Reasons for performing study: Understanding of the biomechanical effects of heel elevation remains incomplete because in vivo studies performed with skin markers do not measure the actual movements of the 3 digital joints.
Objective: To quantify the effects of 6° heel wedge on the 3-dimensional movements of the 4 distal segments of the forelimb in the walking horse.
Methods: Four healthy horses were used. Kinematics of the distal segments was measured invasively with a system based on ultrasonic triangulation. Three-dimensional rotations of the digital joints were calculated by use of a ‘joint coordinate system’ (JCS). Data obtained with heel wedges were compared to those obtained with standard shoes during the stance phase of the stride.
Results: Heel wedges significantly increased maximal flexion of the proximal (PIPJ) and distal (DIPJ) interphalangeal joints and maximal extension (mean ± s.d. +0.8 ± 0.3°) of the metacarpophalangeal joint (MPJ). Extension of the PIPJ and DIPJ was decreased at heel-off. Few effects were observed in extrasagittal planes of movement.
Conclusions: Heel wedges affect the sagittal plane kinematics of the 3 digital joints.
Potential relevance: Controversial effects previously observed on the MPJ may be explained by the substantial involvement of the PIPJ, which was wrongly neglected in previous studies performed on the moving horse.