GADOLINIUM-ENHANCED MR-IMAGING OF PEDIATRIC-PATIENTS AFTER REDUCTION OF DYSPLASTIC HIPS - ASSESSMENT OF FEMORAL-HEAD POSITION, FACTORS IMPEDING REDUCTION, AND FEMORAL-HEAD ISCHEMIA

OBJECTIVE. We describe gadolinium-enhanced MR imaging of position and vascular enhancement of the femoral head in pediatric patients who hav e undergone reduction of hip dislocation. SUBJECTS AND METHODS. Within 24 hr of hip reduction and spica casting, we performed 25 gadolinium- enhanced MR studies in Is infants and young children (15 girls, three boys) with 23 dysplastic hips. All but two patients underwent closed r eductions. We evaluated intraoperative arthrograms for obstacles to re duction and subsequent radiographs for avascular necrosis. RESULTS. MR images showed that all femoral heads were in their respective acetabu la, but several structures interfered with concentric reduction. Obsta cles to reduction included a pulvinar (n = 16), infolding of the capsu le (n = 9), interposition of the labrum (n = 2), and a hypertrophied l igamentum teres and transverse ligament (n = 2). All 50 femoral heads showed enhancement: 35 normally, 10 homogeneously but less than on the contralateral femoral head or the ipsilateral greater trochanter, and five with areas of focally decreased enhancement, Hips that showed de creased enhancement had undergone greater degrees of abduction (r =.38 , p <.01). CONCLUSION. Gadolinium-enhanced MR imaging can reveal abnor malities of hip position and proximal femoral epiphyseal and physeal v ascularity that can occur after hip reduction. Abnormalities of enhanc ement were more frequent in patients who had greater femoral abduction . The effect of decreased epiphyseal vascular enhancement is still unc ertain.