The effect of simulating leg length inequality on spinal posture and pelvic position: a dynamic rasterstereographic analysis

Abstract

Introduction: Leg length inequalities (LLI) are a common finding. Rasterstereography offers a non-invasive, contact-free and reliable method to detect the effects of LLIs on spinal posture and pelvic position.

Materials and methods: A total of 115 subjects were rasterstereographically examined during different artificially created leg length inequalities (5-15 mm) using a platform. The pelvic obliquity and torsion and the lateral and frontal deviation of the spine, as well as the surface rotation, were measured.

Results: Changes in platform height led to an increase of the pelvic tilt and torsion. Only minor changes in the spinal posture were found by different simulated leg length inequalities.

Conclusions: Our study showed that there was a correlation between an artificial leg length inequality up to 15 mm and pelvic tilt or torsion, but only minor changes in the spinal posture were measured. Further studies should investigate the effects of greater leg length inequalities on spine and pelvis.

Figures

Fig. 1

A rasterstereographic measurement of a female test subject with a simulated LLI of +15 mm on the right side. The left image shows the back surface of the female test subject with the projected horizontal light lines. This image is then analysed by the computer and transformed into a 3-D surface map of the back surface (right image). The red colour on the back surface represents a convex surface area, while the blue colour stands for a concave surface area

Fig. 2

The mean pelvic tilt (with SD) in mm for the simulated different platform heights (0, 5, 10, 15 mm) for the right-up and left-up group. The figure demonstrates an increase in the mean pelvic tilt by raising the platform height. The blue and green horizontal lines show the mean pelvic tilt for both groups in the neutral position. Negative values of the platform height mean an elevation of the platform on the left side, and positive values mean an elevation on the ride side

Fig. 3

The mean pelvic torsion in degrees for the different platform heights. For both groups an increase in pelvic torsion by raising the platform can be found

Fig. 4

Only minor changes of the mean frontal deviation in both groups for the different simulated platform heights

Fig. 5

Only minor changes of the mean lateral deviation in both groups for the different simulated platform heights

Fig. 6

Only minor changes of the mean surface rotation in both groups for the different simulated platform heights