In vitro strength of the suspensory apparatus in training and resting horses

Forty-eight limbs of 12 freshly euthanized horses were used to generate data on the strength of the equine suspensory apparatus. The point of failure of the suspensory apparatus of each limb was determined. Immediately before euthanasia, 6 of the 12 horses (thoroughbreds and standardbreds) had been engaged in active training or racing, and six horses in stall and/or pasture activity. In the actively training or racing horses, the point of acute failure of the suspensory apparatus was within the proximal sesamoid bones in 20 (83%) limbs (resulting in 17 apical fractures, 2 basilar fractures, and 1 midbody fracture). In the pasture exercised or stalled horses, the point of failure of the suspensory apparatus was either acutely within the suspensory ligament (10 horses, 42%) or, if no acute failure occurred, insidiously within the suspensory ligament (12 horses, 50%). Active training appeared to have a strengthening effect on the suspensory ligament, causing the weakest point in the suspensory apparatus to become the sesamoid bones rather than the suspensory ligament. An average force of 1338 kg (between 1082 and 1673 kg) was needed to fail the suspensory apparatus in this group of horses. In nontraining horses, the site of failure was most often the suspensory ligament. An average force of 1100 kg (between 918 and 1241 kg) used to fail the suspensory apparatus in this group of horses was significantly (p less than 0.5) less than in the first group.