A Novel Automatic Method to Evaluate Scoliotic Trunk Shape Changes in Different Postures

摘要

We present a novel method to evaluate the external trunk shape of Adolescent Idiopathic Scoliosis (AIS) patients. A patient's trunk surface is acquired in different postures (neutral standing, left and right lateral bending) at their preoperative visit and in standing posture at their postoperative visit following spinal deformity corrective surgery with an optical digitizing system. We use spectral shape decomposition to compute the eigenmodes of the trunk surface. This allows us to intrinsically define the principal shape directions robustly with respect to the patient's posture. We then extract a set of contour levels that follow the trunk's deformation from bottom to top, and characterize the trunk shape as a set of multilevel measurements taken at each level. Changes in trunk shape between postures/visits are calculated as differences between the measurement functionals. We performed a study on a small cohort of 14 patients with right thoracic spinal curves to assess the relationship between shape changes induced by the lateral bending positions and those resulting from surgical correction. The proposed method for scoliotic trunk shape evaluation represents a significant improvement over previous ones, as it is completely automatic and it adapts well to the lateral bending posture without the need to manually define control points/curves on the trunk surface.