Morphology of the knee in adult patients with neglected developmental dysplasia of the hip.

Background: Although there have been numerous studies on the treatment of developmental dysplasia of the hip, few have focused on its natural history into adulthood. We observed valgus deformity of the knee in a group of adult patients with developmental dysplasia of the hip. To the best of our knowledge, there has been no detailed study of that condition. The purpose of this study was to investigate structural changes of the knee in patients with neglected developmental dysplasia of the hip.

Methods: Thirty-four adult patients with neglected developmental dysplasia of the hip and ten healthy adults were evaluated. The lower extremities were grouped according to the severity of the dysplasia. The morphology of the knees was evaluated with radiographic measurements, and the groups were compared.

Results: Compared with the control group, the patients with severe developmental dysplasia of the hip had significant valgus deformity of the knee. This finding was associated with an increased vertical dimension of the medial femoral condyle, which led to a valgus inclination of the distal femoral articular surface. Although the femoral sulcus was shallower in the patients with developmental dysplasia of the hip, patellofemoral congruency was not deranged.

Conclusions: The pathologic condition of the hip joint in patients with developmental dysplasia of the hip results in developmental changes in the osseous anatomy of the knee joint, with the development of a valgus deformity of the lower extremity. If any surgical intervention is planned in a patient with developmental dysplasia of the hip, the whole lower extremity should be carefully analyzed, with special attention to the morphology of the knee, to avoid creating problems of malalignment.