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29 Cards in this Set
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- Back
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What are the two products of stem cell division?
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Another stem cell
Progenitor cell |
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Why is it desirable to select out stem cells from other cells within grafts?
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Because the greater the total number of cells, the greater the metabolic needs
Greater metabolic needs lead to a lower cell survival depth |
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What is the main advantage of fresh allograft?
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Contains osteoinductive BMPs
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What is the main disadvantage?
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Immunogenic
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ls fresh allograft osteoconductive or inductive?
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Both
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What are the two advantages of fresh frozen allograft?
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Still contains osteoincluctive BMPs
Less immunogenic |
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ls fresh frozen allograft osteoconductive or inductive?
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Both
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What is the main advantage of freeze-dried allograft?
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Lowest immunogenicity
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What are the two main disadvantages?
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Does not contain BMPs
Structural properties may be compromised with freeze drying |
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How does freeze-dried stiffness and compactability compare to fresh allograft?
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Same maximal stiffness
More compactable |
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Based on recent literature, what type of allograft results in superior stem fixation?
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Freeze-dried has superior stem fixation
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What does the recent literature on use of freeze-dried allograft in adolescent idiopathic scoliosis surgery indicate?
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Significantly lowers fusion rates
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What is demineralized bone matrix?
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Digested allograft and BMP
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Is it osteoconductive or inductive?
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Both
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What are the three key points to know about BMP mechanism of osteoinductivity?
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Serine/threonine kinase intracellular signaling pathway
Acts via cytokines Facilitated by SMAD proteins |
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What is the main disadvantage of osteochondral allografts?
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Cartilage is immunogenic
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How does cryogenic preservation affect chondrocyte number?
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Very few remain
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After implantation of osteochondral allograft, what happens to host chondrocytes?
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Not preserved
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How long is transplanted cartilage preserved?
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2 to 3 years
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What is the histological appearance thereafter?
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Transplanted cartilage covered by fibrocartilage
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Bottom line: How does the strength of cortical and cancellous grafts change over time?
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Cortical grafts are strongest day 1; then resorbed and remodeled
Cancellous grafts get progressively stronger through process of creeping substitution |
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What is the two-step sequence of chemical conversion of tricalcium phosphate (TCP)?
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TCP rapidly broken down
But slowly converted to hyaluronic acid (HA) |
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Is TCP osteoconductive or inductive?
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Osteoconductive only
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ls TCP immunogenic?
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No
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What is the ideal ceramic pore size?
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150 pm
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What two factors determine the extent of allograft incorporation?
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Cellularity
Major histocompatability complex (MHC) compatibility |
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What cells mediate the immune response?
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T cells
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What surface structure on transplanted cells is recognized by host immune cells?
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Surface glycoprotein
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Mechanical properties of allograft change at what dose of radiation?
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3 Mrad
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