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ortho- lecture 2
bone basics
67
Health Care
Graduate
02/02/2010

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Term
two types of bone
Definition
1)lamellar 2) immature and pathologic
Term
types of lamellar bone (normal bone)
Definition
1) cortical 2) cancellous
Term
immature and pathologic bone
Definition
Woven
More random with more osteocytes than lamellar bone
Increased turnover rate
Weaker and more flexible than lamellar bone
Not stress oriented
Term
Cortical bone
Definition
Compact bone- Composed of tightly packed osteons or haversian systems connected by haversion canal. Slow turnover rate
Term
Which bone makes up 80% of skeleton
Definition
cortical bone
Term
which bone has higher resistance to torsion and bending
Definition
cortical bone
Term
Cancellous bone (spongy bone)
Definition
Less dense than cortical bone
Undergoes more remodeling according to the lines of stress (Wolff’s law)
Higher turnover rate than cortical bone
More elastic than cortical bone
Term
osteoblasts
Definition
form bone
Term
collagen formed by osteolblasts?
Definition
type I collagen
Term
osteocytes
Definition
maintain bone
Term
osteoclasts
Definition
resorb bone
Term
what types of cells make up 90% of cells in mature bone
Definition
osteocytes
Term
osteoprogenitor cells
Definition
osteoblasts arise from. Line haversion canals, endosteum, and periosteum awaiting the stimulus to differentiate
Term
lining cells
Definition
Resting osteoblasts that form an “envelope around bone”, inactive osteoblasts. They cover all of the available bone surface and function as a barrier for certain ions.
Term
percentage of organic and inorganic components of bone matrix
Definition
organic- 40%
inorganic- 60%
Term
Bone matrix organic components
Definition
Primarily type I collagen (cross linking decreases collagen solubility → ↑ tensile strength)
Proteoglycans
Matrix proteins (noncollagenous)
Growth factors and cytokines
Term
Bone matrix inorganic components
Definition
Calcium hydroxyapatite
Calcium phosphate
Term
pizoelectric charges- compression side
Definition
electronegative stimulating osteoblasts (formation)
Term
pizoelectric charges- tensions side
Definition
electropositive stimulates osteoclasts (resorption)
Term
Heutuer Volkmans Law
Definition
Suggests mechanical factors can influence longitudinal growth, bone remodeling, and fracture repair
Term
Volkmans law- compression forces vs tensile forces
Definition
Compressive forces inhibit growth, tensile forces stimulate growth
Term
Bone remodeling- cortical bone
Definition
Remodels by osteoclastic tunneling, f/b layering of osteoblasts and successive deposition of layers of lamellae
Term
bone remodeling- cancellous
Definition
Remodels by osteoclastic resorption f/b osteoblasts laying down new bone
Term
bone circulation
Definition
bone receives 5-10% of cardiac output
Term
3 sources of long bone blood supply
Definition
1)nutrient arteries (2/3 of cortex and medullary cavity)
2)metaphyseal- epiphyseal system (ends of bones)
3) periostal system (capillaries that supply
Term
physiology of blood flow
Definition
centrifugal in normal to mature bone (inside to outside)
Term
if endosteal system (nutrient) is disrupted in fx what happens to blood flow
Definition
blood flow reversed (outside to inside)
Term
most important factor in fx healing
Definition
blood supply
Term
factors with negative effect on fx healing
Definition
smoking, diabetes, advanced age, nutrients, NSAIDS
Term
effects of smoking on healing
Definition
Nicotine increases time to fracture healing, increases risk of nonunion (esp tibia), and decreases strength of the fracture callus
Increases risk of pseudarthrosis after lumbar fusion by up to 500%
Term
stages of fx healing
Definition
inflammation, repair, remodeling
Term
inflammation
Definition
bleeding --> hematoma --> hemopoteic cells secrete growth factors
fibroblasts, mesenchymal cells, osteoprogentior cells --> granulation forms around fx ends --> osteoblasts proliferate
Term
repair- primary callus response occurs when?
Definition
within two weeks
Term
repair
Definition
when bone ends are not in continuity bridging (soft) callus occurs then replaced by hard callus (woven bone)
Term
how is soft callus replaces with hard callus
Definition
endochondral ossifcation
Term
remodeling phase occurs when?
Definition
during middle of repair stage and can last up to 7 years
Term
what occurs during remodeling?
Definition
Allows bone to assume normal configuration and shape
Woven bone is replaced with lamellar bone
Term
what effect does rigid fixation have on repair stage?
Definition
minimizes or eliminates repair stage
Term
stress riser
Definition
length is < diameter of bone
Term
how is a stress riser produced surgically
Definition
when small piece of bone is removed or screw inserted
Term
stress riser effect on bone strength
Definition
reduced because stress is not evenly distributed, particularly marked with torsion l loading (gone when healing complete)↓ up to 60%
Term
open section defects
Definition
length > diameter
Term
open section defects
Definition
Discontinuity in bone caused by surgical removal of bone longer than bone’s diameter
Outer surface of bone x-section is no longer continuous
Term
types of bone grafts
Definition
1) cortical 2) cancellous 3) synthetic
Term
closed fx
Definition
does not penetrate the skin
Term
open fx
Definition
penetrates the skin
Term
green stick fx
Definition
unique to children, fx may be difficult to see on x ray, reduced under anesthesia or dr may complete the fx
Term
torus fx
Definition
unique to children- partial fx with part of the bone intact
Term
stress fx
Definition
one type of incomplete fracture in bones. It is caused by "unusual or repeated stress“
It could be described as a very small sliver or crack in the bone;[2] this is why it is sometimes dubbed "hairline fracture". It typically occurs in weight-bearing bones, such as the tibia (bone of the lower leg) and metatarsals (bones of the foot).
Term
disruption of stress fx
Definition
Tibia 49%
Tarsals 25%
Metatarsals 8.8%
Femur 7.2%
Fibula 6.6%
Pelvis 1.6%
Sesamoids 0.9%
Term
avulsion fx
Definition
An avulsion fracture is an injury to the bone in a place where a tendon or ligament attaches to the bone. When an avulsion fracture occurs, the tendon or ligament pulls off a piece of the bone.
Term
comminuted fx
Definition
A fracture in which bone is broken, splintered or crushed into a number of pieces
Term
spiral fx
Definition
(also called a torsion fracture) is a bone fracture in which the bone has been twisted apart.
Term
oblique fx
Definition
Runs oblique to the axis of the bone
Term
transverse fx
Definition
Right angle to the bone
Term
pathological fx
Definition
Caused by a disease
Term
multiple fx
Definition
multiple fx
Term
depressed fx
Definition
skull
Term
Type I- Salter Harris
Definition
physis fx (pure epiphyseal seperation). if non displaced effusion may be the only sign
Term
Type II- Salter Harris
Definition
metaphysis and physis (metaphyseal fx and epiphyseal seperation)
Term
Type III- salter harris
Definition
epiphyseal and physis fx
Term
Type IV- salter harris
Definition
vertically oriented from epiphyseal to metaphyseal
Term
Type V- salter harris
Definition
crush fx of epiphysis
Term
most common salter harris fx
Definition
type II
Term
best and worst salter harris fx
Definition
Type I- best
Type V- worst
Term
best imaging for soft tissue?
Definition
MRI
Term
imgaing for bone?
Definition
CT
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