Overview
Bone grafting is a surgical procedure used to stimulate bone healing, replace missing bone, or augment bone stock in orthopaedic reconstruction. Bone grafts are widely used in fracture nonunion, spinal fusion, tumor surgery, revision arthroplasty, and reconstructive trauma procedures.
The purpose of bone grafting is to enhance the biological environment for bone healing by providing cells, growth factors, and structural scaffolding that support new bone formation. Successful graft incorporation depends on mechanical stability, vascular supply, and biological compatibility between graft and host bone.
Biological Principles of Bone Grafting
Bone grafts function through three fundamental biological mechanisms that support bone regeneration.
| Mechanism | Description | Clinical Example |
|---|---|---|
| Osteogenesis | Formation of bone by living osteoblasts present in the graft | Autogenous cancellous graft |
| Osteoinduction | Stimulation of stem cells to differentiate into osteoblasts | Bone morphogenetic proteins |
| Osteoconduction | Providing a scaffold for new bone growth | Allografts and synthetic substitutes |
Autografts possess all three biological properties. Allografts and synthetic substitutes primarily provide osteoconduction, although some processed grafts may also provide limited osteoinductive activity.
Classification of Bone Grafts
Bone grafts are classified according to their biological source.
| Type | Source | Key Advantages | Limitations |
|---|---|---|---|
| Autograft | Same patient | Best biological properties | Limited quantity |
| Allograft | Human donor | Large supply | Risk of disease transmission |
| Xenograft | Different species | Abundant supply | Immune reaction risk |
| Synthetic substitute | Artificial material | No donor morbidity | Limited biological activity |
Autogenous Bone Grafts
Autogenous bone grafts are harvested from the same patient and remain the gold standard in bone grafting procedures. Because they contain living osteoblasts and growth factors, they possess the full spectrum of biological activity required for bone regeneration.
Common Donor Sites
- Iliac crest
- Proximal tibia
- Distal radius
- Fibula
The iliac crest is the most commonly used donor site because it provides a large volume of cancellous bone with high osteogenic potential.
Advantages
- Contains viable osteogenic cells
- No risk of immune rejection
- No risk of disease transmission
- Rapid graft incorporation
Disadvantages
- Donor site pain
- Risk of infection
- Limited graft quantity
- Potential for donor site fracture
Allografts
Allografts are obtained from cadaveric donors and processed in bone banks. They provide structural support and an osteoconductive scaffold but lack viable osteogenic cells.
Types of Allografts
- Fresh frozen bone
- Freeze-dried bone
- Demineralized bone matrix
Demineralized bone matrix contains bone morphogenetic proteins that may provide osteoinductive properties.
Synthetic Bone Substitutes
Synthetic substitutes are artificial materials designed to mimic the structural properties of bone. These materials primarily function as osteoconductive scaffolds.
| Material | Characteristics |
|---|---|
| Hydroxyapatite | High osteoconductivity |
| Tricalcium phosphate | Biodegradable scaffold |
| Calcium sulfate | Rapid resorption |
Bone Morphogenetic Proteins
Bone morphogenetic proteins are growth factors belonging to the transforming growth factor beta family. They stimulate mesenchymal stem cells to differentiate into osteoblasts and promote new bone formation.
- BMP-2
- BMP-7
These proteins are used clinically in selected spinal fusion procedures and treatment of nonunions.
Masquelet Technique
The Masquelet technique is a two-stage reconstructive procedure used for management of large bone defects.
- Stage 1: Cement spacer placement
- Stage 2: Bone graft insertion within induced membrane
The induced membrane produces growth factors that enhance graft incorporation and vascularization.
Key Exam Points
- Autograft is the gold standard bone graft
- Iliac crest is the most common donor site
- Autograft provides osteogenesis, osteoinduction, osteoconduction
- Allograft mainly provides osteoconduction
- Hydroxyapatite is a commonly used synthetic substitute
- Masquelet technique used for large bone defects