Effect of anatomical landmark placement variation on the angular parameters of the lower extremities

Gait analysis gets more accessible, accurate, and simple to use as technology advances. The goal of this paper is to explore the accuracy of an advanced optical motion analysis system, where marker clusters mounted on rigid shapes are used to track the movement of body segments. It aims to examine the magnitude and nature of variation of the angular gait parameters of the lower extremities, caused by inaccuracy of the anatomical landmark placement. These landmarks are defined in the local coordinate systems of the rigid clusters through a calibration procedure, eliminating the need for skin-mounted markers. The used protocol makes it possible to evaluate the exact same motion using different calibrations, eliminating any other possible source for the variation of results. As a conclusion, a good estimation for the accuracy of the usual angular parameters in gait analysis is given. Mean anatomical landmark placement variation was found to be around 8.5 mm. The biggest standard deviations were found in the left hip flexion angle, with an average of 4.38°.