if both of a person s legs are so different and asymmetrical in length that it can be 
 observed with the naked eye , the person is said to have a the first is structural leg - length discrepancies , which are 
 innate or acquired differences in the actual lengths of the two legs . the second is 
 functional leg - length discrepancies ; there is no difference in the actual length , but the 
 length can sometimes differ according to changed status in the lower extremity such as the 
 contracture of joints , malalignment of the body , or when the difference in calcaneal 
 eversion between the feet is more than 3 degrees . leg - length discrepancies can cause 
 functional problems like gait abnormalities and/or loss of balance2 , 4 , and many 
 variations can be generated to compensate those inequalities5 , 6 . pelvis tilt in the frontal plane , flexion of the hip extensor and knee joint of the longer 
 leg in the sagittal plane , and increased plantar flexion of ankle in the sagittal plane of 
 the shorter leg are examples of compensations caused by differences in leg length7 . these unnecessary compensations caused by 
 different leg lengths lead to balanced body alignment and minimize sway and energy cost 
 during gait5 , 6 . however , it is not clearly known what changes these unnecessary compensations will show 
 according to different leg lengths5 . most 
 previous studies about different leg lengths have focused on lower extremity and pelvic 
 changes , and the measurements have also been limited to those obtained with 3d 
 equipment7 . therefore , the goal of this study was to investigate how an artificially created leg - length 
 discrepancy would immediately affect the pelvic position and spinal posture in healthy 
 subjects with the rasterstereographic device formetric 4d . the purpose and methods of the study were explained to all of the potential subjects of the 
 study , and all voluntarily agreed to participate . this study was approved by the catholic 
 university of pusan institutional review board ( cupirb-2014 - 007 ) . twenty subjects were 
 selected with leg - length discrepancies of less than 0.5  cm , and no pathological issues 
 related to the ankle joint , knee joint , hip joint and back ( age , 20.101.91  years [ meansd ] ; 
 height , 172.48.55  cm ; weight , 606.99  kg ) . in this cross - sectional study , for the measurements , the subjects stood with a platform 
 ( + 1  cm , + 2  cm , + 3  cm , + 4  cm ) below the right foot , the height of which could be controlled 
 by the measuring device to simulate different leg lengths . the weight distribution between 
 the left and right legs was quantified by the simulation platform prior to measurement to 
 ensure an almost equal weight distribution between both legs . all subjects waited 2  min to 
 adapt to the simulated leg - length discrepancies before performing measurement . after 
 performing measurement , the subjects were given 5  min of normal walking time between 
 measurements to return to a relaxed posture . we measured the pelvic position and spinal 
 posture when subjects were standing in a relaxed posture with fully extended knees on the 
 platform . the leg - length discrepancies were simulated by lifting the platform prior to the 
 rasterstereographic examination by the following amounts : + 1  cm , + 2  cm , + 3  cm , and + 4  cm . the rasterstereographic device formetric 4d ( diers international gmbh , schlangenbad , 
 germany ) measured pelvic tilt , pelvic torsion , inclination , the spinal kyphotic angle , and 
 the lordotic angle . rasterstereography is a method for stereophotogrammetric surface 
 measurement of the back that was developed in the 1980s by hierolzer and derup8 . based on the principle of triangulation , it 
 allows a radiation- and contact - free method of detecting and measuring the human 
 posture9,10,11 . the raster containing the grid 
 on the object under investigation replaces one of the cameras . parallel white light lines 
 are projected on the back surface of the subject by the slide projector . the 
 three - dimensional back shape leads to deformation of the parallel light lines , which can be 
 detected by the camera12 . data were processed using spss 18 for windows . to compare pelvic tilt , pelvic torsion , 
 inclination , the spinal kyphotic angle , and the lordotic angle between 0 and + 1  cm , + 2  cm , 
 + 3  cm , and + 4  cm leg - length discrepancies , one - way anova was used . to identify differences 
 for each muscle , bonferroni s post hoc test was performed . the pelvic position showed significant differences among leg - length discrepancies 
