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Phase II Ortho Chapters > General Ortho > Flashcards

General Ortho Flashcards

1
Q

What are the 2 glycosaminoglycans?

A

heparin & keratan sulfate

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2
Q

What are the 2 galactosaminoglycans?

A

chondroitin & dermatan sulfate

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3
Q

Where are the following located?
- Osteoblasts
- Osteoclasts
- Osteocytes

A
  • Osteoblasts: periosteal/endosteal membrane
  • Osteoclasts: cortical bone
  • Osteocytes: within bone matrix
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4
Q

What is Howship’s lacunae?

A

resorption pit made by osteoclasts

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5
Q

Hyaline cartilage is made up of what % of the following?
- water
- collagen
- proteoglycan
- glycoprotein
- chondrocytes

A
  • water = 70%
  • collagen = 50%
  • proteoglycan = 35%
  • glycoprotein = 10%
  • chondrocytes = 2-10%
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6
Q

What types of collagen are in articular cartilage?

A

Type II = 85, 90%
Type XI & Type IX

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7
Q

What type of collagen is in fibrocartilage?

A

Type I

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8
Q

What are Sharpey’s fibers?

A

dense band of collagen that merges w/ periosteum – where tendons/ligaments insert on bone
(make up the fibrocartilagenous enthesis)

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9
Q

What is a tidemark?

A

separates non-mineralized and mineralized regions

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10
Q

Write the steps of muscle contraction

A

AP release ACh –> sarcolemma –> depolarization (Ca2+ release) –> Ca binds to troponin becomes tropomyosin –> exposes myosin on actin –> myosin engages actin –> uses ATP to slide

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11
Q

Type I/II muscle fibers - white or red? Slow or fast?

A

Type I = SLOW twitch, lots of O2, RED
Type II = FAST twitch, rich myofibers, WHITE

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12
Q

What are the moments of inertia of pin vs. plate?

A

pin = pi(r)^4 / 4
plate = b(h)^3 / 12

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13
Q

What is the stress formula?

A

σ = Force / Area

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14
Q

What is the formula for strain?

A

Epsilon = Δ L / L 0
- epsilon = strain
- delta L = change in length
- L0 = original length

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15
Q

What is Young’s modulus?

A

on stress/strain curve, it’s initial linear component slope (stiffness!)

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16
Q

What are 2 layers of periosteum?

A
  1. Outer - fibroblastoid
  2. Inner - cambial layer - osteogenic precursors for bone growth
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17
Q

What is the function of the endocortical envelope?

A

layer of osteoprogenitor cells that regular Ca2+ exchange

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18
Q

Function of cancellous envelope?

A

ion and nutrient exchange

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19
Q

Function of intracortical envelope?

A

osteoprogenitor cells that regulate nutrient exchange between vascular system and extracellular space within cortical bone

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20
Q

List 5 zones of epiphyseal plate and main cell type

A
  1. Resting - small oval chondrocytes
  2. Proliferative - stacked coin chondrocytes
  3. Hypertrophic - new chondrocytes (bigger) *weakest point, very little matrix
  4. Calcification - chondroclasts remove dead chondrocytes
  5. Ossification - osteoblasts make woven bone then osteoclasts change woven to lamellar
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21
Q

What fracture line is created with the following forces?
- compressive
- bending
- torsion
- shear

A
  • compressive = oblique
  • bending = transverse/short oblique
  • torsion = spiral
  • shear = buttress
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22
Q

What strain can this tissue survive?
- Granulation tissue
- Fibrocartilage
- Bone

A
  • GT = up to 100%
  • fibrocartilage = 10-15% deformation
  • bone = 2%
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23
Q

Do smaller or larger fracture gaps have greater strain potential (with similar loads)?

A

smaller

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24
Q

With contact healing, what is rate of lamellar bone across fracture?

A

50-100 micrometer / day

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25
Q

For gap healing, how many weeks to have new cutting cones develop new osteons?

A

3-4 weeks

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26
Q

List 5 stages of bone healing

A
  1. Inflammation
  2. Intramembranous ossification
  3. Soft callus formation (chondrogenesis)
  4. Hard callus formation (endochondral ossification)
  5. Bone remodeling
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27
Q

During bone healing, is electropositivity on convex or concave surface? Primary cell activity?

