Bone Grafting Techniques

Bone Grafting Techniques - Grafting Goals

• Primary Aims:

  • Promote bone healing & fusion (arthrodesis).
  • Fill bone defects (trauma, tumor, infection).
  • Provide structural support.
  • Induce bone formation where absent.

• Achieved via Key Graft Properties:

  • Osteogenesis: Living cells form new bone.
  • Osteoinduction: Growth factors recruit & stimulate host cells to form bone.
  • Osteoconduction: Scaffold for new bone growth.

⭐ Osteoinduction is the process by which mesenchymal stem cells are recruited and differentiate into osteoblasts, primarily mediated by Bone Morphogenetic Proteins (BMPs).

Bone Grafting Techniques - Sources & Sorts

• Graft Sources & Properties:

  • Autograft: Patient's own bone (e.g., iliac crest, fibula).
    • Gold standard; non-immunogenic.
    • All 3 properties: Osteogenic, osteoinductive, osteoconductive.
    • Cons: Donor site morbidity (pain, infection), limited quantity.
  • Allograft: Human donor (cadaveric/living).
    • Types: Fresh-frozen, Freeze-Dried (FDBA), Demineralized (DFDBA).
    • Properties: Osteoconductive. DFDBA also osteoinductive (BMPs).
    • Cons: Potential immunogenicity, disease transmission risk (low), slower incorporation.
  • Xenograft: Animal source (e.g., bovine, porcine; processed).
    • Properties: Osteoconductive scaffold.
    • Cons: Higher immunogenicity risk, potential for zoonoses.
  • Synthetics (Alloplastics): E.g., Calcium phosphates (HA, TCP), sulfates, bioactive glass.
    • Properties: Osteoconductive. Some osteoinductive if combined with BMPs.
    • Cons: Variable resorption, potential mechanical weakness.

• Key Graft Characteristics (📌 GIC):

  • OsteoGenesis: New bone formation by viable cells from graft.
  • OsteoInduction: Chemical process stimulating host cells to form bone (e.g., BMPs).
  • OsteoConduction: Scaffold guiding new bone growth.

⭐ Autograft is the only graft type possessing all three key properties: osteogenesis, osteoinduction, and osteoconduction.

Bone Grafting Techniques - Technique Tidbits

• Autograft Harvest Sites & Techniques:
  • Iliac Crest Bone Graft (ICBG):
    • Anterior (ASIS): Max 15-20 cc; Risk to Lateral Femoral Cutaneous N. (LFCN).
    • Posterior (PSIS): Max 50-70 cc; Risk to Superior Cluneal Nerves.
  • Reamer-Irrigator-Aspirator (RIA):
    • Intramedullary (femur/tibia).
    • Large volume, morselized cancellous graft.
    • ↓ Donor site pain vs. ICBG.
• Graft Incorporation - "Creeping Substitution":
  • Host vessels invade graft.
  • Osteoclasts resorb dead graft bone.
  • Osteoblasts lay down new viable bone on graft scaffold.
  • Process: Inflammation → Osteogenesis → Angiogenesis → Remodeling.

⭐ ICBG is considered the "gold standard" for bone grafting, providing all three properties: osteoconduction, osteoinduction, and osteogenic cells.

Bone Grafting Techniques - Uses & Uh-Ohs

• Uses (Indications):

  • Non-unions / Delayed unions
  • Arthrodesis (joint fusion)
  • Filling bone defects (trauma, tumor resection)
  • Spinal fusion
  • Augmenting fracture fixation

• Uh-Ohs (Complications):

  • Donor site morbidity (pain, infection, fracture) - 📌 Most common with iliac crest grafts.
  • Graft failure / Non-union
  • Infection (recipient or donor site)
  • Disease transmission (allograft)
  • Rejection / Immunological reaction (allograft)
  • Fracture of the graft

⭐ Exam Favourite: Autografts are considered the gold standard due to their osteogenic, osteoinductive, and osteoconductive properties, minimizing rejection risk but having donor site morbidity as a key drawback. Allografts lack osteogenic cells but provide an osteoconductive scaffold and osteoinductive potential (if processed appropriately, e.g., DBM).

High‑Yield Points - ⚡ Biggest Takeaways

• Autograft: Gold standard; provides osteogenesis, osteoinduction, osteoconduction. Iliac crest common donor.
• Allograft: Osteoconductive, weakly osteoinductive; carries disease transmission and immunogenic risks.
• Synthetic grafts: (e.g., CaSO₄, CaP) Osteoconductive, biocompatible, no donor morbidity or disease risk.
• BMPs: Potent osteoinductive agents, stimulating new bone formation.
• Vascularized grafts: (e.g., fibula) Essential for large defects or avascular beds.
• Papineau technique: Staged open cancellous grafting for infected bone defects.