Basic Science & Non-Tumor pathology Flashcards
Which bone graft substitue disappears the most quickly in vivo?
Calcium sulfate
What is the rate of decay in bone mass after skeletal maturity?
After menopause in women?
0.3-0.5% per year after skeletal maturity
a further 2-3% for untreated women during the decade after menopause
Standard vs. MIPO plating has what effect on blood flow?
Decreased periosteal AND medullary blood flow
What kind of collagen is fibrocartilage?
Type 1
same as bone
So scar = type 1 collagen
What cell type accounts for 90% of the adult skeleton?
osteoCYTE
rhBMP-2 is approved for what uses?
Single level ALIF from L2-S1 in DDD with a fusion device
open tibial shaft fratures stabilized with an IM N and treated with 14 days of initial injury
What is the bending rigidity of a plate proportional to?
Thickness ^3
What is false about osteocalcin?
- It is the most abundant noncollagenous protein of bone
- It is secreted by osteoclasts
- It is involved in mediating calcium homeostasis
- It has been used as a biochemical marker of bone formation
- It is part of the organic matrix of bone
2
It is secreted by osteoBLASTS
What is the increase in mortality risk after a fragility fracture of:
vertebra
hip
Vertebral fragility fracture: 15% increase
Hip fragility fracture: 20% increase
How much devascularization does reaming cause?
It devascularizes 50-80% of the cortex
Muscle duration and speed of contraction are most dependent on what?
Fiber type
Type II (fast twitch) contract faster, stronger and fatigue quicker
What happens with removal of the AER?
Limb truncation
AER controls longitudinal growth
Name the rare, but deadly, complication of Paget’s
What is the prognosis?
Paget’s Sarcoma
secondary transformation into osteosarcoma > chondrosarcoma > spindle cell sarcoma
<1%
5 year survival <5%
Distraction osteogenesis - bone forms by what type of ossifciation?
intramembranous (primary) ossifciation
Name 4 results of joint immobilization on articular cartilage
cartilage thinning
tissue softening
reduced proteoglycan content
cartilage erosion
What’s the role of collagen in artiular cartilage?
Prevent swelling of articular cartilage that would otherwise occur due to the effect of aggrecan in drawing in water
What is the mechanism of botox?
Inhibition of ACh release from presynaptic vesicles
How do local anesthetics works?
Interfere with conduction (depolarization)
Rate of decrease of vertebral fragility fractures after bisphosphonate treatment at 1 & 3 years?
1 year: 60% decrease
3 years: 40% decrease
Also decreased non-vertebral fraglity fractures 40%
Area of growth plate pathology in rickets
zone of provisional calcification
This is why there is a widening of physis on xray, bc the physis doesn’t ossify!
3 radiographic findings in osteopetrosis
Rugger jersey spine
Erlenmeyer flask distal femur
Thickened cortex/lack of a IM canal
Phases of ligament healing
inflammatory
- neutrophils & macrophage mediated with growth factors involved
Proliferative
remodeling
maturation
What happens to water content of cartilage with normal aging? in OA?
Decreases with normal aging
Increases with OA
What supplies the inner and outer parts of bone? (blood vessels)
Nutrient artery system supplies inner 2/3
is a high pressure system
Periosteal system supplies outer 1/3
is a low pressure system
50 year old DM patient comes in with sudden onset of unilateral leg weakness, absent reflexes on that side and weight loss of about 15 - 20 lbs. No history of radiculopathy or back issues. Diagnosis? 1 differential
Diabetic lumbosacral plexopathy (basically diabetic neuropathy)
Acute, stepwise onset of unilateral weakness
Associated with poor diabetic control, absent reflexes and weight loss (up to 40 lbs)
dDx: tumour
When does enchondral ossification occur in fracture healing (what stage)?
repair
Why don’t you want your anesthesiologist to use nitrous oxide as an inducin agent for spine or pelvic surgery?
Causes abdominal distension and makes fluoroscopy difficult to interpret
Descirbe direct insertion of ligament or tendon onto bone:
= fibrocartilagenous insertion
via 4 transition zones:
Zone 1: tendon or ligament
Zone 2: fibrocartilage
Zone 3: mieralized fibrocartilage
Zone 4: bone
Effect of tapping prior to screw insertion on pullout strength
decreases it
The femur radiograph of a healthy 25-year-old female is compared to the femur radiograph of a healthy 85-year-old female:
What best describes the 25-year-old’s femur in terms of cortical thickness and medullary canal volume?
Increased cortical thickness
Decreased medullary canal volume
As you age, you get thinner cortices and therefore larger canal volumes
Function of PTH
Increases blood Ca
Decreases phosphate
What is the effect of physiological stress on cartilage?
physiologic stress stimulates chondrocyte synthesis and protects against chondrolysis
vs
excessive stress promotes chondrolysis (in-vitro only)
Why do you place a concave bend when putting on a compression plate for a transverse fracture?
To achieve compression on both the near and and far cortices
After 5 year, what percentage of donor and recipieint chondrocytes will be present on an osteoarticular allograft?
None
5 years after implantation, allograft articular cartilage is completely acellular
No donor or recipient chondrocytes will be present
What is the primary pathologic process in Paget’s disease?
Increased osteoclastic mediated bone resorption
Where do SH I fracture occur through?
zone of provisional calficiation (part of hypertrophic)
Name the only irreversible COX inhibitor
ASA
What side of the fracture should compression plating be done?
