Rotation assessment in adolescent idiopathic scoliosis with rod derotation

Abstract

Objective: Adolescent idiopathic scoliosis (AIS) is characterized by rotational and lateral deformity of the spine. The measurement of vertebral rotation is important for prognosis and treatment. Our objective was to evaluate whether the Nash-Moe method can be used to measure axial deformity correction with surgical treatment using the rod derotation maneuver at both the apex and extremities of the deformity in patients with AIS. Methods: Rotation was assessed using the Nash and Moe criteria, on preoperative and postoperative radiographs. We also evaluated the severity on the coronal plane using the Cobb method, ratio of correction achieved, screw density, and number of vertebrae involved in the instrumentation. Results: The Cobb method correction average was 54.8%. When we disregarded vertebrae that presented preoperative Nash-Moe grade 0, the average measurable correction was 54.5% in the first non-instrumented vertebra above, 69.2% in the first instrumented vertebra, 32.2% in the apical vertebra, 36.8% in the last instrumented vertebra, and 30% in the first non-instrumented vertebra below. In our study, 32.14% of the patients presented a measurable correction in the apical vertebra. Conclusion: On the axial plane, correction can be satisfactorily evaluated using the Nash-Moe method.