3D RECONSTRUCTION MRI: A NEW TECHNIQUE TO ANALYSE EPIPHYSIODESIS BONE BRIDGING

Abstract

Purpose: Partial epiphysiodesis of the growth plate due to physeal aggression is a common problem in paediatric patients. Surgical management requires precise imaging. We recall other imaging techniques currently employed and describe a novel method for studying the characteristic features of epiphysiodesis bridges of the growth plate: 3D-magnetic resonance imaging (3D-MRI).

Material and methods: We analysed retrospectively MRI series of 27 epiphysiodesis bridges in 23 children (ten boys and thirteen girls) aged 11.3 years (range 2.5 – 15). We recorded information concerning the cause of the physeal aggression, the joint involved, the type of bony bridge (Ogden classification), the clinical deformation, and the proposed treatment. The 27 bridges were studied on coronal MRI acquired with echo-gradient and fat suppression sequences. Data were processed with a manual 3D reconstruction program in 15 minutes to precisely define the localisation, the volume, and the morphology of the bony bridge and the active physis.

Results: The epiphysiodeses were caused by trauma (65%), iatrogenic aggression (17%), ischemia-infection (purpura fulminans) (9%), juxta-physeal essential cyst (4.5%), and unknown causes (4.5%). Eighty-seven percent involved a lower limb joint, 75% of which involved the tibia. The surface of the epiphysiodesis bridge covered 20% of the physis. The bridges were peripheral (46.5%), central (46.5%), and linear (7%).

Discussion: It is difficult to determine the position and the 3D relations of an epiphysiodesis bridge in a healthy active physis with imaging techniques such as plain x-rays, scintigraphy, tomography and computed tomography. The 3D-MRI method described here provides a sure way to distinguish the active growth plate which gives a high intensity signal and the epiphyseal bridge which gives a low intensity signal. Morphological (size, form) and topographic characteristics of the bony bridge and the physis can be described with precision facilitating therapeutic decision making and guiding surgery. The lack of radiation risk is also an advantage of MRI.

Conclusion: The quality of the images obtained, the safety of MRI and the easy interpretation of 3D reconstructions makes this imaging technique an excellent method for pre-therapeutic analysis of epiphysiodesis bridges.