Editor's Note: This article is part of TheHorse.com's ongoing coverage of topics presented at the British Equine Veterinary Association's 51st annual Congress, held Sept. 12-15 in Birmingham, U.K.
Bone fractures in horses, whether catastrophic or microscopic, heal through a complex sequence of events. Owners and veterinarians who understand this process can take steps to improve a fracture's outcome and a horse's prognosis.
Peter Clegg, MA, VetMB, PhD, Dipl. ECVS, CertEO, MRCVS, from the University of Liverpool Veterinary Teaching Hospital, in Cheshire, U.K., reviewed these influences on fracture healing at the British Equine Veterinary Association's 51st annual Congress, held Sept. 12-15 in Birmingham, U.K.
Clegg described the fracture healing process in three stages: The initial inflammatory response that debrides (removes dead tissue) the fracture site; the repair phase that produces a callus (bony tissue that develops around the ends of a fracture during healing); and remodeling, during which scar tissue becomes bone. The variables that impact this process include loading, strain, and infection.
"One of the key determinants of fracture healing is the degree of immobilization," Clegg explained. Immobilization (e.g., stall rest) decreases strain, improves healing and osteogenesis (bone production), and decreases callus, while mobilization (e.g., controlled exercise) increases strain, osteogenesis, and fracture healing. So which approach do veterinarians recommend?
"There is a complex relationship between mechanical loading and fracture healing," Clegg said. "Many fractures are probably rested too long. At a certain point strain encourages fracture healing and exercise is beneficial."
Clegg said controlled exercise can also help prevent other fracture-related diseases, such as osteoarthritis in cases with joint involvement.
Another hindrance to fracture healing is infection. "Infection is always a risk and contributes greatly to both failure in fracture repair and substantial increase in veterinary costs of treatment," said Clegg.
Horses at most risk of infection include those with open fractures, ischemia (lack of blood flow), necrosis (tissue death), and long bone fractures, which have a fivefold increased risk of infection, he said.
"Risk of infection of fractures can be reduced by appropriate antibiosis, good (and speedy) surgical techniques, and appropriate debridement of any contaminated or devitalized tissues," Clegg explained.
Other factors he suggested considering during fracture healing include the horse's age and size, any concurrent systemic disease, and the horse's weight-bearing ability immediately after surgery.
Recently, veterinarians and researchers have pursued a variety of tools and techniques to further improve fracture healing such as:
- Bone grafts.
- Mesenchymal stem cell therapy and growth factors called bone morphogenic proteins that increase the rate of bone formation and maturation. These are "receiving current research interest, although they have not so far reached mainstream clinical practice," Clegg added.
- Stimulatory therapies such as pulsed ultrasound, electromagnetic therapy, shockwave therapy, and body vibration to increase bone density. "But these approaches have yet to achieve any clinical acceptance or evidence for clinical efficacy," he cautioned.
Clegg said future treatments might include gene therapies involving the sclerostin gene for accelerated fracture healing. For the time being, owners and veterinarians can best influence healing through a combination of proper surgical technique, infection prevention, and a controlled exercise plan during rehabilitation, he concluded.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.
