RESUMEN
The sagittal balance of the body is jointly maintained the by spine,pelvis and lower limb.Spino-pelvic alignment plays an important role on body sagittal balance,it is also involved in the pathogenesis of lumbar spondylolisthesis,adolescent idiopathic scoliosis,lumbar degeneration and other diseases.In addition,the sagittal spino-pelvic alignments are also related closely to the surgery strategy formulation of spinal deformity and clinical outcome.Coronal and sagittal parameters of the spine and pelvis are numerical representations of the spino-pelvic alignment which are usually obtained by imaging data.For the reason that X-ray radiography is economical,convenient and avaiable auxiliary examination to perform direct visualization of spine in the standing position.It provides an important way for the study of spino-pelvic alignment.But in the lateral pelvis X-ray films,arms at sides in relaxed standing position prevents adequate visualization of the spine on a lateral radiograph,resulting in difficulty measuring the relevant parameters.Thus,flexion of shoulders is required to bring the upper limbs forward by the early researchers to obtain a clearer lateral spino-pelvic radiograph.The variation in position has been confirmed to have significant effects on the sagittal spinal alignment.Even in the same position,slight variations in positioning may also mask or increase the difference between multiple radiographs.For example,in spine surgery,the erroneous judgment of the degree of correction when comparing radiographs before and after operation.Therefore,the important influence by the various standing position on our clinical treatment and research can not be ignored.In summary,providing an accurate,consistent and representative position is urgently significant.Some scholars propounded proper positioning of the subjects during lateral radiographs of the spine to yield and evaluate sagittal spinal alignment.The body position includes the passive upper body support position and unsupported active position,involving varying degrees of flexion about shoulders and knees.This paper summarize the related literature to make a review.