Three-Dimensional Vertebral Wedging in Mild and Moderate Adolescent Idiopathic Scoliosis

Abstract

BackgroundVertebral wedging is associated with spinal deformity progression in adolescent idiopathic scoliosis. Reporting frontal and sagittal wedging separately could be misleading since these are projected values of a single three-dimensional deformation of the vertebral body. The objectives of this study were to determine if three-dimensional vertebral body wedging is present in mild scoliosis and if there are a preferential vertebral level, position and plane of deformation with increasing scoliotic severity.MethodologyTwenty-seven adolescent idiopathic scoliotic girls with mild to moderate Cobb angles (10° to 50°) participated in this study. All subjects had at least one set of bi-planar radiographs taken with the EOS® X-ray imaging system prior to any treatment. Subjects were divided into two groups, separating the mild (under 20°) from the moderate (20° and over) spinal scoliotic deformities. Wedging was calculated in three different geometric planes with respect to the smallest edge of the vertebral body.ResultsFactorial analyses of variance revealed a main effect for the scoliosis severity but no main effect of vertebral Levels (apex and each of the three vertebrae above and below it) (F = 1.78, p = 0.101). Main effects of vertebral Positions (apex and above or below it) (F = 4.20, p = 0.015) and wedging Planes (F = 34.36, p<0.001) were also noted. Post-hoc analysis demonstrated a greater wedging in the inferior group of vertebrae (3.6°) than the superior group (2.9°, p = 0.019) and a significantly greater wedging (p≤0.03) along the sagittal plane (4.3°).ConclusionsVertebral wedging was present in mild scoliosis and increased as the scoliosis progressed. The greater wedging of the inferior group of vertebrae could be important in estimating the most distal vertebral segment to be restrained by bracing or to be fused in surgery. Largest vertebral body wedging values obtained in the sagittal plane support the claim that scoliosis could be initiated through a hypokyphosis.

Three-dimensional vertebral wedging and pelvic asymmetries in the early stages of adolescent idiopathic scoliosis

“…The 3D angular error was determined by the mean absolute difference between 16 measured and reconstructed angles. The mean error on the wedging angles was estimated at 0.1 61.0 [15]. These values are comparable with those reported by Ill es and Somoske€ oy [39] when using the EOS reconstruction software system.…”

“…The 3D reconstruction errors were estimated from 26 fiducial marks fixed to a calibration object to cover a volume of 210 by 210 by 410 mm. The mean absolute difference between the measured and calculated 3D coordinates was 1.3560.79 mm [15]. The 3D angular error was determined by the mean absolute difference between 16 measured and reconstructed angles.…”

“…Clinical studies with regard to this novel technology remain limited. Recently, the EOS system was used by Scherrer et al [15] to document 3D vertebral wedging, but pelvis abnormal growth and its relation to scoliosis progression in a longitudinal study are yet to be addressed.…”

“…Only a few studies reported wedging in mild scoliotic girls before any orthopedic treatment [15,16]. The latter included a single evaluation of the patient before orthopedic treatment rather than implementing consecutive observations to quantify the progression of the deformities.…”

Hypothesis about an existent biomechanical cause–effect relationship between Schëuermann’s kyphosis and scoliosis

“…On the other hand, few studies document the scoliotic spine wedging in the frontal and sagittal planes at the same time. These studies are limited to cadaveric spine specimens, and none of them focus on the population affected by Schëuermanń s kyphosis [38,39].…”