Douglas Wayne Goodwin MD, Presenter: Nothing to Disclose

Bryan Mitchell, Abstract Co-Author: Nothing to Disclose

David Pastel, Abstract Co-Author: Nothing to Disclose

William Abdu, Abstract Co-Author: Nothing to Disclose

Yvonne Yee Cheung MD, Abstract Co-Author: Nothing to Disclose

The purpose of our study was to calculate the precision error of Cobb’s angle measurements on lateral cervical spine films utilizing a technique that accounts for the error associated with differences in radiographic positioning.

We collected flexion and extension lateral radiographs of 36 patients with single level anterior cervical fusions. The fusions were judged to be solid based on radiographic and clinical criteria. Two investigators drew Cobb’s angle at the level of the fusion on both the flexion and extension films by drawing intersecting lines perpendicular to the superior endplate of the superior body and the inferior endplate of the inferior body. At that time, the angle on the flexion image was measured and recorded. One week later the angle on the extension view was measured. Using these 36 pairs of measurements, the mean of the differences between measurements on the flexion and extension views and the standard deviation (SD) was calculated for each of the two observers.

The mean measurement variability and standard deviation of the two observers was 2.1º, SD 2 and 2.3º, SD 1.6.

We have described a technique for determining the error associated with measuring Cobb’s angle on lateral radiographs that accounts for error introduced by differences in patient positioning.

Any consideration of the significance of a change in Cobb’s angle on lateral flexion and extension radiographs must account for error associated with differences in patient positioning.

Goodwin, D, Mitchell, B, Pastel, D, Abdu, W, Cheung, Y, Measuring Cobb's Angle on Lateral Flexion and Extension Cervical Spine Films: A Technique for Calculating Precision Error.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4430520.html