A model for evaluating injectable bone replacements in the vertebrae of sheep: radiological and histological study

We developed a bone-defect model in the vertebrae of sheep. Forty four cavi ties were prepared in the upper lumbar vertebrae of 11 sheep using a biopsy trocar via a posterior-lateral extracanal percutaneous route and the locat ion was monitored by radiology with a brilliance amplifier. The cavities we re 3 mm in diameter. The histological study was performed on 15 cavities wh ich were left empty to give reference data for the model. Histological and histomorphometry results showed that 67% of the surface area of the empty c avities was still empty 3 months after their preparation. Thus, the natural regenerative capacity of vertebral trabecular bone is limited. We performe d preliminary percutaneous injections of polymethylmethacrylate (PMMA) and nacre powder to assess whether this bone-defect model would be suitable for further studies on bone repair. Cavities were successfully filled with nac re powder (21 cavities) or PMMA (8 cavities) while monitoring the process b y interventional radiology. The experimental sheep vertebrae defect system is reproducible and appears to be a suitable model for testing injectable b iomaterials for treating bone loss. (C) 1999 Elsevier Science Ltd. All righ ts reserved.