Etiology of Congenital Dislocation of the Hip Joint

Summary

Although many anatomical, biochemical, and hereditary factors have been proposed as causative factors for congenital dislocation of the hip joint (CDH), the pathomechanism of CDH can not be explained by these factors alone. In addition to these factors, it is necessary to consider the special forces which lead the femoral head to dislocate from the acetabulum. Activated muscle tone and contraction are primary intrinsic forces that are developed by postural neurophysiological reflexes in a limited number of muscle groups. These forces, plus the increased tension of muscles and tendons around the hip joint, produced by passive extension of the hip and knee joints in the presence of flexion contractures of these joints, are considered to be especially important in the establishment of CDH. Under some conditions, e.g., in the presence of neonatal structural instability of the hip joint, neonatal joint laxity, increased antetorsion of the femur, or primary acetabular dysplasia, passive or explosive active extension of the iliopsoas and hamstring muscles affected by contractures can produce dislocating forces that work against keeping the femoral head in its proper position in the acetabulum. Prevention of CDH has been partially accomplished by improving the method of applying diapers and by permitting free movement of the lower extremities in the neonatal period. The elimination of CDH, however, will be very difficult until new diagnostic measures for early detection and new approaches to treatment are developed for such causative factors as primary acetabular dysplasia, familial joint laxity, and so on.