Categorization of Bone Grafts

An essential component of any bone healing procedure is the selection of bone graft. Bone grafts are implanted materials that support or promote bone healing through an osteogenic, osteoconductive and/or osteoinductive mechanism to the local site.

Osteogenesis

Osteogenesis is the development and formation of bone. Bone grafts that work through an osteogenic mechanism provide the appropriate cellular elements, which survive transplantation and synthesize new bone at the recipient site.1

For any bone grafting procedure to be successful, the graft site must contain a sufficient number of bone-forming (osteogenic) cells to form new bone and remodel the residual graft into viable bone. For example, cancellous autograft, derived from iliac crest or tibial plateau, contains enough cells to be considered osteogenic. Local bone from the primary surgical site generally contains cortical bone with much fewer cells.

Examples of osteogenesis include:

Osteoconduction

Osteoconduction is a passive process which refers to the ability of bone forming cells in the grafting area to move across a scaffold and slowly replace it with new bone over time. Osteoconductive materials serve as a scaffold onto which bone cells—osteoblasts and osteoclasts—can attach, migrate, grow and/or divide.

In this way, the bone healing response is conducted through the graft site, just as a vine uses a trellis for support. Bone-forming cells require a matrix or scaffold for attachment. Many osteoconductive scaffolds fall in the category of autograft extender or bone void filler.

Examples of osteoconduction include:

Osteoinduction

Osteoinduction is an active process during which bone graft recruits bone-forming cells to the site of implantation and induces them to form new bone.

Osteoinduction refers to the ability of the graft to send a signal to attract, proliferate, and differentiate early-lineage cells (e.g., mesenchymal stem cells or osteoprogenitor cells) into bone-forming cells, resulting in the formation of healthy mineralized bone. These signals are part of a group of naturally occurring proteins called BMPs and are found in normal bone in picogram quantities.

BMPs are the only protein(s) known to be osteoinductive; however, not all members of the BMP family are capable of osteoinduction. Highly osteoinductive bone grafts containing BMP-2 have been evaluated and approved by the U.S. Food and Drug Administration (FDA) as an alternative to autograft in certain spine, orthopedic trauma, and oral-maxillofacial indications.*

*BMPs have been tested as an autograft alternative in multiple clinical studies for certain indications in spine, orthopedic trauma, and oral-maxillofacial surgery.2–5

Some BMPs with carriers exhibit osteoinduction.

INFUSE BMP Examples

Download a guide to proper categorization of bone grafting options
 

References

  1. Greenwald AS, Boden SD, Goldberg VM, Khan Y, Laurencin CT, Rosier RN; Bone-graft substitutes: facts, fictions, and applications. American Academy of Orthopaedic Surgeons. The Committee on Biological Implants. J Bone Joint Surg Am. 2001;83-A Suppl 2 Pt 2:98-103.
  2. Burkus, et al. Anterior Lumbar Interbody Fusion Using rhBMP-2 With Tapered Interbody Cages. J Spinal Disorders. 2002; 15(5): 337-349.
  3. Boyne PJ, Lilly LC, et al. De Novo Bone Induction by Recombinant Human Morphogenetic Protein-2 (rhBMP-2) in Maxillary Sinus Floor Augmentation. J Oral Maxillofac Surg. 2005; 63:1693-1707.
  4. Fiorellini JP, Howell TH, et al. Randomized Study Evaluating Recombinant Human Bone Morphogenetic Protein-2 for Extraction Socket Augmentation. J Periodontol. 2005; 76(4): 605-613.
  5. Friedlaender, et al. Osteogenic Protein-1 (Bone Morphogenetic Protein-7) in the Treatment of Tibial Nonunions: A Prospective, Randomized Clinical Trial Comparing rhOP-1 with Fresh Bone Autograft. J Bone Joint Surg Am. 2001; 83-A Suppl 1(Pt 2): S151-S158.