Bone grafting: autograft, allograft, and substitutes
The established clinical standard for replacing missing bone, and the trade-offs that motivate engineered alternatives.
Autograft — bone taken from the patient, typically the iliac crest — remains the reference standard, because it is the only material that supplies all three of what bone repair needs: osteogenic cells, an osteoconductive structure to grow along, and osteoinductive signals. Its limits are supply and donor-site morbidity: there is only so much, and harvesting it hurts.
Allograft, from a donor, is available in quantity but is processed to reduce immunogenicity and disease transmission, which strips most of its cells and much of its osteoinductive activity. It is largely a scaffold. Synthetic substitutes — calcium phosphate ceramics and composites — go further in that direction: reliable structure, no biology.
This trade-off is the entire motivation for engineered bone. Adding cells and osteoinductive factors to a synthetic scaffold is an attempt to reconstruct autograft's three properties from parts that can be manufactured at scale.
Related articles
- BoneCritical-size bone defectsThe threshold beyond which bone cannot bridge a gap on its own — and the problem most bone engineering exists to solve.
- BiomaterialsCalcium phosphate ceramicsHydroxyapatite and tricalcium phosphate — synthetic analogues of bone's own mineral.
- BiomaterialsScaffold design principlesPorosity, strength, and degradation rate — the competing requirements every scaffold has to reconcile.
- BoneBMP-2: bone morphogenetic protein 2The osteoinductive growth factor that moved from a laboratory curiosity to approved clinical use — and the lessons of its dosing.
- CellsMesenchymal stem cellsThe most widely studied cells in regenerative medicine — and a reassessment of what they actually do.
- BoneBone remodelingThe continuous cycle of resorption and formation that rebuilds the skeleton throughout life.