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ABOS PART ONE > Recon > Flashcards

Recon Flashcards

1
Q

acetabular dysplasia quantitative definition

A

anterior or lateral CE angle less than 20, acetabular index greater than 5

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2
Q

measured on the false profile view

A

anterior CE angle

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3
Q

besides crossover sign, often see this in acetabular dysplasia on the AP

A

ischial spine sign

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4
Q

abnormal acetabular contact point in FAI

A

anterosuperior labrum, leads to contracoup at the posteroinferior acetabulum

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5
Q

lesion described by a high ALPHA angle

A

Cam lesion of FAI. Normal alpha is ~40*

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6
Q

distinguish the tissues affected by the two types of FAI

A

in cam impingement the neck travels under the labrum rather than hitting it, so affects the chondral surface of the pelvis more than in pincer, where the labrum itself gets trapped

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7
Q

this is most common reason for conversion of hip fusion to THA, and a technical reason it can occur

A

disabling back pain, which is more common when there is hip abduction component to the fusion

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8
Q

preop planning for takedown of a hip fusion and conversion to THA

A

need to know if the gluteus medius works: EMG. If it doesn’t there will be a severe lurching gait and you will need constrained liner

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9
Q

can be used for medical mgmt of precollapse AVN

A

bisphosphonates. Have to be started before stage 3 (crescent +)

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10
Q

these 3 pts don’t have as good of an outcome with core decompression for AVN

A

pts with crescent sign, pts on chronic steroids, or pts that have larger than 15% head involvement (go on to collapse)

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11
Q

deciding between core decompression or fibular strut graft

A

grafting done for the pts that wouldn’t do well with decompression: lesion more than 15%, those with a crescent sign (prefer not to have one though)

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12
Q

ingrowth surface

A

porous coating

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13
Q

ongrowth surface

A

grit blasted coating

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14
Q

why do cemented cups fail when cemented stems don’t

A

stems are loaded mainly in compression, whereas cups see shear and tension forces

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15
Q

optimal ingrowth of metallic components based on these 6 factors

A

viable bone, implant in contact with cortical bone, micromotion less than 30 microns, gap less than 50 microns, metal pore size between 50 and 150 microns, with 50% porosity

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16
Q

algorithm for for acetabular fx while implanting THA cup

A

Cup is stable? Then add screws. If cup is unstable, take it out, fix the fx, then put it back in and add screws

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17
Q

algorithm for for femoral fx while implanting stem

A

If the crack is small and stem is stable, just limit weightbearing, keeping the stem. If the stem is unstable, take it out, fix the fx, and replace with same stem or revision stem.

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18
Q

linear relationship between this and implant ongrowth fixation strength

A

surface roughness, Ra. Difference between peaks and valleys.

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19
Q

two complications of bone ongrowth implants

A

fracture and aseptic loosening (initial rigid fixation not strong enough to allow osteointegration)

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20
Q

osseous properties of hydroxyapatite

A

osteoconductive only; no biology

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21
Q

purpose of HA on implants

A

shortens time to biologic fixation

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22
Q

optimal thickness of HA coating on implants

A

Any thicker than 50 microns will crack and shear off

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23
Q

indications for cementless femoral stem

A

young male patient and higher-activity level pt. Both instances related to mechanical properties of the cement. Activity because of cyclic failure, young male bc of higher stress-loading

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24
Q

this is more to blame for stress shielding than the amount of porous coating

A

the modulus mismatch, i.e. stem stiffness

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25
Q

worst scenario for proximal femoral stress shielding in THA

A

round, solid, large diameter, extensively-coated, cobalt stem

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26
Q

segmental deficiency in the context of cup fixation

A

loss of the main bony supports: acetabular rims or columns, or the medial wall

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27
Q

why cementing a poly into a damaged cup is less than optimal

A

higher dislocation rate

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28
Q

“safe zone” of acetabular screw placement

A

posterior-superior quadrant

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29
Q

“zone of death” for acetabular screw placement

A

anterior-superior, external iliac arteries

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30
Q

major artery injury during THA

A

pack, flip if need be, anterior incision and control/repair

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31
Q

mgmt of femoral segmental defect in revision THA

A

cementless, extensively porous-coated revision stem that bypasses the most distal defect by 2 cortical diameters is preferred

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32
Q

why a longer femoral revision stem provides better initial rigid fixation

A

increased resistance to torsional loads

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33
Q

This is mainly to blame for PE-related osteolysis, and the process that causes it

