Histologic, histochemical, and ultrastructural studies of the hip joint capsule and ligamentum teres in congenital dislocation of the hip.

The histology, histochemistry, and ultrastructure were investigated in 12 ligamentum teres and 11 hip joint capsule biopsies obtained at open reduction of 9 patients with congenital dislocation of the hip (CDH) and of 2 normal hips. The ages of the patients ranged from 2 months to 4 years and 2 months. In the joint capsule of the dislocated hips, the cells were irregularly distributed, had different shapes, and appeared to be in different stages of functional activity. The collagen fiber bundles were thicker than in the normal capsule, distributed and of varied thickness. The collagen fibrils in the younger patients were thinner than in the normal hip and their diameter increased slightly with age. In the ligamentum teres of the dislocated hips the elastic fibers were thicker and more numerous than in the normal hip, whereas the cells and collagen fibrils showed changes similar to those observed in the capsule. Fibrocartilaginous metaplasia was found in both the capsule and the ligamentum teres in areas compressed by the femoral head. The morphologic and histochemical changes observed in the joint capsule in CDH appeared to be secondary to the mechanical stresses caused by the dislocation.