A Comprehensive Guide to Bone Grafts in Orthopedic Surgery

What are Bone Grafts?

Bone grafts are pieces of bone transplanted from one place to another in the body to help repair and regenerate damaged or missing bone. They play an important role in orthopedic surgeries like fracture repair, fusion of bones, reconstruction after tumor removal, and treating non-union fractures.

Types of Bone Grafts

There are several different types of bone grafts that orthopedic surgeons use depending on the specific situation:

Autografts

Autografts are bone grafts taken from another part of the patient's own body. They are considered the "gold standard" because they carry no risk of rejection by the body. Common sites to harvest autografts from include the pelvis (iliac crest) and tibia. Autografts have excellent osteoconductive, osteoinductive, and osteogenic properties. However, harvesting bone does increase operative time and can cause donor site pain and morbidity.

Allografts

Allografts are bone grafts obtained from tissue banks containing donor bone from other human cadavers. While they avoid donor site issues, they carry a small risk of disease transmission or immune rejection. Allografts are processed to minimize these risks, which reduces their osteoinductive capacity compared to autografts. The most common allograft types are cancellous chips, cortical wedges/rings, and demineralized bone matrix.

Demineralized Bone Matrix (DBM)

DBM is processed allograft bone that has been treated to remove mineral but retain collagen and non-collagenous proteins, growth factors, and bone morphogenetic proteins (BMPs). It has osteoconductive and osteoinductive properties that stimulate bone formation and healing. Commercial formulations of DBM are widely used.

Synthetic Bone Graft Substitutes

These are artificially manufactured bone graft alternatives made of materials like calcium sulfate, calcium phosphates, bioglasses, and polymers. They provide a scaffold for bone regeneration but lack the cellular components and growth factors of autografts and allografts. Advantages are unlimited supply and avoidance of harvest risks/rejection. Common synthetic options are β-tricalcium phosphate and hydroxyapatite.

Bone Morphogenetic Proteins (BMP)

BMPs such as BMP-2 and BMP-7 are recombinant growth factors that have potent osteoinductive properties and stimulate bone formation. They are often combined with a carrier substance and implanted at orthopedic sites to enhance or replace bone grafting. BMPs carry significant cost but have shown efficacy in certain clinical scenarios like spinal fusions.

Factors in Choosing a Bone Graft

In determining which type of bone graft to use, surgeons consider the clinical situation, risks vs. benefits, healing biology required, structural needs, and cost-effectiveness. Autografts are best for their regenerative potential but harvesting bone leads to donor site pain/morbidity. Allografts and synthetic/biologic options avoid these issues while stimulating healing to varying degrees depending on their osteoconductive, osteoinductive, and osteogenic properties. A multidisciplinary decision balances these variables for optimal patient outcomes.