Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Biomaterials Help Animals With Bone Problems

Pet Column for the week of September 30, 2004

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Kim Marie Labak
Information Specialist

Bone grafts are not just for people anymore; now pets and horses can benefit from biomaterials that human medicine has been using for years. Biomaterials made from real bone or synthetic materials, such as plaster, can be used to help heal bone fractures, hold screws in place, fix implants in hip replacement, and deliver antibiotics to infected bone.

Dr. Dominique Griffon, surgery specialist at the University of Illinois Veterinary Teaching Hospital in Urbana, explains that many biomaterials now used by veterinarians come from the human medicine market, and there are few products especially made for use in animals.
One type of biomaterial, bone cement, is a paste that can be injected into bone, where it hardens and supports damaged or fractured bone.

The type currently being used is polymethylmethacrylate, or PMMA, an extremely strong polymer once used in human medicine. PMMA is not biologically "resorbable," so it cannot be degraded by the body. Therefore, one downside of using PMMA is that it prevents the bone from healing, since the cement remains as a foreign material.

This type of polymer is effective for external fixation of fractured bones, in which surgical pins are placed in the bone and protrude out of the body. The cement can be molded outside the body to secure the pins, holding the bone in place for healing. This procedure is commonly used for fixing fractured jaws and bones of small animals.
For internal fixation, in which the polymer is placed inside the body, sterile PMMA can stabilize pins for spinal fractures, or hold implants in place for hip replacements.

PMMA is currently the most widely used bone cement in veterinary medicine, and although resorbable bone cements, made from purified plaster and ceramics, exist for human medicine applications, the technology must be adjusted to meet the financial restraints of veterinary orthopedics.

PMMA and the more expensive resorbable bone cements can be used to deliver a steady dose of drugs directly into bone, without the toxicity associated with their circulation in the blood stream. Beads made from the bone cement can be infused with an antibiotic and surgically placed in bone to treat osteomyelitis, or bone infection.

These beads are especially useful for patients who have received a segment of bone allograft following removal of a bone tumor and must undergo chemotherapy, predisposing them to surgical infection. If PMMA is used, the beads eventually need to be removed. A resorbable cement does not have to be removed, eliminating the need for another surgery.

Veterinarians can also use bone allografts to repair fractures. An allograft is a transplant between different individuals of the same species. Bone allograft materials, made of chips of natural bone, are resorbable, so they dissolve and leave room for patients' own bone to heal. In addition, demineralized allografts contain growth factors, natural components of bone that induce bone growth and healing.

Dr. Griffon states that the future of biomaterials in veterinary medicine looks good. Although there are few products specifically made for veterinary use, the teaching hospitals at the University of Michigan, Colorado State University, and the University of Illinois are currently using bone cements, beads, and allografts in patients, and clinicians at Illinois, including Dr. Griffon, are conducting clinical research on biomaterials.

Dr. Griffon points out that medical companies are now recognizing the need and demand for veterinary biomaterials, and as products improve and become more readily available and affordable, veterinarians will be able to use them to help more animals.

For more information about biomaterials, contact your veterinarian.