Tension side
But may be sacrificed to have a plate lie flat on the bone
(JAAOS 2014)
Diagnosis and cause of x-ray findings (see pic)
Osteogenesis imperfecta
Multiple bands caused by bisphoshonate usage (specifically Pamidronate)
Function of Retinoic acid in embryology. What happens when it’s knockedout
Regulates zone of polarizing activity
if blocked, get limb bud abortion
WNT7 function
dorsoventral patterning of limb
A 27-year-old male undergoes intramedullary nailing of a midshaft tibia fracture with static locking proximally and distally. There is minimal healing noted 3 months postoperatively and the decision is made to dynamize the nail. For intramedullary nail dynamization, an interlocking screw should be placed in which of the holes shown in Figure A?
A
see pic
what is the effect of bisphosphonates take post lumbar fusion?
Decreases fusion rates
(it increases the fusion mass itself but decreases the actual rate of fusion)
When do you achieve peak bone mass?
Between at 16-25
Carrying a load in the ipsilateral hand does what to joint reactive forces at the hip?
decrease it
Increases A
Stages of tendon healing
Hemostasis
Inflammation
Organogenesis
Remodeling
Main risk of interscalene block?
sensory neuropathy
Investigations for Gaucher’s
CBC - thrombocytopenia, anemia
cardiac exam: murmurs
GI exam: hepatosplenomegaly
What is the torsional rigidity of solid and cannulated IM nail proportional to?
Solid: r^4
Cannulated: r^3
A bicortical locking screw has what biomechanical advantage over a non-locked bicortical screw?
Significantly more resistance to all applied forces
Just better
Describe the screw home mechanism
The tibia (not femur) ERs 5 degrees during the last 15 degrees of knee extension
This locks the knee, decreasing work performed by the quad during standing
(so the femur IRs)
A long oblique diaphyseal fracture is internally fixed with 2 lag screws. There is 2 mm of residual fracture fragment gap following screw fixation. This construct has which of the following compared to a comminuted diaphyseal fracture internally fixed with a long bridge plating technique?
Greater interfragmental strain
Greater ductility
Greater primary Haversian remodeling
Greater union rate
Greater callus volume formation
Greater interfragmental strain
What kind of bone healing involves cutting cones?
Primary bone healing (intramembranous)
What is the only zone where articular cartilage progenitor cells have been found?
Superficial (tangential) zone
8 ways to increase stability in a circular ex-fix (Ilizarov)
Wire factors:
- Larger diameter wires
- Olive wires
- Extra wires
- Wires crossing perpendicular to each other
- Increased wire tension
Ring factors:
- Decreased ring diameter
- Placement of two central rings close to the fracture
- Increased number of rings
Inheritance of osteopetrosis?
AR: infantile form
AD: Adult form
Where do muscle strains and tears normally occur?
Myotendinous junction
Patient with degenerative arthritis and this urine sample.
Diagnosis?
What is the pathophys?
Ochronosis (Alkaptonuria)
Degenerative arthritis + black urine
Due to defect in homogenistic acid oxidase enzyme
Leads to excess deposition of homogenistic acid in joints
No treatment available
How do bisphosphonates work?
inhibits osteoclasts by inhibiting ruffled border (where the bone resorption occurs)
Name the 5 things that make up articular cartilage
Extracellular matrix, made up of:
- water (highest percentage by weight)
- collagen
- proteoglycans
- noncartilagenous proteins
Cells, made up of:
- Mature & immature Chondrocytes
4 factors that can alter neuromonitoring signals:
Halogenated anesthetics
Nitrous oxide
Hypothermia
Hypotension
Define working length
distance between the two screws that are closest to the fracture
it is the distance between the SCREWS, not the screw to the fracture
Name 4 manifestations of osteopetrosis
anemia
hearing loss
cranial nerve palsies
fractures
Blindness, hearing loss, dental abscesses, OM in severe (AR) form
Osteopetrosis: what is the defect?
Inactive osteoclast carbonic anhydrase
What does the zone of polarizing activity do?
What 4 molecules control/are associated with it?
Controls AP development of the limb bud
THINK: ZPA controls PA (posterior to anterior) growth
Which phase of bone healing is abnormal in OI?
remodeling
So they heal normally, but don’t remodel so are more fragile
7 orthopaedic manifestations of osteogenesis imperfecta
Bone fragility and recurrent fractures
ligamentous laxity
short stature
scoliosis
codfish vertebrae
basilar invagination
olecranon apophyseal avulsion fracture
What happens to chondrocytes in articular cartilage with normal aging
Decreases in amount (hypoplastic)
increases in size (hypertrophic)
Why is the increased water content of cartilage in OA pathologic. Describe in 3 lines
Increased water content leads to:
increaed permeability of cartilage
decreased strength of cartilage
Decreased Young’s modulus of elasticity
What is Substance P? What does capsaicin do to it?
Substance P plays a role in pain neurotransmitting
Capsaicin decreses substance P
3 technical considerations when operating on a patient wtih osteopetrosis
Cannot use intramedullary guides
Will need several drills
Risk of fracture with implantation (brittle bone)
Where does Vit D get hydroxylated?
Where does it exert it’s effect?
Hydroxylated in Liver (25-OH) & Kidney (1,25-OH)
Increases calcium absorption from intestines and bone, along with PTH
No effect for calcium in kidneys
Factor deficiencies for hemophilia A & B
A: FVIII
B: FIX
Diagnosis?
Pseudogout
X-ray shows chondrocalcinosis (calcification in fibrocartilage strucutres (menisci))