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Tibial Torsion
KEY POINTS
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Rotational abnormalities of the lower extremities (in-toeing and out-toeing) are common in young children, and abnormal rotation is termed torsion .
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In-toeing is caused by one of three types of deformities: metatarsus adductus (during the first year), internal tibial torsion (in toddlers), and increased femoral anteversion (in early childhood).
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Tibial torsion is especially likely with fetal constraint of the legs in a folded and flexed position, and it is frequently associated with positional equinovarus deformity and metatarsus adductus, which each derives from similar types of mechanical constraints.
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Because spontaneous resolution occurs in 95% of cases by 7 to 8 years of age, management is seldom required.
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Surgery is usually only contemplated in skeletally mature individuals with insufficient spontaneous correction. In such cases, an underlying disorder such as cerebral palsy, hip dysplasia, or skeletal dysplasia should be evaluated.
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Angular deformities, such as genu varum (bowlegs) and genu valgum (knock-knees), need to be distinguished from rotational abnormalities.
GENESIS
Rotation refers to the twist of the tibia along its long axis. Normal rotation in direction and magnitude is termed version , and normal values are determined according to age. Abnormal rotation is termed torsion , and the degree of rotation is determined by the angle between the transmalleolar axis at the ankle and the bicondylar axis of the proximal tibia at the knee. Rotational abnormalities of the lower extremities (in-toeing and out-toeing) are common in young children. These abnormalities vary by site with advancing age and usually respond to conservative treatment. In-toeing is caused by one of three types of deformities: metatarsus adductus (during the first year), internal tibial torsion (in toddlers), and increased femoral anteversion (in early childhood). Internal tibial torsion may occur in combination with metatarsus adductus, and it can be accentuated by postures such as prone sleeping with the toes turned in (see Fig. 4.2 C) or sitting in a W position.
Torsion of the tibia is sufficiently common in the normal newborn to be considered a normal variant; however, more severe variations are seen in about 3% of infants. Tibial torsion is especially likely with fetal constraint of the legs in a folded and flexed position, and it is frequently associated with positional equinovarus deformity and metatarsus adductus, each of which derives from similar types of mechanical constraints. During the seventh week of gestation, the lower limb buds rotate internally, bringing the great toe to the midline from its initial lateral position. During fetal life, the legs are molded so that the femurs rotate externally and the tibiae rotate internally. Internal tibial torsion averaging 4 degrees is normal at birth, after which the tibiae rotate externally to an average of 23 degrees in adulthood (as measured by the transmalleolar axis). In support of the concept that tibial torsion occurs late in gestation because of fetal constraint, this deformation is not encountered in premature infants born before 30 weeks of gestation.
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