Metatarsus adductus is the most common foot disorder in infants. It is characterized by a convexity of the lateral foot (Fig. 201-2) and is caused by in utero positioning. It is bilateral in half of cases. Occurring equally in boys and girls, it is more common in first-born children because of the smaller primigravid uterus. Two percent of infants with metatarsus adductus have developmental dysplasia of the hip.
The forefoot is adducted and sometimes supinated, but the midfoot and hindfoot are normal. The lateral border of the foot is convex, while the medial border is concave. Ankle dorsiflexion and plantar flexion are normal. With the midfoot and hindfoot stabilized, the deformity can be pushed beyond a neutral position (into abduction). Older children may present with an in-toeing gait.
True metatarsus adductus resolves spontaneously over 90% of the time without treatment, so reassurance is all that is needed. Metatarsus adductus that does not improve within 2 years needs evaluation by a pediatric orthopedist. Persistent cases may benefit from serial casting or bracing, and potentially surgery. The deformity is not associated with a disability.
It is important to differentiate among metatarsus adductus, metatarsus varus, and skewfoot. Metatarsus varus looks like metatarsus adductus, but it is an uncommon rigid deformity that will need serial casting. Skewfoot is an uncommon deformity thatis characterized by hindfoot plantar flexion, midfoot abduction,and forefoot adduction, giving the foot a Z or serpentine appearance. This needs to be managed very carefully with serial castingand surgery to help reduce the risk of disability in adulthood.
The calcaneovalgus foot is another common foot disorder innewborns that is secondary to in utero positioning. It is characterized by a hyperdorsiflexed foot with forefoot abduction andheel valgus. It is usually unilateral. The appearance may be quitesevere dorsiflexion, but it is not a rigid deformity like congenital vertical talus. Simulated weight-bearing radiographs may benecessary for questionable diagnoses. The calcaneovalgus footwill appear normal or have minimal hindfoot valgus.
This disorder requires no treatment beyond reassurance. Parents can be taught passive stretching exercises for their infant’s foot. Most affected infants realign by 2 years. A calcaneovalgus foot can be associated with bowing of the tibia, whichresolves spontaneously, but a leg length discrepancy may exist.
Hypermobile or pronated feet are seen in 15% of adults. Thechild with flatfeet is usually asymptomatic and has no activitylimitations. Newborn and toddler flatfoot is the result of ligamentous laxity and fat in the medial longitudinal arch. This iscalled developmental flatfoot and usually improves by 6 yearsof age. In older children, flatfoot is typically the result of generalized ligamentous laxity, and there is often a positive family history. Hypermobile flatfoot can be thought of as a normal variant.
In the non–weight-bearing position, the older child with a flexible flatfoot will have a medial longitudinal arch. When weight bearing, the foot pronates (arch collapse) with varying degrees of hindfoot valgus. Subtalar motion (essentially all ankle motion except plantar and dorsiflexion) is normal. Any loss of subtalar motion may indicate a rigid flatfoot, which can be related to tarsal coalition, neuromuscular disorders (cerebral palsy), and heel cord contractures. Radiographs of hyper-mobile flatfeet are usually not indicated.
Hypermobile pes planus cannot be diagnosed until after 6 years ofage; before that, it is developmental pes planus. Reassurance thatthis is a normal variant is very important. Patients who are symptomatic with activity may require education on proper, supportivefootwear, orthotics/arch supports, and heel cord stretching.