The Complete Guide to Bone Grafts in Orthopedic Surgery

Bone grafts play an important role in orthopedic surgery, helping to facilitate bone healing when patients have fractures, non-unions, or bone defects. Surgeons use different types of bone grafts depending on the clinical situation. In this blog post, we will explore the various bone graft options available and their applications.

Autografts

Autografts, also known as autogenous bone grafts, are considered the gold standard as they provide the highest chances of successful fusion. With autografts, bone is harvested from one area of the patient's body and transplanted to another site, allowing for complete histocompatibility. Some common types of autografts include:

Cancellous Bone Graft

Cancellous bone, also called spongy or trabecular bone, has a high concentration of osteoblasts and osteocytes, giving it superior osteogenic potential. It is often used to fill bone voids or integrate implants. While it provides no structural support, its large surface area promotes revascularization.

Cortical Bone Graft

Cortical bone, also known as compact bone, has excellent structural integrity but lower cellularity. It is slower to incorporate than cancellous bone via creeping substitution. Cortical grafts are useful for filling structural defects or providing load-bearing support.

Vascularized Bone Graft

This type of graft involves preserving the bone's nutrient blood vessels. This maintains viability of osteocytes and osteoprogenitor cells, allowing for primary bone healing versus creeping substitution. Commonly used vascularized grafts include the fibula and iliac crest.

Allografts

Allografts involve transplanting bone from a human cadaver. While available off-the-shelf, allografts lack osteogenic potential and carry infection/disease risks. Processings like irradiation compromise properties. Allografts exhibit osteoconductivity and sometimes osteoinductivity. Common types include cancellous, cortical, and demineralized bone matrix (DBM).

Synthetic Grafts

Calcium-based synthetic grafts are osteoconductive alternatives. Common varieties are calcium sulfate, calcium phosphate, and tricalcium phosphate. They degrade at different rates, have varying strengths, and come in multiple forms like powders, cements, or coatings. While promoting bone ingrowth, they lack living cells.

Orthobiologics

Growth factors like BMPs and PTH augment healing by recruiting stem cells to form new bone. Recombinant human BMP-2 and BMP-7 specifically induce osteoblast differentiation and are FDA-approved for certain applications. Delivery methods continue to be refined to better control diffusion.

In summary, orthopedic surgeons choose between autografts, allografts, synthetics, and biological factors based on a patient's specific clinical situation, balancing immunogenicity, structural support needs, healing properties, risks, and costs. No single option is universally superior. A judicious, customized approach leads to the best outcomes.