Abstract
In a prospective study we assessed the accuracy of 3D-CT in defining the acetabular deficiency in developmental dysplasia of the hip (DDH), comparing pre-operative 3D-CT with plain radiographs, intraoperative stability testing and intraoperative acetabular morphology.
Twenty children (25 hips) with DDH who had open reduction and/or pelvic osteotomy from 1999 to 2001 were studied. On 3C-CT the morphology of the deficiency was described as normal, anterolateral deficient (overlapping shadows), lateral (increased acetabular index only) and global (double acetabulum). At open reduction, the position in which the hip was most stable with axial loading was assessed (Zadeh and Caterall, 2001). The surgeon’s assessment of the acetabular morphology intraoperatively was the standard against which the other modalities were tested. One hip was normal, five had a global and 19 an anterolateral deficiency.
3D-CT correlated well with the acetabular morphology (84%). Plain radiography correlated poorly, especially with the global type (60%). Mid-superior appearance on 3D-CT and lateral appearance on plain radiograph equated with an anterolateral deficiency morphologically. In the global type the hip was unstable in all positions, while the anterolateral type, while in the anterolateral type the hip was always stable in flexion and abduction and in only 31% of hips stable also in abduction and internal rotation.
The mean age at surgery was 3 years (1 to 7). The one hip with a normal acetabulum required open reduction only, the five global types an acetabuloplasty (Tonnis), and the 19 hips with anterolateral deficiency a redirectional (Salter) osteotomy.
3D-CT is helpful in appropriate osteotomy for a specific type of acetabular deficiency in DDH.
The abstracts were prepared by Professor M. B. E. Sweet. Correspondence should be addressed to him at PO Box 47363, Parklands, Johannesburg 2121, South Africa.