Electronegativity?

A
  1. Electropositive = CONCAVE = osteoclastic
  2. Electronegative = CONVEX = osteoblastic
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28
Q

For elastic plate osteosynthesis, how can you generate a more compliant structure?

A
  • implant system with lower moment of inertia (e.g. smaller plate)
  • implant system with lower modulus of elasticity
  • increasing overall length & functional working length of bone plate
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29
Q

List ways that elastic plate osteosynthesis fails

A
  • plate bending from being overly compliant
  • fatigue fx of plate (with short working length)
  • fatigue failure +/- screw pull-out (too short plate with short working length)
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30
Q

Described classifications of open fractures according to the Gustilo-Anderson scheme

A
  1. Type I = wound <1cm, mild ST contusions (inside out)
  2. Type II = wound >1cm without extensive ST damage (outside in)
  3. Type IIIa = adequate ST coverage, extensive damage, high energy trauma
  4. Type IIIb = extensive tissue loss, periosteal stripping, bone exposure, massive contamination
  5. Type IIIc = open fx with associated arterial injury that needs repair (+ all above in Type III)
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31
Q

What is the interobserver agreement for Gustilo-Anderson open fx classification scheme?

A

60%

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32
Q

What are the 5 factors of orthopedic trauma association classification scheme?

A
  • S 1-3 = skin defect
  • M 1-3 = muscle injury
  • A 1-3 = arterial injury
  • B 1-3 = bone loss
  • C 1-3 = contamination
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33
Q

What are delayed union/nonunion rates for Type I-III open fractures?

A

Type I = 0-5%
Type II = 1-14%
Type III = 2-37%

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34
Q

What are the diameter and relative tensile strength of orthopedic wire?

A
  • 16g = 1.2mm; 1.4x
  • 18g = 1mm; 1x
  • 20g = 0.8mm; 0.64x
  • 22g = 0.6mm; 0.36x
  • 24g = 0.5mm; 0.25x
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35
Q

For twist knot, how many twists to maintain tension?

A

1

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36
Q

For a single loop cerclage, how many twists need to be in the loop?

A

1.5

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37
Q

For twist vs. single loop (SL) vs. double loop (DL), list the loop tension and load resisted before loosening

A

Twist
- Loop tension = 70.3N
- Load resisted = 268 N

SL
- Tension = 165 N
- Load resisted = 259 N

DL
- Tension = 391 N
- Load resisted = 661 N

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38
Q

What are the principles of cerclage?

A
  • choose size for patient
  • length of fx should be 2.5x diameter of bone
  • should go around entire circumference
  • full contact of bone & wire
  • 1.5-3 twists for security
  • at least 2 wires used
  • not used alone for fixation
  • only oblique fractures
  • space 1/2 bone diameter apart
  • place 1/2 bone diameter from fx line
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39
Q

What makes stronger ILN construct?

A
  • fill 80% medullary cavity
  • nail with smaller bolts
  • bolts that lock to nail
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40
Q

What are the benefits of an angle-stable nail?

A
  • morse taper screw-cone pegs & shape of holes eliminates slack
  • stability with forces from several angles
  • hour glass shape (improved area moment of inertia & place lock device with larger diameter)
  • smaller deformation
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41
Q

Guidelines for sizes of ILNs?

A
  • 3-4mm = cats/dogs 5-15kg
  • 6mm = 15-30kg
  • 7mm = up to 40kg
  • 8-10mm = > 40kg
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42
Q

What diameter of nail for what size of bone?

A

basically 70-90% of isthmus

43
Q

When placing ILN, which bolt is placed 1st?

A
  • Tobias says proximal to give stability to alignment guide
  • AO handbook says distal 1st so whole construct is stable & easier to place proximal ones after final adjustments
44
Q

For ILNs, where do you insert for femur, tibia, humerus?

