Abstract
BackgroundThree-dimensional idiopathic scoliosis cannot be accurately assessed with the aid of a single plane parameter – the Cobb angle. We propose a novel method for evaluating the three-dimensional (3D) pattern of scoliosis based on two X-rays (PA and lateral). The proposed method consists of the measurements of the angles between the upper endplate of the upper-end vertebra and the lower endplate of the lower-end vertebra (3D scoliosis angle).MethodsThe 3D-angles of thirty scoliosis curves were measured with either computed tomography (CT) or digitally reconstructed radiographs (DRRs): PA and lateral. CT was used as a reference. In the case of CT, the 3D angle was calculated based on the coordinates of three points situated on the upper endplate and those of three points situated on the lower endplate of the scoliosis curve. In the case of the DRR, the 3D angle was calculated using the four-angle method: the angles formed by the endplates of the curve with the transverse plane. The results were tested with the Student’s t-test, and the agreement of measurements was tested with the intraclass correlation coefficient.ResultsThere was no significant difference between the 3D-angle measurements obtained with DRRs versus CT, p > 0.05. There was, however, a significant difference between the 3D-scoliosis angle and the Cobb angle measurements performed based on the X-rays. The reproducibility and reliability of 3D angle measurements were high.ConclusionsBased on two standard radiographs, PA and lateral, it is possible to calculate the 3D scoliosis angle. The proposed method facilitates 3D-scoliosis assessment without the use of sophisticated devices. Considering the 3D nature of AIS, the 3D parameters of the spine may help to apply a more effective treatment and estimate a more precise prognosis for patient with scoliosis.
Highlights
Three-dimensional idiopathic scoliosis cannot be accurately assessed with the aid of a single plane parameter – the Cobb angle
The introduction and validation process of the method for Three dimensional (3D) scoliosis angle calculations was accomplished in four steps: 1) calculation of the 3D scoliosis angle based on computed tomography (CT); 2) calculation of the 3D scoliosis angle based on digitally reconstructed radiographs (DRRs); 3) comparison of the 3D scoliosis angle calculations: CT versus DRRs; and 4) evaluation of the reproducibility and reliability of the proposed method based on X-rays (PA and lateral)
There was no significant difference between the measurements of the 3D scoliosis angle calculated based on measurements obtained with CT versus DRR (Table 1)
Summary
Three-dimensional idiopathic scoliosis cannot be accurately assessed with the aid of a single plane parameter – the Cobb angle. We propose a novel method for evaluating the three-dimensional (3D) pattern of scoliosis based on two X-rays (PA and lateral). The magnitude of scoliosis is typically measured with the Cobb angle on posteroanterior (PA) X-rays of the spine. Two cases of scoliosis with similar two-dimensional morphologies may have different three-dimensional morphologies [4] These findings emphasized the importance of 3D parameters. The evaluation of three-dimensional deformities has the following feasible parameters: the axial rotation of the vertebra, the orientation of the plane of maximum curvature (PMC) [4, 6], the angle of scoliosis observed in the PMC, and the top view parameters [7–9]
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