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Basic Science Flashcards

1
Q

Strain and stress definitions and units

A

Strain = percentage change in length (given as %)
Stress = force per unit area (N/mm2 or Pa)

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2
Q

Hooke’s Law

A

Stress = Young’s modulus (E / Elastic modulus) x strain
i.e. E is slope of the line

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3
Q

Poisson’s ratio
Range
- cork
- rubber

A

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)

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4
Q

Isotropic
Anisotropic
Orthotropic
How many constants to define their elastic modulus
How many constants to define deformation

A

Isotropic - same properties each direction - 2 constants
Anisotropic - different properties in each direction - 5 constants
Orthotropic - three perpendicular planes of symmetry - 9 constants
6

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5
Q

Draw stress strain curve

A
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6
Q

Definition and example:
- Creep + e.g.
- Stress relation + e.g.
- Endurance limit
- Stress shielding

A

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

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7
Q

3x types of wear and definition

A

Abrasive - friction between hard and soft material
Adhesive - molecular affinity between two surfaces
Fatigue - delamination / microscopic wears

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8
Q

Mechanism of osteolysis around biomaterials

A

Macrophages ingest particles, release TNF-alpha and IL-1 - osteoclastic resorption

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9
Q

Definition
- casting
- machining
- forging
- cold working
- annealing
- sintering

A

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

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10
Q

Effects of cold working and of annealing

A

Cold working - harder, stiffer, stronger, but less plastic so cracks easier. Decreases grain size
Annealing - more ductile, less hard

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11
Q

Cold working effect on
- toughness
- hardness
- tensile strength
- yield stress
- ultimate stress
- brittleness
- ductility

A
  • toughness - ↑
  • hardness - ↑
  • tensile strength - ↑
  • yield stress - ↑
  • ultimate stress - ↑
  • brittleness - ↑
  • ductility - ↓
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12
Q

Stainless steel
- composition
- carbon content and why
- corrosion
- one good specific property

A

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&raquo_space;> yield stress)

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13
Q

Cobalt chrome
- composition
- what type of alloy
- ductility and wear

A

60% cobalt / 28 % chromium
Biphasic alloy
very low ductility, very good wear properties

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14
Q

Titanium
- grade 5 alloy
- good and bad property for arthroplasty
- compared with pure titanium, the alloy is__
- resistance to corrosion

A
  • Ti6Al4V
  • rough finish allows for interlocking
    poor wear properties
  • stronger
  • better than steel and cobalt alloys
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15
Q

Standard THR composition

A

Titanium cup
Titanium uncemented stem
Stainless steel cemented stem
Co-Cr or ceramic head

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16
Q

Young’s modulus of:
stainless steel
Co-Cr
titanium
cortical bone

A

190 GPa
230 GPa
110 GPa
17 GPa

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17
Q

Polyethylene
- type of bonds
- strength depends on
- stability depends on

A

covalent and van der Waals
strength - molecular weight
stability - temperature

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18
Q

Bone cement
- name
- powder consists of:
- liquid consists of:
- viscosity is:
- Young’s modulus is

A

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

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19
Q

Density of UHMWPE is close to:
Method of irradiation
How does irradiation change UHMWPE

A

Closer to low than high density PE
Gamma irradiation with Co60 source
improves wear characteristics but decreases fatigue and fracture resistance

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20
Q

Ceramics
- Friction coefficienty
- Hardness
- Brittleness
- Biocompatibility
- Strength is inversely proportional to:
Aluminia -
Zirconia -

A

very low
high
high
high
grain size and porosity
very low coefficient of friction, high wettability, fractures
stronger and denser but rougher

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21
Q

Metallic bonds
- structure
- charge

A

crystalline array - positive nuclei with loose valence electrons
Neutral

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22
Q

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 ___

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

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23
Q

Newtonian fluid definition

A

Viscosity remains at a constant no matter the shear forces applied. And energy is not stored

