Basic science random facts Flashcards
Fracture healing pizoelectric changes
compression side is electronegative and stimulates osteoblast formation
tension side is electropostive and simulates osteoclasts
Inflammation phase of fracture healing
Hematoma –> Fibroblasts and mesenchymal migrate (granulation tissue) —> Osteoblasts and fibroblasts proliferate
Repair phase of fracture healing
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
The process of host repair following osteonecrosis is referred to as
creeping substitution
The application of 149 degree F (65 degree C) heat to collagen tissue immediately results in
decreased tissue stiffness
Pacinian corpuscles
ovoid in shape, measuring approximately 1 mm in length. They respond to high-frequency vibration and rapid indentations of the skin
Ruffini corpuscles
slowly adapting receptors that detect stretching of the skin
Meissner corpuscle
rapidly adapting sensory receptor, is very sensitive to touch
Merkel’s skin receptors (disc)
slowly adapting skin receptors that detect pressure (steady indentation), texture, and and can be appropriately evaluated by static two-point discrimination
Creep definition
progressive deformation of a material in response to a constant force over an extended period
load relaxation definition
decreased peak loads over time with the same amount of elongation
Plastic deformation definition
irreversible change in length after removing the load
Fatigue
failure at a submaximal tensile strength after numerous loading cycles
Ultimate strength
Load at which a material fractures
anisotropic
Change in mechanical properties as a result of the direction of a load
viscoelasticity
Change in the stress-strain relationship dependent on the rate of loading i
galvanic corrosion
corrosion resulting from an electrochemical potential created between two metals in conductive medium
yield strength (yield point)
the stress at which a material begins to undergo plastic deformation
toughness
amount of energy a material can absorb before failure
Endurance limit
maximum level of stress that can be applied to a material cyclically and never cause failure
Fretting
physical movement (micro motion) of two plates against each other leading to mechanical wear and material transfer at the surface
Moduli of Elasticity (GPa)
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
etanercept (Enbrel) mechanism of action
TNF receptor - IgG1 fusion protein
infliximab (Remicade) mechanism of action
chimeric mouse/human monoclonal Ab to TNF
anakinra mechanism of action
recombinant IL1 receptor antagonist
rituximab mechanism of action
monoclonal Ab to CD20 antigen (B cell inhibition)
most common immunosuppressive agent in RA
leflunomide (inhibits T cells)
initiates platelet activation and release of growth factors contained within the platelets
calcium chloride and thrombin
Tendon strength after repair
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
working length (distance) - plate
working length - rod
maximal amount of antibiotic to be added to PMMA for optimizing antibiotic elution without deleterious effects on mechanical strength
5% of the total weight
antibiotic that is bacteriostatic at therapeutic serum concentrations
clindamycin
(pen/ceph/vanc all bictericidal per AAOS)
A brittle material such as a ceramic femoral head prosthesis undergoes what type(s) of deformation when loaded to failure?
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)
most common bacterium found in an infection caused by a human bite
Eikenella
Oral drug combo (synergistic) for MRSA
quinolone + rifampin
abx quick mech of action
- Beta-lactam antibiotics inhibit cell wall synthesis
- Quinolones inhibit DNA gyrase
- Aminoglycosides inhibit protein synthesis by binding to ribosomal RNA
- Rifampin inhibits RNA synthesis
COX-2 facts (3)
- 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
AA metabolism figure
changes in structure and function with immobilization of TENDON
decreases tensile strength, stiffness, and total weight
Microscopically, there is a decrease in cellularity, overall collagen organization, and collagen fibril diameter
muscle fiber types 1
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.
oxazolidinone (linezolid) mech of action
inhibit protein synthesis 70S ribosomal subunit
aminoglycosides mech of action
disrupt protein synthesis, 30s ribosome subunit
Lyme’s treatment
amoxicillin, doxycycline, or cefuroxime
4 weeks
oral abx generally ok
