Prediction of the 3D Spinal Alignment from External Shape of the Back in AIS Patients Using Regression Model

Abstract

One of the most important challenges in diagnosis of Adolescent Idiopathic Scoliosis (AIS) is to find a correlation between internal spinal deformity and external shape of the back and to create a model to predict internal curve from 3D scans of back surfaces. In this way, X-ray imaging and analysis could be potentially avoided, which lead to reducing cumulative dose to the patient and decreasing the risk for malignancy development later in life. We propose a regressive model that considers correlation between 3D coordinates of internal spinal alignment and 3D coordinates of external curve, and between internal parameters (e.g., Cobb angles, vertebrae rotations) and external back surface, and predicts from external curve coordinates of the internal spinal line. With a limited number of samples used to create it, this model is able to provide a good approximation of the shape of the spine, with a mean 3D displacement between predicted and real curve of around 10 mm. Quality of prediction could be anyway significantly improved by simultaneously acquiring 3D scans of the back surface and X-ray scans of the patient, and adding to the model external features like scapulae or rib cage.

Measurement of distances and locations of thoracic and lumbar vertebral bodies from CT scans in cases of spinal deformation

“…These measurements may help to further understand the pathomechanisms of spinal deformations [35] or to identify reference points in X-ray examination that could be used for reconstruction of a 3D spinal model [36,37]. Or in another example, they could be used in combination with other morphological data and anatomical information to improve the prediction of 3D spinal alignment from external shape [38], or the fitting of individually distorted biomechanical models of the vertebral column to body scanner images in the course of developing scoliosis assessment methods that do not require the use of ionizing radiation during follow ups [16]. Although young patients who show signs of scoliosis and are particularly affected by regular X-rays usually have idiopathic or neurogenic scoliosis, the methods presented here can also be transferred to other types of scoliosis, such as muscular, degenerative, and congenital scoliosis at all ages.…”

3D Inference of the Scoliotic Spine from Depth Maps of the Back

“…This 3D transformation allows a simpler representation of the spine while keeping the vertebrae alignment information. It differs from [14] and [21] which are regressing absolute positions.…”