Intra and interindividual variations of pelvic mobility in normal adult walk

PURPOSE OF THE STUDY: Pelvis motion appears as a main human gait component, it is linked to the lower limb joints and to the spine. Current devices, especially the opto-electronical systems, allow quantitative and tri-dimensional gait studies. The purpose of this study was to quantify the pelvic motion individual variability in a sample of healthy subjects. MATERIALS AND METHODS: The study based on a 18 volunters sample. 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 system with five cameras. Nine records were performed for each subject during a free-speed walking. These nine records were distributed on three different days. RESULTS: The step length medianes varied from 1100 to 1600 mm with a significantly (p < 0.05) regression between the step length, the walking speed and the subjects height. Vertical pelvic oscillations varied in this sample from 25 to 60 mm and linked with step length and walking speed. Pelvic rotation around the vertical axis varied from 1.5 to 15 degrees. We did not found regression between this pelvic rotation and the length step. It seems there are three types of pelvic rotation around the vertical axis. At the beginning of the stance 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 value of pelvic rotation is very low. The successive lateral inclinations of pelvic described a complex motion which varied from 1.5 to 9 degrees. The rotation of shoulders around the vertical axis varied from 4 degrees to 13 degrees and the successive inclinations varied from 3.25 degrees to 12 degrees. We did not found any regression between the pelvic and shoulders motion values. DISCUSSION: This study showed that the pelvis motion varied considerably from one subject to another. These variations induce different ways of walking with various consequences on the hip joint and the spine. We suppose that these variations could take a part in etiology of some diseases as hip arthritis or in total hip arthroplasty failure, especially in cup wearing.