Intraoperative Computed Tomography versus Perdriolle and Scoliometer Evaluation of Spine Rotation in Adolescent Idiopathic Scoliosis

Figure 6

A new method of derotation assessment on the CT scans, two-step procedure. (a) Before correction, (b) after rod derotation, and (c) after DVD. Upper window: upper instrumented screw (UIS), middle window: apical screw (AS), and lower window: lower instrumented screw (LIS). The longitudinal axis of the particular screw was marked which crossed the middle of the head, the body, and tip of the screw. This line created an angle with the horizontal reference line. The difference of these angles between AS and UIS and AS and LIS before and after surgery allowed the real apical vertebral derotation (AVD) assessment. AS (°)-UIS (°): bigger windows in upper section, AS (°)-LIS (°): bigger windows in the lower section.

(a)

(b)

(c)