[Role of magnetic resonance in the evaluation of the normal and osteochondrosis hip in early and late childhood].

INTRODUCTION: Despite MR potentials, few studies investigate the features of normal hips and of hip osteochondrosis in early and late childhood. We report our personal experience with MRI of hip osteochondrosis in pediatric patients.

MATERIAL AND METHODS: MR images were obtained with total body MR equipment at medium and high fields. The normal hips were studied in children aged 34 months to 6 years with abdominal-urinary tract disorders and in 9 patients of the same age with unilateral Perthes disease. Hip osteochondrosis was studied in 6 children with Catteral's type III and IV and in 3 with type I and II disease. General anesthesia was never necessary to perform MRI.

RESULTS: MRI exactly defined the cephalic anatomic profiles of normal hips which are not depicted with conventional radiography before the femoral head cartilage ossifies completely. MR contrast resolution was very high in depicting the maturation of the epiphyseal nucleus and its exact site in the cartilagineous epiphyseal hemisphere proximal to the femur. The analysis of MR morphological and structural changes permitted to correlate MR findings with the histopathologic features described in the literature. In addition, MRI of childhood hip osteochondrosis showed maked structural changes of the epiphyseal nucleus which are usually missed with conventional radiography. MRI permits early location of the abnormal area and the recognition of growing disk abnormalities; it also shows the whole cephalic cartilage and the changes of the epiphyseal nucleus evolution, which permits to differentiate osteochondrosis evolution from recessive patterns. Finally, MRI clearly showed the increased equatorial diameters of the involved femoral heads and the associated decrease in polar diameters, which is essential to study the biomechanics of hip osteochondrosis and therefore to plan treatment.

CONCLUSIONS: MRI, even with coronal sequences and T1-weighting only, permits: 1) to image normal hips and hip osteochondrosis, especially in early and late childhood; 2) to clearly define cephalocotyloid relationships; 3) to depict the actual anatomic margins of the head and its structure; 4) to investigate the head cartilage extent and to locate the ossification nucleus. These morphologic and structural data are very useful to diagnose and manage hip osteochondrosis in the evolutive age. MRI shows abnormal changes in anatomic structures which are not seen with conventional radiography and demonstrates the evolution of the osteochondrosis process over time. In children over six, at the end of the ossification process of the head cartilage, conventional radiography alone is often sufficient to depict cephalocotyloid relationships and the MR diagnostic criteria of bone-cephalic diseases are similar to those used in adult hip studies.