OITE - Basic Science Flashcards
Calcitonin’s role in bone metabolism?
-Inhibits osteoclastic bone resorption, by binding CTR (receptor)
-decreases osteoclast resorption at the ruffled border
“calcitOnin Opposes bOne resOrption”
Which Ig subtype does rheumatoid factor target?
- Rheumatoid factor (IgM) attaches to IgG forming imm complex
- IgM is only one that is a pentamer
- IG is only Ab which can cross placenta giving passive immunity to fetus
Psoriatic arthritis, what is it?
- Seronegative spondyloarthropathy in 5-20% with psoriasis
- Distal phalax acrolysis
- Dactylitis “sausage digits”
- Pencil in cup xray of phalanges
Herniated disks are associated with spontaneous increase in production of:
- OPG (osteoprotegerin)
- IL-1 beta
- RANKL
- PTH
COX action?
-catalyze formation of PG and thromboxane from arachidonic acid
COX-1 action?
-generates PG responsible for maintenance/protection of GIT
COX-2 action?
-generates PG responsible for inflammation and pain
Function of hemeobox gene product?
regulates somatization of the axial skeleton
What is the function of Cathepsin K, produced by osteoclasts?
- released by osteoclasts at the ruffled border to function to RESORB bone
- Cathepsin K inhibits (role for osteoporosis?)
GILT enzymes?
Reduce di-sulfide bonds
3 features of bone grafting to know?
- Compression strength
- Resorption rates
- Drainage (calcium sulfate)
Which bone graft substitute have the fastest resorption characteristics?
Calcium sulfate
Is COX-2 expressed under normal condiitons?
No, only found during general states of inflammation
What zone do physeal fx typically occur?
Zone of provisional calcification in HYPERTROPHIC zone
Peak bone mass in men and woman is most dependent on which sex steroid?
Estrogen - prevents bone loss by inhibiting bone resorption
Osteocalcin?
- most abundant noncollagenous protein in bone
- secreted by OSTEOBLASTS
- promotes mineralization and bone formation
- inhibited by PTH and stimulated by VitD
Organic components of bone?
Collagen
Proteoglycans
Matrix protein (osteocalcin, osteonectin, osteopontin)
What is renal osteodystrophy?
- Pathologic bone condition in pts with underlying kidney disease
- increased PTH secretion
Renal osteodystrophy, what is the key pathophysiological step leading to osteomalacia?
-Uremia related phosphate retention
-inadequate phosphorus secretion
-insoluble calcium phosphate removes calcium from circulation
hypocalcemia occurs
What is hypopohsphatasia and what lab values does it lead to?
- AR disorder due to inborn error in production of alk phosphatase
- Low serum alkaline phosphatase levels
- ALP is a marker of bone formation
What is Rickets?
Defect in mineralization of osteoid matrix caused by inadequate calcium and phosphate
Which serum marker is most closely associated with colorectal carcinoma?
CEA - colorectal
CA 19-9 pancreatic
CA 125 ovarian
CA 15-3 breast AFP - hepatocellular carcnioma
Muscle injury, what is the first listed cells to appear following acute injury?
-Neutrophils
Then macrophages
SOX-9 is a key transcription factor in the differentiation of what cell lineage?
Cartilage differentiation from chondrocytes
Vitamin B12 deficiency causes what?
-peripheral sensory neuropathy
Signs
-Decreased DTR, babinski, fatigue/depression
How do you increase strength and stability of an exfix construct?
2 cortices better than 1 separating the pins is better
pins closer to fx
shorter pins better
bigger pins better
Adductor myodesis benefit in AKA?
- improves outcomes by creating dynamic balance force facilitating ambulation
- provides soft tissue cushion beneath osseous amputation and
- enhances prosthetic fitting
Myoelectric prosthesis candidate? its features?
- best candidate is transradial amputation
- good cosmesis
- heavier, but good for overhead activities, sedentary
- less sensory feedback
Galvanic corrosion?
wear in dissimilar metals in proximity with difference between their electric potentials, results in a flow of current between them
4 types of corrosion?
- crevice corrosion
- fretting corrosion
- pitting corrosion
- galvanic corrosion
Chromium, molybdenum and cobalt are basic components of which implant material?
Cobalt alloy
Which metal is closest to bone in Youngs modulus?
Titantium
Stainless steel?
