Download - Bone Grafts
BONE GRAFTS
Historical background:
Surgeons have gained their experience in reconstruction from the numerous wars
It started in WW I and concentrated around reconstruction of the mandible but without antibiotic support
In WW II distant bone blocks were transplanted from the ilium, rib and tibia with routine use of antibiotic No cancellous cellular marrow
Mowlem in 1944, introduced the concept of “Iliac cancellous bone chips” beginning the evolution of predictable bony reconstruction of the jaw bone
Boyne brought about the “use of particulate bone and cancellous marrow” with metallic trays splinted to large acellular cortical bone
Unlike other tissues, the bone can regenerate and repair itself: in many instances, bone injuries and fractures heal without scar formation .
Nevertheless, in pathological fractures or large and massive bone defects, bone healing and repair fail. Insufficient blood supply, infection of the bone or the surrounding tissues, and systemic diseases can negatively influence bone healing, resulting in delayed unions or non-unions .
Bone is the second most commonly transplanted tissue after blood.
Bone graftsautograftsallografts
demineralized bone matrix (DBM)syntheticsbone morphogenetic protein (BMP)stem cells
Epidemiologyincidence
almost 1 million bone grafting procedures performed in US each year, with a growth of almost 13% per year
Indicationsassist in healing of fractures, delayed unions,
or nonunionsassist in arthrodeses and spinal fusionsreplace bone defects from trauma or tumor
Properties
Bone graft has aspects of one or more of these three propertiesosteoconductive
material acts as a structural framework for bone growth demineralized bone matrices (DBMs)
osteoinductive material contains factors that stimulate bone growth
and induction of stem cells down a bone-forming lineage bone morphogenetic protein (BMP) is most common
from the transforming growth factor beta (TGF-B) superfamily
osteogenic material directly provides cells that will produce bone
including primitive mesenchymal stem cells, osteoblasts, and osteocytes mesenchymal stem cells can potentially differentiate
down any cell line osteoprogenitor cells differentiate to osteoblasts and
then osteocytes cancellous bone has a greater ability than cortical bone
to form new bone due to its larger surface area autologous bone graft (fresh autograft and bone
marrow aspirate) is the only bone graft material that contains live mensenchymal precursor cells
AutograftBone graft transferred from one body site to another in the
same patientIndicationsgold standardProperties
osteogenic, osteoinductive, and osteoconductiveleast immunogenic cortical, cancellous, or corticocancellousvascular or nonvascularFresh autografts contain surviving cells and osteoinductive proteins such as BMP-2, BMP-7, FGF, IGF, and PDGF
Donor sites
iliac crest is the most common site for autograft provides both cancellous and cortical graft 2% to 36% complication rate
blood loss and hematoma injury to lateral femoral cutaneous or cluneal nerves hernia formation infection fracture cosmetic defect chronic pain
fibula and ribs are most common sources of vascularized autografts
tibial metaphysis
Allograft
Bone graft obtained from a cadaver and inserted after processing
Most commonly used bone substituteProperties
osteoconductive only due to lack of viable cells the degree of osteoconduction available depends on
the processing method (fresh, frozen, or freeze-dried) and type of graft (cortical or cancellous)
cortical, cancellous, corticocancellous,
Processing methods debridement of soft tissue, wash with ethanol (remove live cells),
gamma irradiation (sterilization) dose-dependent higher doses of irradiation kills bacteria and viruses but may
impair biomechanical properties fresh allograft
cleansing and processing removes cells and decreases the immune response improving incorporation
indications rarely used due to disease transmission and immune response of recipient
frozen or freeze-dried reduces immunogenicity while maintaining osteoconductive properties reduces osteoinductive capabilities shelf life
one year for fresh frozen stored at -20 degrees C five years for fresh frozen stored at -70 degrees C indefinite for freeze-dried
Demineralized bone matrix (DBM)Acidic extraction of bone matrix from
allograft removes the minerals and leaves the
collagenous and noncollagenous structure and proteins
Propertiesosteoconductive without structural supportminimally osteoinductive despite preservation
of osteoinductive moleculesinterproduct and interlot variability is common
Synthetics
Alternative to autografts and allograftsVarious compositions availableMade in powder, pellet, or putty formProperties
osteoconductive only Outcomes
Level I evidence shows that calcium-phosphate bone substitutes allow for bone defect filling, early rehabilitation, and prevention of articular subsidence in distal radius and tibial plateau fractures
Bone morphogenetic proteins (BMP)Osteoinductive properties
stimulates undifferentiated perivascular mesenchymal cells to differentiate into osteoblasts through serine-threonine kinase receptors
rhBMP-2 and rhBMP-7 are FDA-approved for application in long bones and spine
Complicationsunder or overproduction of boneinflammatory responsesearly bone resorption