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

Abstract

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.