A bone graft is a surgical procedure that involves transplanting bone material to repair damaged bone tissue. This material acts as a filler for bone voids and provides a structural scaffold for the body’s own bone to grow across. The goal is to encourage natural bone regeneration, often necessary for repairing fractures, fusing joints, or restoring bone lost due to trauma or disease. The selected material must be biocompatible and facilitate the biological processes of new bone formation.
Autografts: Bone From the Patient
An autograft is bone harvested directly from the patient’s own body. This graft is unique because it contains living bone cells (osteocytes) and osteoprogenitor cells capable of forming new bone. These living cells contribute directly to osteogenesis, the formation of new bone tissue. Autografts also contain natural growth factors that trigger local cells to become bone-forming cells, a process called osteoinduction.
This graft eliminates the risk of immune rejection or disease transmission, providing a complete biological package for healing. Common harvest sites include the iliac crest, the fibula, the ribs, or the chin, depending on the required volume. The structural matrix offers a physical framework, known as osteoconduction, allowing new blood vessels and bone cells to infiltrate and mature.
Allografts: Donor Bone Tissue
Allografts are bone materials sourced from human donors, typically obtained from tissue banks after screening and processing. Since the bone comes from a different individual, it must be treated extensively to remove all living cellular components that could trigger an immune reaction. The resulting non-living tissue is often stored through deep-freezing or lyophilization (freeze-drying) to maintain structural integrity.
This processing effectively removes immunogenic cells and lipids but leaves the mineralized collagen matrix intact to act as a scaffold. Allografts function mainly through osteoconduction, providing a physical structure that the patient’s own bone cells can use to grow across the defect. A variation of this is demineralized bone matrix (DBM), where the mineral content is stripped away with acid to expose the native growth factors embedded in the bone’s protein structure, enhancing its osteoinductive properties.
Manufactured Synthetic Materials
Synthetic bone grafts are lab-created materials designed to mimic the structure of natural bone, offering an unlimited and consistent supply. These materials are primarily composed of highly biocompatible ceramics and various calcium compounds. Widely used calcium phosphates include hydroxyapatite (HA), the main mineral component of human bone, and tricalcium phosphate (TCP).
These ceramic materials provide a porous, stable structure that acts as a scaffold for bone ingrowth. Other compositions include bioactive glasses, which are silica, calcium, and phosphorus compounds that actively release ions to stimulate bone regeneration. Polymers, such as polylactic-co-glycolic acid (PLGA), are also used to create biodegradable scaffolds that slowly dissolve as new host bone replaces the material. The ability to customize the shape and porosity of these substitutes makes them a valuable option for various surgical needs.
Xenografts: Animal Derived Materials
Xenografts are bone graft materials derived from a different species, most commonly bovine or porcine sources. The material must undergo rigorous processing, involving heat and chemical treatments, to remove all organic matter, including proteins and cells. This intense treatment eliminates the risk of disease transmission and prevents rejection. What remains is a pure mineral matrix, primarily a calcium structure resembling the inorganic component of human bone. Xenografts function exclusively as an osteoconductive scaffold, providing a long-lasting framework that is slowly replaced by the patient’s new bone.