bone Flashcards
what are some gross functions of bone?
protection for internal function
rigid levers for attachment of muscles to allow motion
harbors hemopoietic tissue for production of blood cells
serves as a reservoir for calcium, phosphate and other ions
where is blood made
BONE
what are key features of bone structure?
highly vascular, innervated, dynamic CT, capable of repair and remodeling
what are osteocytes?
mature bone cells
what are osteoblasts?
young cells-growth
what are osteoclasts?
phagocytic (break down bone-eat it)
applying wolff’s law to bone after a period of immobilization what would be expected with casting and NWB status following 8 weeks of immobilization?
may see a 3 fold decrease in load to failure, stiffness and energy storing capacity
applying wolff’s law to bone after a period of immobilization why are plates/screws impanted?
to reduce stress at fracture site but they may reduce/slow healing, but the fixation site strength may increase
which is stiffer: cortical/compact bone or cancellous bone?
compact bone is stiffer because steeper slope of stress/strain curve
what is the point of cancellous/trabecular bone’s porous structure?
great capacity for energy storage
T/F bone becomes brittle with age?
True
is bone more brittle with increasing or decreasing velocity of laoding?
increasing. increasing velocity increases severity of fracture
bone demonstrates what mechanical behavior? and what does it mean?
anisotropic. tissue responds to direction of force applied
which direction is strength greatest in for bone?
the direction in which loading is most common
T/F strength decreases as direction of loading changes from compression to transverse loading?
True
what is the best loading for bone to resist?
compression
what is the second best loading for bone to resist?
longitudinal tension
what is the third best loading for bone to resist?
obliwue tension
what is the worst loading for bone to resist?
transverse loading
which is stiffer: cortical bone or cancellous bone?
cortical bone is stiffer
Pick the correct pair to complete the sentence: cortical bone can withstand (greater/lesser) stress but (more/less) strain than cancellous bone.
greater, less
what percent of cancellous bone can sustain strains before failing?
75%
what percent of cortical bone can sustain strains before failing?
2%
what is compression?
when the structure “shortens and widens”
what does compression commonly produce in vertebrae?
fractures
T/F constant compression may hinder growth?
true
what may unequal loading produce with compression?
valgus or varus deformity
which is the best loading parameter to facilitate growth and repair?
cyclic
what is the piezo electric effects of bending forces?
negative charge on side of compression and positive on side of tension
for healthy bone where do osteoblasts and osteoclasts tend to migrate with load?
osteoblasts tend to migrate toward negative electrode while osteoclasts tend to migrate toward positive electrode
which side is bone deposition increases on when loaded?
side of compression
which side is bone reabsorption increased on when loaded?
side of tension
what is the effect of muscle contractions on bone?
usually oppose antagonist or gravity to counterbalance bending
acting independently create bending of bones
create tension at tendon-bone junction
create tuberosities/trochanters developmentally
pathologically may create avulsion fractures
T/F yielding in bone under tension occurs by debonding of osteons at cement lines
true
what does this mean: constant compressive loading produces increase in endosteal diameter and increase in intracortical porosity
constant compressive loading makes bone porous which is bad because it makes them weak example with braces
is intermittant loading good and why?
good because produces increased bone mass
what kind of fractures are common with torsion loading forces?
spiral fractures
what is most sensitive to torsion forces and why?
epiphyseal plate. under torsional load, newly forming bone will grow away from epiphysis in a spiral fashion
for a cross sectional area greater are leaders to…
stiffer and stronger bne
what do healing fractures begin with?
large callus. first soft then hard
what do we do to stabilize fracture sites and what does this do to them?
screw holes. it initially weakens the bone then in 8 weeks returns to normal strength due to the remodeling
what intervention tactics should we use to facilitate growth with regard to intensity?
loading within tissue structural tolerance
move carefully into the plastic zone
pain free loading
what intervention tactics should we use to facilitate growth with regard to duration or frequency?
many repetitions cyclical loading
what intervention tactics should we use to facilitate growth with regard to mode?
attempt to mimic functional loading characteristics
