Journal List > J Korean Orthop Assoc > v.43(5) > 1012829

Oh, Chung, Kang, Kim, Kwag, and Lee: Changes in Vertebral Axial Rotation after Thoracoscopic Scoliosis Correction



In this study, we investigated whether thoracoscopic anterior correction can effectively derotates the scoliotic spine and we also evaluated the patterns of derotational changes inside the instrumented area and at the junction between the instrumented and uninstrumented area.

Materials and Methods

Preoperative and postoperative MR images with single axial cuts through each vertebral level were obtained in 20 patients who underwent thoracoscopic anterior instrumentation. Each vertebral rotation was measured by the use of Aaro's method. Vertebral axial derotation of the apical zone (AZ), upper instrumented zone (UIZ), lower instrumented zone (LIZ) and junctional segment were compared. The amount of segmental rotation and segmental derotation in each zone was calculated. Statistical analysis was performed by the use of by 2-way ANOVA and the Wilcoxon signed ranks test.


The average axial rotations at AZ were 10.1° preoperatively and 5.3° postoperatively with an average correction rate of 48%. Derotation of the AZ was greater than the UIZ and LIZ. For the LIZ derotation was not significant (p=0.023) while for the UIZ there was a significant derotation (p<0.001). Postoperatively, the first uninstrumented vertebra rotated significantly in the direction of rotation of the instrumented end vertebra. Preoperative and postoperative segmental rotation was higher in the UIZ and LIZ than in the AZ. However, segmental derotation occurred uniformly in the instrumented area. At the junctional segment, preoperative segmental rotation was same as that of the UIZ and LIZ and segmental derotation was not significant.


Thoracoscopic scoliosis correction can achieve effective axial correction by causing derotation of each of the vertebral bodies and segmental derotation.

Figures and Tables

Fig. 1
MRI scans of axial slices through each vertebral level (A). Vertebral rotation (RA sag) measures the angle between the long axis of the vertebra subtended at the posterior central aspect of the spinal canal, and the sagittal plane (B).
Fig. 2
Definitions of zone and segment. The apical zone was defined as the apical vertebra and the vertebra above and below it. The upper instrumented zone consisted of the two most cranial vertebra within the instrumentation and the lower instrumented zone consisted of the two most caudal vertebrae within the instrumentation. The segment just outside of instrumentation was defined as the upper and lower junctionnal segment. UEV, upper end vertebra; AV, apical vertebra; LEV, lower end vertebra.
Table 1
Changes of Vertebral Rotation (Degree of RA Sag)

UEVZ, upper endvertebral zone; AZ, apical zone; LEVZ, lower end vertebral zone; UEVZ, UEV (upper end vertebra), UEV±1; AZ, AV (apical vertebra), AV±1; LEVZ, LEV (lower end vertebra), LEV±1.

Table 2
Changes of Segmental Rotation (Degree)

UJZ, upper junctional zone; UEZ, upper end vertebral zone; AZ, apical zone; LEZ, lower end vertebral zone; LJZ, lower junctional zone; UJS, upper junctional segment; UIZ, upper-instrumented zone; UAZ, upper apical zone, LAZ, lower apical zone; LIZ, lower instrumented zone; LJS, lower junctional segment.


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