Evaluation of equine cortical bone transplantation in a canine fracture model

Freeze-dried bovine bone transplantation is commonly used for orthopaedic surgery. Equine bone, which is available in great quantity, can be obtained as easily as bovine bone, and so represents a potential source of bone for transplantation. In the present study freeze-dried equine cortical bones were transplanted into experimentally-induced fibular defects in canines to evaluate xenogenic implantation of equine bone. Cortical bones that had been freed of antigens and defatted with chloroform and methanol were freeze-dried at -80 °C for preservation of bone morphogenetic protein, sterilized with ethylene oxide gas and stored at room temperature. The experimental osteotomy was performed in a 15 mm-long bilateral region of each proximal metaphyseal fibula. The area of defect in eight beagle dogs (n = 16) received a transplanted freeze-dried equine cortical implant. The control group consisting of two beagles dogs (n = 4) received an autograft of a similar implant. The experiment region was radiographically monitored for bone union and host serum osteocalcin level was determined to assess osteoblast activity every two weeks for 24 weeks. In 14 of the 16 experimental cases, the graft was not associated with new bone formation. Resorption after new bone formation and remodelling with new bone formation each occurred in a single case. The results support the potential of using freeze-dried equine cortical bones as a xenogenic bone graft material in canines.