Critical size defect in the goat's os ilium - A model to evaluate bone grafts and substitutes

Bone defects and their treatment are a well known problem in orthopaedic su rgery.(2) A critical size defect is a suitable model to study bone replacem ent materials. This study describes a critical size defect in the goal and the evaluation of three bone fillers (particulate autograft, particulate al lograft, and a polyethylene oxide/polybutylene terephthalate copolymer) in this defect. The goat allows for implantation of large implants and has a m etabolic rate more comparable with that of humans than small animals, The c ritical size defect, located in the goat's iliac wing, is easily reproducib le and allows qualitative and quantitative evaluation of bone grafts and bo ne graft substitutes. After 3 months of healing, the unfilled defects showe d 13.5% bone in the defect, the autografted defects 36.3%, and the allograf ted 18.5%. The copolymer gave only 1.5% bone in the defect; this is in cont rast to previous reports, The described model allows for the evaluation of bone graft substitutes before introduction into clinical practice.