A review of the back surface metrics used as scoliosis evaluation indices

Introduction Although scoliosis is characterized by lateral deviation of the spine, a 3D deformation actually is responsible for geometric and morphologic changes in the trunk and rib cage. Since scoliotic deformations occur in 3D space, it is common in medical practice to use three mutually perpendicular planes to describe it: the transverse, the sagittal, and the coronal plane. In a vast related medical literature, one can find quite a few scoliosis evaluation indices, which are based on back surface data and generally measured along these planes, ie. angle of trunk rotation (ATR) or angle of trunk inclination (ATI) simulating the scoliometer measure, the Crude Trunk Asymmetry Score (CTAS), the back surface rotation (BSR) index, the volumetric asymmetry (VA), the hump severity (HS), the shoulder asymmetry index, the waist asymmetry index, the scapulae asymmetry index, the lumbar lordosis, the thoracic kyphosis, to name just a few.