Basic Science Flashcards
1
Q
What are the mechanisms of wear
A
adhesion
abrasion
transfer
fatigue
third body
2
Q
What are the 5 forms of lubrication
A
-
elastohydrodynamic
- main mechanism during dynamic joint function
- elastic deformation of articular surfaces
- thin films of lubricant separate the surfaces
-
boundary (slippery surfaces)
- bearing surface is non-deformable
- lubricant only partially separates surfaces
- superficial zone proteins have a role in this lubrication mechanism
-
boosted (fluid entrapment)
- concentration of lubricating fluid in pools
- trapped by regions of bearing surfaces that are making contact
-
hydrodynamic
- fluid separates surfaces when one surface is sliding on the other
-
weeping
- fluid shifts out of articular cartilage in response to load
- surfaces separated by hydrostatic pressure
3
Q
What changes occur in aging cartilage
A
-
increases in
- chondrocytes size
- protein content
- stiffness (passive glycation leads to increased stiffness of collagen)
- increase in ratio of proteoglycan keratin sulfate to chondroitin sulfate
-
decrease in
- absolute number of cells (becomes hypocellular, despite the fact that individual chondrocytes are increasing in size)
- water content (differentiates from osteoarthritis where water content actually increases)
- solubility
- proteoglycan size
- elasticity
4
Q
What are the 5 forms of articular cartilage
A
hyaline or articular cartilage fibroelastic cartilage (meniscus) fibrocartilage (at tendon and ligament insertion into bone) elastic cartilage (trachea) physeal cartilage (growth plate)
5
Q
What is the function of cartilage
A
- decreases friction
- distributes loads
- cartilage exhibits stress-shielding of the solid matrix components
- high water content
- incompressibility of water
- structural organization of the proteoglycan and collagen molecules
6
Q
What are the extracellular components of cartilage
A
-
water
- makes up 65% to 80% of mass of the cartilage
- accounts for 80% of the weight near the surface
- 65% at the deep zone
-
collagen
- makes up 10 to 20% of total cartilage mass
- type II collagen accounting for 90% to 95% of the total collagen content.
- functions to provide cartilagenous framework and tensile strenth
- small amounts of types V, VI, IX, X, and XI collagen are also present
-
proteoglycans
- makes up 10 to 15% of cartilage
- functions to provide compressive strength and attract water
- produced by chondrocytes
- composed of GAG subunits
- chondroitin sulfate
- keratin sulfate
- noncollagenous protein
7
Q
What are the zones of articular cartilage
A
-
Superficial zone (tangential zone)
- Type II collagen orientation is parallel to joint
- Has flattened chondrocytes, condensed collagen fibers, and sparse proteoglycans
- only zone where articular cartilage progenitor cells have been found
-
Intermediate zone
- Type II collagen has an oblique or random organization
- Is the thickest layer with round chondrocytes, and abundant proteoglycan content
-
Deep layer (basal layer)
- Type II collagen is perpendicular to joint and crosses tidemark; has the highest concentration of proteoglycans
- Round chondrocytes arranged in columns
-
Tidemark
- Is deep to the basal layer and separates the true articular cartilage from the deeper cartilage that is a remnant of the cartilage anlage, which participated in endochondral ossification during longitudinal growth in childhood.
