Quantification of Skin Displacement in the Walking Horse

Abstract

Kinematic gait analysis techniques normally rely on skin markers for determination of the position of certain palpable skeletal structures. As it is well known that during movement the skin shifts over the underlying bone, a biological error is inevitably introduced by this procedure. A method is presented for quantitative determination of skin movement over the underlying skeletal structures during normal locomotion of the walking horse. The principle of the method is based upon simultaneous visualization of the positions of the skin and the underlying bony structures, by marking the bones with implanted Light-Emitting Diodes (LEDs) and the skin with self adhesive spot labels. Recordings are made using photography. The major direction of movement is along the bone axis and a gradual increase is found from the foot in a proximal direction. It is concluded that skin displacement in the walking horse is substantial around carpus and tarsus and is very probably even larger around the more proximally located joints. Thus for correct interpretation of kinemtic data, correction factors should be established.