Superior osteogenesis in transplanted allogeneic canine skull following chemical sterilization

Sterilization of allogeneic bone increases the availability of this tissue for supplanting skeletal defects and effecting fusions. The optimal sterilant destroys micro-organisms, preserves the physical and chemical integrity of bone and possibly even reduces immunogenicity. Cortical bone of skull heals slowly and is variably resorbed. Of 36 dogs, spontaneous regeneration in 72 paired 20 mm defects was constant but always incomplete, and restored only about one third of the cross-sectional area of the defect at six months. The repair in defects replaced with canine allogeneic bony disc, sterilized with ethylene oxide (n = 9), gamma irradiation (n = 7), or methanol/chloroform/iodoacetic acid (n = 7) and then lyophilizedd, was compared with repair in defects filled with aseptically procured lyophilized only (n = 23) discs from the same donor. Criteria for evaluation of implants at six months included volume of defect filled, radiodensity, extent of fusion around circumference, revascularization, and remodeling. Bony discs sterilized with methanol/chloroform/iodoacetic acid remodeled at a superior rate (p less than 0.01). Radiation sterilization resulted in diminished density and inferentially reduced protection of the brain (p less than 0.025). Ethylene oxide, lyophilized implants, and implants lyophilized only produced comparable repair. Whereas an acceptable cranioplasty was achieved in 86% of methanol/chloroform/iodoacetic acid, lyophilize implants, all other alloimplants served an osteoconductive function with a successful repair occurring in 56% to 58%.