Measurement of Lumbar Lordosis using Fluoroscopic Images and Reflective Markers

Lumbar lordosis is defined as the anterior convexity of the lumbar spine in the sagittal plane. Its degree is variable between individuals, affected many other factors. Clinical methods to define lumbar lordosis are Cobb's angle measurement and the angle between extension line of boundary of the first and fifth vertebral body. In this study, the lordotic angle calculated by reflective markers when the three dimensional motion capture system was used compared to the angle calculated from fluoroscopy. The coordinates of vertebral body center from fluoroscopic images were digitized. The vertebral body center coordinates from fluoroscopic image and the coordinates from markers were used to calculate lumbar lordotic angle with three different method - ratio method, three point method and curve-fit method. The lordotic angles from fluoroscopic image(f) were larger than the angles from markers(m) in all three methods. The ratio method using fluoroscopic image and the curve-fit method using markers showed the largest coefficient of variance(f - m)and the coefficient of variances in all three methods using fluoroscopic image were smaller than using markers. However, the analysis according to Bland-Altiman plot showed a good agreement between both methods(fluoroscopy and marker).