Overview
Bone grafts combine structural support and osteogenesis, which is one of their main advantages. For a graft to succeed, the patient's overall condition and the recipient site preparation must be optimal. This guide summarizes the biology of graft incorporation, graft sources and substitutes, and the main graft techniques. (Campbell)
Indications
Bone grafts are used to: (Campbell)
Fill cavities or defects from cysts, tumors or other causes.
Bridge joints to perform arthrodesis.
Bridge major defects or re-establish the continuity of a long bone.
Provide bone blocks to limit joint motion (arthroereisis).
Establish union of a pseudarthrosis.
Promote union or fill defects in delayed union, malunion, fresh fractures or osteotomies.
Biology of Graft Incorporation
Structure. Cortical grafts give structural support and cancellous grafts give osteogenesis. Most or all cellular elements in grafts, particularly cortical ones, probably die and are slowly replaced by "creeping substitution," with the graft acting as a scaffold for new bone. This replacement is far slower in hard cortical bone than in cancellous bone. Cancellous bone is more osteogenic but not strong enough for efficient structural support. Once the graft has united and is strong enough for unprotected use, the bone remodels according to functional demands. (Campbell)
Three biologic properties.
Osteogenesis: the ability of surviving cellular elements within the graft to synthesize new bone.
Osteoinduction: the ability to recruit host mesenchymal stem cells that differentiate into osteoblasts, facilitated by bone morphogenetic proteins and other growth factors in the graft.
Osteoconduction: the ability to facilitate blood vessel ingrowth and bone formation into a scaffold structure. (Campbell)
Properties by graft type (Table 2.8, qualitative). Autograft bone marrow and cancellous bone are osteogenic; cancellous autograft is also osteoconductive; cortical autograft provides mechanical strength; vascularized autograft combines osteogenesis, osteoconduction and mechanical properties with its own vascularity. Cancellous allograft is osteoconductive but neither osteogenic nor osteoinductive. Cortical allograft is mainly mechanical. Demineralized allograft is strongly osteoinductive. (Campbell)
Factors influencing incorporation (Table 2.7).
Local positive: electrical stimulation, good vascular supply, growth factors, large surface area, mechanical loading, mechanical stability.
Local negative: denervation, infection, local bone disease, radiation, tumor, mechanical instability.
Systemic positive: growth hormone, insulin, parathyroid hormone, somatomedins, thyroid hormone, vitamins A and D.
Systemic negative: chemotherapy, corticosteroids, diabetes, malnutrition, metabolic bone disease, NSAIDs, sepsis, smoking. (Campbell)
Sources of Graft
Autogenous grafts
Usually from the fibula or ilium, providing cortical grafts, whole-bone transplants and cancellous bone. Autologous cancellous and cortical grafts remain the standard against which other grafts are judged.
Tibia is rarely used because it jeopardizes the normal limb, prolongs the procedure, delays ambulation until it partially heals, and requires protection for 6 to 12 months. If used, suturing the periosteum over the defect acts as a limiting membrane to prevent irregular callus.
Fibula: the proximal two-thirds can be removed without disabling the leg (mild muscular weakness is common). The rounded proximal end, partly covered by hyaline cartilage, makes a satisfactory transplant for the distal third of the radius or fibula. The middle third can be a vascularized free graft on the peroneal artery and vein pedicle. Vascularized grafts need expert microvascular technique, have limited indications and carry donor-site morbidity (particularly at the ankle). The iliac crest can also be used as a free vascularized graft.
Reamer–irrigator–aspirator (RIA): a good source of bulk cancellous autograft with a reported complication rate under 2%. RIA debris and iliac crest graft have similar RNA transcriptional profiles for bone repair genes. One study reported transfusion in 44% of RIA patients vs 21% of iliac crest patients.
Induced membrane technique (Taylor et al.; Masquelet) for segmental bone loss: a two-stage procedure. A methyl methacrylate spacer placed in the defect induces a bioactive membrane. The spacer is removed 4 to 8 weeks later and cancellous autograft is placed in the membrane-surrounded defect. The membrane helps prevent graft resorption and promotes revascularization and consolidation. (Campbell)
Allogenic grafts
Indications: small children (donor cortical grafts too small to bridge defects, risk to a physis), the elderly, poor operative risks, and patients from whom not enough acceptable autogenous bone can be harvested. Large structural allografts are used in revision total joint surgery, periprosthetic long bone fractures and tumor reconstruction. Osteochondral allografts are used in some centers for distal femoral osteonecrosis and in limb salvage after tumor resection.
Mixing with autograft. Small amounts of autogenous cancellous bone can "seed" allograft to add osteogenic potential. Mixed grafts incorporate more rapidly than allograft alone. In large acetabular defects, allografts loaded with bone marrow–derived mesenchymal stem cells showed increased union rates and less resorption.
Incorporation. Cancellous allografts incorporate to host bone like autogenous cancellous grafts. They are mineralized and osteoconductive but not osteoinductive. A demineralized form increases osteogenic potential but greatly reduces compressive strength. Cortical allografts are invaded by host vessels and slowly (and limitedly) replaced, particularly in massive allografts, probably explaining the high fracture incidence: dead bone cannot remodel in response to cyclic loading and fails.
