Basic science random facts

Question 1

Fracture healing pizoelectric changes

Answer 1

compression side is electronegative and stimulates osteoblast formation

tension side is electropostive and simulates osteoclasts

Question 2

Inflammation phase of fracture healing

Answer 2

Hematoma –> Fibroblasts and mesenchymal migrate (granulation tissue) —> Osteoblasts and fibroblasts proliferate

Question 3

Repair phase of fracture healing

Answer 3

Primary callus within two weeks --\>
 Enchondral ossification (woven bone) --\>
 Type II (+IV) collagen is produced early --\> type I collagen--\>
 Type X collagen types is expressed by hypertrophic chondrocytes as the extraarticular matrix undergoes calcification

Question 4

The process of host repair following osteonecrosis is referred to as

Answer 4

creeping substitution

Question 5

The application of 149 degree F (65 degree C) heat to collagen tissue immediately results in

Answer 5

decreased tissue stiffness

Question 6

Pacinian corpuscles

Answer 6

ovoid in shape, measuring approximately 1 mm in length. They respond to high-frequency vibration and rapid indentations of the skin

Question 7

Ruffini corpuscles

Answer 7

slowly adapting receptors that detect stretching of the skin

Question 8

Meissner corpuscle

Answer 8

rapidly adapting sensory receptor, is very sensitive to touch

Question 9

Merkel’s skin receptors (disc)

Answer 9

slowly adapting skin receptors that detect pressure (steady indentation), texture, and and can be appropriately evaluated by static two-point discrimination

Question 10

Creep definition

Answer 10

progressive deformation of a material in response to a constant force over an extended period

Question 11

load relaxation definition

Answer 11

decreased peak loads over time with the same amount of elongation

Question 12

Plastic deformation definition

Answer 12

irreversible change in length after removing the load

Question 13

Fatigue

Answer 13

failure at a submaximal tensile strength after numerous loading cycles

Question 14

Ultimate strength

Answer 14

Load at which a material fractures

Question 15

anisotropic

Answer 15

Change in mechanical properties as a result of the direction of a load

Question 16

viscoelasticity

Answer 16

Change in the stress-strain relationship dependent on the rate of loading i

Question 17

galvanic corrosion

Answer 17

corrosion resulting from an electrochemical potential created between two metals in conductive medium

Question 18

yield strength (yield point)

Answer 18

the stress at which a material begins to undergo plastic deformation

Question 19

toughness

Answer 19

amount of energy a material can absorb before failure

Question 20

Endurance limit

Answer 20

maximum level of stress that can be applied to a material cyclically and never cause failure

Question 21

Fretting

Answer 21

physical movement (micro motion) of two plates against each other leading to mechanical wear and material transfer at the surface

Question 22

Moduli of Elasticity (GPa)

Answer 22

1) UHMWPE = 0.8-1.5.
* *2) Cancellous Bone = 2**
3) PMMA = 3.1

• *4) Cortical Bone = 18**
  5) Titanium = 115
  6) Tantalum = 186
  7) Stainless Steel = 240

8) Cobalt-Chromium Alloy = 240
9) Zirconia (Ceramic) = 248
10) Alumina = 340

Question 23

etanercept (Enbrel) mechanism of action

Answer 23

TNF receptor - IgG1 fusion protein

Question 24

infliximab (Remicade) mechanism of action

Answer 24

chimeric mouse/human monoclonal Ab to TNF

Question 25

anakinra mechanism of action

Answer 25

recombinant IL1 receptor antagonist

Question 26

rituximab mechanism of action

Answer 26

monoclonal Ab to CD20 antigen (B cell inhibition)

Question 27

most common immunosuppressive agent in RA

Answer 27

leflunomide (inhibits T cells)

Question 28

initiates platelet activation and release of growth factors contained within the platelets

Answer 28

calcium chloride and thrombin

Question 29

Tendon strength after repair

Answer 29

weakest at 7-10 days most of strength by 21-28 days maximum strength at 6 months * final strength only reaches 2/3 of normal even years after repair

Question 30

working length (distance) - plate

Answer 30

Question 31

working length - rod

Answer 31

Question 32

maximal amount of antibiotic to be added to PMMA for optimizing antibiotic elution without deleterious effects on mechanical strength

Answer 32

5% of the total weight

Question 33

antibiotic that is bacteriostatic at therapeutic serum concentrations

Answer 33

clindamycin (pen/ceph/vanc all bictericidal per AAOS)

Question 34

A brittle material such as a ceramic femoral head prosthesis undergoes what type(s) of deformation when loaded to failure?

Answer 34

Elastic! Brittle materials undergo only fully recoverable (elastic) deformation prior to fracture. Brittle materials have little or no capacity to undergo permanent (plastic) deformation prior to fracture. The properties of brittle materials are neither temperature nor rate dependent (viscoelastic)

Question 35

most common bacterium found in an infection caused by a human bite

Answer 35

Eikenella

Question 36

Oral drug combo (synergistic) for MRSA

Answer 36

quinolone + rifampin

Question 37

abx quick mech of action

Answer 37

* Beta-lactam antibiotics inhibit cell wall synthesis * Quinolones inhibit DNA gyrase * Aminoglycosides inhibit protein synthesis by binding to ribosomal RNA * Rifampin inhibits RNA synthesis

Question 38

COX-2 facts (3)

Answer 38

- expressed at low levels unless it is induced by cytokines/inflammatory mediators, responsible for the upregulation of the inflammatory system - function to break down arachidonic acid into prostaglandins, thereby increasing their concentration at the site of injury under the influence of osteotropic factors such as TNF-alpha - KO mice problems with endochondral ossification

Question 39

AA metabolism figure

Answer 39

Question 40

changes in structure and function with immobilization of TENDON

Answer 40

decreases tensile strength, stiffness, and total weight Microscopically, there is a decrease in cellularity, overall collagen organization, and collagen fibril diameter

Question 41

muscle fiber types 1

Answer 41

Type I muscle, also known as slow-twitch muscle, is responsible for aerobic, oxidative muscle metabolism. It has a much lower strength and speed of contraction than fast-twitch type II muscle but is significantly more fatigue resistant.

Question 42

oxazolidinone (linezolid) mech of action

Answer 42

inhibit protein synthesis _70S ribosomal subunit_

Question 43

aminoglycosides mech of action

Answer 43

disrupt protein synthesis, 30s ribosome subunit

Question 44

Lyme's treatment

Answer 44

amoxicillin, doxycycline, or cefuroxime 4 weeks oral abx generally ok