- The tidemark divides
- the superficial uncalcified cartilage from the deeper calcified cartilage
- division between nutritional sources for the chondrocytes
- The tidemark is found only in joints
- Most prominently in the adult and nongrowing joint
- Subchondral Bone
8
Q
What nurishes cartilage
A
surface - synovial fluid
subchondral bone at base
9
Q
What are the 8 components of SF-36
A
vitality
physical functioning
bodily pain
general health perceptions
physical role functioning
emotional role functioning
social role functioning
mental health
36 questions; SF17 is a more condested version
10
Q
What are the 4 components of the HHS
A
-
pain
- no pain given 44 points
-
function
- no limp, walks without aid, and can walk more than six blocks given 33 points
-
function activities
- no disabilities given 14 points
-
physical exam
- based on range of motion with max score of 9
out of 100
11
Q
What are the components of the WOMAC score
A
pain
stiffness
function
total score
30 questions on a likert scale; scored out of 100
12
Q
Compare observational and experimental designs for research studies
A
-
observational
- researchers observe patient groups without allocation of intervention
- may be either prospective or retrospective
- may be descriptive or analytic
-
descriptive
- useful for obtaining background information for more advance studies
- examples
- case reports
- case series
- cross-sectional studies
-
analytic
- explores the association between a given outcome and a potentially related variable
- examples
- case-control
- cohort
- meta-analysis
-
descriptive
-
experimental
- researchers allocate treatment
- allows the evaluation of efficacies of therapeutic interventions
- examples
- double-blinded, prospective, randomized clinical trial is the gold standard for evidence based medicine
13
Q
What are the key aspects of a randomized control trial
A
-
Definition
- a study in which patients are randomly assigned to the treatment or control group and are followed prospectively
- provides the most compelling evidence that the study treatment causes the expected effect on human health
- randomization minimizes study bias
-
Crossover design
- administration of two or more therapies, one after the other, in a random order
- susceptible to bias if washout period is inadequate
- single blinded study vs. double blinded study
- double = participant and administrator
-
Analysis
-
intent-to-treat analysis
- outcomes based on the group into which they were randomized, regardless of whether the patient actually received the planned intervention
- minimizes non-responder bias
-
per protocol
- excludes patients who were not compliant with the protocol guidelines
-
intent-to-treat analysis
14
Q
What are the key aspects of a cohort study
A
-
Definition
- a study in which patient groups are separated non-randomly by exposure or treatment, with exposure occurring after (prospective), or before (retrospective), the initiation of the study
-
Evidence
- Level II or III evidence
-
Analysis
- results usually reported as relative-risk
- Example
- you want to determine if smoking is a risk factor for the development of lung cancer. You identify a group of smokers and a group of non-smokers, and follow them over time measuring the desired outcome, in this case, lung cancer.
15
Q
What are the key aspects of a case control study
A
-
Definition
- a study in which patient groups are separated by the current presence (cases) or absence (controls) of disease and examined for the prior exposure of interest
-
Evidence
- Most are Level III evidence
-
Analysis
- usually reported as odds-ratio
-
Example
- you want to determine if smoking is a risk factor for the development of lung cancer. You compare the smoking history of individuals with lung cancer (cases) and those without (controls).
16
Q
What is a cross-sectional study
A
-
Definition
- study group is analyzed at a given time (“snapshot”) with no follow-up
-
Example
- you want to determine the prevalence of baseball injuries during the 2003 little-league season
Example of an observational study
17
Q
What are the levels of evidence
A
-
Level 1
- Randomized controlled trial (RCT)
- Meta-analysis of randomized trials with homogeneous results
-
Level 2
- Prospective comparative study (therapeutic)
- Meta-analysis of Level 2 studies or Level 1 studies with inconsistent results
-
Level 3
- Retrospective cohort study
- Case-control study
- Meta-analysis of Level 3 studies
-
Level 4
- Case series
-
Level 5
- Case report (a report of a single case)
- Expert opinion
- Personal observation
18
Q
What are some of the most common surgical medical errors
A
- Communication errors are the leading cause of wrong-side surgeries, medication errors, diagnostic delays or loss to follow-up
-
Wrong site surgery
- involve the patient in identifying correct side
- response when performed
- address by immediate discussions with family revealing errors
- apologize and accept responsibility, but not blame
-
Surgical “time-out” should include the following according to JCAHO
- identify correct side, site, and patient
- verify the correct procedure
- surgeon is most effective OR team member at reducing complications when using surgical checklist and “time-out”
-
Medication prescribing errors
- reduced when physicians use computerized order entry
-
errors in medical documentation
- It is illegal to alter the medical record for any reason
- no one has the authority to authorize a physician to alter the medical record
- errors can be noted and addendums can be added
19
Q
What is the definition of medical negligence
A
- Negligence is the failure to provide the standard of health care resulting in medical injuries
- A second-opinion physician has an ethical obligation, but not legal obligation, to disclose if the standard of care has been breached by a treating physician.
- A successful patient-plaintiff lawsuit for medical negligence against a physician requires that the following FOUR elements be alleged and proven in a court of law
-
duty
- the duty of the physician is to provide care equal to the same standard of care ordinarily executed by surgeons in the same medical specialty.
-
breach of duty
- breach of duty occurs when action or failure to act deviates from the standard of care.
-
causation
- causation is present when it is demonstrated that failure to meet the standard of care was the direct cause of the patient’s injuries.
