Relationship of anatomic classifications to degenerative changes in untreated developmental dysplasia of the hip

Background and Purpose: In untreated developmental dysplasia of the hip (DDH), degenerative changes of the femoral heads develop mainly in hips with pseurloacetabular formation. But degenerative changes may also occur due to friction between the femoral heads and surrounding soft tissues after prolonged walking. The purpose of this study was to investigate the relationship between anatomic classifications of DDH and clinical manifestations. Methods: Twenty five consecutive patients with untreated DDH who underwent open reduction and reconstructive surgery between 1982 and 2001 were included in this retrospective analysis. All of the patients were female and had unilateral dislocation. The age of the patients ranged from 12 to 28 years (median, 17 years). The relationships among preoperative and postoperative radiographs, and between clinical symptoms, and gross pathology at surgery were analyzed. Results: Based on the height of dislocation and pseudoacetabular formations on plain radiographs, 3 types of dislocations were recognized: 1) low dislocation with pseudoacetabular formation in 6 hips; 2) high dislocation with definite pseudoacetabular formation in 4 hips; and 3) high dislocation without definite pseudoacetabular formation in 15 hips. The incidence of pain, dystrophic radiographic change of the femoral head and the presence of degenerative change at the time of surgery were significantly greater in hips with high dislocation and pseudoacetabular formation and patients with high dislocation without pseudoacetabulum formation (p < 0.05). Conclusion: Degenerative change of the femoral heads can develop in untreated dislocated hips of patients with skeletally mature DDH regardless the height of dislocation and pseudoacetabular formation.