NORMAL AND PATHOLOGICAL SAGITTAL BALANCE OF THE SPINE AND PELVIS

Purpose of the study The authors examined the modifications of sagitta l shape and muscular functions in differents vertebral diseases in ord er to investigate their correlations and to specify the role of hip ex tension in standing posture Materials and methods We included 57 patie nts presenting various diseases, among which lumbar kyphosis, spondylo sis and spondylolisthesis, backhache and lumbar stenosis. We mesured j oint mobility (hip extension, lumbar flexion), muscular retractions (i lio-psoas, hamstrings, rectus femoris), and muscular strength (spine f lexors and extensors, hamstrings, quadriceps femoris). On standing lat eral x-rays, measurements were made of various spinal and pelvic param eters, among which the pelvi-femoral angle proposed by the authors for hip extension evaluation. Results There was a significant correlation between pelvi-femoral angle and pelvic backward tilting (r 0.8037 p < 0.01). This angle can therefore be considered as fundamental for eval uation of sagittal posture. Characteristic abnormalities were found fo r each pathogenic group, notably for lumbar kyphosis and spondylolisth esis. Discussion Upright posture is secondary to hip extension and lum bar lordosis, and an optimal and economic standing posture is obtained when balance between these two phenomena is correct. In lumbar kyphos is pelvic modifications such as hip extension, and pelvic backward til t-up arise compensating the anterior displacement of the center of gra vity, while In spondylolisthesis, anterior displacement is secondary t o sacral obliquity. Conclusion It is very important to evaluate the pe lvis position in sagittal spinal diseases, in order to understand post ural deterioration mechanisms. Lumbar kyphosis and spondylolisthesis a re two examples of failure of upright posture.