-
damages
- damages are monies awarded as compensation for injuries sustained as the result of medical negligence
-
duty
20
Q
Definition of workers compenstation
A
- A workmans’ compensation patient is determined to reach maximum medical improvement when further restoration of function is no longer anticipated and can then settle his/her claim.
- Ability for worker’s compensation patients to choose their own physician varies by the statutes of each state.
-
Legal definitions
-
impairment
- loss of function resulting from an anatomic or physiologic derangement.
-
disability
- limitation of an individual’s capacity to meet certain personal social or occupational demands.
-
impairment
21
Q
What are factors that contribute to radiation exposure from flouro in the OR
A
-
Factors which increase radiation exposure levels during use of fluoroscopy
- imaging large body parts
- positioning extremity closer to the x-ray source
- use of large c-arm rather than mini c-arm
- radiation exposure is minimal during routine use of mini-c-arm fluoroscopy unless the surgical team is in the direct path of the radiation beam
-
Factors to decrease radiation exposure to patient and surgeon
- maximizing the distance between the surgeon and the radiation beam
- minimizing exposure time
- manipulating the x-ray beam with collimation (coning)
- orienting the fluoroscopic beam in an inverted position relative to the patient
- strategic positioning of the surgeon within the operative field to avoid direct path of beam
- use of protective shielding during imaging
22
Q
What are the risk of HIV and hepatitis transmission in orthopedics
A
-
Risk of HIV transmission
- needlestick
- seroconversion from a contaminated needlestick is ~ 0.3%
- exposure to large quantities of blood increases risk
- seroconversion from exposure to HIV contaminated mucous membranes is ~0.09%
- seroconversion from a contaminated needlestick is ~ 0.3%
- frozen bone allograft
- risk of transmission is
- donor screening is the most important factor in prevention
- no reported cases of transmission from frozen bone allograft since 2001
- blood transfusion
- risk of transmission from blood transfusion is 1/500,000 per unit transfused
- seronegative blood may still transmit virus due to delay between HIV infection and antibody development
- needlestick
-
Risk of Hepatitis B transmission
- needlestick
- 37% to 62% eventually seroconvert following needlestick
- 22 to 31% develop clinical Hepatitis B infection following needlestick
- needlestick
-
Risk of Hepatitis C transmission
- needlestick
- 0.5 to 1.8% risk of transmission
- needlestick
23
Q
What are the major and minor criteria for fat emboli syndrome
A
-
Major (1)
- hypoxemia (PaO2
- CNS depression (changes in mental status)
- petechial rash
- pulmonary edema
-
Minor (4)
- tachycardia
- pyrexia
- retinal emboli
- fat in urine or sputum
- thrombocytopenia
- decreased HCT
-
Additional
- PCO2 > 55
- pH
- RR > 35
- dyspnea
- anxiety
24
Q
What is virchows triad DVT
A
venous stasis
hypercoagulable state
intimal injury
25
Q
What is the pathophysiology of clot formation
A
- stasis
- fibrin formation
- thromboplastin (aka Tissue Factor (TF), platelet tissue factor, factor III, or CD142) is released during dissection which leads to activation of the extrinsic pathway and fibrin formation
- clot retraction
- propagation
26
Q
What are primary hypercoagulopathies
A
factor V Leiden mutation
antithrombin III deficiency
protein C deficiency
protein S deficiency
activated protein C resistance
27
Q
What are secondary factors that contribute to DVT
A
-
malignancy
- recently been associated with up to 20% of all new diagnoses of VTE
- elevated hormone conditions
- recombinant erythropoeitin
- hormone replacement
- oral contraceptive therapy
- late pregnancy
- elevated antiphospholipid antibody conditions
- lupus anticoagulant
- anticardiolipin antibody
- history of thromboembolism
- obesity
- aging
- CHF
- varicose veins
- smoking
- general anesthesics (vs. epidural and spinal)
- immobilization
- increased blood viscosity
28
Q
What are aquired risk factors for DVT in athletes
A
- Hemoconcentration
- dehydration, trauma, immobilization, travel, blood hyperviscosity, OCPs
- Recent travel >4 h have 4x risk of VTE; however, varying results of studies…
- dehydration, trauma, immobilization, travel, blood hyperviscosity, OCPs
- Marathon running + air travel >4h
- acute hypercoagulable state exaggerated with increasing age >35
- add in a thrombophilia and you have even higher risks
- Hypoxia at high altitude
- body increases RBC production
- hyperviscocity – risk in climbers
- Females on OCPs have 4x the risk
- those with inherited thrombophilias and on the OCP have even higher risk (up to over 30 fold, they say..)