A
  • Femur = intertrochanteric fossa
  • Tibia = just cranial to intermeniscal ligament
  • Humerus = slight lateral to junction of crest of greater tubercle & greater tubercle
45
Q

For humerus use of ILN, which parts fractured can be used with regular vs. angle-stable ILN?

A
  • regular = proximal and central only
  • angle-stable = proximal and distal
46
Q

What direction should you place locking device for ILN? Why?

A

place at 45 degree angle from frontal place in craniocaudal direction

this decreased the risk of hitting brachial and radial nerves

47
Q

List complications of using ILN

A

1 = bend, break bit, nail, screw

  • radial n paralysis
  • “windshield wiper effect” around distal tip
  • seromas
  • fracture of bone through drill hole
  • sciatic n damage
  • pain from long screws / bone sequestra
  • Lick granulomas
  • fx bone near IN
  • quadriceps femoris contracture
  • coxofemoral luxation
  • skin irritation/lesions
  • rotational instability
  • pseudoarthrodesis
  • distal stifle pain
  • embolism
  • osteomyelitis
  • granuloma formation
  • superficial wound infection
48
Q

On the stress/strain curve, which has a higher strain rate - gunshot wound or walking? Which releases greater energy at the fracture?

A

Gunshot has higher strain rate

WALKING = fracture releases greater energy

49
Q

Describe 5 types of locking screws

A
  1. Threaded head (LCP)
  2. Cut own threads (Pax securos)
  3. Bushing & conical taper screw head (Fixin)
  4. Pearl = SOP with thread at base
  5. Taper/press fit
50
Q

With regards to screws, what determines pull-out strength? What determines bending strength?

A

Pull-out = outer diameter and strength of material

Bending = core diameter

51
Q

For DCP…
- you can angle the screw to what degrees transverse-wise?
- Angle for longitudinal?

A

Transverse = 7 degrees

Longitudinal = 25 degrees

52
Q

For LC-DCP…
- you can angle the screw to what degrees transverse-wise?
- Angle for longitudinal?

A

Transverse = 7 degrees

Longitudinal = 40 degrees

53
Q

List some general guidelines for locking plates and screws

A
  • Span long segments of bone (3x fracture length)
  • Limit screw-to-hole ration <0.5
  • limit distance between plate and bone <2mm
  • Leave 2-3 holes empty over fracture defect (1-2 if small gap)
  • Screw at end of plate and near fracture
54
Q

For comminuted fracture - plate length should be ____x the fx length? Simple?

A

Comminuted = 2-3x
Simple = 8-10x

55
Q

Why is core diameter larger for locking screws?

A

Addresses increased stress at screw/plate interface

56
Q

How much greater insertional torque is there with the Unique Star Drive head?

A

65%

57
Q

For plate-rod constructs, every ___% increase in canal filling decreased plate strain by ___%?

A

10% canal decreases strain by 20%

58
Q

Total stiffness increases by ___, ___, ___ % with rods filling the medullary canal 30, 40, 50%

A

6%
40%
78%

59
Q

For DCP, the gold drill guide is held ___ mm off center for compression. How many mm for green guide?

A

Gold = 1mm
Green = 0.1mm

60
Q

For DCP, the 4.5/3.5 plate allows ____ mm displacement per hole.
2.7 plate?
2.4 plate?

A

4.5/3.5 = 1mm/hole

2.7 = 0.8mm/hole

2.4 = 0.6mm/hole

61
Q

Smooth pins for ESF inserted up to ___ degrees off from each other to decrease pull-out

A

70 degrees

62
Q

Duraface pins: compared to positive profile pins
1. ___% increase in fixation pin stiffness, ____% increase in strength, and ___ fold increase in cyclic failure

A

55% increase in fixation pin stiffness

54% increase in strength

2.3-4.9 fold increase in cyclic failure

63
Q

What situations would be useful for use of Duraface?

A
  • smaller segments
  • non-load sharing conditions
  • biologically compromised bone
  • treatment of fracture with large ST envelope (so need longer working length)
64
Q

List 3 types of ESF clamps
- what are the sizes?
- what bar do they go with?

