Four types of bone grafts

In the United States alone, more than 500,000 bone grafts are performed each year, making bone tissue the second most common tissue transplanted after blood tissue. The autologous bone graft is the gold standard by which all other alternatives are measured. It has the lowest risk of immune rejection, as well as strong osteoconductivity, osteoinductivity, and osteogenesis, making it an effective adjunct in the treatment of post-traumatic conditions such as fractures, delayed healing, non-union, and deformity healing.

Here is the content:

l  Autologous bone grafts

l  Allografts

l  Artificial bone graft substitutes

l  Bone morphogenetic protein

Autologous bone grafts

Autogenous bone grafts can be taken from the skeletal crus, posterior superior skeletal spine, femur, proximal tibia, distal radius, and hawk's beak. Cancellous bone fills bone defects but does not provide significant mechanical support, so it is often used as an adjunct to various types of internal or external fixation. Autologous cancellous bone grafts are osteogenic, osteoinductive, and osteoconductive because they contain a large number of osteoblasts, mesenchymal mill cells, bone morphogenetic proteins, and growth factors. And because the cancellous bone matrix provides a good scaffold for inward vascular growth and infiltration of osteoblasts. Cancellous bone grafts fuse rapidly and can reach strengths close to those of cortical bone grafts after 6 months to 1 year.

Allografts

Allografts are commonly used in acute fracture and trauma revision reconstructive surgery. Bone blocks removed from the pelvis, ribs, fibula, and femur can be used as intact bone grafts for limb-preserving surgery. And can be used as longitudinally incised columnar bone blocks to fill bone defects, or as replacements for cortical bone after trauma. Because of their relative inertness, they are difficult to incorporate into host bone, but they provide mechanical and structural stability not found in collagen bone graft substitute granules.

Artificial bone graft substitutes

The use of non-biological porous materials as bone graft substitutes to develop artificial osteoconductive matrices is of great importance. The artificial material must mimic the host cancellous bone structure and allow for the fusion and proliferation of host mesenchymal stem cells. Commonly used artificial collagen bone graft substitute blocks include calcium phosphate (CaP) and calcium sulfate (CaS) compounds.

Bone morphogenetic protein

BMP is in the transforming growth factor-beta superfamily, a family of 20 different cytokines, each with varying degrees of osteoinductivity. Currently, the only FDA-approved BMP for trauma treatment is recombinant human bone morphogenic protein-2 (rhBMP-2), which can be used within 14 days of initial injury in open tibial stem fractures fixed with intramedullary nails.

In conclusion, except for autologous bone, the existing bone replacement materials have some defects and cannot fully meet the needs of clinical treatment. The future bone graft material should be a combination of advantages, not only osteoconductive matrix but also various growth factors that can promote bone healing, containing matrix stem cells capable of osteogenesis, receiving BMP stimulation. Both have high biomechanical stability but are also capable of complete degradation and integration. With the development of biomedical engineering technology, the introduction of new bone graft materials is expected.