bone grafting bone grafting bone grafting is a surgical procedure that replaces missing bone in order to repair bone fractures that are extremely complex, pose a significant health risk to the patient, or fail to heal properly. some small or acute fractures can be cured without bone grafting, but the risk is greater for large fractures like compound fractures. bone graftinga surgeon places a bone graft into position during a limb salvage.icd-9-cm78.0meshd016025medlineplus002963 bone generally has the ability to regenerate completely but requires a very small fracture space or some sort of scaffold to do so. bone grafts may be autologous (bone harvested from the patient's own body, often from the iliac crest), allograft (cadaveric bone usually obtained from a bone bank), or synthetic (often made of hydroxyapatite or other naturally occurring and biocompatible substances) with similar mechanical properties to bone. most bone grafts are expected to be resorbed and replaced as the natural bone heals over a few months' time. the principles involved in successful bone grafts include osteoconduction (guiding the reparative growth of the natural bone), osteoinduction (encouraging undifferentiated cells to become active osteoblasts), and osteogenesis (living bone cells in the graft material contribute to bone remodeling). osteogenesis only occurs with autograft tissue and allograft cellular bone matrices. biological mechanism properties of various types of bone graft sources. osteoconductiveosteoinductiveosteogenic alloplast + – – xenograft + – – allograft + +/– – autograft + + + bone grafting is possible because bone tissue, unlike most other tissues, has the ability to regenerate completely if provided the space into which to grow. as native bone grows, it will generally replace the graft material completely, resulting in a fully integrated region of new bone. the biologic mechanisms that provide a rationale for bone grafting are osteoconduction, osteoinduction and osteogenesis. osteoconduction osteoconduction is termed as "the property of a material to support tissue ingrowth, osteoprogenitor cell growth, and development for bone formation to occur". in the context of bone grafting it occurs when the bone graft material serves as a scaffold for new bone growth that is perpetuated by the native bone. osteoblasts from the margin of the defect that is being grafted utilize the bone graft material as a framework upon which to spread and generate new bone. osteoblasts do not originate from the donor tissue, but through the internal ingrowing of the host's cells. the proper bonding of bioactive chemicals (beta-tricalcium phosphate) in implants used in bone grafting surgery allow the promotion of osteoconductivity in the area of a defect. in the very least, a bone graft material should be osteoconductive by being made up of these bioactive chemicals. osteoinduction osteoinduction involves the stimulation of osteoprogenitor cells to differentiate into osteoblasts that then begin new bone formation. the most widely studied type of osteoinductive cell mediators is bone morphogenetic proteins (bmps). a bone graft material that is osteoconductive and osteoinductive will not only serve as a scaffold for currently existing osteoblasts but will also trigger the formation of new osteoblasts, theoretically promoting faster integration of the graft. osteopromotion osteopromotion involves the enhancement of osteoinduction without the possession of osteoinductive properties. for example, enamel matrix derivative has been shown to enhance the osteoinductive effect of demineralized freeze dried bone allograft (dfdba), but will not stimulate new bone growth alone. osteogenesis osteogenesis occurs when vital osteoblasts originating from the bone graft material contribute to new bone growth along with bone growth generated via the other two mechanisms. method depending on where the bone graft is needed, a different doctor may be requested to do the surgery. doctors and physicians that perform bone graft procedures are commonly orthopedic surgeons, otolaryngology head and neck surgeon, neurosurgeons, craniofacial surgeons, oral and maxillofacial surgeons, podiatric surgeons and periodontists, dental surgeons, oral surgeons and implantologists. autograft illustration of an autograft harvested from iliac crest autologous (or autogenous) bone grafting involves utilizing bone obtained from the same individual receiving the graft. bone can be harvested from non-essential bones, such as from the iliac crest, or more commonly in oral and maxillofacial surgery, from the mandibular symphysis (chin area) or anterior mandibular ramus (the coronoid process); this is particularly true for block grafts, in which a small block of bone is placed whole in the area being grafted. when a block graft will be performed, autogenous bone is the most preferred because there is less risk of the graft rejection because the graft originated from the patient's own body. as indicated in the chart above, such a graft would be osteoinductive and osteogenic, as well as osteoconductive. a negative aspect of autologous grafts is that an additional surgical site is required, in effect adding another potential location for post-operative pain and complications. autologous bone is typically harvested from intra-oral sources as the chin or extra-oral sources as the iliac crest, the fibula, the ribs, the mandible and even parts of the skull. all bone requires a blood supply in the transplanted site. depending on where the transplant site is and the size of the graft, an additional blood supply may be required. for these types of grafts, extraction of the part of the periosteum and accompanying blood vessels along with donor bone is required. this kind of graft is known as a vital bone graft. an autograft may also be performed without a solid bony structure, for example, using bone reamed from the anterior superior iliac spine. in this case, there is an osteoinductive and osteogenic action, however, there is no osteoconductive action, as there is no solid bony structure. chin offers a large amount of cortico-cancellous autograft and easy access among all the intraoral sites. it can be easily harvested in the office settings under local anaesthesia on an outpatient basis. proximity of the donor and recipient sites reduce operative time and cost. convenient surgical access, low morbidity, elimination of hospital stay, minimal donor site discomfort and avoidance of cutaneous scars are the added advantages. a bone allograft dentin graft dentin bone, made from extracted teeth, dentin comprises more than 85% of tooth structure, the enamel consists of ha mineral and comprises 10% of tooth structure. dentin is similar to bone in