Abstract:

Objective    To investigate pathological changes of the acetabulum by observing magnetic resonance imaging(MRI) of normal and dislocated hips in children with developmental dysplasia of the hip (DDH).  Methods      12 children with DDH(8 unilateral and 4 bilateral dislocated ones) had MRI of acetabulum, and 8 normal and 16 abnormal hips were observed. Acetabular indexes of bone (BAI) and cartilage (CAI) were measured on the coronal sections, and acetabular anteversion indexes of bone (BAAV) and cartilage (CAAV)were measured on the cross sections. The data were statistically analyzed. Results      There was a correlation between BAI and CAI, and the correlation coefficient of normal hips (0.945) was larger than that of abnormal hips (0.814). Differences in BAAV and CAAV between dislocated and normal groups were significant(P<0.01), and CAAV of abnormal hips was larger than their BAAV(P<0.01). There were correlations between BAI and BAAV, as well as between CAI and CAAV, and corresponding correlation coefficients were 0.884 and 0.822, respectively. Conclusion      Pathological changes of the acetabulum in children with DDH are reflected not only in the acetabular index but also in the direction of acetabulum, and there is a correlation between these two changes. Deformity of the acetabulum is reflected in two aspectsbone and cartilage, which have different degrees of deformity. MRI can be used to evaluate deformity of the cartilage before operation, which is helpful for choosing operative methods and guiding surgery process.

Key words: Developmental dysplasia of the hip; Magnetic resonance imaging; Acetabular anteversion; Acetabular index of bone; Acetabular index of cartilage