Chapter 44 - Primary Hip Arthroplasty

Question 1

first generation cementing techniques

Answer 1

cement mixed by hand, open bowl, no pressurization, no gun, no canal prep

Question 2

second gen cementing techniques

Answer 2

pressurizing via cement gun, mixing bowl, restrictor/plug

Question 3

third general cementing techniques

Answer 3

goal: porosity reduction
pulse lavage, canal prep, pressurization, vacuum mixing

Question 4

what does vacuum mixing do for cement properties?

Answer 4

minimizes porosity
increases fatigue strength

Question 5

what are the indications for cementing an acetabular cup?

Answer 5

something wrong with the bone - eg radiation, sometimes osteonecrosis

retained hardware that you cannot get out and get in the way of solid fixation without cement

Question 6

what does the taper of a stem do for loading characteristics?

Answer 6

taper allows subsidence into a tight fit and optimizes proximal load sharing, optimizes bony ingrowth, and minimizes stress shielding

Question 7

what do cylindrical stems initially rely upon?

Answer 7

tight diaphyseal fit. see “cylindrical stem” = diaphyseal fit

Question 8

downsides of a cylindrical stem

Answer 8

high rates of thigh pain, high rates of stress shielding

Question 9

what pore size is ideal for bony ingrowth in arthroplasty

Answer 9

100-500um

Question 10

osteolysis cell that predominates

Answer 10

macrophage

Question 11

with a acetabular cup with multiple holes, where is most of the osteolysis?

Answer 11

retroacetabular

Question 12

wit

Question 13

with an acetabular cup without holes, where is the majority of the osteolysis?

Answer 13

proximal femoral osteolysis

Question 14

what types of corrosion are modular taper necks susceptible to?

Answer 14

fretting and crevice corrosion

Question 15

how does head size relate to risk of trunnionosis?

Answer 15

larger head size -> increased risk of trunnionosis, 2/2 increased moment arm/torques felt at junction, especially in metal on metal hips

Question 16

what bearing combination has the lowest wear rates?

Answer 16

ceramic on ceramic (.5-2.5um/yr)

then metal on metal bearings (2.5-5um/year) .1mm/yr for metal on poly

Question 17

where are metal ions cleared

Answer 17

kidneys

pass thru the placenta, eg fetus is exposed

Question 18

hemiarthroplasty indications

Answer 18

1. displaced femoral neck fracture in the elderly
2. osteonecrosis in a young person
3. rare - salvage when not enough bone for cup

Question 19

indications for hip resurfacing

Answer 19

general: advanced hip arthosis with preserved femoral bone stock

1. proximal femoral deformity that makes standard THA difficult

Question 20

indications for hip resurfacing

Answer 20

general: advanced hip arthosis with preserved femoral bone stock

1. proximal femoral deformity that makes standard THA difficult
2. hx of immunosuppression or rigk of sepsis
3. neuromuscular - huge fem heads -> decreased dislocation risk

Question 21

Contraindications

Answer 21

1. women of childbearing age - big head diameters -> increased risk of metallosis -> metal particles pass thru placenta
2. femoral bone loss or large femoral neck cysts found in OR
3. small acetabuli

Question 22

Most common complication of hip resurfacing requiring revision?

Answer 22

femoral neck fracture

Question 23

when do majority of tha dislocations occur

Answer 23

70% occur with in one month of surgery

Question 24

most common reason for revision THA

Answer 24

1. infection
2. dislocation

Question 25

what to use for HO prophylaxis?

Answer 25

indomethacin
700g radiation within 72 hours of surgery

Question 26

where do PEs originate post op from THA?

Answer 26

popliteal veins or proximal

Question 27

LMWH vs warfarin for dvt ppx

Answer 27

studies demonstrate decresed symptomatic DVT with LMWH but more bleeding events with LMWH

Question 28

pathogenesis for osteolysis

Answer 28

particulate wear triggers macrophage activation then osteoclast activation and osteolysis

osteolysis is a MACROPHAGE driven process

Question 29

what cytokines are involved in osteolysis?

Answer 29

IL-1, IL-6, tnf-a, pge2

Question 30

what cell type mediates metallosis?

Answer 30

lymphocytes

Question 31

what is the. mechanism of action of LMWH

Answer 31

activate ANTIthrombin -> inhibit factor Xa