Basic Science Flashcards
Strain and stress definitions and units
Strain = percentage change in length (given as %)
Stress = force per unit area (N/mm2 or Pa)
Hooke’s Law
Stress = Young’s modulus (E / Elastic modulus) x strain
i.e. E is slope of the line
Poisson’s ratio
Range
- cork
- rubber
Ratio of transverse strain an object undergoes to the axial strain that is applied
Higher ratio = more “squash able”
Must be -1 to 0.5 Most between 0 - 0.5. Cork 0 (compressible), rubber 0.5 (incompressible)
Isotropic
Anisotropic
Orthotropic
How many constants to define their elastic modulus
How many constants to define deformation
Isotropic - same properties each direction - 2 constants
Anisotropic - different properties in each direction - 5 constants
Orthotropic - three perpendicular planes of symmetry - 9 constants
6
Draw stress strain curve
Definition and example:
- Creep + e.g.
- Stress relation + e.g.
- Endurance limit
- Stress shielding
Stress remains constant and strain increases - ACL graft
Constant strain and a reduction in stress - Ponsetti casting
Highest stress to withstand >10 million cycles
Bone protected from stress so less load so loss of bone mass
3x types of wear and definition
Abrasive - friction between hard and soft material
Adhesive - molecular affinity between two surfaces
Fatigue - delamination / microscopic wears
Mechanism of osteolysis around biomaterials
Macrophages ingest particles, release TNF-alpha and IL-1 - osteoclastic resorption
Definition
- casting
- machining
- forging
- cold working
- annealing
- sintering
casting - melted, moulded and cooled
machining - removing small imperfections
forging - compressed between moulds into final shape
cold working - shaped below its recrystallisation temperature
annealing - heated to just above recrystallisation temperature
sintering - compressing by heat and/or pressure without melting it
Effects of cold working and of annealing
Cold working - harder, stiffer, stronger, but less plastic so cracks easier. Decreases grain size
Annealing - more ductile, less hard
Cold working effect on
- toughness
- hardness
- tensile strength
- yield stress
- ultimate stress
- brittleness
- ductility
- toughness - ↑
- hardness - ↑
- tensile strength - ↑
- yield stress - ↑
- ultimate stress - ↑
- brittleness - ↑
- ductility - ↓
Stainless steel
- composition
- carbon content and why
- corrosion
- one good specific property
Iron > chromium > nickel > carbon
Carbon <0.03% - reduces corrosion
Resists corrosion well, but susceptible to crevice corrosion and to galvanic corrosion at boundaries (e.g. with CoCr head)
Ductile (ultimate stress»_space;> yield stress)
Cobalt chrome
- composition
- what type of alloy
- ductility and wear
60% cobalt / 28 % chromium
Biphasic alloy
very low ductility, very good wear properties
Titanium
- grade 5 alloy
- good and bad property for arthroplasty
- compared with pure titanium, the alloy is__
- resistance to corrosion
- Ti6Al4V
- rough finish allows for interlocking
poor wear properties - stronger
- better than steel and cobalt alloys
Standard THR composition
Titanium cup
Titanium uncemented stem
Stainless steel cemented stem
Co-Cr or ceramic head
Young’s modulus of:
stainless steel
Co-Cr
titanium
cortical bone
190 GPa
230 GPa
110 GPa
17 GPa
Polyethylene
- type of bonds
- strength depends on
- stability depends on
covalent and van der Waals
strength - molecular weight
stability - temperature
Bone cement
- name
- powder consists of:
- liquid consists of:
- viscosity is:
- Young’s modulus is
polymethylmethacrylate
powder - PMMA beads, radio pacifier (barium), initiator (dibenzyl peroxide), dye
liquid - activator (methacrylate monomer), accelerator (toluidine), hydroquinone (stabiliser)
viscosity is low
between cortical and cancellous bone
Density of UHMWPE is close to:
Method of irradiation
How does irradiation change UHMWPE
Closer to low than high density PE
