Visualisation of the brace effect on the spinal profile in idiopathic scoliosis

Abstract

We studied the brace effect on the spinal profile in idiopathic scoliosis, using a MR procedure visualising the complete scoliotic spine in any vertical plane, while rotating it 180° on the longitudinal axis of the patient. Thirty-eight female patients (mean age, 14.5 years) were included in the study. Inclusion criteria were an idiopathic scoliosis, a Cobb angle greater than 20°, age of 10–17 years and bracing with a Chêneau brace. The brace effect was studied in 38 thoracic curves. The MR examinations were carried out in direct sequences, with and without brace. A reconstruction algorithm allows visualising the whole spine in vertical projections, with rotational steps of 2°, from −90° to 90°, referred to as MR animation. In various vertical MR projections, the changes of the curves were evaluated by measuring the Cobb angle. Additionally, a translation angle of the apical vertebra was determined, representing the lateral deviation of the apical vertebra from a defined midline. Testing the reproducibility of the Cobb angles, the standard deviation of the intra-individual differences was 1.7° and of the inter-individual differences, 2.1°. For the translation angles, the standard deviation of the intra-individual differences was 0.8° and of the inter-individual differences, 0.9°. With brace the mean Cobb angle of the thoracic curves was significantly reduced in the various vertical MR projections. The mean translation angle was also reduced. MR analysis showed that the brace effect is a translation process, straightening the profile of the scoliotic spine in all vertical planes. MR animation allows visualising the brace effect on the spine in scoliosis based on a 3D data set, without additional radiation exposure. It showed the straightening effect of the brace leading to a flattening of the sagittal spinal profile.