A novel evaluation index for adolescent idiopathic scoliosis progression measurement and diagnosis

Adolescent idiopathic scoliosis is a trunk deformity of the spine with lateral deviation and rotation in the transverse plane. The most traditional measurement index and parameter for scoliosis diagnosis is the Cobb's angle, which evaluates the curves of the scoliotic spine on the radiographic projection of the trunk. Although this method is widely accepted as the benchmark in scoliosis assessment, it has some limitations and restrictions in practical applications because it is measured on a PA (posterior-anterior or back to front) X-ray image, such as potential harmfulness from radiation exposure and high cost.In this paper, a novel evaluation index for adolescent idiopathic scoliosis measurement and diagnosis is introduced to complement the existing assessment index, such as the Cobb's angle, the differences of shoulder height, etc. The new evaluation index is based on the phenomenon of the tilt and deviation of the vertebras in a scoliotic spine, which forms the tilt angles between each pair of adjacent vertebras.A data sample of 30 X-ray images of scoliotic spines was used in this research to evaluate and examine the usability and validity of the new index. The Cobb's angle and the new index were calculated and compared using the same data sample. The correlation between the Cobb's angle and the index was also determined, and a high correlation is found which demonstrated the usefulness of this proposed index. In this paper, it has been shown that the newly-proposed index has the potential to be used as a tool to support the traditional scoliosis measurement methods.This method can also be generalized on the sagittal plane to define other evaluation indices for assessing the severity of kyphosis and lordosis. The idea of using angular separation to evaluate spinal deformity in multiple planes or in three-dimensional spaces will be discussed in future research.