A

submicron-sized particles are generated by adhesive wear, that get phagocytosed by macrophages and then become activated

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34
Q

The molecular basis for PE-related osteolysis

A

submicron particles eaten by macrophages. Macrophages activated, then release TNFa, IL1, TGFb, PDGF. PDGF is activator of RANKL. Leads to osteoclast activation. No other cell besides osteoclasts eat bone…

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35
Q

mechanism for PE distribution through the effective joint space

A

PE particle generation and the resultant biologic response creates hydrostatic pressure that pushes fluid into the effective joint space

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36
Q

the main determinant of the number of PE particles generated

A

volumetric wear, which is directly related to head size

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37
Q

volumetric wear determinant

A

directly related to the square of the radius of the head

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38
Q

These wear rates of X are associated with osteolysis

A

Linear wear rates more than 0.1mm per year

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39
Q

why 28mm heads are common size

A

Older 22mm heads had too much linear wear and failed through the cup. Larger heads, 32mm, have more volumetric wear and failed by osteolysis

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40
Q

non-technique ways to reduce osteolysis

A

alternative bearings, bisphosphonates, or OPG

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41
Q

this is associated with acetabular fx while performing THA

A

cementless cup, underreaming more than 2mm

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42
Q

fracture patterns of intraop femoral fxs during THA

A

wedge-taper designs break proximally, cylindrical fully-coated stems break distally

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43
Q

vancouver B class

A

B1 - well-fixed, good bone. B2 - loose, good bone. B3 - loose, shitty bone.

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44
Q

the periprosthetic fx where extensively-coated long-stem prosthesis is the ONLY answer

A

Vancouver B in CEMENTED stem that compromises the cement mantle

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45
Q

contraindication for THR

A

coxa vara

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46
Q

% of pts with nerve injury after THA that will recover strength

A

35-40%

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47
Q

where the sciatic nerve is closest to the acetabulum (THA)

A

at the level of the ischium

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48
Q

4 risk factors for sciatic nerve injury in THA

A

female, post-traumatic, revision, DDH

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49
Q

risk for nerve injury increases with lengthening of nerve over X

A

3.5 cm

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50
Q

positional foot-drop after THA

A

flat in bed, knee on a pillow

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51
Q

Two explanations for sciatic palsy after THA that was not complicated by intraop nerve injury

A

Hematoma (evacuate it) and spinal stenosis (image it, MRI Lspine)

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52
Q

Retractor placement under the TAL during THA

A

obturator artery at risk down there

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53
Q

THA in sickle cell

A

early loosening

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54
Q

THA in psoriatics

A

infection

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55
Q

THA in ankylosing spondylitis

A

HO formation. Increased risk for anterior dislocation.

56
Q

THA in Parkinsons

A

higher dislocation, mortality, medical complications, and reoperation rates

57
Q

intraoperative hypotension

A

fat emboli syndrome, pressure from femoral stem insertion

58
Q

Which 7 pts dislocate the most after THA?

A

female, post-AVN, posterior approach, small head-size, alcoholics, neuromuscular dz, revisions

59
Q

lever range in THA

A

after the neck hits the cup, the arc allowed before the hip dislocates

60
Q

excursion distance in THA

A

distance the head must travel to dislocate. Equal to radius of the head.

61
Q

primary arc range in THA, and its determinant

A

Controlled by the head/neck ratio, the arc a femur travels before impinging on the cup. Anything that decreases the head/neck ratio decreases the primary arc range.

62
Q

4 problems with decreased THA offset

A

weakened abductor moment, increased JRF, increased risk of dislocation, trendelenberg gait

63
Q

4 assessments of the unstable THA

A

design, position, soft tissue tension, soft tissue function

64
Q

4 indications for constraint in THA

A

Components well aligned #1, then: elderly, abductor-deficient, CNS decline, or revision with a cage (approach causes soft tissue damage)

65
Q

when a THA would get converted to a hemi

A

recurrent dislocator that has no segmental bone loss and good bone density

66
Q

this type of PE manufacturing has the best wear properties

A

direct compression molding, because there is no machining involved

67
Q

what is cross-linked poly and how is it better than non-cross-linked

A

when irradiated in a vacuum, the free radicals produced will bond with an adjacent PE chain. Improves resistance to adhesive and abrasive wear

68
Q

what causes oxidized PE, and the term for its molecular basis

A

after formation of free-radicals by irradiation, presence of oxygen will allow bonding between O2 and the free radicals. Called “chain scission”.

