A NEW SYSTEM FOR 3-DIMENSIONAL GAIT RECORDING USING ELECTROMAGNETIC TRACKING

A new methodology for three-dimensional gait recording was tested. It was based upon an electromagnetic tracking instrument. It repeatedly g enerates three different magnetic fields from orthogonal coils in a tr ansmitter. A sensor in these fields measures the magnetic flux in thre e orthogonal coils. From the resulting nine signals of magnetic flux, sensor position in x, y and z coordinates, and orientation in sagittal , coronal and transverse planes can be obtained. The errors in records of position and orientation were determined from recordings with a se nsor in a series of well-defined positions within an area sufficiently large to record the movements of a stride. Due to environmental distu rbances of the generated magnetic fields, the errors were too large to allow relevant recordings of gait movements. After compensation for t he local environmental disturbances, the errors of x, y and z coordina tes were < 2.0 cm, and the error of angle in the sagittal, coronal and transverse planes < 1.0 degree. Measurements of rotations with the se nsor in unchanged position had an error < 2.5%. With four sensors fixe d to pelvis and leg segments, records of three-dimensional gait moveme nts were obtained viith well-defined precision in all dimensions. (C) 1997 Elsevier Science B.V.