Gamma irradiation with Co60 source
improves wear characteristics but decreases fatigue and fracture resistance
Ceramics
- Friction coefficienty
- Hardness
- Brittleness
- Biocompatibility
- Strength is inversely proportional to:
Aluminia -
Zirconia -
very low
high
high
high
grain size and porosity
very low coefficient of friction, high wettability, fractures
stronger and denser but rougher
Metallic bonds
- structure
- charge
crystalline array - positive nuclei with loose valence electrons
Neutral
Synovial fluid
- Components missing from plasma
- viscosity
- Newtonian? and why
- effect on coefficient of friction of the joint
- change in septic arthritis
- change in rheumatoid arthritis
- hyaluronate is a ___ and not a ___
no clotting factors / erythrocytes
high viscocitiy
NOT newtonian because of hyaluronate
lowers coefficient of friction, at low loads
higher glucose, but not as high as plasma
less viscous due to degraded hyaluronate
GAG, not a PG
Newtonian fluid definition
Viscosity remains at a constant no matter the shear forces applied. And energy is not stored
Draw the growth plates
Growth plates:
Reserve zone
- oxygen tension
- collagen
- chondrocytes
- calcium
Proliferative zone
- cell shape
- oxygen tension
- specific disease affects here
- calcium
- fails here in ___
Hypertrophic zone
- responsible for ___
- vascularity
- strength
- low oxygen, disorderly collagen, single layer chondrocytes, high calcium
- flattened cells, highest oxygen, achondroplasia, high calcium but more ionised, tension
- mineralisation, avascular, weakest point
Draw the growth plates
Where is fibrocartilage and elastic cartilage
- transitionally in fractures. Menisci, TMJ and IV discs
- Eustachian tube, epiglottis
Cartilage ECM
- what are the regions
- what is it made up of
pericellular - thinnest, no collagen, high PG
territorial - protects chondrocytes
interterritorial - largest, packed collagen
- water, aggrecan, type II collagen, lubricant
What is the tidemark and where is it
junction between calcified and uncalcified cartilage - lacerations that don’t cross it don’t heal - it is beneath the deep zone
Zones of cartilage cartilage
- thickness, collagen, chondrocytes, aggrecan, water
Collagen
- isotropic / orthotropic / anisotrophic
- tensile strength compared with meniscus
- type in cartilage
orthotropic
less
type II (except type 5 around chondrocytes)
Collagen
Type 1 found in
Type 2 found in
Type 2 cross linked by
Type 3 found in
Type 5 found in
1- bone, outer meniscus, ligaments, tendons, scar in articular cartilage
2 - articular cartilage, inner meniscus, woven bone
cross linked by type IX
3 - sites of healing and repair
5 - peri-cellular matrix of cartilage
What are the proteoglycans in articular cartilage
What is their function
What properties do they provide
What increases proteoglycan release/breakdown from cartilage
aggrecan
dermatan
chondroitin
keratan
- to attract water
- compressive stiffness and durability
- IL-1 and immobilisation
Percentage dry weight that is collagen in
- fibrocartilage
- hyaline cartilage
- tendons
- ligaments
70
50-80
86
70
Menisci
- composition
- types of collagen
- percentage load of knee taken
- when does collagen decrease
- ligaments from lateral meniscus
- structure of layers (which one responsible for load transmission)
- cells in layers
70% water, most of rest collagen
outer type 1, inner 60/40 2/1
50% ext, 85% flex
collagen decreases after 80
to MFC with Wisberg and Humphrey
random superficially, middle parallel (load transmission), deep circumferential
fusiform in superficial, ovoid in deep
Composition of bone
60% inorganic
- hydroxyapatite - calcium and phosphate
30% organic
- type 1 collagen 90%
- proteoglycans
10% water
Haversian systems and Volkmann’s canals
Haversian systems - tubes that run within axis of bone
Volkmann’s canals - perforating channels that run transversely
Bone
- tropic?
