A common cause of in-toeing in the pediatric patient is a foot deformity called metatarsus adductus. This is a condition in which the metatarsals, the bones in the foot that connect the toes to the midfoot, are pointed towards the direction of the midline of the body. Metatarsus adductus may be present on it’s own, or may be a component of a more extensive deformity, such as clubfoot. It’s incidence is approximately one in every one thousand live births, which is roughly ten times as common as clubfoot.
The exact cause of metatarsus adductus is not known, though there are several theories of how it develops. An increase in intrauterine pressure and a position in the womb that causes the feet to drift inward is the cause that is most commonly accepted. There also may be a familial pattern of metatarsus adductus, indicating that there may be genetic pre-disposition to the deformity. Conditions that cause an increase in ligament laxity, such as Ehlers-Danlos Syndrome, may also contribute to the development of metatarsus adductus.
The evaluation of metatarsus adductus typically involves clinical evaluation as well as x-rays of the foot to determine the position of the developing bones. Clinically, the toes will be pointed inwards towards the midline of the body. Sometimes only the great toe will be involved, in which case the condition is called metatarsus primus adductus. More commonly, however, all five digits are involved. The outside of the foot, or the lateral side, may show a prominent bump right in the middle of the foot. This is most likely the styloid process at the base of the fifth metatarsal, a very good indicator of metatarsus adductus. There also may be an increased gapping between the first and second toes when the child is standing, another classic finding.
X-rays will often reveal the extent of the deformity. The foot and ankle physician evaluating the patient will measure the angle that the forefoot points away from the midfoot and towards the middle of the body. The higher the angle, the more severe the deformity.
Important factors in determining the treatment of metatarsus adductus are the angle of deviation from the midfoot, the involvement of the midfoot and/or rearfoot in the deformity, and the reducibility of the deformity. Reducibility refers to whether or not the forefoot can be corrected with manipulation.
Conservative therapy is typically employed first, especially in children under the age of two years old. Most commonly conservative therapy involves manipulating the foot into a corrected position, and casting the foot so it stays that way. Depending on the degree of deformity, several rounds of casting may be used. This is referred to as serial casting. Besides casting, a splint such as a Ganley splint may be used as well as special shoes to prevent the deformity from recurring.
Surgical therapy is sometimes necessary to correct the deformity in the older child, or a child that has a more severe deformity. Surgical procedures involve both soft tissue and bone surgery, or a combination of both. Soft tissue procedures may include tendon releases and/or ligament release. These types of procedures will allow the foot to be manipulated more easily so that a corrected position can be attained. Bone work may involve taking small wedges of bone out of either the metatarsals or the midfoot in order to straighten out the foot.
After surgery, the patient is typically casted for a period of no less than 8-12 weeks in order to maintain the corrected position. Special shoes may still be required for some time to prevent the deformity from recurring.
There are a number of other musculoskeletal deformities that may be present in the lower extremity that lead to in-toeing. A thorough evaluation of the legs, knees, and hips is warranted in any child that has significant in-toeing. The incidence or torsional deformities of the tibia and femur is increased in the presence of metatarsus adductus, possibly due to the same reasons that the foot deformity develops in-utero. An increased incidence of hip dysplasia has also been reported by some authors, though other refute this correlation.
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