Porth's Essentials of Pathophysiology, 4e

Disorders of the Skeletal System: Trauma, Infections, Neoplasms, and Childhood Disorders 1099

C h a p t e r 4 3

The foot progression value serves only to define whether there is an intoeing or outtoeing gait. Intoeing may be secondary to foot deformities or may be due to inward rotation of the femur or tibia, or a combination of the two. 54 Increased internal torsion of the femur (femoral anteversion) is the most common finding. In many cases intoeing is a variation of normal development. Outtoeing is a common problem in chil- dren and is caused by external femoral torsion. Because the femoral torsion persists when a child habitually sleeps in the prone position, an external tibial torsion also may develop. External tibial torsion rarely causes outtoeing; it only intensifies the condition. Outtoeing usually corrects itself as the child becomes proficient in walking. Intoeing due to a condition called metatarsus adduc- tus is a common congenital deformity characterized by forefoot adduction with a normal hindfoot, giving the foot a kidney-shaped appearance 55–57 (Fig. 43-14). It may occur in one foot or both feet. Diagnostic meth- ods include examination of the plantar aspect of the foot, noting the overall shape of the foot and the pres- ence or absence of an arch. The severity of the deformity can be determined by assessing the flexibility of the foot and using a heel bisection line. Normally, a line bisect- ing the heel crosses the forefoot between the second and third toes. In mild metatarsus adductus, the foot is flexible and can be passively manipulated and the line crosses the third toe; in a moderate deformity, the foot is less flexible and the line falls between the third and fourth toes; and in a severe deformity, the foot is more rigid and the line crosses between the fourth and fifth toes. Most infants do not require treatment, although parents are advised to avoid positioning the infant in the prone position with the feet turned in, a position that accentuates metatarsus adductus. Because the condition often corrects itself spontaneously, treatment is usually not instituted until the infant is 6 months of age. 56 When needed, treatment consists of serial long leg casting or a brace that pushes the metatarsals (not the hindfoot) into abduction. Femoral Torsion. Femoral torsion refers to abnormal variations in hip rotation. 54 Hip rotation is measured at the pelvic level with the child in the prone position and the knees flexed at a 90-degree angle (Fig. 43-15A).

A

Medial rotation

Lateral rotation

1

2

3

Thigh–foot angle B

In this position, the hip is in a neutral position. Rotating the lower leg outward produces internal or medial femoral rotation; rotating it inward produces external or lateral rotation. During measurement of hip rotation, the legs are allowed to fall to full inter- nal rotation by gravity alone; lateral rotation is mea- sured by allowing the legs to fall inward and cross. Hip rotation in flexion and extension also can be measured with CT. Excessive internal femoral anteversion is a normal variant commonly seen during the first 6 years of life, especially in 3- and 4-year-old girls. 55 Characteristically, there is 80 to 90 degrees of internal rotation of the hip in the prone position. 54,56 The condition is thought to be related to increased laxity of the anterior capsule of the hip such that it does not provide the stable pres- sure needed to correct the anteversion that is present at birth. Children are most comfortable sitting in the “W” position, with their hips between their knees. It is believed that this position allows the lower leg to act as a lever, producing torsional changes in the femur. When the child stands, the knees turn in and the feet appear to point straight ahead, and when the child walks, the FIGURE 43-15. (A) Hip rotation is measured with the child prone and knees flexed at a 90-degree angle. On outward rotation the leg produces internal (medial) hip and femoral rotation; on inward rotation the leg produces external hip and femoral rotation. (B) Assessment for tibial torsion using thigh–foot angle. When the child is in the prone position with the knee flexed, with normal alignment there is slight external rotation (2); internal tibial torsion produces inward rotation (3); external tibial torsion produces outward rotation (1). (Adapted from Staheli LT.Torsional deformity. Pediatr Clin North Am. 1986;33(6):1373–1383; and Kliegman RM, Neider MI, Super DM, eds. Practical strategies in pediatric diagnosis and therapy. Philadelphia, PA: W.B. Saunders; 1996.)

Back part straight

Only front part bent

FIGURE 43-14. Shape of foot.The left foot is normal, whereas the right foot has metatarsus adductus.