 ( p<0.05 ) and tended to increase as the leg - length discrepancies increased . the spinal 
 kyphotic and lordotic angles at the five different leg - length discrepancies did not show 
 significant differences ( table 1table 1.changes in pelvic position and spine posture for the different simulated platform 
 heightssph01  cm2  cm3  cm4  cmpelvic tilt ( )2.03.05.74.510.46.514.26.918.36.7pelvic torsion ( )2.21.43.31.94.05.34.72.03.81.7kyphotic angle ( )45.59.545.29.744.910.044.710.741.014.3lordotic angle ( )35.34.135.55.336.06.137.26.736.74.7each value represents the mean se . the present study aimed to investigate how an artificially created leg - length inequality 
 would affect the pelvic position and spinal posture . the study used the rasterstereographic 
 device formetric 4d , which can observe pelvic position and spinal posture together by 
 overcoming limitations of the previous studies on leg - length inequalities . if x - ray , ct , or mri are used to diagnose pelvic position and spinal posture , some negative 
 effects can be generated by radiation exposure that can be measured with radiation measuring 
 devices . on the other hand , the formetric 4d is strongly beneficial , since it does not lead 
 to radiation exposure and thus can be easily applied to most patients , from children to 
 adults . it is particularly convenient to measure of pelvis torsion , lordotic and kyphotic 
 angles of the pelvis , and vertebral rotation13 . some significant changes were found in pelvic position as a result of an artificially 
 created leg - length inequality . pelvic tilt is an indicator for observing pelvic changes in 
 the coronal plane according to leg - length inequalities , and it can be considered the most 
 sensitive factor subject to change due to leg - length inequalities , since it shows 
 significant increases as the length of the inequality increases in 1-cm increments . pelvic torsion is an indicator used to observe pelvic changes in the sagittal plane . as the 
 leg - length inequality increased from 0 to 1  cm , there was a significant difference , but there was no significant 
 difference for the leg - length inequalities of 2  cm , 3  cm , and 4  cm . pelvic torsion is also 
 likely to increase as a leg - length inequality increases , but the change is highest for a 
 1-cm gap , and the range of the change decreases as the leg - length inequality increases . 
 therefore , it seems like the pelvic torsion reacts the most for the first 1-cm gap , and even 
 though pelvic torsion can still be observed a little bit thereafter , a compensation tactic 
 is more likely to be generated as a result of pelvic tilt than by a change in torsion . these 
 findings are similar to that of the study of young et al.17 , who found a significant increase in pelvic tilt and pelvic torsion 
 resulting from a leg - length inequality of 1.5  cm . there was no significant difference in spinal posture resulting from the leg - length 
 inequalities . there appeared to be no significant changes in the trunk resulting from the 
 temporal leg - length inequalities , but spinal changes were observed with different leg 
 lengths for short periods of time in healthy adult male and female groups . the temporal 
 changes in the pelvis and the trunk resulting from leg - length inequalities seem to show more 
 of a compensation mechanism in the pelvis than the trunk . therefore , it is necessary to perform further research to observe the changes in the pelvis 
 and trunk resulting from leg length - inequalities in selected subjects with real leg - length 
 inequalities , not with artificially created ones .
[ purpose ] the purpose of this study was to examine how a leg - length discrepancy 
 contributes to the pelvic position and spinal posture . 
 [ subjects and methods ] a total of 
 20 subjects ( 10 males , 10 females ) were examined during different artificially created 
 leg - length inequalities ( 04 cm ) using a platform . the pelvic tilt and torsion and the 
 sagittal deviation of the spine 
 were measured using the rasterstereographic device 
 formetric 4d . 
 [ results ] changes in platform height led to an increase in pelvic tilt and 
 torsion , while no changes in the spinal posture were found with the different simulated 
 leg - length inequalities . 
 [ conclusion ] our study showed that a leg - length discrepancy may 
 cause pelvic deviation and torsion , but may not lead to kyphosis and lordosis . 
 therefore , 
 we consider that an artificially created leg - length discrepancy has a greater effect on 
 pelvic position than spine position .