Rotational Changes Following Use of Direct Vertebral Rotation in Adolescent Idiopathic Scoliosis

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 t test (paired means) was used for continuous variables, and the χ 2 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. LEVEL OF EVIDENCE: 4.