69
Q

why is oxygen bad for PE manufacture

A

O2 bonds with free radicals, causing oxidation. Oxidation makes poly more vulnerable to pitting, delamination and fracture. (more brittle, less strong, less ductile)

70
Q

how is standard PE better than cross-linked poly

A

although the cross-linking improves the wear properties, it makes nearly all the mechanical ones worse.

71
Q

why does the dose matter in sterilizing PE by radiation

A

the higher the dose of radiation, the more free radicals are formed. The more free radicals, the higher the chance that some bond with oxygen and cause oxidation

72
Q

irradiation in PE production essentially targets this structure

A

the amorphous phase is the only part of a poly that cross-links, however it forms free-radicals throughout the poly

73
Q

the mechanical properties of PE are related to this structure

A

the crystalline phase provides the mechanical strength of a poly. Free radicals are not able to cross-link here.

74
Q

why does melting a poly reduce the mechanical properties and annealing does not

A

melting further increases the cross-linking, but that prevents recrystallization. Since the mechanical properties are related to the crystalline phase, they decrease.

75
Q

this process creates free radicals and causes cross-linking

A

irradiation in vacuum

76
Q

this process eliminates all free radicals

A

melting

77
Q

this process eliminates some free radicals

A

annealing, which does not remove them from the crystalline phase of a poly. Oxidation risk, but with less reduction in mechanical properties than melting.

78
Q

rationale for vit E treatments with poly production

A

free radical scavenger

79
Q

this has the largest effect on “on-the-shelf” poly wear

A

type of packaging

80
Q

MoM wear

A

nanometer-sized particles, low volumetric and linear wear, but the number of particles is actually higher than PE wear

81
Q

responsible for the biologic response to metal debris

A

T cell mediated. Contrast with PE wear which is due to macrophages

82
Q

why women are more likely to get MoM PITR

A

Co-Cr ions bind with a serum protein seen as antigen by the T-cells, the inflammatory cascade of which includes RANK/RANKL system. This process is already influenced by sex hormones

83
Q

2 contraindications for MoM bearings

A

women of child-bearing age (DOES cross placenta) and pts with renal failure

84
Q

bearing used in revision of ceramic THA failure

A

have to use ceramic again; microscopic particles of ceramic that remain would destroy a poly bearing too quickly

85
Q

osteotomy for knee arthritis indications

A

young active pt under ~45

86
Q

osteotomy for mgmt of varus knee arthritis

A

valgus-producing tibial

87
Q

osteotomy for mgmt of valgus knee arthritis

A

varus-producing femoral

88
Q

3 contraindications for osteotomy as mgmt of varus knee arthritis

A

inflammatory, less than 90* of flexion or flexion contracture more than 10*, varus thrust gait. NOT contraindicated in cruciate-deficient knees

89
Q

4 contraindications for osteotomy as mgmt of valgus knee arthritis

A

inflammatory, flexion contracture more than 10, prior medial menisectomy, or more than 15 valgus

90
Q

4 contraindications for UKA

A

inflammatory, ACL deficient, FIXED deformity, flexion contracture more than 10*

91
Q

these TKA candidates get full-length standing AP legs

A

very tall, very short, or angular bony deformity

92
Q

the distal femoral cut is perpendicular to this

A

the mechanical axis of the femur, not the anatomic axis

93
Q

the valgus cut angle

A

usually between 4-7, it is the difference between the MAF and the AAF. Affected by the length of the femur, as hip offset is pretty standard

94
Q

sequence of release for varus malalignment of TKA

A

osteophytes, deep MCL, posteromedial corner, superficial MCL

95
Q

medial structure tight in flexion during balancing of TKA

A

anterior portion of the superficial MCL

96
Q

medial structure tight in extension during balancing of TKA

A

posterior oblique portion of the superficial MCL

97
Q

lateral structure tight in flexion during balancing of TKA

A

popliteus

98
Q

lateral structure tight in extension during balancing of TKA

A

IT band

99
Q

sequence of release for valgus malalignment of TKA

A

osteophytes, capsule, popliteus, IT band, LCL

100
Q

instance where LCL is released first in valgus malaligned TKA

A

something to do with if only tight in flexion or extension? might be esoteric…

101
Q

sequence of release for flexion contracture of TKA

A

osteophytes, posterior capsule, gastroc origin. All performed with knee flexed to protect vessel

102
Q

fracture patterns with anterior nothing of a TKA

A

in torsional loads there is no difference, but in bending loads the fx starts at the notch. DON’T MUA a notched femur…

103
Q

mgmt of most common nerve palsy after TKA

A

peroneal nerve palsy. Most resolve on own in 3 mos. If doesn’t and nerve is intact by EMG, explore and decompress.

