The accuracy of computed tomography in assessing hip reduction in developmental dysplasia of the hip

Abstract

Introduction: Developmental dysplasia of the hip (DDH) is a condition that can have significant consequences on hip function in childhood and adult life if a concentric reduction is not obtained. Confirmation of reduction through a hip spica can be challenging especially when plain radiography relies on indirect measurements to identify the location of an un-ossified ossific nucleus. Imaging techniques such as computed tomography (CT) may add value in improving detection rates following attempts at hip reduction and maintenance of reduction. Hypothesis: CT adds value in more accurately assessing hip reduction after a closed or open reduction in the patient with DDH in a hip spica cast. Study Objectives: The primary objective is to assess the accuracy of hip reduction in a hip spica comparing X-rays and CT scans. The secondary objective is to establish measurement parameters that may be used in both these imaging modalities to assist in determining the adequacy of hip reduction. Methods: A retrospective analysis of X-rays and CT scans of 8 patients with DDH following hip reduction and application of a hip spica cast. Results: Eight children with nine dislocated hips were included in the study. Five required closed reduction and four required open reduction (with one femoral shortening). CT scans are more accurate and offer more measurable parameters in assessing hip reduction through a hip spica. Conclusion: Plain radiography may be misleading in confirming the presence or absence of hip reduction and may in certain scenarios lead to unnecessary revision surgery in cases of poor penetrance and improper anatomical definition. Limited CT reduces paediatric pelvic organ radiation exposure and assists in more accurately assessing hip reduction.