Compressed homologous cancellous bone and bone morphogenetic protein (BMP)-7 or bone marrow accelerate healing of long-bone critical defects

We studied 18 adult male New Zealand rabbits with a critical right-sided ulnar defect of 15 mm. In six animals the defect was grafted with homologous compressed cancellous bone, in six animals with homologous compressed cancellous bone including 300 µg bone morphogenetic protein (BMP)-7 and in six animals with homologous compressed cancellous bone including 0.5 ml autologous bone marrow. The defect was studied using radiographs every second week for 10 weeks. At the conclusion of the experiment the animals were killed and the defect studied by histology and histomorphometry. In all animals treated with the addition of autologous bone marrow and in five of six animals treated with the addition of BMP-7, the defect healed. There was no union in animals treated with homologous compressed cancellous bone without additive. The histological picture of the regenerated area was similar in the two experimental groups. Woven bone contained small marrow spaces with fibrous tissue and capillaries. The osteoid seams were on average greater in animals that received autologous bone marrow as compared to animals that received BMP-7.