- Iron with chromium in it
- resistant to corrosion
Lead toxicity affects growth by inhibiting what?
PTHrP (parathyroid hormone related peptide)
and TGH-beta1
3 P for Plumbism?
Painful belly (colic constipation) Polka-dotted RBC Peripheral palsies: RADIAL NERVE
3 b’’s for Plumbism?
Blue (burton’s) gum lines
Basophilic Blue stippling
Bright BONY BANDS metaphysis (in growing bones)
Which medication replaces normal coagulation factors with Decarboxylated factors?
- Warfarin prevents Vit K gamma carboxylation
- II, VII, XI, X, Protein C and S
Etiology of FES (fat embolism syndrome) in TKA ?
intramedullary instrumentation
CXR of FES
like ARDS, “Snow Storm Lung”
What are the Biphasic Clinical stages of FES?
- Immediate, fat emboli i 90% of long bone fx, block vessels
- Delayed 24-72 hrs (Facids stimulate complement to ARDS)
What part of the articular cartilage has the highest concentration of proteoglycans and lowest conc of Water?
Deep layer
What type of collagen starts at Tidemark in cartilage?
Cartilage Type 10
What kind of collagen is found predominantly in cartilage?
Type 2 (90-95%) Type X is only in calcified cartilage zone
What is the result of a Type 1 collagen defect?
bONE collagen
-Type 1 defect leads to OI
Ehlers-Danlos syndrome defect?
Type 1 and Type 3 collagen defect
Gout “YUPAN”
Yellow Urate Parallel ( to compensator)
Negative birefringence
Needle Shaped
What about CPPD?
Positive birerefringence
Blue crystals
Which genetic polymorphisms are associated with osteoporosis?
Calcitonin
Estrogen receptor-1
Vit D receptor
Type 1 collagen alpha-1 chain
MED spinal involvement?
No
Pseudoachondroplasia, spine involvement? Genetic mutation?
Yes
COMP
Daily calcium and Vit D recommendation for women?
age >50 –1200 mg calcium, 800-1000 IU Vitamin D
age
Longterm bisphosphates associated with what kind of fx?
- Atypical Subtroch femoral stress fx
- Jaw osteonecrosis
What is the primary mode of bisphosphonate excretion?
-Renal excretion
is contra-indicated in pts with severe renal disease
What mode of inheritance are structural protein deficits in ortho?
Autosomal dominant (collagen, fibrillin, FGF)
If it is enzymatic defect, what is the typical mode of inheritance?
autosomal recessive (cerebrosidase, carbonic anhydrASE, etc).
What is genetic anticipation?
=disease develops earlier in life in each successive generation
What is genetic imprinting?
A single working copy of a gene is inherited
nonworking or silenced gene is usually methylated
What species of bacteria is known to produce MecA?
- MRSA is most common carrier
- MecA forms penicillin binding protein 2A
- alters efficacy of beta-lactam antibiotics
Clinical trials pyramid?
Level 1 - RCT
Level 2 - Prospective cohort
Level 3 - Retrospective cohort, or Case control study
Level 4 - Case series Level 5 - Case report
HOw is radiation exposure increased?
- Larger body part is imaged
- Extremity is positioned closed to X-ray source
- Large C-arm > mini C arm
What factors can one use to decrease radiation exposure?
- Minimizing exposure time -protective shielding
- Maximizing distance
- Colliminator
- Inverted position relative to patient
What term in stats defines accepting the null hypothesis, when it is in fact not true?
Type 1 error - null hypothesis is REJECTED even though it is correct
Type II error - nuLL hypothesis is aCCepted, even though it is in fact not correct
What are type 2 errors due to ?
Inappropriate study power
AKA false negative rate
Study power formula?
Power = 1 - beta (type2 error)
- is an estimate of probability of finding an association in a research study when on actually exists
- 80% is appropriate power
What injury independently predicts poor outcome in polytrauma pts?
Foot injury
-SF 36, WOMAC, and other validated outcome measure tools
Joint reaction force increases or decreases, as the acetabular component is moved medial in THA?
Joint rxn force decreaes, due to decreasing abductor tension
in a single-sided leg stance, what is the body and leg weight relative to total body weight?
5/6th of total body weight
What cell expresses RANKL?
- Expressed on osteoblasts
- RANK receptor is on osteoclast precursor cell (causing bone resorption)
