Rotational Changes Following Use of Direct Vertebral Rotation in Adolescent Idiopathic Scoliosis: A Long-Term Radiographic and Computed Tomography Evaluation

Study Design. A retrospective cohort study. Objective. To evaluate long-term rotational changes in the vertebrae of patients with adolescent idiopathic scoliosis (AIS) who underwent direct vertebral rotation (DVR). Summary of Background Data. DVR using thoracic pedicle screws, a rotational corrective maneuver used in the surgical treatment of AIS, was introduced in 2004. Although DVR is considered to be the main axial corrective maneuver, the long-term rotational changes of vertebrae following this treatment are not well understood. Materials and Methods. A total of 135 vertebrae that underwent DVR using thoracic pedicle screws with a minimum five-year follow-up were retrospectively assessed for the vertebral rotation angle. The vertebral rotation of the apical vertebra (AV) and distal end vertebra (EV) was evaluated using the Nash-Moe scale, the rotational angle to the sacrum (RAsac), and the Aaro and Dahlborn method. The Student ttest (paired means) was used for continuous variables, and the χ² test was used for categorical variables, as appropriate. A comparison of two and three groups used a one-way repeated measures analysis of variance, and the post hoc analysis used the Bonferroni test. Results. The mean Nash-Moe scale of distal EV showed statistically significant differences between preoperative and postoperative values (P=0.034) and no statistically significant difference between postoperative and last follow-up values (P=1.000). The last follow-up RAsac of AV did not differ significantly from the preoperative RAsac of AV (P=0.515). The last follow-up RAsac of distal EV was significantly lower than the preoperative RAsac of distal EV (P=0.001). The Pearson correlation analysis showed that the last follow-up RAsac of distal EV was correlated with the Cobb angle of the main curve (r=0.459, P=0.004), loss of correction (r=0.541, P=0.001), and lowest instrumented vertebra tilt angle (r=0.504, P=0.001) Conclusions. The rotation regression phenomenon in AV and rotation maintenance in distal EV were observed after DVR over an average 10-year follow-up. These findings suggest that the DVR in the surgical treatment of AIS has a positive long-term effect on the stabilization of distal EV from the point of view of axial rotation.