A

Titan, Imex (SK), U-clamp

  1. Large Titan = 9.5mm (3/8” Al or C-fiber)
  2. Small Titan = 6.3mm (1/4” C-fiber)
  3. Large U-clamp = 3/16” stainless steel
  4. Small U-clamp = 1/8” stainless steel
  5. Large SK Imex = 9.5mm, C-fiber
  6. Small SK Imex = 6.3mm, C-fiber, titanium
  7. Mini SK Imex = 3.2mm (1/8”) stainless steel
65
Q

List materials available to be connecting bars.

A

Titanium, aluminum, C-fiber, acrylic, stainless steel

66
Q

Which connecting bars are radiolucent?

A

Titanium, aluminum, C-fiber

67
Q

List type, # pins, connecting bar #, and pin geometry for all linear ESF

A

Ia = half pins, 1 bar, unilateral, uniplanar

Ib = half pins, 2 bars, unilateral, biplanar

I-II = half and 1 full pin, 2 bars, bilateral, uniplanar

II mod = half and 2 full pins, 2 bars, bilateral, uniplanar

II = full pins, 2 bars, bilateral, uniplanar

III mod = half and full pins, 3 bars, bilateral, biplanar

68
Q

For ESF, what is an articulation vs diagonal?

A

articulation = interconnecting bars don’t cross fracture gap

diagonal = do cross fracture gap

69
Q

For a Ib ESF frame, pins can enter the bone up to what angle from each other?

A

35 degrees

70
Q

An IN + ESF frame decreases torsional compliance by ___% and bending compliance by ___%?

A

Torsional = 25%

Bending = 60%

71
Q

For acrylic ESF, a column of ___mm provides stiffness of 3.2ss and 4.8ss?

A

9.53mm = 3.2

15.9mm = 4.8

72
Q

What are the suggested diameters of acrylic columns for ESF?

A

2-2.5 x diameter of bone and 3-4x diameter of comparable stainless steel bar

73
Q

How do epoxy and PMMA compare biomechanically to acrylic ESF?

A

Epoxy - elastic modulus 4x of PMMA

PMMA absorbs 4-6x the energy of epoxy before failure

Epoxy bond with smooth pin = 4x stronger than PMMA and smooth pin

74
Q

What is knurling?

A

when you make notches to increase surface area

75
Q

What are the two names of MMA acrylic? What are set times?

A
  1. Acrylx (Imex)
  2. APEF

12-15min set times

76
Q

What are the 2 different epoxy resins? Cure time?

A
  1. Fastfix (securos)
  2. Epoxy putty

*Both need catlyst
10-12min cure time

77
Q

What is the purpose of an Oliver wire?

A

prevents translation along wires and maintains oblique fracture in compression

78
Q

what is the purpose of Drop wire?

A

fixed to ring a distance away from ring using posts to provide 3rd point of fixation along bone

79
Q

What is a stretch ring?

A

partial ring with elongated straight segment (horseshoe)

80
Q

At extreme angles, threaded rods attach via spherical washers and can be angled up to ___ degrees?

A

10 degrees

81
Q

What are advantages of ESF over linear ESF?

A
  • tensioned wires = non-linear stiffness response to axial loading
  • Low stiffness initially, then increase as load increases
  • Allows axial micro motion limited to range gap strain (<2%)
  • tensioning - low stiffness micro motion is more like a stiff pin
  • cycled between compression/distraction at fracture site to stimulate bone callus maturation
82
Q

For distraction osteogenesis, how many mm/day do you draw apart the ESF to regenerate bone?
How many days do you wait following osteotomy to start?

A

1mm/day
3-5 day period of latency

83
Q

For hybrid fixators, the hybrid adaptor gives ___ degree adjustments for bars?

A

65 degrees

84
Q

For hybrid fixators, the VariBall locking hybrid rod permits ___ degrees of angular freedom?

A

100 degrees

85
Q

Describe hinged vs. flexible ESF (transarticular)

A

Hinged
- hybrid connecting bars threaded into female hinges of circular ESF, acrylic connecting bars secured to circular ESF, or joint ROM hinge
- motion limited to single plane

Flexible
- most often for elbow
- 2 central threaded pins parallel to articular surface either side of joint
- pins secured with rigid connecting bars at standing angle of 140 degrees
- once ST swelling decreases, replace C3 with elastics for ROM

86
Q

How long should rigid transarticular ESF be limited to? Why?