- compression modulus ___x higher than tension
- tension modulus ___x higher than shear
transversely isotropic
1.5x higher
5x higher
Osteoblasts
- function
- at end of life span the:
- surface receptors for:
Osteoclasts
- surface receptors for:
- how to distinguish from macrophages
- how are they made
- lie within:
Osteocytes
- connected by:
OB
- synthesise the extra-cellular matrix
- 10-20% become osteocytes, 10-20% bone lining cells, 60-80%apoptose
- PTH and 1.25 vit D
OCL
- calcitonin only
- secrete enzymes including TRAP
- fusion of monocytes
- Howships lacunae
OCY
- canaliculi
Difference in bone loss in osteoporosis between males and females
Males lose more cortical
Females lose more cancellous
Woven bone
- collagen is:
- cells are:
- where is it seen
randomly aligned type II
ovoid cells
neonates, metaphysis of growing bones, callus, tumours, Paget’s, OI
Primary bone healing:
- how much strain is acceptable
- what initiates remodelling
- gap must be:
2%
cutting cones
<500 microns
Oxygen tension in:
- fibrous tissue
haematoma
new bone
high
low
low
intramembranous ossification occurs in:
which bones are made from IM ossificatioN:
callus, under the periosteum, NOT in the formation of cartilage or in epiphyses
clavicle and cranial bones
3x methods of blood supply to bone
reaming does what
nutrient canals
- high pressure system supplies inner 2/3 of cortex
- arterioles into Volkman’s canals into Haversian system
metaphyseal-epiphyseal system
periosteal system
- low pressure system supplies outer 1/3 of cortex
- dominant system in children, and dominant after reaming
lost nutrient system for 4 weeks, returns after 3 months
Changes in aging vs in osteoarthritis
- water, PGs, collagen cross linking and content, chondrocyte density and size, synthetic activity, modulus of elasticity, hyaluronate, permeability
One motor unit is composed of:
One motor neuron and all of the fibres that it innervates
Draw a sarcomere
Which bands stay same / reduce
A band stays same, others reduce
Thin filament composed of:
Thick filament composed of:
Tropomyosin does what:
Most important contractile protein is:
actin + troponin + tropomyosin
myosin filaments - 2 heavy and 4 light changes
prevents cross bridge binding to actin
titin (connectin)
Muscle contraction pathway
Action potential
→ Ach released and binds receptors
→ ↑ permeability to sodium
→ depolarisation
→ calcium released from sarcoplasmic reticulum
→ binds to troponin allowing myosin to slide past actin
Type I and type II muscle fibres
I - small, slow, less force, fatigue resistant
II - large, fast, forceful, fatigues
ATP per glucose for aerobic and anaerobic
What converts ADP to ATP
glycogen levels are always ___
38 and 2
creatine phosphate
constant
Tendons
- % water weight
- collagen type
- % dry weight that is collagen
- ___ at low loads and ___ at high loads
- which is weakest FDS tendon
50-60%
type I
86%
viscous and elastic
ring finger
Ligaments compared with tendons
___ vacsular
Collagen is more ____
More type ___ collagen
__% elastin
Stiffness and ultimate loads ___
Healed ligament is ___% of native tissue quality
Less vascular
cross linked and disorganised
III
1%
increase until skeletal maturity then are constant
30-50%
What are the glial cells
- which in CNS and PNS
- which is most abundant
oligodendrocytes (CNS) (several axons)
Schwann cells (PNS) (single axon)
astrocytes
microglia
Nodes of Ranvier are:
There are no Schwann cells where
There is/are ___ axon per cell body
Schwann cells originate from___
gaps between Schwann cells that allow conduction
dorsal root ganglion
one
macrophages
Ohm’s law
What does and does not obey Ohm’s law
current through a conductor is directly proportional to the voltage across
Action potential does NOT
Graded potential does
Grades of nerve injury
1 - neuropraxia
2 - damaged axon with in tact endoneurium
3 - damaged axon and endoneurium with in tact perineurium
4 - damaged axon, endoneirum and perineurium with in tact epineurium
5 - complete transection
Nerve tracts
- spinothalamic
- dorsal columns
- corticospinal
- dorsal roots
- ventral roots
pain and temperature
proprioception and vibration
voluntary muscle
afferent
efferent
Nerve conduction studies
- only can evaluate ___ nerves
- latency measures ___
- amplitude measures ___
- M wave reflects ___
- F wave ___
- H reflex
large myelinated nerves
quality of conduction
quantity of axons
action potential
follows M wave, tests motor axons proximal to stimulation site, first sign neuropathy
deep tendon reflex
Knee
- which FC larger
- which FC distal
- which TP concave
- in extension the tibia ___ on the femur
- which side has more rollback
- in 140 deg of flexion, how much ACL movements from at tibia and femur
- roll to slide ratios at beginning and end of flexion
