Biomechanics of Pediatric Hip

Abstract

Congenital dislocation of the hip joint includes prenatal, acquired, and developmental dislocation (i.e., femoral head dislocates from the acetabulum gradually after birth). Most of this disease occurs while this disease is named as “congenital”. True congenital dislocation is often intractable, as it has severe dislocation and is accompanied by considerable anomalies. In true congenital dislocation, the acetabulum is extra remarkably shallow and steep, and anterosion of the femur is severe. In acquired or developmental dislocation, environmental factors have more influence on the occurrence of the dislocation than congenital ones. The kind of diaper is one of the most important factors. The prevalence of dislocation is high in some cold areas. In such area, diaper or clothes is set to fix the knee and the hip in the extended position to keep the children from the coldness. In hemilateral dislocation after birth, lying position has influence on its occurrence. Joint instability, which is caused by hormone around birth, and contracture due to the position may cause dislocation. In left wryneck position (i.e., the face rotates in the right and the neck flexes in the left), the trunk often takes right lateral position. In such position, the left hip joint takes adducted position and tends to have adduction contracture, and dislocation may occur in the left hip. The degree of the dislocation varies from children. Hamstring muscles have strong influence on the occurrence of the dislocation. These muscles push the femoral head proximally.