A

<4 weeks
to limit arthrosis

87
Q

What are guidelines for ESF associated with
- pin position
- pin #, configuration, size
- insertion

A
  • center of bone
  • cis & trans cortex
  • 3-4 per bone segment
  • 2 for pins & next to joints 1st
  • 3/4 bone diameter from joint
  • 1/2 bone diameter from fracture line
  • aligned parallel along plane of connecting bar (if threaded)
  • Smooth/neg profile ~70 degrees from long axis of bone
  • clamps 2cm from surface of skin
  • pins on either side of connecting bar up to 35 degrees but perpendicular to surface
  • pin diameter < or = to 25% bone diameter
  • use drill sleeve
  • use pretrial (0.1mm smaller than core)
  • use low insertion speed (<300)
  • use appropriate size connecting bar
  • use bone graft
88
Q

For ESF, pre drilling increases pin tightness ___%, increases pull-out strength ___ % and increased thread contact area ___%

A

Tightness = 25%

pull-out strength = 13.5%

contact = 18%

89
Q

What are 6 frame modification techniques for frame destabilization?

A
  1. remove augmentation
  2. remove connecting components
  3. replace component material
  4. downsize components
  5. remove fixation pins
  6. dynamization clamps
90
Q

With ESF, what are safe corridors for the humerus, femur, antebrachium, and metacarpal/tarsals?

A
  • Humerus = lateral / craniolateral
  • Femur = lateral / craniolateral
  • Antebrachium = medial / craniomedial
  • Crus = craniomedial
  • metacarpal/tarsal = medial/lateral
    2nd-3rd = caudomedial to craniolateral
    4th-5th = caudolateral to craniomedial
91
Q

List complications of ESF

A
  • skin trauma/irritation
  • impaled muscles/neurovascular structures
  • hemorrhage
  • peripheral nerve damage
  • pin tract infection
  • pin/wire loosening or breakage
92
Q

List 3 other methods of treatment for nonunion / delayed union fractures?

A
  1. Extracorporeal shockwave therapy
  2. Pulsed electromagnetic field
  3. Low-intensity pulsed ultrasonography
93
Q

What are the 2 types of osteomyelitis?

A
  1. Post-traumatic (most common)
  2. Hematogenous (young, blood stream)
94
Q

What are the 3 mechanisms of resistance to antibiotics by biofilm?

A
  1. Genotypic & phenotypic alterations
  2. Extracellular matrix is a barrier preventing Abx penetration
  3. Extracellular environment affects antimicrobial activity (e.g. pH, paO2)
95
Q

What is quorum sensing?

A

ability of bacteria to coordinate gene expression based on population density and role of secreted signal molecules

96
Q

What is the sensitivity of radiographs to detect osteomyelitis? Specificity?

A

Sensitivity = 62.5%

Specificity = 57%

97
Q

For hematogenous osteomyelitis treatment, IV Abx should be given for a minimum of ___ days, then oral for ___ days

A

IV = 3-5 days
Oral = 21 days

98
Q

What are the 5 major growth factors that are contributed via bone graft?

A
  1. Transforming growth factor B
  2. Bone morphogenic protein (BMP 2, 4, 7)
  3. Fibroblast growth factor
  4. Insulin-like growth factor
  5. Platelet derived growth factor
99
Q

What are examples of osteopromotion?

A

PRP, hydrogels, biphasic CaPO4

100
Q

List most common sites for acquiring cancellous bone graft

A
  • Proximal humerus
  • Wing of ilium
  • Proximal tibia
101
Q

How long should you wait until you can collect graft from the same humerus or tibia?

A

Humerus = 8 weeks
Tibia = 12 weeks

102
Q

With autogenous bone graft healing, what is creeping substitution?

A

cyclical pattern of vascular invasion, subsequent bone formation, resorption

103
Q

What do allografts lack?

A

osteogenic cells

Phase II Ortho Chapters (3 decks)

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