3D reconstruction of adolescent scoliotic trunk shape from biplanar X-rays: a feasibility study

Abstract

ABSTRACTAdolescent idiopathic scoliosis (AIS) is a 3D deformity of the spine detectable by trunk asymmetry. As a decision-aid tool, body scanners can assess non-invasively the external shape of the trunk. If AIS is diagnosed, additional 3D reconstructions of the spine, rib cage and pelvis are useful to plan a treatment such as bracing. Body scanners cannot currently guarantee reliable bones reconstruction but low-dose biplanar X-rays (BXR) is a relevant alternative. Recently, 3D body shape reconstruction of asymptomatic subjects from BXR was also proved to be accurate. To prevent AIS patients from multiple examinations, we investigated the feasibility of trunk shape reconstruction from BXR. The proposed method relied on the 3D reconstructions of the spine, rib cage and pelvis on which a statistical shape model was fitted. Additional 10 radio-opaque markers could also be considered yielding automatic deformations of the model. Finally, few manual adjustments were performed. This method was evaluated on 15 scoliotic subjects (13.7 ± 1.3 years, Cobb = 23.3° ± 8.5°). Using a larger set of markers, signed marker-to-surface differences were computed and appeared unbiased. Reproducibility on mesh nodes distribution was lower than 7mm. This study is a first step toward computer-aided brace design with a single examination.