Effects of egg‐bar shoes on the 3‐dimensional kinematics of the distal forelimb in horses walking on a sand track

Abstract

Understanding of the biomechanical effects of egg-bar shoes remains incomplete because kinematic studies are usually performed on hard tracks and with skin markers that do not measure the actual 3-dimensional (3D) movements of the 3 digital joints. To quantify the effects of egg-bar shoes on the 3D kinematics of the distal forelimb in horses walking on a sand track. Four healthy horses were equipped with ultrasonic markers fixed surgically to the 4 distal segments of the left forelimb. The 3D movements of these segments were recorded while the horses were walking on a sand track. Rotations of the digital joints were calculated by use of a joint coordinate system. Data obtained with egg-bar shoes were compared to those obtained with standard shoes. Mean differences were expressed in a 0.95 confidence interval. With egg-bar shoes, the initial sinking of the heels into the ground during landing was reduced and the heels were raised by up to 5.1 degrees (3.5-6.7 degrees) compared to standard shoes at mid-stance. Concurrently, maximal flexion of the distal (DIPJ) and proximal (PIPJ) interphalangeal joints was increased by up to 3.2 degrees (2.2-4.2 degrees) and 1.8 degrees (1.1-2.5 degrees), respectively, at the beginning of the stance phase. At heel-off, extension of the DIPJ was reduced by 3.8 degrees (2.6-5.0 degrees). In extrasagittal planes of movement, egg-bar shoes prevented sinking of the medial quarter into the ground which led to a slight decrease of DIPJ medial rotation and lateromotion. Egg-bar shoes prevent the heels and, to a lesser extent, the medial side of the hoof from sinking into the ground on a sand track. They contribute to a decrease of DIPJ maximal extension at heel-off and to hoof stabilisation in the transversal plane. Such quantitative results support the clinical indications of egg-bar shoes.