Lumbar spine intersegmental motion analysis during lifting.
UNLABELLED: There are a lot of in vitro and also in vivo studies under strictly restricted and subject-demanding laboratory conditions using X-ray or MRI recordings, but very few studies give information about the lumbar spine intersegmental behavior in daily life activities. Aims of this study were to measure the intersegmental lumbar spine motions during lifting trials and to determine the different motion patterns of different subjects performing comparable lifting tasks. First, 11 healthy volunteers had to perform lifting tasks (box weight 4-15 kg) using their favorite lifting technique (no instructions by the researcher). The coordinates of skin-markers attached on lumbar spines of the subjects were measured using 3D-motion capturing and then transformed to Cardan-angles. Second, 23 volunteers performed lifting tasks (box weight 4-15 kg) with the instruction to bend their knees during lifting. Coordinates of this smaller set of markers on lumbar spines of the subjects were transformed to intersegmental angles using a spline-method. From the first experiment three groups of motion patterns are distinguishable: subjects who used only small intersegmental range of motion within their upper lumbar spine and bended their knees during lifting were in contrast to subjects who used 3.25 times wider range of motion in the upper lumbar spine and did not bend the knees (cluster analysis, c = 0.76). The third group was not assignable to these other two groups. Within all lifting trials of the second experiment different groups were detectable also: in spite of all subjects bended their knees, there were subjects with wide range of motion of lumbar spine motion segments. Other subjects were able to reduce intersegmental range of motion (k-means clustering, msv > 0.47). From this it follows that the intersegmental motion of lumbar spine is individually different and not equal for all lumbar levels. Furthermore, lifting technique influenced the motion of the lumbar spine. But not for all subjects, the advice to bend the knees during the lifting effectively reduced the lumbar motion ranges. IN CONCLUSION: special instructions to reduce lumbar spinal motion are recommended. Due to different lumbar spine motion patterns, different loading situations are anticipated because of changing lever arms and angular accelerations. This understanding is important in reducing spinal loading and to prevent spinal disorders in manual material handling tasks.