Study of marker placements in the back for opto-electronic motion analysis.

Various investigations into anatomical landmarks that could be employed in spine and back surface measurement have highlighted the usefulness of the spinous processes of the vertebra and the posterior superior iliac spines of the pelvis. Earlier studies used an opto-electronic gait analysis system to examine the motion of skin markers and compared results with similar inter-vertebral movement recorded through radiographs. Consistent patterns of movement suggested a relationship between spinal and back surface motion. Further investigations into the use of opto-electronic gait analysis systems to measure dynamic back movements showed the capability of producing repeatable patterns of back movements. However, these studies, mainly measuring the range of movement (ROM) of spine, have not examined the effects of marker placements. While most ROM studies concentrate on stationary repetitive flexion/extension and bending movements, spinal ROM during walking and in scoliosis has not been widely reported. Spinal range of motion is an important indicator of spinal function and is used in the determination of disability and compensation. The present study has evaluated the placement of markers on the back and pelvis, used in three-dimensional opto-electronic systems for gait and movement studies. Various marker configurations have been compared and reported. The findings highlight the drawbacks of previously reported techniques, and particularly indicate that skin movement can adversely affect findings. However, the results confirm the feasibility of application of this technique to investigate dynamic trunk and spinal movement in both normal and deformed spines.