The osteogenic effect of bone marrow was tested in rabbits, using
chambers that had been implanted in the peritoneal cavity (ectopic site)
and in a delayed-union model (orthotopic site). Osteogenesis was
accelerated in both sites after concentration of marrow elements by
centrifugation, but not after unit gravity sedimentation. Chambers that
were implanted with marrow that had been processed by simple and isopyknic
centrifugation demonstrated a more pronounced increase in deposition of
calcium compared with whole-marrow implants of equal volume (101 compared
with 193 per cent). Orthotopic grafting of a rabbit delayed-union model
with whole marrow and marrow that had been processed with simple
centrifugation significantly increased osteogenesis, as measured
biomechanically and biochemically. Significantly improved healing was
evident radiographically at five weeks after grafting with bone marrow that
had been concentrated by simple centrifugation.