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Millers > Recon 2 (THA) > Flashcards

Recon 2 (THA) Flashcards

1
Q

Interval for anterior approach, cons

A

Ant = Smith Pete
Sup: sart (fem) + TFL (SGN)
Deep: rect (fem) + glut med (SGN)

Cons: difficult femoral exposure can undersize and varus stem

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2
Q

Interval for lateral approach

A

Lateral = Hardinge

Medius + vastus splitting (both SGN)

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3
Q

Interval for ant-lat approach, pro/cons

A

Ant lat = Watson Jones

Medius + TFL (both SGN)

Pro: lowest dislocation
Cons:
1. Limp because violate the abductors
2. If you split the muscle too high up, hit the gult art/n and deinnervate glut med

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4
Q

What is normal femoral and tab version

A

Fem: 15 deg AV
Fem NSA 120-135
Tab: 45deg caudal, 15deg ant

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5
Q

What is the difference between femoral implants for cementing vs press fit

A

Cement: stainless steel or CoCr, stiff and smooth
- If flexible will move within the cement mantle
- Precoated have higher failure rates in cement (fails at the cement/bone interface because cement sticks to the precoat)
Only cement elderly + Dorr C bone

Pressfit: titanium porous coat, flexible to avoid cortex engagement

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6
Q

Tab components:
- Cement vs press fit
- Screws vs no screws
- Position

A

Always press fit, cement can’t resist the shearing forces (fast failure)

Screws vs none = equiv

Position:
- 40deg aBd (AP)
- 20deg AV (lat)

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7
Q

What is the modern bearing?

A

Ceramic head on poly tab

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8
Q

What is the 3 step process of preparing poly to make wear resistant?

A
  1. Irradiate in inert gas = create free radicals that cross links the poly
  2. Eliminate free radicals via reheating/melting
    Melting = reduces mechanical properties so not ideal
    Annealing = heat to a sub melting point to maintain mechanical properties
  3. Sterilize
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9
Q

What is the best way to manufacture poly

A

Compression molding

Not: ram bar, sheet molding, Ca stearate, gamma irradiation in air

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10
Q

Write out the Young’s modulus for materials (8 total)

A

Sir Kobe Steels Tricks
Ceramic CoST Could Cement Polly to Cancel her Telephone Carrier

Ceramic (Sir)
Co Cr (Kobe)
Stainless steel (steels)
Titanium (tricks)
Cortical bone
Bone cement
UH ME PE
Cancellous bone

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11
Q

Define creep

A

Progressive deformation over time

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12
Q

What is a ductile vs brittle material

A

Ductile = large plastic deformation (chewing gum)
Brittle = NO plastic deformation (glass)

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13
Q

What is stress shielding? What stems are at risk for this?

A

Distal spot weld, proximal osteopenia

Fully coated, CoCr large stems
- Larger (radius^4) = stiffer

Distal fixation stems stress shield vs proximal fixation stems osteolysis

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14
Q

If you see a distal fixation stem broken in the implant, what happened?

A

Cantilever bending
Stem is fixed distally, sees a load, stem flexes but is too stiff, breaks at a point between the stem being fixed vs not
Breaks at the proximal junction

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15
Q

What is the difference between ingrowth and ongrowth stems?

A

Ingrowth = bone grows into a porous structure

Ongrowth = prosthesis surface is rough and the bone grows into the roughening, LESS COMMON

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16
Q

What do you need for good ingrowth
1. Host
2. Material properties
3. Motion?

A
  1. ALIVE bone
  2. Material - rule of 50
    50% porosity
    50 microns deep pores
    <50 microns between gaps
  3. NO motion (motion = fibrous ingrowth)
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17
Q

What is the formula for hydroxyapatite

A

Ca10 (PO4)6 (OH)2
Osteoconductive
Bone grows onto the HA then must continue to grow into the stem

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18
Q

What is jump distance? How does head diameter change jump distance?

A

Distance the head must displace before dislocating

Larger head = larger jump distance
Literally just harder to get a big ball out of a big hole

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19
Q

How do these parameters affect soft tissue balance?
Liner offset
Neck length
High off set / lateral offset femur
High off set / 127 neck (normal 132)

A

Liner offset : leg length + offset

Neck length: “ “

High offset / lateral offset : offset only

High offset / 127 neck : offset, inverse leg length (127 decreases LL)

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20
Q

Difference between linear and volumetric wear

A

Linear = in 1 direction (smaller heads)

Volumetric = 3D aka poly wear
- Larger heads
- In theory more volumetric wear yields more wear particles (osteolysis), but doesn’t seem to be true for HW CL poly

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21
Q

What is abrasive wear

A

Difference in material hardness
Poly wears more than the femoral head

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22
Q

What is adhesive wear?
What can you do to protect against adhesive wear?