medial
medial
medial
ERs
lateral
100 from femur, 40 from tibia
1:2 beginning, 1:4 end
Patella
- patellectomy reduces strength by __%
- patella moves ___ during full ROM
- primary constraint from 0 - 20 deg is ___
- Q angle is males and females
- sulcus angle in skyline view
- cartilage thickness
- PTF pressure at -body weight -upstairs -downstairs -deep knee bend
20%
7cm
MPFL
13 male, 18 female
140 deg
5mm
0.5, 2.5, 3.3, 7
Stability at the knee
- anterior translation
- posterior translation
- valgus
- varus
ACL 87% at 30 deg, then deep MCL and posterior medial meniscus
PCL 95% at 90 deg, then PLC
superficial MCL
LCL, then ACL and PCL
Forces through hip
- walking
- walking fast
- single leg stance
3x
7x
2-3x
Shoulder
- neck-shaft angle of humerus
- scapula version compared to coronal plane
- glenoid version and vertical tilt
- glenoid surfaces covers ___ humeral head
- GH to ST movement ratio beyond 30 and beyond 120 deg
- labrum increases depth by ___ and stability by ___
- weakest part of the capsule
- primary stabilising ligament of the GHJ
- 50% reduction in RC strength results in ___
- difference in conoid and trapezoid ligaments
- primary ER
- pull angle of supraspinatus
130-140
30-40 anteverted
0 - 7 retroverted, 3-5 vertical
1/3
2:1 then 1:1
50%, 20%
posterosuperior
inferior glenohumeral ligament
50% anterior displacement humeral head
conoid is weaker, but resists 4x the force
infraspinatus
75 deg angle
Elbow
- varus / valgus is along
- rotational axis is ___
- flex / ext is along
- most force in which position
- valgus stabilisers
- varus stabilisers
- posterolateral rotatory instability
radial head to distal ulna
bicondylar line
pronated an extended
medial collateral ligament, then RC and UH joints
UH joint, then anterior capsule in flexion and LCL in flexion
lateral ulna collateral
Hand
- IPJ collaterals are tight in
- MCPJ collaterals are tight in
- weakest thenar muscle
all positions
flexion
APB
Wrist
% force through the radius
no tendons attach ___
FDS or FDP stronger
TFCC made up of___
80%
to proximal row
FDP 50% stronger
articular disc, meniscal homologue, volar and dorsal radio ulna ligaments, ulnocarpal ligaments, ECU sheath
what is required for tendon transfer
adequate power and passively mobile joint
Foot and ankle
- supination is which movements
- axis of calcaneus is which direction
plantarflexion, varus, adduction
forwards, medial, upwards
F&A joints
- Chopart’s joints are ___
- TNJ which type of joint
- CC which type of joint
- transverse metatarsal ligaments are from
- most important medial arch stabilising ligament
transverse tarsal joints + TN + CC
ball and socket
saddle
2-5
calcaneonavicular (Spring) ligament
How does DEXA work
2x X-ray beams of different energies that are absorbed in different proportions
How does MRI work
magnet aligns atoms
Then atoms are “excited” which produces synchronised spinning
Then excitement stops and time is meausured to stop spinning (T2) and to return to aligned atoms (T1)
MRI
- TR
- TE
- TR and TE lengths in T1, T2, proton density
- what does gadolinium do
repetition time
echo time
both short T1, both long T2, short TE and long TR for PD
reduces the T1 time of some tissues and leads to increase signal on T1
Radioisotopes
- emit what
- fluorine used where
- technetium-99 is a ___ and affinity for __, half life of ___
- gallium, affinity for ___, half life of ___
- indium is for ___, half life of ___
- which one bad in pregnancy
gamma radiation
PET scans
phosphate complex, hydroxyapatite portion of bones where osteoblasts are, 6 hours
inflammatory proteins (both infection and neoplasia), 3.2 hours
indium is WCC so for infection only. 68 hours
gallium
Nuclear bone scan
- 3x phases
Findings in:
- Paget’s
- fibrous dysplasia
- OM
- cellulitis
- septic arthritis
- aseptic loosening
flow - 1-2 mins
blood pool - 5 mins
delayed 2-4 hours
increased uptake like metastatic lesion
increased uptake like metastatic lesion
all 3 phases
phases 1 and 2
increased in 1 and 2, then increased AROUND the joint in 3
increased in delayed only
PET scan
need cyclotron make positron emitting isotope such as fluorine 18
expensive
FDG taken up by rapidly turning over cells
Perichondral ring of LaCroix is ___
what is it made up of
Groove of Ranvier is ___
Epiphyseal arteries supply __
Perichondral arteries supply __
fibrous tissue that supports the physis
chondrocytes, fibroblasts, osteoblasts
circumferential ring bridging the epiphysis to the diaphysis
resting zone and upper proliferative zone only
groove and ring
Difference between graded and action potential
Graded potential - chemically gated channel. Obey’s Ohm’s law
Action potential - voltage-gated channel. Does NOT obey Ohm’s law
viscoelasticity
- definition
- examples
- PMMA viscoelastic?
