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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
Q

Osteolysis with well fixed implants, how to manage?

A
  • No pain = well fixed implants
  • Look at implant position
  • -acceptable - exchange poly and bone graft
  • -poor position - revise the shell
26
Q

Indications for conversion arthrodesis to THA?

A
  • painful pseudoarthrosis
  • mechanical low back pain
  • ipsilateral knee pain (hip fused with increased adduction)
27
Q

Outcome of arthrodesis conversion to THA?

A

walking function depends on abductor function

pre-op glut strength predicts post-op ambulatory status

28
Q

Increased Q angle leads to what?

A

=bad

Increased lateral patellar subluxation

29
Q

Hypoplastic lateral femoral condyle will lead to what in a posterior condylar axis reference system?

A

Using posterior condylar axis will IR femoral implant

-Use the trans-epicondylar axis instead!

30
Q

Advantages of UKA vs TKA

A
  • 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
Q

UKA-specific complication?

A

Stress fx - best visualized on bone scan

32
Q

Contra indications to UKA?

A
  • ACL def -fixed varus or valgus deformity > 10 deg
  • restricted ROM (10 deg flexion contraction, or
33
Q

What enhances bone-cement fixation?

A
  • limit porosity of cement
  • cement mantle > 2mm
  • stiffer femoral stem
  • smooth femoral stem (no sharp corners)
34
Q

Bone-cement interface stronger or weaker in osteopenic bone?

A

Bone-cement interface is mechanically stronger in osteopenic bones due to deeper cement penetration into pore

35
Q

Hydroxyapatite (HA) coated stems has what benefit?

A
  • shorter time to biologic fixation in animal models, but no advantage clinically in humans
  • osteoconductive
36
Q

PE sterilization by radiation (during sterilization) can lead to what?

A
  • 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
Q

Most common complication with hip resurfacing?

A

Femoral neck fx (peri-prosthetic) , 1-3 %

38
Q

Hip resurfacing advantages?

A
  • Low dislocation rate (preserved h-n ratio, ie larger head)
  • preserve femoral bone stock
  • maintains anatomic femoral neck offset and anteversion
39
Q

Hip resurfacing disadvantages?

A

Requires larger exposure than conventional THA

-risk of peri-prosthetic femoral neck fx

40
Q

What medical tx is shown to decrease hip AVN progression to collapse?

A

Bisphosphonates

  • inhibits osteoclast formation, and slows down bone resorption
  • Ficat stages 0 - 2 (pre-collapse AVN)
41
Q

When do you see Crescent sign in AVN? implicates?

A

Transition from Stage 2 to Stage 3

Implicates impending collapse of head of femur

42
Q

Risk factors for AVN?

A

-trauma, ETOH, steroids

43
Q

What is femoral rollback?

A

Posterior transition of the femoral-tibial contact with progressive flexion

44
Q

In non-constrained CR knee, what is relied on for rollback?

A
  • Native PCL

- but rollback not anatomic

45
Q

non-constrained PS (cruciate substituting) knee, what is relied on for rollback?

A

Tibial post engages on the femoral cam and forces mechanical roll back

46
Q

Indication for a cruciate substituting TKA?

A
  • previous patellectomy
  • inflammatory arthritis
  • deficient PCL
47
Q

In a constrained non-hinged knee, what subs for MCL and LCL?

A

Large central post

-gives V/V stability and rotational stability

48
Q

Indications for constrained non hinged?

A

Flexion gap laxity

MCL or LCL deficiency

49
Q

THA, what most often leads to SCN palsy? What portion of SCN affected?

A

-Lengthening
-80% involve peroneal portion
risk factors: dysplasia, female gender, revision sgx

50
Q

Optimal hip arthrodesis position?

A

25-30 deg flexion
0-5 deg adduction
0-5 deg ER

51
Q

Hip arthrodesis expends how much more energy?

A
  • 30% more nrg expenditure for ambulation

- accelerates degeneration of adjacent joints

52
Q

Golfing following THA or TKA,

A

Rise in their handicap
decrease in driving distance
mild ache while playing
90% use a cart

53
Q

Mechanical axis of a limb passes where relative to centre of the knee?

A

It passes slightly medial

54
Q

Order of soft tissue release of valgus knee?

A
  • osteophyte
  • lateral capsule
  • ITB if tight in extension -popliteus if tight in flexion
  • release LCL if tight in BOTH
55
Q

Abx-impregnated bone cement, most effective in who?

A
  • Revision TKA

- most pronounced in pts whose risk of post-TKA infection is greatest

56
Q

What ROM component is most important predictor of post-op TKA motion?

A
  • Pre-op flexion is most important

- CPM not sown to improve outcome or longterm ROM

57
Q

Patella Baja?

A

=shortened patellar tendon length

-limits flexion

58
Q

Risk factors for patella baja?

A
  • Proximal tibial osteotomy (both lat closing and medial opneing)–> tendon scarring
  • tib tub shift or transfer
  • prox tibia previous trauma
59
Q

Highly cross linked UHMWPE vs conventional poly?

A
  • more irradiation = better wear, but decreased mechanical strength
  • increased resistance to abrasive wear

Orthobullets (6 decks)

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