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24
Q

Draw the growth plates

A
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25
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
26
Draw the growth plates
27
Where is fibrocartilage and elastic cartilage
- transitionally in fractures. Menisci, TMJ and IV discs - Eustachian tube, epiglottis
28
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
29
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
30
Zones of cartilage cartilage - thickness, collagen, chondrocytes, aggrecan, water
31
Collagen - isotropic / orthotropic / anisotrophic - tensile strength compared with meniscus - type in cartilage
orthotropic less type II (except type 5 around chondrocytes)
32
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
33
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
34
Percentage dry weight that is collagen in - fibrocartilage - hyaline cartilage - tendons - ligaments
70 50-80 86 70
35
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
36
Composition of bone
60% inorganic - hydroxyapatite - calcium and phosphate 30% organic - type 1 collagen 90% - proteoglycans 10% water
37
Haversian systems and Volkmann's canals
Haversian systems - tubes that run within axis of bone Volkmann's canals - perforating channels that run transversely
38
Bone - tropic? - compression modulus ___x higher than tension - tension modulus ___x higher than shear
transversely isotropic 1.5x higher 5x higher
39
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
40
Difference in bone loss in osteoporosis between males and females
Males lose more cortical Females lose more cancellous
41
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
42
Primary bone healing: - how much strain is acceptable - what initiates remodelling - gap must be:
2% cutting cones <500 microns
43
Oxygen tension in: - fibrous tissue haematoma new bone
high low low
44
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
45
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
46
Changes in aging vs in osteoarthritis - water, PGs, collagen cross linking and content, chondrocyte density and size, synthetic activity, modulus of elasticity, hyaluronate, permeability
47
One motor unit is composed of:
One motor neuron and all of the fibres that it innervates
48
Draw a sarcomere Which bands stay same / reduce
A band stays same, others reduce
49
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)
50
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
51
Type I and type II muscle fibres
I - small, slow, less force, fatigue resistant II - large, fast, forceful, fatigues
52
ATP per glucose for aerobic and anaerobic What converts ADP to ATP glycogen levels are always ___
38 and 2 creatine phosphate constant
53
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
54
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%
55
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
56
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
57
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
58
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
59
Nerve tracts - spinothalamic - dorsal columns - corticospinal - dorsal roots - ventral roots
pain and temperature proprioception and vibration voluntary muscle afferent efferent
60
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
61
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
62
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
63
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
64
Forces through hip - walking - walking fast - single leg stance
3x 7x 2-3x
65
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
66
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
67
Hand - IPJ collaterals are tight in - MCPJ collaterals are tight in - weakest thenar muscle
all positions flexion APB
68
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
69
what is required for tendon transfer
adequate power and passively mobile joint
70
Foot and ankle - supination is which movements - axis of calcaneus is which direction
plantarflexion, varus, adduction forwards, medial, upwards
71
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
72
How does DEXA work
2x X-ray beams of different energies that are absorbed in different proportions
73
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)
74
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
75
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
76
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
77
PET scan
need cyclotron make positron emitting isotope such as fluorine 18 expensive FDG taken up by rapidly turning over cells
78
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
79
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
80
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 ↓
81
aPTT assesses ____ warfarin initially ___ platelet derived growth factors include ___
intrinsic pathway makes pro-coagulopathic PDFG, EGF, IGF-1
82
Clotting cascade

83
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
84
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
85
nominal stress also known as ___ nominal stress based on the ___ nominal or true stress used in most clinical settings
engineering stress original dimensions nominal
86
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
87
which type of bone is more isotropic peak strains in bone are cortical bone is ___ longitudinally and ___ transversely
cancellous 2000-3000µ anisotropic / isotropic
88
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
89
induced electrical fields in fracture repair - optimal Hz - what can they NOT do
15-30 revscularise necrotic bone
90
during fracture repair - what regulates callus - chondrocytes produce ___ - fibroblasts produce ___
IL-6 chondroitin dermatan
91
metalloproteinases require ___ but not ___
zinc, not a low pH
92
number of motor units is ___ number of fibres per unit is ___ number of fibres relates to
variable variable size of cell body
93
what happens to muscle during strength training
fibre hyperplasia increased motor unit recruitment increased phosphagens increased contractile proteins
94
microglial cells are produced by ___ myelin is composed of ___ lipid bilayer is ___ permeable
macrophages 70% lipid, 30% protein selectively
95
epineurium protects in ___ perineurium protects in ___ which layer is thickest
compression tension epineurium
96
which is most and least transmissible HIV / hep C / hep B
hep B most HIV least
97
H wave characteristics different from M wave
lower stimulus threshold constant fixed waveform found consistently only in calf and FCR after age 1
98
flattened ruffled border seen with:
- bisphosphonates and calcitonin
99
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
100
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
101
types of corrosion
galvanic - dissimilar metals - electrochemical destruction crevice - differences in oxygen fretting - destruction at contact site from relative micro motion of two materials
102
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
103
primary bone healing is ___ ossification secondary is ___ ossification
primary = intramembranous secondary = endochondral
104
factors that stimulate and inhibit bone resorption
INHIBIT - calcitonin - oestrogen - IL10 STIMULATE - RANKL - PTH - IL1 and IL6 - 1.25 vitamin D
105
haemophilia clotting factors coagulation factors
A - 8 B - 9 aptt long, PT normal
106
composition of collagen
triplex helix of 2x alpha1 and 1x alpha2
107
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

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