- energy exerted on viscoelastic properties is converted to ___
what does increasing loading rate on viscoelastic material do to:
- elastic modulus
- yield stress
- ultimate stress
- strain rate
- ductility
- material exhibits stress-strain relationship that depends on duration and rate of load applied
- ligaments and bone
yes
heat
temperature - elastic modulus ↑
- yield stress ↑
- ultimate stress ↑
- strain rate ↓
- ductility ↓
aPTT assesses ____
warfarin initially ___
platelet derived growth factors include ___
intrinsic pathway
makes pro-coagulopathic
PDFG, EGF, IGF-1
Clotting cascade

creep of bone relates to ____
internal friction of ligaments and tendons is accounted for by ___
predominant cause of viscous behaviour of cartilage is ___
solid phase is ___
fluid phase is ___
frictional drag is ___
viscous behaviour depends on both ___ and ___
inter lamellar sliding of osteons
uncrimping
viscous drag
linearly elastic
incompressible
time dependent
time and strain
frictional force is proportional to ___ and independent of ___
coefficient of friction =
articular surfaces ___ than prostheses
fatigue wear independent of ___
applied load, contact area
force / load
rougher
lubrication
nominal stress also known as ___
nominal stress based on the ___
nominal or true stress used in most clinical settings
engineering stress
original dimensions
nominal
Density bone must reduce by to be appreciated on XR
DEXA or QCT more radiation
DEXA or QCT gold standard
QCT good for
DEXA good for
30%
QCT
DEXA
trabecular bone, specifically of vertebrae
both axial and peripheral measurements
which type of bone is more isotropic
peak strains in bone are
cortical bone is ___ longitudinally and ___ transversely
cancellous
2000-3000µ
anisotropic / isotropic
can woven/lamellar be differentiated radiologically
which is more cellular
woven has more ___ cells, lamellar more ___ cells
most common cell in bone is
osteoblasts produce what
no
woven
ovoid / round
osteocyte
ALP, type 1 collagen, osteocalcin, RANKL
induced electrical fields in fracture repair
- optimal Hz
- what can they NOT do
15-30
revscularise necrotic bone
during fracture repair
- what regulates callus
- chondrocytes produce ___
- fibroblasts produce ___
IL-6
chondroitin
dermatan
metalloproteinases require ___ but not ___
zinc, not a low pH
number of motor units is ___
number of fibres per unit is ___
number of fibres relates to
variable
variable
size of cell body
what happens to muscle during strength training
fibre hyperplasia
increased motor unit recruitment
increased phosphagens
increased contractile proteins
microglial cells are produced by ___
myelin is composed of ___
lipid bilayer is ___ permeable
macrophages
70% lipid, 30% protein
selectively
epineurium protects in ___
perineurium protects in ___
which layer is thickest
compression
tension
epineurium
which is most and least transmissible
HIV / hep C / hep B
hep B most
HIV least
H wave characteristics different from M wave
lower stimulus threshold
constant fixed waveform
found consistently only in calf and FCR after age 1
flattened ruffled border seen with:
- bisphosphonates and calcitonin
stopping RA meds prior to surgery
- which continue
- which cease
- cont: NSAIDs, methotrexate, sulfasalazine, hydroxychloroquine
stop - leflunomide if major
- TNF antagonists - etanercept, infliximab, adalimumab - surgery end of dosing + 1 week
2x tendon syndromes associated with RA
Mannerflet syndrome - rupture of FPL in CT due to scaphoid spur
Vaughan-Jackson syndrome - attritional rupture of extensor tendons from DRUJ instability and prominent ulna head
types of corrosion
galvanic - dissimilar metals - electrochemical destruction
crevice - differences in oxygen
fretting - destruction at contact site from relative micro motion of two materials
nail torsional rigidity
nail bending rigidity solid nail
nail bending rigidity hollow nail
plate bending rigidity
radius 4th power
radius 4th power
radius 3rd power
thickness 3rd power
primary bone healing is ___ ossification
secondary is ___ ossification
primary = intramembranous
secondary = endochondral
factors that stimulate and inhibit bone resorption
INHIBIT
- calcitonin
- oestrogen
- IL10
STIMULATE
- RANKL
- PTH
- IL1 and IL6
- 1.25 vitamin D
haemophilia clotting factors
coagulation factors
A - 8
B - 9
aptt long, PT normal
composition of collagen
triplex helix of 2x alpha1 and 1x alpha2
4 immunological reactions
type 1 - anaphylaxis - IgE mast cells
type 2 - IgG and IgM antibody dependent hypersensitivity
type 3 - IgG and IgM immune complex hypersensitivity
type 4 - delayed hypersensitivity - T cells
