Magnesium Bone Cement Aids Fracture Repair

Biocompatible magnesium phosphate bone cement might be a better option for aiding fracture healing in horses than the calcium phosphate cement more commonly used today, according to a study performed by researchers at The Ohio State University.

Equine fractures are often complicated by extensive soft tissue damage, reduced blood supply in the area, and the need for immediate weight bearing on the affected limb. Bone cement can be used to support internal fixation (such as plates and screws), bond loose bone fragments, provide filler, and act as a scaffold for new bone growth. However, there can be problems with calcium cement, including slow absorption and lack of adhesion. Additionally, calcium-based cements can activate a clotting response.

Bone Cement

On radiographic study, four weeks after osteotomy, bone fragments affixed with magnesium phosphate cement (Mg, far right) were found to be significantly closer to the parent bone than fragments affixed with calcium (Ca, middle) phosphate or no cement (left). The arrows indicate the length and width of the greater bone callus (the new bone) and bone remodeling activity.

Researchers replicated comminuted (multiple) fractures by creating 1-centimeter Y-shaped osteotomies (surgical cuts in bone) in the second and fourth metatarsal bones of eight clinically normal mares for a total of 32 osteotomies. The resulting triangular fragments were then replaced using the magnesium cement, the calcium cement, or nothing. The researchers took radiographs of the osteotomies at regular intervals during the seven-week healing period. The mares were euthanatized and the metatarsal bones examined using computed tomography (CT) and bone histology (microscopic evaluation) for adverse reactions, for signs of healing (including closure between the fragment and the parent bone), and callus formation.

The fragments affixed with the magnesium cement were found to be significantly closer to the parent bone during all stages of healing as compared to fragments with either calcium cement or no treatment. Mature woven bone and fibrous tissue were more abundant in the sites treated with magnesium, indicating active healing was taking place. Additionally, the magnesium cement remained at the site 94% of the time, while the calcium cement persisted in 25% of the treated fractures. The handling characteristics of both cements were similar, but researchers noted that the magnesium provided immediate adhesion, whereas the calcium did not adhere immediately, but provided some cementing when it hardened.

Researchers performing the study were Martin Waselau, DrMedVet, MS; Valerie F. Samii, DVM; Steven E. Weisbrode, VMD, PhD; Alan S. Litsky, MD, ScD; and Alicia Bertone, DVM, PhD. The study was published in the April 2007 edition of the American Journal of Veterinary Research.

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care.

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