a medial release followed by serial casting can be considered.⁴ After 6 years of age, tarsal or metatarsal osteotomies are necessary.

REFERENCES:1. Crawford AH, Gabriel KR. Foot and ankle problems. Orthop Clin North Am. 1987;18:649-666.
2. Farsetti P, Weinstein SL, Ponseti IV. The long-term functional and radiographic outcomes of untreated and non-operatively treated metatarsus adductus. J Bone Joint Surg. 1994;76A:257-265.
3. Bleck EE. Metatarsus adductus: classification and relationship to outcome of treatment. J Pediatr Orthop. 1983;3:2-9.
4. Asirvatham R, Stevens PM. Idiopathic forefoot-adduction deformity: medial capsulotomy and abductor hallucis lengthening for resistant and severe deformities. J Pediatr Orthop. 1997;17:496-500.