ASSESSMENT OF ANATOMY IN THE NEGLECTED DEVELOPMENTAL DISLOCATED HIP

Abstract

We assessed the management of 11 neglected developmental dislocated hips in terms of shape of the acetabulum and femoral head pre-operatively and the level of the position of the reduction immediately post-operatively. We compared it with medium term clinical and radiological results.

The shape of the acetabulum and the femoral head can be determined in two planes doing CT or MR of the pelvis. The studies were done to determine the development of the acetabulum and the anatomical fit of the femoral head in the acetabulum. Radius of curvature in the axial and coronal planes was determined of the acetabulum and the femoral head. MR spin echo specification for visualization of the cartilage bone was used. Post-operative radiological namely CT when still in spika, and Shenton’s line and central location of the hip in the direction of the triradiate were subsequently assessed.

Radius of curvature was determined in 6 cases. It varied according to age, but for the older patients the acetabulum was 5mm smaller on average on the coronal views. Eight hips were treated with open reduction. Postoperatively one hip gradually subluxed and dislocated eventually. The hips that remained reduced were initially inferiorly located with an irregular Shenton’s line. Three were treated conservatively with pelvic support osteotomies and planned bone lengthening procedures.

Shape of the femoral head and acetabulum is the most important determining factor in open reduction of neglected DDH. Axial plane MR radius of curvature is not necessarily a true reflection of the shape of the acetabulum. MR coronal views with cartilage enhancement are necessary in assessing the shape of the acetabulum. The inferior position of the reduced hip can be ascribed to the conical shape of the acetabulum and is associated with a maintained reduction.