Bone and Fracture Treatment in Horses
Following his in-depth presentation on bone remodeling and bucked shins, David M. Nunamaker, VMD, Dipl. ACVS, Jacques Jenny Orthopedic Surgery Chair at the University of Pennsylvania's New Bolton Center, continued the Milne State of the Art Lecture at the 2002 American Association of Equine Practitioners Convention with a focus on bone properties and fracture treatment in horses.
"Bone is a unique and fascinating material," he began. "People often think of bone as being relatively inert, but I'd like to dispel that concept. Modeling and remodeling can be occurring in the same bone at the same time–bone is always in all stages of remodeling. Bone does not heal, incorporating the scar tissue as seen in most all other tissues–it regenerates itself. It changes its shape and structure based on its use, and if broken can resume 100% of its former strength and function."
Nunamaker described in great detail and with many microscopic views the microstructure and modeling/remodeling processes of bone, beginning with bone composition–which includes osteogenic (bone-building) cells, organic matrix, and mineral. The cells include osteoblasts (which create new bone, are very metabolically active, and participate in matrix mineralization), osteoclasts (which resorb, or break down, bone), and osteocytes. The latter connect with other osteocytes and osteoblasts to cover more than 90% of mature bone matrix, forming a network that controls mineral exchange between bone and blood, and might act as chemical/mechanical transducers to initiate bone modeling or remodeling.
Osteoblasts follow osteoclasts when remodeling, building new bone in the resorbed cavities or depressions on the surface in the wake of osteoclast activity (see image here). "Since bone can only form on surfaces, resorption creates the surface on which the bone forms to replace itself," Nunamaker explained
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