Paper #54 - ISHA Annual Scientific Meeting 2016

Differences of the Curvature Radius and the Curvature Center between Acetabulum and Femoral Head in Dysplastic Hip Joint

Hironobu Hoshino, MD, PhD, Hamamatsu, Shizuoka JAPAN
Shoichi Nishikino, MD, Hamamatsu, Shizuoka JAPAN
Hiroshi Koyama, MD, PhD, Hamamatsu, Shizuoka JAPAN
Hiroki Furuhashi, MD, Hamamatsu, Shizuoka JAPAN
Yukihiro Matsuyama, Prof., Hamamatsu, Shizuoka JAPAN

Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, JAPAN

FDA Status Not Applicable

Summary: Our study shows that the curvature radius of the acetabulum in dysplastic hips was significantly larger than those in control hips, and the distances between the curvature center of the acetabulum and that of the femoral head were longer in dysplastic hip than in normal hip, which might be responsible for the dynamic instability of dysplastic hips.

Abstract:
Introduction
Acetabular dysplasia is said to be associated with the instability of the hip joint in addition to the stress concentration by less acetabular coverage of the femoral head. If there is the gap between the rotation center of the acetabulum and the rotation center of the femoral head, or the femoral head or the acetabulum is not spherical, that might lose the stability of the hip joint followed by labrum tear or progression of osteoarthritis. The purpose of this study is to investigate the differences of the curvature radius and the curvature center between acetabulum and femoral head in dysplastic hip.
MATERIALS AND METHODS:
Thirty contralateral non-affected hip joints of 30 female patients with labrum tear (control group) and 30 dysplastic hips of 30 female patients with lateral center-edge angle less than 20 degrees (dysplastic group) were recruited in this study. In each case, computed tomography (CT) image was taken from knee joint to pelvis for diagnosis and further treatment of the affected side. The CT data were imported to the three-dimensional analysis software. The curvature radius of the acetabulum, the curvature radius of the femoral head, and the distance between the curvature center of the acetabulum and that of the femoral head were measured.
RESULTS:
The curvature radius of the acetabulum in dysplastic group was significantly larger than those in control group and the distance between the curvature center of the acetabulum and that of the femoral head were longer in dysplastic group than in control group. There were significant negative correlations between the lateral center-edge angle and the curvature center distance in both groups. The direction of deviation in the curvature center of the femoral head to the curvature center of the acetabulum were 2.96mm laterally, 0.29mm anteriorly, and 1.66mm superiorly in dysplastic group, while those were 2.60mm laterally, 0.65mm posteriorly, and 0.51mm inferiorly in control group. The superior deviation of the curvature center of the femoral head to the rotation center of the acetabulum in dysplastic group was significantly higher than those in control group.
CONCLUSIONS:
This study shows that the curvature radius of the acetabulum in dysplastic hips was significantly larger than those in control hips, and the distances between the curvature center of the acetabulum and that of the femoral head were longer in dysplastic hip than in normal hip. Also, the degree of the acetabular coverage of the femoral head was associated with the gap between the curvature center of the acetabulum and that of the femoral head, which might be responsible for the dynamic instability of dysplastic hips. This gap measured in this study might be one of the indices for evaluation of instability in dysplastic hips.