Prediction of scoliosis progression with serial three-dimensional spinal curves and the artificial progression surface technique

Adolescent idiopathic scoliosis (AIS) progression is clinically monitored by a series of full spinal X-rays. To decrease radiation exposure, an artificial progression surface (APS) is proposed to predict progression. Fifty-six acquisitions (posteroanterior radiographs, 0° and 20°) were obtained from 11 AIS patients (29.8 ± 9.6° Cobb angle). Three-dimensional curves were constructed through vertebral pedicle centers. Three previous serial spinal curves (6-month intervals) were used to construct an APS with a Non-uniform Rational B-Spline surfacing technique. Future progression was achieved by aligning the curves on the APS using the generalized cross-validation extrapolation technique. With three and four previous serial spinal curves, the prediction accuracies of future progression at the next 6-month interval were 4.1 ± 3.3° for Cobb angles and 3.6 ± 3.5 mm for apex lateral deviations. Apex locations and Cobb regions varied within one vertebral level. The proposed technique shows potential as an accurate three-dimensional prediction method for AIS progression and could help pediatricians make decisions about treatment. However, it could only be applied once before more radiographic data would be needed.