Characterisation of torso segmental rotation changes after surgical correction of adolescent idiopathic scoliosis

INTRODUCTION A plethora of measurements are available to characterise scoliosis, but a mismatch remains between cosmesis, radiological parameters and patient functional outcomes. Better assessment of cosmesis, through quantitative techniques, may help address this mismatch. We propose a new method of quantifying external scoliotic deformity, by assessing rotation and symmetry in transverse slices across the length of the torso, using 3D photography. METHODS 3D surface scanning is conducted routinely at the Queensland Children’s Hospital spine deformity clinic, for patients with a diagnosis of Adolescent Idiopathic Scoliosis (AIS). From an ongoing database of pre- and post-operative scans a series of 6 patients with similar curve type (Lenke Type 1) were selected for analysis. Lenke Type 1 is defined as major thoracic structural curves, with any adjacent curves present being deemed compensatory. The mean age pre-operatively was 15.4 ± 1.6 years, and the mean major curve Cobb angle was 65.7 ± 13.3deg. 3D scans were captured (Artec Eva, Artec Group Inc., Luxembourg) at the preoperative surgical planning appointment, and again at either their immediate postoperative (6-8 weeks), or subsequent follow up appointments (6-12 months). Using the surface scan data, 3D virtual representations of the patient’s standing body shape were created (Figure 1). From these reconstructions, transverse cross-sectional profiles for the outer torso skin surface were created at 10% intervals between their pelvis and C7 prominence. A line of maximum symmetry was determined, that defined the angle of rotation of each profile (positive: right) relative to the sagittal plane. The range of profile rotations along the length of each individual patient’s spine (minimum to maximum) was compared pre- to post-operatively. Additionally the ratio of corresponding pixels about the line of maximum symmetry of each profile was assessed along the length of the spine, pre- and post-operatively. A healthy adult female with no spinal deformity, who ...