29
Q
What are the increased risk for DVT with various thrombophilic diseases
A
- Factor V Leiden mutation
- Heterozygous 7×
- Homozygous 80×
- Prothrombin G20210A mutation 2.8×
- Antithrombin III deficiency 5–20×
- Protein C deficiency 2–10×
- Protein S deficiency 2–10×
- Hyperhomocysteinemia 2.5×
- Elevated factor VIII 5×
- Elevated factor XI 2.2×
30
Q
What are prevention strategies for DVT in athletes
A
- screening
- prior to race
- family history
- previous VTE
- medications (OCP)
- Prevention
- LMWH for high risk situation
- hydration
- early mobilization after surgery
- avoidace of high risk situations
31
Q
What is the wells criteria to predict PE
A
- Clinical signs and symptoms of DVT (3)
- (ie, minimum leg swelling, pain on palpation of deep veins)
- An alternative diagnosis is less likely than PE (3)
- Heart rate >100 BPM (1.5)
- Immobilization or surgery in previous 4 weeks (1.5)
- Previous DVT/PE (1.5)
- Hemoptysis (1)
- Malignancy (1)
- (on treatment, treated in last 6 months, or palliative)
32
Q
Ca requirements per population
A
children - 600
adolescents - 1300
adults - 750
pregnant women - 1500
Lactating women - 2000
33
Q
Contraindications to bisphosphanates
A
- severe renal disease
- primary mode of excretion is renal
- following lumbar fusion
- decreased spinal fusion rates in lab animal models (increased fusion mass size, but decreases the actual fusion rate)
34
Q
side effects of bisphosphonates
A
Jaw osteonecrosis
Atypical subtrochanteric and femoral stress fractures
Radiographic changes consistent with osteopetrosis
39
Q
Important concepts of a stress-strain curve
A
-
Elastic zone
- the zone where a material will return to its original shape for a given amount of stress
-
“toe region”
- applies to a ligaments stress/strain curve
- represents straightening of the crimped ligament fibrils
-
Yield point
- the transition point between elastic and plastic deformation
-
Yield strength
- the amount of stress necessary to produce a specific amount of permanent deformation
-
Plastic zone
- the zone where a material will not return to its orginal shape for a given amount of stress
-
Breaking point
- the object fails and breaks
-
Ultimate (Tensile) strength
- defined as the load to failure
-
Hooke’s law
- when a material is loaded in the elastic zone, the stress is proportional to the strain
-
Young’s modulus of elasticity
- measure of the stiffness (ability to resist deformation) of a material in the elastic zone
- calculated by measuring the slope of the stress/strain curve in the elastic zone
- a higher modulus of elasticity indicates a stiffer material
62
Q
What is are the orthopedic associations and presentation of hypophosphatasia
A
-
Associated conditions
-
orthopaedic manifestations
- similar to rickets
- bow legs
- short stature
-
non-orthopaedic manifestations
- abnormal tooth formation
- loss of teeth
-
orthopaedic manifestations
-
Clinical findings
- presentation similar to rickets
- genu varum
- short stature
- abnormal dentition
-
Radiographs
- abnormal bone formation
- “deossification of bone” adjacent to growth plate
- physeal widening
68
Q
What is the pathology and conditions associated with rickets
A
- A defect in mineralization of osteoid matrix caused by inadequate calcium and phosphate
- prior to closure of physis known as rickets
- after physeal closure called osteomalacia
-
Pathophysiology
- disruption of calcium/phosphate homeostasis
- poor calcification of cartilage matrix of growing long bones
-
occurs at zone of provisional calcification
- leads to increased physeal width and cortical thinning and bowing
- Vitamin D and PTH play an important role in calcium homeostasis
-
Associated conditions
- brittle bones with physeal cupping/widening
- bowing of long bones
- ligamentous laxity
- flattening of skull
- enlargement of costal cartilage (rachitic rosary)
- kyphosis (cat back)
69
Q
What is the differential for looser zones
A
- Insufficient nutritional quantities or faulty metabolism of vitamin D or phosphorus
- Renal tubular acidosis
- Malnutrition during pregnancy
- Malabsorption syndrome
- Hypophosphatemia
- Chronic renal failure
- Tumor-induced osteomalacia
