Cross-validation of marker configurations to measure pelvic kinematics in gait.

External tracking of three-dimensional lumbar spine and pelvic oscillations is a method recently used in clinical gait analysis. This investigation validated the use of plate mounted marker configurations overlying the median sacral crest (S1) against single marker sets placed over the anterior and posterior superior iliac spine for the assessment of angular kinematic profiles of the pelvis during treadmill ambulation. Rotational pelvic movements of 12 asymptomatic male subjects were recorded by a 3D-ultrasonic measurement device using four single markers placed over the anterior and posterior superior iliac spine. Additionally, three external ultrasound markers were mounted on a rigid plate placed over S1. No significant differences (P > 0.05) for movement variability or range of motion between marker configurations could be obtained. It could be concluded that trucking of plate-mounted markers overlying S1 seems to be adequate for monitoring rotational pelvic motions in normal gait.