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Orthobullets > OITE - Recon > Flashcards

OITE - Recon Flashcards

1
Q

Effective joint space?

A

Any contigous area around the implant

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2
Q

Osteolytic process involves?

A
  • phagocytosis of submicron PE particles by macrophages

- Bone reorption by osteoclasts

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3
Q

PE manufacturing, 4 methods?

A

1- ram bar extrusion (machine)
2- sheet molding (machine)
3 - compression molding (isostatic) - machine
4 - direct compress molding (is best option)

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4
Q

Good or bad, gamma irradiation in air?

A

Bad

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5
Q

Direct compression molding from PE powder to desired product has what advantage?

A

Lowest susceptibility to fatigue crack formation and propagation in joint bearing

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6
Q

McPherson’s Rule for sagittal plane (gap) balancing?

A

Symmetric problem - tinker with tibia

Asymmetrical problem - tinker with femur

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7
Q

Closed suction drain in TKA typically results in what?

A

Drain = increased rate of transfusion

meta-analysis study proves this

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8
Q

Peri-prosthetic fx key concepts (two)

A

1) Implant loose = REVISE + ORIF
2) Implant stable =
- non displaced – cast/brace
- displaced – ORIF vs nail (supracondylar), ORIF tibia

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9
Q

Paterllar clunk syndrome due to?

A

Internal rotation (femur or tibia component)
Medialization (femur or tibial component)
-investigate with CT scan

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10
Q

Anterior dislocation

A

ER + extension

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11
Q

posterior hip dislocation?

A

Flexion + IR

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12
Q

Highest patient factor for THA dislocation?

A

Female gender

Other, abductors

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13
Q

Head neck ratio and head size relevance to THA design?

A

If head-neck ratio is smaller will impinge sooner (ie more unstable)
Bigger head size = increased jump distance before dislocation

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14
Q

Trendelenburg sign in THA stability?

A

Weak abductors

turnk lurches to weakened side to keep level pelvis

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15
Q

Use of a skirted femoral head can lead to what?

A

Increase risk of hip dislocation

(smaller head to neck ratio), ie earlier impingement

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16
Q

Lowest values suggestive of infection of a joint aspirate (chronic)?

A

Chronic: WBC > 1,100 cells/ml PMN > 64 %

Acute (early post op): 27,800 cells PMN > 89% at 6wks

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17
Q

Inconclusive aspirate and peripheral lab data for joint infection, do what?

A

Repeat aspiration

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18
Q

What does inconclusive mean?

A

high inflam marker
hx concerning for infection (drainage)
unusual clinical presentation (early loosening)
additional imaging concerning for infection

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19
Q

THA peri-prosthetic fx, implant loose or not?

A
  • question will lead you “no symptoms” = well fixed
  • if loose - revise - cementless fully porous coated
  • if stable - ORIF
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20
Q

Revision stem surgery (femur), cement or not cement?

A

Uncemented

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21
Q

Factors affecting fluid-film lubrication (metal on metal bearings)?

A

Radial clearance - defines contact area of bearing

  • Want polar contact with high conformity.
  • Dont want equatorial contact and seizing (complete congruence)
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22
Q

“Zone of death” in acetabular screw safe zone?

A

Anterior-superior zone (external iliac vessels)

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23
Q

Safe zone in acetab screw fixation?

A

Posterior superior zone

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24
Q

How can you look for polywear on xray of THA?