A

Bonds between surfaces need to be broken down for movement - the weaker material breaks
Head forms bonds to the poly, break and reform through motion, submicron poly particles
Highly cross linking poly increases adhesive wear

23
Q

Mechanism of osteolysis

A

Submicron particles -> marcophage activation -> blasts activate clasts = bone resorption

TNFa
IL1 beta
IL6

24
Q

2 CI to metal on metal prosthesis

A

Female child bearing age
Renal failure

Theoretical risk

25
Q

Pseudotumor
- Metals that cause this
- Histo changes
- Immune cells involved
- Workup

A

CoCr
Direct tissue necrosis = aseptic lymphocytic vasculitis
T4 HST rxn = T & B cells
Workup:
1. Aspiration - manual cell count bc dead cell burden messes up automatic count
2. MARS MRI
3. Serum ion levels - anything >2ppb = elevated

26
Q

4 known RF for pseudotumor

A

F
Smaller components (aka women)
<40
Hip dysplasia (think eccentric wear)

27
Q

3 complications associated with MOM revisions

A

Dislocation - soft tissue damage
Infection - necrotic tissue
Lack of ingrowth - dead bone

28
Q

How to differentiate between MOM vs trunnion pseudotumor

A

Just have to look at the XRs
Both cause pseudotumor and elevator serum ion levels

29
Q

Define corrosion
1. Fretting
2. Crevice
3. Galvanic

A

Corrosion = how a metal reacts w/ environment and gradually breaks down

Fretting = small cyclic motion disrupts the protective oxide layer -> metal exposed to O2
- Any modular junction

Crevice = pits form -> accelerate corrosion -> increased wear
- Metal on poly hip w/ metal ions >1ppb
- Revise to ceramic head w/ titanium sleeve and poly (remove CoCr)

Galvanic = battery corrosion 2 different metals (CoCr)

30
Q

What bearing surface has the lowest wear couple

A

Ceramic on ceramic
Cons: squeaking, fracture risk

31
Q

Where does the sciatic n come closest to the tab?
What is the most common injury

A

Level of the ischium
Compression -> peroneal division bc peripheral fibers
- Retractor vs hematoma

50% resolve

32
Q

HO
- Which approach is a RF
- Prophylaxis

A

Direct lateral (Hardinge)

Prophylaxis
1. 24pre op 700G
OR 48hr post op 700G
2. Indomethacin - 1-6wks post op, dosing variable

33
Q

What is the Brooker classification

A

HO - takes up to a year to fully mature/declare

B1 = bone islands in the soft tissues
B2/3 = bone islands grow together
B4 = ankylosis

34
Q

When to revise for iliopsoas tendonitis

A

> 8mm prominent cup overhang

If no overhang, IP tenotomy

35
Q

Treat poly wear (see eccentric head position and osteolysis)

A

Well fixed/positioned implants - head/liner exchange
- Use as big head as possible to increase stability

Lytic defect - revision

36
Q

What is start up pain a sign of?

A

Aseptic loosening

Groin = cup
Thigh = stem

37
Q

XR signs for aseptic loosening for a cemented vs cementless stem

A

Cementless: subsidence, distal pedestal

Cemented: lucent lines, stem migration, cement mantle fracture

38
Q

Describe 4 levels of Paprosky femoral bone loss and how to revise

A

T1 = normal (metaphyseal but not structural) - use anything

T2 = metaphy bone loss - cementless diaphyseal stem

T3 = metaph + diaph bone loss - cementless res mod

T4 = structural diaph bone loss - APC, metaprosthesis

39
Q

What is the most common revision cementless stem

A

Tapered fluted modular stem (titanium)
I.e. res mod

40
Q

Revision tab principles :
- How much rim must be intact for press fit
- What is your first choice revision tab
- What do you use for pelvic discont

A

2/3 rim intact to use press fit

1st choice = large, cementless cup w/ screws

Pelvic discon = cup/cage, plate, custom triflange

41
Q

What is the safe zone for screws?

A

Post sup > post inf

Ant sup = ext iliac A/V = bleed out and die
Ant inf = ob N/A/V - more from retractor placement

42
Q

What are the aspiration threshold for acute vs chronic PJI

A

All must be off abx for 2wks

Acute <6wks = WBC > 10K, PMN > 90%
Treat if <1mo = I&D, comp change bc no biofilm

Chronic = WBC > 3K, PMN > 80%
Treat 2 stage revision

43
Q

When can alpha defensin be false positive?

A

Metallosis/corrosion

44
Q

When is TXA CI

A

Active DVT or renal failure

45
Q

Why do you want to avoid transfusion in total joint patients?

A

Increases risk PJI

46
Q

What is the mechanism of dual mobility increasing stability?
Who should you use it for?

A

Increases head diameter + jump distance even in small cups

High risk patients:
- Hip frx
- L spine pathology (fusion)
- Revision

47
Q

Vancouver classification femur fractures

A

A: troch
B: diaphyseal
1 - stable
2 - loose, good bone
3 - loose, bad bone
C: distal

48
Q

Treat an intraop calcar fracture

A

Remove stem
Does not go past LT - cable, re-press fit
Past LT - revision implants

49
Q

Imaging + treat transient osteoporosis of hip

A

Signal everywhere in prox fem (not just neck/head)
Protected WB

50
Q

What are the deformities of DDH

A

Tab + fem neck are AV
Hip COR lateralized
Less shallow socket

Trt = PAO as long as posterior col intact

51
Q

Describe trendelenburg gait

A

Weak abductors
Lean TOWARDS the weak side
Put the cane in the CL hand

52
Q

What is the goal abduction and anteversion for tab component

A

30-50deg abd
5-25deg anteversion

Too high - risk ant dislocation w/ ext
Too low - risk post dislocation w/ flex

53
Q

What head size for MOM vs THA increases risk of ALTR?

A

MOM <46mm - small
- Larger brings more fluid in the articulation

THA >32mm

54
Q

How do Co/Cr levels differ for hip resurfacing vs taper corrosion

A

Resurfacing - both high TOGETHER (equally)

Taper/fretting - Co > Cr

Millers (29 decks)

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