Module 5 Tissue Loading

stress fracture

*fracture caused by overuse low load conditions *functioanl ability often retained *could be warning of other nutritional or pathological conditions

trabecular bone

-bone type -high strain but low stress before fracture -deforms easily and lower stiffness

cortical bone

-bone type -stiffer --> HIGH MODULUS -accepts large loads but cannot deform much with out risking fracture -withstand more stress but less strain before fracture

cortical (compact) bone

-compact mineralized connective tissue -strong/dense -low porosity (60% non mineralized) -found in shafts and long bones

macrotruama

-from acute loading -ligament tear -bone fracture

microtrauma

-from repetitive loading -shin splints -stress fractures -tendonitis

trabecular (cancellous)/spongy bone

-less compact mineralized connective tissue -high porosity (30-90% non mineralized) -found in vertebrae and ends of long bones

factors for injury in spinal laoding

-load magnitude and direction: greater loads especially shear loads increase the risk for slippage and disc herniation -muscle tension: poor lifting form and increase load torque can cause tension which also contributes to excess loading of the spine -time dependent: under sustained land intervertebral discs lose water and height and more load is transmitted through the facets of the vertebrae

anistrophy of the bone

-loading angle matters -more axial the load the greater ability to withstand the load

high porosity

30-90% non mineralized

low porosity

60% non mineralized

bone hyertrophy

__ __ increase in bone mass w stress

longitudinal growth

__ ___: -growth at the epiphyseal plate (cartilaginous disc) -most fuse by age of 18 ending ____ ____

osteocytes

__ direct bone remodeling activity

yield point

__: end of the elastic region; if you put any more load to material you will begin to cause permanent damage to the material

rate of loading

___ __ ____ refers to how quickly a load is applied

bone atrophy

___ ___ decrease in bone mass w disuse

epiphyseal fracture

___ ___: -damage to the growth plate area of younger <18yrs -if hyaline cartilage is disrupted bone growth may end -can be difficult injury to treat, often with long term effects

circumferential growth

___ ____: -increases bone diameter -occurs throughout most of the lifespan -periosteum builds concentric layers of bone -bone is simultaneously reabsorbed on the medullary side

minerals water

___ and ___ contribute greatly to bones' compressive strength

linear

___ elastic material: stress is linearly proportional to strain

wolffs

___ law = bone (strength and mineral content) changes based on the stresses applied to the bone

bone

___ loss in jaw due to: -gum disease -dentures -loss of teeth

osteoclast

___ reabsorb bone

collagen

___: -type of bone composition -material constituent -protein, cable like and adds tensile strength

minerals

___: -type of bone composition -material constituent -calcium carbonate, calcium phosphate -stiffness = compression strength

plastic materials

___: deform instantaneously when they are subjected to externally applied loads and do not fully recover their shape when load is removed

elastic materials

___: deform instantaneously when they are subjected to externally applied loads and resume their shape when load is removed

anistrophy

___: some materials act better under different directions of load because of the microstructure of the material *bone has ____ *wolf's law - body will adapt to loads under which it is placed

collagen

____ allows for flexibility in the bone... maintains ductility in lifespan

osteoblast

____ deposit new bone

stress

____ is a function of strain only (no time dependent behavior) *___ doesn't necessarily need to be elastic

inverse

____ relationship between the magnitude of the load and the number of cycles/repetitions the tissue can withstand before there's a high likelihood for injury

water

____: -type of bone composition -material constituent -carries nutrients to and waste away and adds to compressive strength

ultimate stress

____: max load the material can withstand in the curve; not necessarily the same point as fracture point

fracture point

____: point at which the tissue will rupture; not necessarily the same as ultimate stress

ductile

able to yield at normal temps *large plastic deformation prior to failure (ex: steel)

strain

amount of deformation with respect to the structure *in compressive or tensile loading *normal ___ (greek e): ratio of the change in length (unitless) --> greek e = change in length /original resting length

acute loading

application of a single force of succulent magnitude to cause inury to a biological issue *macrotrauma

energy stored

area under the curve = ___ ___ in the tissue as it deformed

strain

as you get older not able to handle as much ___ before fracturing --> becomes more and more brittle

way to mitigate risk for injury

avoid twisting while lifting

compression

boens perform best with ____

composite

bone is a ___ material

axial

bone is much better at withstanding ___ loading than a load applied at an oblique angle

jaw

bone loss in jaw can lead to: -loss of teeth -non retentive dentures -mandibular fractures -inability to get implants -jaw joint issues due to abnormal loading

compressive tensile

bones can withstand ___ loads more than ___ loads

shear stress

bones perform least with ___

porous

containing pores or cavities

cortical, trabecular

cortical vs trabecular stress strain curve: ___ can withstand more stress ____ withstands less stress but more strain

modulus of elasticity

defines the slope of the linear region of the stress strain curve (E) = stress (omega) / strain (greek e) *uses Hooke's law for ONLY elastic region *represents the stiffness of material *where stress is directly proportional to strain

anistropic

exhibiting different mechanical properties in response to loads from different directions

stress strain curve

he relationship between the stress and strain that a particular material displays *Graphical representation of a material's mechanical properties. *help us predict how a material will deform w a given load *each material has its own curve

osteoporosis

low bone density; brittle bones that cannot undergo much stress without fracturing *lifestyle disease dependent on habits *no clear onset *peak bone mass during childhood is important predictor *weight bearing exercises in pre-puberty years can help *dietary calcium

way to mitigate risk for injury

maintain neutral spine

way to mitigate risk for injury

maintain upright posture

elastic

materials may exhibit ___ behavior up to certain loads beyond which they will exhibit plastic behavior

bone type

mechanical properties depend on ___ ___

spiral fracture

oblique break due to torsional loading

elastic, linear

on a stress strain curve: *graph becomes non linear — DOESN'T mean that it isnt _____anymore *during ____ portion — use the modulus of elasticity (slope of the curve)

decreasing

pressure in the L3 intervertebral disc changes with position -- listed in order of ____ internal pressure -sitting sloched -standing leaning forward -sitting erect -standing erect -lying flat

atrophy

problems related to ____: -loss of bone mineral density reduces bone strength --> increased likelihood of injury -space flight, bed-ridden patients and aging -osteoporosis

way to mitigate risk for injury

reduce moment arm of the load during lifting

repetitive loading

repeated application of a sub acute load that is usually of relatively low magnitude *microtrauma

buccal exostosis

results of clenching teeth

brittle

rupture occurs during elastic deformation *failure without undergoing plastic deformation (ex: cast iron, glass, stone) *can undergo a lot of stress -- just not plastic deformation before fracturing

combined loading

simultaneous action of more than one of the pure forms of loading

way to mitigate risk for injury

sustain intra-abdominal pressure during lifting

brittle

the FASTER you load bones the more ___ they are... more likely to rupture QUICKLY

ductile

the SLOWER you load bones the more ___ they are... will have plastic deformation without rupture

elasticity

the ability of a material to resume its original size and shape

brittle

the older you are the more brittle your bones are

ductile

the younger you are the more ____ your bones are

thoracic, sacral

to maintain upright position and have neutral spine which parts of the spine should be KYPHOTIC? cervical thoracic lumbar sacral *kyphotic is a a hump back shape

cervical, lumbar

to maintain upright position and have neutral spine which parts of the spine should be LORDOTIC? cervical thoracic lumbar sacral *lordotic is a C shape