Joints flashcards

Question 1

percent of THA in 2012 that are cementless

Answer 1

93%

Question 2

How to calculate Dorr

Answer 2

radio of canal diameter 10 cm distal to midportion of lesser trochanter / inner canal diameter at midportion of lesser trochanter

Question 3

Dorr Type A

Answer 3

Ratio <0.5 (canal is less than half the thickness 10 cm distal to lesser troch than the canal at the troch itself). Cortices seen on both AP and Lateral XR. Uncemented is good.

Question 4

Dorr Type B

Answer 4

0.5-0.75. Thinning of posterior cortex on lateral XR. Uncumeneted

Question 5

Dorr Type C

Answer 5

> 0.75, thinning of cortices on both views. Cemented fixation (bad case if you do uncemented.

Question 6

how does cement act

Answer 6

acts as grout by interlocking fit between surfaces

Question 7

stovepipe femur is also known as

Answer 7

Dorr C femur. enlarged metaphysis and lack of supporting isthmus.

Question 8

cementing the cup?

Answer 8

not as good, higher failure rate, cement resists shear poorly

Question 9

1st generation cement technique

Answer 9

Hand mix, finger packed cement, no canal preparation or cement restrictor

Question 10

2nd generation cement technique

Answer 10

Cement restrictor, cement gun, femoral canal preparation with brush and dry

Question 11

3rd generation cement technique

Answer 11

vacuum-mixing to reduce porosity, cement pressurization, femoral canal preparation with pulsatile lavage.

Question 12

Porosity good or bad for cement

Answer 12

bad, more points of stress if high porosity

Question 13

Cement mantle thickness

Answer 13

> 2mm to decrease risk of mantle fractures

Question 14

Mueller type prosthesis difference

Answer 14

French paradox, it aims for a press fit mediolaterally so the cement mantle is <2 mm, but it has shown to have good results as well.

Question 15

stiff femoral stem for cement

Answer 15

titanium is bad, flexes too much

Question 16

stem centralizatier for cement

Answer 16

avoid malpositioning

Question 17

Smooth femoral stem

Answer 17

sharp edges increase stress concetration

Question 18

Varus or valgus for cement

Answer 18

want to avoid either, especially varus

Question 19

Barrack and Harris garding system for cement

Answer 19

….do I need to know…

Question 20

Good indication for cementless THA

Answer 20

younger patient, older patient with good bone stock, revision THA (cemented is not good for revision)

Question 21

Indications for cemented THA

Answer 21

poor acetabular bone stock, irradiated bone - very rare though

Question 22

Biologic fixation Pore Size

Answer 22

50-300 microm (preferable 50-150)

Question 23

biologic fixation porosity

Answer 23

40-50%, if too porous leads to shearing of metal

Question 24

biologic fixation gaps

Answer 24

<50 um (distance between bone and prosthesis)

Question 25

micromotion biologic fixation

Answer 25

<150 um (leads to fibrous ingrowth)

Question 26

grit blasted is what kind of surface

Answer 26

onlay, EXTENSIVELY COATED

Question 27

onlay vs. inlay

Answer 27

onlay is weaker, which means you need greater surface coating

Question 28

hydroxyapatite effect on bone

Answer 28

osteoconductive (not osteoinductive)

Question 29

signs of a wellxed cementless femoral component

Answer 29

spot welds (new endosteal bone that contacts porous surface of implant. No radiolucenet lines around porous portion of femoral stem, proximal stress shielded in extensively coated stems is good, absence of stem subsidence on serial radiographs

Question 30

signs of well fixed cementless acetabular component

Answer 30

no migration on serial xrays, no progressive radiolucent lines, intact acetabular screws

Question 31

aseptic loosening cause

Answer 31

poor initial fixation, mechanical loss of fixation over time, particle induced osteolysis

Question 32

loose acetabular component symptoms

Answer 32

groin/buttock pain

Question 33

femoral loosening symptoms

Answer 33

thigh pain and startup pain

Question 34

how to eval for aseptic loosening

Answer 34

sequential xrays adn bone scan

Question 35

risks for stress shielding

Answer 35

stiff femoral stem is the most important, extensively porous coated stem (in a revision stem scenarior - not an extensively coated ongrowht but an ingrowth extensivelyc oated stem). Large diameter stem. greater preop osteopenia

Question 36

causes of aseptic loosening

Answer 36

poor initial fixation, loss of fixation over time, particle induced osteolysis

Question 37

treat stress shielding?

Answer 37

no

Question 38

unstalbe fmeur fracture intraop treatment

Answer 38

remove prosthesis, stabilize fracture, reinsert new stem that bypasses fracture by two cortical diameters