its chemical composition, by volume 70–75% is ha mineral and 20% organic matrix, mostly fibrous type i collagen. dentin, like bone, may release growth and differentiating factors while being resorbed by osteoclasts. in order to make the dentin graft usable and bacteria-free some companies have developed clinical procedures which include grinding, sorting and cleaning of the teeth for immediate or future use. in korea, the korea tooth bank performed bio-recycling of 38 000 patients' own teeth from january 2009 until october 2012. allografts allograft bone, like autogenous bone, is derived from humans; the difference is that allograft is harvested from an individual other than the one receiving the graft. allograft bone can be taken from cadavers that have donated their bone so that it can be used for living people who are in need of it; it is typically sourced from a bone bank. bone banks also supply allograft bone sourced from living human bone donors (usually hospital inpatients) who are undergoing elective total hip arthroplasty (total hip replacement surgery). during total hip replacement, the orthopaedic surgeon removes the patient's femoral head, as a necessary part of the process of inserting the artificial hip prosthesis. the femoral head is a roughly spherical area of bone, located at the proximal end of the femur, with a diameter of 45 mm to 56 mm in adult humans. the patient's femoral head is most frequently discarded to hospital waste at the end of the surgical procedure. however, if a patient satisfies a number of stringent regulatory, medical and social history criteria, and provides informed consent, their femoral head may be deposited in the hospital's bone bank. there are three types of bone allograft available: fresh or fresh-frozen bone freeze-dried bone allograft (fdba) demineralized freeze-dried bone allograft (dfdba) alloplastic grafts alloplastic grafts may be made from hydroxyapatite, a naturally occurring mineral that is also the main mineral component of bone. they may be made from bioactive glass. hydroxylapatite is a synthetic bone graft, which is the most used now among other synthetic due to its osteoconduction, hardness and acceptability by bone. tricalcium phosphate which is now used in combination with hydroxylapatite thus give both effect osteoconduction and resorbability. polymers such as some microporous grades of pmma and various other acrylates (such as polyhydroxylethylmethacrylate aka phema), coated with calcium hydroxide for adhesion, are also used as alloplastic grafts for their inhibition of infection and their mechanical resilience and biocompatibility. calcifying marine algae such as corallina officinalis have a fluorohydroxyapatitic composition whose structure is similar to human bone and offers gradual resorption, thus it is treated and standardized as "fha (fluoro-hydroxy-apatitic) biomaterial" alloplastic bone grafts. synthetic variants flexible hydrogel-ha composite, which has a mineral-to-organic matrix ratio approximating that of human bone artificial bone can be created from ceramics such as calcium phosphates (e.g. hydroxyapatite and tricalcium phosphate), bioglass and calcium sulfate; all of which are biologically active to different degrees depending on solubility in the physiological environment. these materials can be doped with growth factors, ions such as strontium or mixed with bone marrow aspirate to increase biological activity. some authors believe this method is inferior to autogenous bone grafting however infection and rejection of the graft is much less of a risk, and the mechanical properties such as young's modulus are comparable to bone. the presence of elements such as strontium can result in higher bone mineral density and enhanced osteoblast proliferation in vivo. temporary spacer a synthetic material may be used as a temporary antibiotic spacer before being replaced by a more permanent material. for example, the masquelet procedure consists of initially using pmma mixed with an antibiotic (vancomycin or gentamicin) for 4–12 weeks, and then replacing the space with an autologous bone graft. it can be used to treat posttraumatic bone defects. xenografts bone xenografts are an alternative form of bone grafts that involve transplanting different animal species cells into humans. this graft can range from orthopedic to dental uses. most xenografts are derived from bovine sources such as cows or pigs and are sterilized and processed for safe implantation into human tissue. they can be freeze dried or demineralized and deproteinized. xenografts are usually only distributed as a calcified matrix. madrepore and or millepore type of corals are harvested and treated to become 'coral derived granules' (cdg) and other types of coralline xenografts. coral based xenografts are mainly calcium carbonate (and an important proportion of fluorides, useful in the context of grafting to promote bone development) while natural human bone is made of hydroxyapatite along with calcium phosphate and carbonate: the coral material is thus either transformed industrially into hydroxyapatite through a hydrothermal process, yielding a non-resorbable xenograft, or simply the process is omitted and the coralline material remains in its calcium carbonate state for better resorption of the graft by the natural bone. the coral xenograft is then saturated with growth-enhancing gels and solutions. health risks studies show that xenografts can be used, however they are closely monitored due to their risk of rejection. zoonoses, which are diseases that arise from the crossing of animal and human tissue, pose a threat to the success of xenograft implantation. specifically, these diseases are referenced as “xenozoonoses”. they can be categorized in 3 different groups: viral infection, prion-mediated infection, and bacterial infection. they have the potential to create a public health risk if they are not closely monitored, as they can cause diseases to be more easily transmissible through different species. growth factors growth factor enhanced grafts are produced using recombinant dna technology. they consist of either human growth factors or morphogens (bone morphogenic proteins in conjunction with a carrier medium, such as collagen). recovery and aftercare the time it takes for an individual to recover depends on the severity of the injury being treated and lasts anywhere from two weeks to two months, with a possibility of vigorous exercise being barred for up to six months. distal femoral bone graft takes up to six months to heal. uses dental implants the most common use of bone grafting is in the application of dental implants to restore the edentulous area of a missing tooth. dental implants require bones underneath