Comparison of Cobb angle measurement of scoliosis radiographs with preselected end vertebrae: traditional versus digital acquisition.
METHODS
Prospective study.


OBJECTIVE
To compare variability in Cobb angle between digitally and traditionally acquired scoliosis radiographs.


BACKGROUND
Previous studies have shown that the 95% confidence interval for Cobb angle can vary from 2.6 degrees to 8.8 degrees. No study directly comparing Cobb angles measured from traditional and digitally acquired radiographs has been reported.


METHODS
A spine model simulating 25 single right thoracic curves (range, 20 degrees-60 degrees) was imaged using traditional and digital techniques. Traditional films and miniaturized printed digital films were each measured twice manually. Digital films were also measured twice using computer imaging software.


RESULTS
Overall mean angle and (95% confidence interval) were 41.7 degrees (39.1 degrees-44.3 degrees) for traditional, 40.6 degrees (37.4 degrees-43.8 degrees) for digital, and 39.7 degrees (36.3 degrees-43.1 degrees) for computer measurements. Overall correlation was 0.994 for traditional and digital, 0.987 for traditional and computer, and 0.993 for digital and computer. Fixed effect model analysis demonstrated that, although a statistically significant difference existed between the 3 methods of measuring the Cobb angle (P < 0.0001), the difference between methods was less than 2 degrees.


CONCLUSIONS
Any of the 3 evaluated methods of measurement can be used to measure Cobb angles. Additionally, the methods can be used interchangeably.
Wills
Brian P D
BP
Department of Orthopedics and Rehabilitation, University of Wisconsin, Madison, WI, USA.
Auerbach
Joshua D
JD
Zhu
Xiaowei
X
Caird
Michelle S
MS
Horn
B David
BD
Flynn
John M
JM
Drummond
Denis S
DS
Dormans
John P
JP
Ecker
Malcolm L
ML
D007090:Image Interpretation, Computer-Assisted / Q000379:methods / Q000592:standards*; D008953:Models, Anatomic; D011446:Prospective Studies; D011856:Radiographic Image Enhancement / Q000379:methods / Q000592:standards*; D012107:Research Design / Q000592:standards*; D012600:Scoliosis / Q000000981:diagnostic imaging*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*