BONE GRAFT

• The treatment of posttraumatic skeletal conditions such as delayed unions, nonunions, malunions, and other problems of bone loss is challenging. • In most cases, restoration of alignment and

stable fixation of the bone is all that is necessary to achieve a successful reconstruction. • Sometimes, adjunctive measures such as bone-

grafting or bone transport are required to stimulate bone-healing and fill bone defects

BIOLOGICAL CONCEPT OF GRAFTS

• the biology of each of these grafts varies and may provide one or several essential components:

1. an osteoconductive matrix, which is a scaffold or trellis that supports the ingrowth of new bone

2. osteoinductive proteins, which stimulate and support mitogenesis of undifferentiated perivascular cells to form osteoprogenitor cells

3. osteogenic cells (osteoblasts or osteoblast precursors), which are capable of forming bone if placed into the proper environment.

The surgeon’s choice of the proper graft must be based on what is required from the graft (structural or bone-forming function, or both), the availability of the graft, the recipient bed, and the cost.

BONE GRAFT AND BONE GRAFT SUBSTITUTES

• The orthopaedic surgeon currently has several options:• autologous or allogeneic cancellous or cortical

bone• demineralized bone matrix• calcium phosphate-based• bone-graft substitute• autologous bone marrow• Recombinant bone morphogenetic proteins or

growth factors

AUTOLOGOUS BONE GRAFT

• Autologous bone grafts have osteogenic, osteoconductive, and osteoinductive properties.

• Available autologous bone grafts include Cancellous, vascularized cortical, nonvascularized cortical, and autologous bone marrow grafts

• Advantages:• The advantages of autologous cancellous or

cortical bone grafts are their excellent success rate, low risk of transmitting disease, and histocompatibility. • Disadvantages:• Limited Quantity.• High Rate of Complication :• Rate of major complications of 8.6%• Rate of minor complications of 20.6%

BONE MARROW GRAFT

• Injections of autologous bone marrow provide a graft that is osteogenic and potentially osteoinductive through cytokines and growth factors secreted by the transplanted cells.• Bone marrow can be aspirated from he posterior

iliac wing in volumes of 100 to 150 mL and can be injected into a fracture or nonunion site to stimulate healing.

ALLOGRAFT

• Allogeneic bone, with variable biologic properties, is availablem in many preparations: • demineralized bone matrix,• Morselized and cancellous chips• corticocancellous and cortical grafts,• osteochondral and whole-bone

segments.

DEMINERALIZED BONE MATRIX

• Demineralized bone matrix acts as an osteoconductive, and possibly as an osteoinductive, material. • does not offer structural support, but it is well

suited for filling bone defects and cavities. Demineralized bone matrix revascularizes quickly. • suitable carrier for autologous bone marrow

PREPARATION

• Demineralized bone matrix is prepared by a standardized process, as originally described by Urist et al and modified by Reddi and Huggins• allogeneic bone is crushed or pulverized to a

consistent particle size (74 to 420 μm) followed by demineralization in 0.5N HCL mEq/g for three hours. The resi dual acid is eliminated by rinsing in sterile water, ethanol, and ethyl ether.

BIOLOGICAL CONCEPT AND DBM TYPE

• presumably attributable to proteins and various growth factors present in the extracellular matrix and made available to the host environment by the demineralization process.

OSTEOCHONDRAL AND CORTICAL ALLOGRAFTS

• Osteochondral and cortical allografts are harvested from various regions of the skeleton, such as the pelvis, ribs, femur,tibia, and fibula, for reconstruction after major bone or joint loss. • The grafts are available as whole-bone or joint

segments (i.e., as the whole or part of the tibia, humerus, femur, talus, acetabulum, ilium, or hemi pelvis) for limb salvage procedures or as cortical struts to buttress existing bone, to stabilize and reconstitute cortical bone after periprosthetic fractures, and to fill bone defects.

• These grafts are osteoconductive and provide immediate structural support. They are preserved by either deep-freezing or freeze-drying.

• Fresh allografts that require no preservation are available, but they incite an intense immune reaction, making them less attractive than autografts. These fresh allografts have limited applications and are currently being used mainly for joint resurfacing

GRAFT SUBSTITUTE

• Ceramic and Ceramic composites:• Calcium based bone graft substitute

• coralline hydroxyapatite grafting of the metaphyseal defect

• Bioactive glass :• composed of silica (45%), calcium oxide (24.5%),

disodium oxide (24.5%), and pyrophosphate (6%). When implanted, they bind to collagen, growth factors, and fibrin to form a porous matrix to allow infiltration of osteogenic cells. The matrix provides some compressive strength, but it does not provide structural support.