PELVIC MOTION - INDIVIDUAL VARIATIONS IN NORMAL ADULT GAIT

Purpose of the study Pelvis motion appears as a main human gait compon ent, it is linked to the lower limb joints and to the spine. Current d evices, especially the opto-electronical systems, allow quantitative a nd tri-dimensional gait studies. The purpose of this study was to quan tify the pelvic motion individual variability in a sample of healthy s ubjects. Materials and methods The study based on a 18 volunters sampl e. There were 14 men and 4 women, ranged in age from 25 to 37 years. A clinical examination and a AP radiograph of pelvis allowed to include healthy subjects. We used the three-dimensional analysis VICON(TM) sy stem with five cameras. Nine records were performed for each subject d uring a free-speed walking. These nine records were distributed on thr ee different days. Results The step length medianes varied from 1100 t o 1600 mm with a significantly (p < 0.05) regression between the step length, the walking speed and the subjects height. Vertical pelvic osc illations varied in this sample from 25 to 60 mm and linked with step length and walking speed. Pelvic rotation around the vertical axis var ied from 1.5 to 15 degrees. We did not found regression between this p elvic rotation and the length step. it seems there are three types of pelvic rotation around the vertical axis. At the beginning of the stan ce phase, in type I, the pelvis is in the transversal plane whereas in the type II, it appears with the maximal rotation. In type III, the v alue of pelvic rotation is very low. The successive lateral inclinatio ns of pelvic described a complex motion which varied from 1.5 to 9 deg rees The rotation of shoulders around the vertical axis varied from 4 degrees to 13 degrees and the successive inclinations ions varied from 3.25 degrees to 12 degrees. We did not found any regression between t he pelvic and shoulders motion values. Discussion This study showed th at the pelvis motion varied considerably from one subject to another. These variations induce different ways of walking with various consequ ences on the hip joint and the spine. We suppose that these variations could take a part in etiology of some deseases as hip arthitis or in total hip arthroplasty failure, especially in cup wearing.