Freeze-dried cortical bone can be used as a biological plate, either alone or in combination with other internal fixation devices, to stabilize fractures. In addition to it conferring mechanical stability, freeze-dried cortical bone may enhance fracture-healing and increase the bone stock. This study examined the effect of a freeze-dried allograft cortical bone plate (FACBP) on the biomechanical properties of an implant site in a canine bone defect model. Twelve adult mongrel dogs (around 4.8 kg) were used. A segmental critical-size defect (5 mm in length) at ulna diaphysis was created using an oscillating saw. The experimental animals were divided into two groups: eight dogs treated with an absorbable bone plate (FACBP) fixed by metal bone screws (Group A) and four dogs treated with a commercial stainless steel bone plate and metal bone screws (Group B). Bone healing was assessed by radiography, Dual-energy x-ray absorptiometry and a three-point bending test. The FACBP incorporated in the host bone produced complete remodeling of the cortical bone. There was no significant difference in the bone mineral density and biomechanical tests between the FACBP application site and normal ulna or a stainless steel bone plate of the ulna. These results suggest that FACBP facilitates recovery from a bone fracture by assisting in the induction of new bone formation in a defected fracture.

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.