STRAIN OF THE MUSCULUS INTEROSSEUS-MEDIUS AND ITS RAMI-EXTENSORII IN THE HORSE, DEDUCED FROM IN-VIVO KINEMATICS

The in vivo strains of the musculus interosseus medius (suspensory lig ament) and its rami extensorii (extensor branches) in the forelimb of the horse were determined from angular changes of the metacarpophalang eal and the distal interphalangeal joints. For this purpose, regressio n models were fitted to strains and joint angle combinations measured in in vitro limb loading experiments. The in vivo strains were compute d from the kinematics of 8 horses at the walk. the trot and the canter . It was found that the extensor branches were strained about 1.0% at hoof impact, which indicates that they passively extend the interphala ngeal joints just prior to impact and prevent flexion of the pastern j oint just thereafter. The maximal strain of the suspensory ligament am ounted to 3.4% at the walk, 5.6% at the trot and 6.3% at a slow canter .