A

ECCENTRIC position of the femoral head

25
Osteolysis with well fixed implants, how to manage?
- No pain = well fixed implants - Look at implant position - -acceptable - exchange poly and bone graft - -poor position - revise the shell
26
Indications for conversion arthrodesis to THA?
- painful pseudoarthrosis - mechanical low back pain - ipsilateral knee pain (hip fused with increased adduction)
27
Outcome of arthrodesis conversion to THA?
walking function depends on abductor function | pre-op glut strength predicts post-op ambulatory status
28
Increased Q angle leads to what?
=bad | Increased lateral patellar subluxation
29
Hypoplastic lateral femoral condyle will lead to what in a posterior condylar axis reference system?
Using posterior condylar axis will IR femoral implant | -Use the trans-epicondylar axis instead!
30
Advantages of UKA vs TKA
- faster rehab, preserve normal kinematics (ACL and PCL retained) - better ROM short term, no difference at long term - shorter LOS and less narcotic use
31
UKA-specific complication?
Stress fx - best visualized on bone scan
32
Contra indications to UKA?
- ACL def -fixed varus or valgus deformity > 10 deg - restricted ROM (10 deg flexion contraction, or
33
What enhances bone-cement fixation?
- limit porosity of cement - cement mantle > 2mm - stiffer femoral stem - smooth femoral stem (no sharp corners)
34
Bone-cement interface stronger or weaker in osteopenic bone?
Bone-cement interface is mechanically stronger in osteopenic bones due to deeper cement penetration into pore
35
Hydroxyapatite (HA) coated stems has what benefit?
- shorter time to biologic fixation in animal models, but no advantage clinically in humans - osteoconductive
36
PE sterilization by radiation (during sterilization) can lead to what?
- free radical formation of PE - if O2 rich environment --- oxidized, delamination, wear, failure - if O2 depleted env (argon/vacuum/nitrogen) - radicals cross link and lead IMPROVED wear, BUT decreased mechanical properties
37
Most common complication with hip resurfacing?
Femoral neck fx (peri-prosthetic) , 1-3 %
38
Hip resurfacing advantages?
- Low dislocation rate (preserved h-n ratio, ie larger head) - preserve femoral bone stock - maintains anatomic femoral neck offset and anteversion
39
Hip resurfacing disadvantages?
Requires larger exposure than conventional THA | -risk of peri-prosthetic femoral neck fx
40
What medical tx is shown to decrease hip AVN progression to collapse?
Bisphosphonates - inhibits osteoclast formation, and slows down bone resorption - Ficat stages 0 - 2 (pre-collapse AVN)
41
When do you see Crescent sign in AVN? implicates?
Transition from Stage 2 to Stage 3 | Implicates impending collapse of head of femur
42
Risk factors for AVN?
-trauma, ETOH, steroids
43
What is femoral rollback?
Posterior transition of the femoral-tibial contact with progressive flexion
44
In non-constrained CR knee, what is relied on for rollback?
- Native PCL | - but rollback not anatomic
45
non-constrained PS (cruciate substituting) knee, what is relied on for rollback?
Tibial post engages on the femoral cam and forces mechanical roll back
46
Indication for a cruciate substituting TKA?
- previous patellectomy - inflammatory arthritis - deficient PCL
47
In a constrained non-hinged knee, what subs for MCL and LCL?
Large central post | -gives V/V stability and rotational stability
48
Indications for constrained non hinged?
Flexion gap laxity | MCL or LCL deficiency
49
THA, what most often leads to SCN palsy? What portion of SCN affected?
-Lengthening -80% involve peroneal portion risk factors: dysplasia, female gender, revision sgx
50
Optimal hip arthrodesis position?
25-30 deg flexion 0-5 deg adduction 0-5 deg ER
51
Hip arthrodesis expends how much more energy?
- 30% more nrg expenditure for ambulation | - accelerates degeneration of adjacent joints
52
Golfing following THA or TKA,
Rise in their handicap decrease in driving distance mild ache while playing 90% use a cart
53
Mechanical axis of a limb passes where relative to centre of the knee?
It passes slightly medial
54
Order of soft tissue release of valgus knee?
- osteophyte - lateral capsule - ITB if tight in extension -popliteus if tight in flexion - release LCL if tight in BOTH
55
Abx-impregnated bone cement, most effective in who?
- Revision TKA | - most pronounced in pts whose risk of post-TKA infection is greatest
56
What ROM component is most important predictor of post-op TKA motion?
- Pre-op flexion is most important | - CPM not sown to improve outcome or longterm ROM
57
Patella Baja?
=shortened patellar tendon length | -limits flexion
58
Risk factors for patella baja?
- Proximal tibial osteotomy (both lat closing and medial opneing)--> tendon scarring - tib tub shift or transfer - prox tibia previous trauma
59
Highly cross linked UHMWPE vs conventional poly?
- more irradiation = better wear, but decreased mechanical strength - increased resistance to abrasive wear

Orthobullets (6 decks)

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