Disease transmission. Safe allograft requires a bone bank with thorough donor screening (bacterial, viral including HIV and hepatitis, and fungal infections), rapid procurement and sterile processing, following FDA and American Association of Tissue Banks standards. Malignancy (except basal cell skin carcinoma), collagen vascular disease, metabolic bone disease and toxins are contraindications to donation. No system is perfect, and transmission from a single donor to multiple recipients has been reported.
Storage. Bone can be harvested in a clean, nonsterile environment, sterilized (irradiation, strong acid or ethylene oxide) and freeze-dried, or banked deep-frozen under sterile conditions (−70 to −80 °C). Fresh-frozen bone is stronger than freeze-dried bone and better for structural allograft. Cartilage and menisci can also be cryopreserved. (Campbell)
Cancellous bone graft substitutes and biologics
Classified by property (Parikh): (Campbell)
Osteoconductive: calcium sulfate, ceramics, calcium phosphate cements, collagen, bioactive glass, synthetic polymers (passive porous scaffolds).
Osteoinductive: demineralized bone matrix, bone morphogenetic proteins, growth factors, gene therapy.
Osteogenic: bone marrow aspirate.
Combined: composites.
Substitutes can replace or expand available graft. FDA-approved indications vary and change, so manufacturers' indications and instructions must be reviewed.
Stem cells and DBM. Stem cell use in graft substitutes is investigational. DBM is considered minimally processed allograft tissue and does not require FDA approval. Stem cells (autograft or allograft) alone or combined with substitutes are investigational, and whether DBM plus stem cells counts as minimally processed tissue is controversial.
Complications of substitutes. rhBMP-2 has been associated with increased cancer risk: in a randomized trial of over 500 patients with single-level lumbar fusion using rhBMP-2 in a compression-resistant matrix, cancer events were significantly higher in the rhBMP-2 group. Soft-tissue inflammation occurred in 16% in one study of 31 patients after tricalcium phosphate and calcium sulfate. Retrograde ejaculation has been reported after anterior lumbar interbody fusion with rhBMP-2. Products with recombinant proteins or synthetic peptides are not FDA-approved in children, and off-label juvenile use has produced reports of fluid accumulation, excessive bone growth, delayed healing and swelling. (Campbell)
Techniques of Grafting (Campbell)
Onlay cortical grafts. Historically the simplest and most effective treatment for most ununited diaphyseal fractures, usually supplemented with cancellous bone. Fixation as a rule is better given by internal or external metal devices. Thick cortical graft has largely been replaced by thin cortical and cancellous bone from the ilium for osteogenesis. Dual onlay grafts help difficult nonunions and massive defects, especially near a joint where the fragment is small, osteoporotic and cancellous (a single graft's screws pull out and wire sutures cut through): dual grafts grip like forceps.
Advantages of dual onlay grafts: better mechanical fixation than a single onlay; added strength and stability; a trough for cancellous bone; and prevention of contracting fibrous tissue compromising the cancellous graft.
Disadvantages: not as strong as metal fixation, usually an extremity serves as the donor site, less osteogenic than iliac autograft, and the surgery has more risk.
Inlay grafts. A slot is cut in the host cortex and a graft of the same size or slightly smaller is fitted. For diaphyseal nonunion, onlay is simpler and has almost replaced inlay, but inlay is still sometimes used in arthrodesis, particularly at the ankle.
Multiple cancellous chips. The best osteogenic material available. Used to fill cavities or defects, establish bone blocks, and wedge in osteotomies. The ilium is a good source, and the anterior crest can be harvested easily with an acetabular reamer with excellent results and no graft-related complications. In most procedures using cortical bone or metal fixation, supplementary chips or strips speed healing. Cancellous grafts suit spinal arthrodesis, where osteogenesis is the prime concern. Large-volume cancellous graft can be harvested from the femoral canal with RIA.
Hemicylindrical grafts. For obliterating large defects of the tibia and femur: a massive hemicylindrical cortical graft from the affected bone is placed across the defect, supplemented by iliac cancellous bone. Limited use, applicable to tumor resections where amputation is to be avoided.
Whole-bone transplant. The fibula is the most practical graft for long diaphyseal defects of the upper extremity unless the nonunion is near a joint. A fibular graft is stronger than a full-thickness tibial graft, and a wound that cannot be closed over dual grafts can often be closed over a fibular graft. Disability after fibular harvest is less than after tibial harvest. In children, the fibula can span a long tibial gap, usually in two stages. A free vascularized fibular graft has greater osteogenic potential but is technically demanding. Whole segments of tibia or femur (freeze-dried or fresh frozen) are used mainly for defects after massive tumor resections or complex joint revisions.
Complications
Graft resorption, nonunion and fracture of the graft, especially cortical allograft. (Campbell)
Donor-site morbidity (fibular weakness and ankle morbidity with vascularized fibula; tibial protection for 6–12 months). (Campbell)
Disease transmission with allograft. (Campbell)
Complications of biologics (rhBMP-2: cancer risk signals, soft-tissue inflammation, retrograde ejaculation, off-label pediatric adverse events). (Campbell)
References
Medina O. Perioperative patient optimization and overview of tendon-to-bone fixation and bone grafting. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Philadelphia: Elsevier; 2026. Chapter 2.