Radiographic Study And Clinical Significance About Measurements Of Sagittal Plane Curves In Adjacent Segments Of The Thoracic And Lumbar Spine

Abstract: objective: To study three measuring methods about the sagittal plane curves in adjacent segments of the thoracic and lumbar spine on the digital radiography;To study the anatomy about the sagittal plane curves of the adjacent segments of the thoracic and lumbar spine on the radiographs of standing position about normal adult;To analyze long-term radiographic changes in all unfused lumbar segments after instrumented posterolateral lumbar fusion. Methods : 42 different posture digital x-ray figures about six modeling of human skeleton and 79 standing posture digital x-ray figures about normal adult were obtained, measuring the sagittal angle by using distortion compensated roentgen analysis (DCRA method); measuring the sagittal angle formed by two vertical lines perpendicular to the lines parallel to the superior endplate of the above vertebra and to the inferior endplate of the below adjacent vertebral body (Cobb1 method) ; measuring the sagittal angle by two vertical lines perpendicular to the lines parallel to the superior endplate of the above vertebra and the superior endplate of the below adjacent vertebral body (Cobb2 method). Using the distortion-compensated roentgen analysis (DCRA) method, sagittal angle, disc height, and dorsoventral displacement were measured in 211 unfused segments from 57 patients, on digitized radiographs taken before fusion surgery and after a mean follow-up of 2.5 years (range, 1.5-4 years). The results were studied statistically. Results: There was statistical significance between of the three measurements in clockwise or anticlockwise posture (P<0.05) about modeling of human skeleton. There was no statistical significance in different posture digital X-ray figures about six modeling of human skeleton by using DCRA method (P>0.05).There was statistical significance in clockwise or anticlockwise posture by using Cobb1 method and Cobb2 method (P<0.05). The 95% confidence interval of sagittal plane curves about normal adult in adjacent segments were respectively obtained by the three measurements above . No changes were observed at the segments located below the fusion. All the unfused segments above the fusion showed the same significant change of sagittal angle and disc height. Conclusion:Measuring the sagittal angle by using DCRA method was accurate, different posture would not influence the accuracy of measurement. There would be an influencing parameter in clockwise or anticlockwise posture around central axis by using Cobb1 and cobb2 methods. Measuring the sagittal angle, disc height, and dorsoventral displacement by using DCRA method was accurate. It was uninfluenced by distortion with respect to axial rotation, lateral tilt, and off-center positioning of the vertebrae. After posterior lumbar instrumented fusion, radiographic changes suggesting disc degeneration appear homogeneously at several levels cephalad to fusion.