Role of 3 dimentional CT in the management of developmental dislocation of hip

Objective This study was designed to investigate the role of three-dimensional computed tomography(3D-CT)in imaging bony pathology of developmental dislocation of hip(DDH).Methods Fifty-two patients with DDH underwent CT study preoperatively. There were 17 males and 35 females. The age at the surgery ranged from 1~13 years old. Fifty-eight hips were operated. According to Tnnis classification,six hips were graded as I°,10 as II°,37 as III°,and 5 as IV°. PQ6000 spiral CT machine(Picker) was used for this study. The hips and femoral condyles were scanned and the 3D-CT images were constructed at an independent computer workstation. The acetabulum and femoral head were viewed anterior-posteriorly,laterally and cephalo-caudally. The acetabular index(AI) and femoral neck anteversion(FNA)were measured respectively using the MPR technique.Results The bony pathology of DDH included the abnormalities of acetabulum, femoral head and the congruous relationship between acetabulum and femoral head. FNA abnormality was one of the main elements in the DDH pathology. The value of AI was 32.5° and FNA was 50.2° at the involved side, which were significantly larger than that of the control. The surgical treatment was therefore required. 2. According to the 3D-CT imaging findings and geometric measurement, appropriate treatment was undertaken. Open reduction was performed in 52 hips. Pemberton or Salter type procedures were performed in 32 hips,San Diego or Staheli type procedures in 26 hips,derotational osteotomies in 50 femurs,shortening procedures in 21 femurs. The satisfactory congruity between acetabulum and femoral head was achieved in all the cases at the early stage postoperatively.Conclusions 3D-CT reconstruc-tion is a use-ful means for the preoperative recognition and planning for surgical correction of bony abnormalities because of the close correlation between the intra-operative findings and imaging. However, the pathologies of cartilage and soft tissue structures were not clearly shown by 3D-CT image.