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During fracture healing, granulation tissue tolerates the greatest strain before failure so that mature bone can eventually bridge the fracture gap during healing. What is the definition of strain?
Amount of force an object can withstand until plastic deformation is lost
Change in length / original length of an object due to an external force
Relationship of stiffness to time-dependent loading
Force intensity / volume
Force intensity / cross sectional area
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Which of the following is a mechanism by which low-intensity pulsed ultrasound is reported to stimulate fracture healing?
decreasing intracellular calcium concentration
produces nanomotion at the fracture site
decreases proteoglycan synthesis
Which of the following statements regarding COX-2 is FALSE?
It causes mesenchymal stem cells to differentiate into osteoblasts
COX-2 knockout mice heal fractures more quickly than control mice
COX-2 is an enzyme which converts arachidonic acid to prostaglandin endoperoxide H2
Most NSAIDS non-specifically inhibit both COX-1 and COX-2 enzymes
The expression of COX-2 is upregulated in several human cancers
Which of the following is most often implicated as an etiology for a hypertrophic nonunion?
Malreduction with open plating
Inadequate mechanical stability
Open injury with significant soft tissue stripping
The nonunion as seen in Figure A will most likely unite by what intervention?
Increased mechanical stability
Decreased mechanical stability
Increased biology at the fracture site
Decreased biology at the fracture site
Antibiotics and resection of pseudoarthrosis
In rat models looking at the effect of malnutrition on fracture healing, amino acid supplementation in a nutritionally deprived rat increases all of the following EXCEPT
Quadriceps total protein content
Fracture callus mineralization
Insulin-like growth factor 1 (IGF-1) mRNA expression
What is the mechanism of action of capacitive coupling (CC) stimulation when used as an adjunctive therapy for bone healing?
Reduces oxygen concentration and increases local tissue pH
Stimulates transmembrane calcium translocation via voltage-gated calcium channels
Upregulates TNF alpha
Transmits mechanical energy to stimulate bone formation
Upregulates osteoclast activity
Type X collagen expression by hypertrophic chondrocytes is characteristic of which of the following aspects of fracture healing?
Granulation tissue formation
Cartilage callus formation and calcification
Level 1 evidence has shown Low-intensity Pulsed Ultrasound Stimulation (LIPUS) decreased the time to fracture union in all of the the following injuries EXCEPT?
Radius shaft fracture
Distal radius fracture
Tibia shaft fracture treated with casting
Tibia shaft fracture treated with reamed intramedullary nailing
What type of fracture healing occurs in a femoral shaft fracture treated with an intramedullary nail?
Primary fracture healing
Secondary fracture healing
"Cutting cone" remodelling