104
Q

artery at risk with lateral retinacular release for patellar maltracking

A

lateral superior geniculate artery

105
Q

intraoperative MCL injury

A

Convert to revision prosthesis, then primary repair is acceptable. postop brace x6wks.

106
Q

the only thing i can’t fix if you fuck it up during a TKA

A

extensor tendon disruption can’t be repaired intraop, nor does nonop mgmt work. Fresh frozen allograft is close to the best shot.

107
Q

this can be done in extra-articular femoral deformities (TKA)

A

can add distal femoral angular osteotomy at the time of TKA if cuts would be extreme

108
Q

this influences femoral rollback in TKA

A

PCL tension

109
Q

3 causes of loose flexion gap

A

over-release of popliteus, anterior portion of the superficial MCL, or anterior translation of the femoral component

110
Q

maximal joint line elevation in TKA

A

8mm, or risk patella baja

111
Q

specific indications for PS TKA

A

inflammatory (erosive chg if you leave PCL), post-traumatic PCL rupture or attenuation, after patellectomy (anterior subluxation with a flat CR poly)

112
Q

3 advantages and 1 disadvantage of anterior stabilization in CR TKA

A

Has to be more highly congruent, which decreases the contact stresses. This results in less poly wear, lower fracture rate, and less delamination. BUT there is increased shear stress but it takes away the femoral rollback.

113
Q

this is a debated relative indication for use of constrained TKA in primary setting

A

charcot arthropathy

114
Q

polio in TKA

A

hyperextension instability, absolute indication for a hinge

115
Q

diagnosis of metal hypersensitivity

A

made with serum lymphocyte T-cell proliferation test NOT skin patch testing

116
Q

after 2 yrs from TKA most common cause for TKA failure

A

poly wear

117
Q

most common complications in TKA

A

patellar maltracking

118
Q

causes of patellar maltracking in TKA

A

internal rotation or medialization of either side, lateralization of the patellar component

119
Q

proximal tibial closed wedge osteotomy

A

patella baja: loss of knee flexion

120
Q

contraindications to shoulder arthroplasty

A

deltoid AND cuff deficiency (?), and charcot arthropathy

121
Q

requirements for TSA

A

Intact cuff, although isolated infraspinatus tear without retraction at surgery isn’t reason to convert to something else

122
Q

incidence of full thickness RTC tears at time of TSA

A

5-10%

123
Q

better pain relief long term, hemi or TSA?

A

TSA. Conversion from hemi to TSA not as successful (issues with glenoid bone loss)

124
Q

humeral stem position in TSA

A

35* of RETROversion

125
Q

glenoid position in TSA

A

neutral. Avoid retroversion

126
Q

why are passive ER exercises avoided after TSA

A

risk of subscap tear

127
Q

result of subscap tear after TSA

A

anterior instability

128
Q

critical to success of hemi if done for RTCA

A

preservation of the CA ligament; if disrupted can lead to anterior-superior escape

129
Q

deltoid power and effiency are improved by this in RTSA

A

medialization of the center of rotation, which increases the humeral head offset

130
Q

biofilm is 85% this

A

polysaccharide matrix

131
Q

within 2-4 weeks after a TJA this fluid WBC is suggestive of infxn

A

~11,000

132
Q

in the chronic setting after a TJA this bug is most common pathogen

A

staph epi

133
Q

in the acute setting after a TJA this bug is most common pathogen

A

staph aureus

134
Q

Routine use of this in TKA may be associated with aseptic loosening

A

antibiotic-impregnated cement

135
Q

blood supply to the medial gastroc flap

A

medial sural artery. Has good excursion.

136
Q

blood supply to the lateral gastroc flap

A

lateral sural artery. Not as much excursion, so not used for anterior deficiencies. Can have peroneal palsy from tension.

ABOS PART ONE (11 decks)

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