Reliability of lateral bending and axial rotation with validity of a new method to determine axial rotation on anteroposterior cervical radiographs

Objective: To investigate the reliability of a new radiographic measurement of axial rotation and lateral bending on anterior-posterior cervical views by using a computer and sonic digitizer. Design: A blind, repeated-measure design was used. Anteroposterior cervicot horacic radiographs were presented to each of 3 examiners in random, order. Each film was digitized, and 1 week later the turns were randomized for a second run. Setting: Private, primary-care chiropractic clinic. Main Outcome Measures: The interclass and intraclass correlation coefficien ts (ICC) for intraexaminer and interexaminer reliability were calculated fr om measurements on radiographs for determining axial rotations (Ry) and lat eral bending (Rz) of C3 to T3. Results: When the new axial rotation method was applied to small rotations of a C3 plastic model, the average error was less than 1 degrees. For the c alculations of axial rotation (Ry), the ICC values were in the good to exce llent range. For axial rotation, the intraclass correlation coefficients we re ICCs greater than or equal to 0.78, and the interclass correlation coeff icients were ICCs greater than or equal to 0.67. For lateral flexions (Rz) of C3 to T3, all intraclass and interclass correlation coefficients were in the excellent range (ICCs > 0.87). Conclusions: Methods of calculating axial rotations in the spine have been reported for large angles (5 degrees to 30 degrees) but not for smaller ang les. A method for determining axial rotations of the cervical segments on A P views, based on the chord across the are displaced by the spinous-lamina junction, had reliability (ICC values) in the good to excellent range. Comp ared with measured rotations of a C3 model (-5 degrees to +5 degrees), the new method had an average error of less than 1 degrees and approximately 11 .5%. The reliability for the axial rotation measurements was in the good to excellent range, and the lateral bending measurements were all in the exce llent range.