Methods: Six Thoroughbred racehorses were used, who had all completed at least 4 years of race training at a commercial stable. The approximate change in I that had occurred during race training was computed from radiographic measurements at the start and end of training using a simple model of bone shape. Results: A significant (P<0.001), approximately linear pattern of change in I was observed in each horse, with the maximum change occurring proximally and the minimum change occurring distally. Conclusions: The pattern of change in I was compatible with the hypothesis that sagittal-plane cantilever bending governed changes to the shape of the metacarpal bones during race training. The <a href="http://www.selleckchem.com/products/PD-0325901.html
">Selleckchem PD0325901 mechanical loading of the equine third metacarpal bone (MC3) during locomotion has been investigated using strain gauge methods (Turner et?al. 1975; Rybicki et?al. 1977; Biewener et?al. 1983; Gross et?al. 1992; Merritt et?al. 2006) and studies of limb dynamics (Biewener et?al. 1983; Merritt et?al. 2008). These studies all agreed that axial compression dominated MC3 loading at various gaits and speeds. Sagittal plane bending, although reported in many of these studies, did not appear to be EPZ-6438 cost
consistent in nature and is still poorly understood. For example, Rybicki et?al. (1977) found that bending of the MC3 at walk and trot was directed such that the dorso-medial side of the bone was under tension. Biewener et?al. (1983) used 2 different methods to compute loading of the MC3: a bone strain analysis which GDC-941
did not reveal substantial bending, and a biomechanical model driven by force plate and kinematic data, which predicted substantial sagittal plane bending. The differences between the results of the 2 models were partially ascribed to the simplicity of the latter model, which lacked a representation of the force acting upon the distal metacarpus due to the paired proximal sesamoid bones (Biewener et?al. 1983). The dominance of axial compression was explained by Thomason (1985), who investigated the trabecular structure of the MC3 condyle and described a mechanism in which the paired proximal sesamoid bones and the first phalanx created a dorso-palmar force balance. The net force on the distal MC3, arising from the sum of articular contact forces, was thus proximally directed and aligned with the MC3 axis, resulting in axial compression. Merritt et?al. (2008) showed that this mechanism was mechanically valid throughout the stride at walk and trot, using a model that incorporated the major bones, ligaments and tendons of the distal limb. Due to the strong fibrous union between the 3 metacarpal bones, which often becomes ossified, they have previously been treated as a single beam (Piotrowski et?al. 1983), which we shall refer to in this paper as the metacarpal complex (MC).