Acetabular Component

Question 1

How can wear be reduced?

Answer 1

reduce joint loading

keep sliding distance as small as practically possible

find alternative materials for the replacement head that reduce wear in the HDP

Question 2

What ceramic materials are used? Which one is more promising?

Answer 2

Alumina and zirconia

Zirconia

Question 3

Why is a small head disadvantageous?

Answer 3

rate of depth of wear is greater due to smaller contact area - Range of motion is reduced as the head wears into the cup

There is an increased likelihood of dislocation in the post-op period due to increased chance of neck impingement on the edge of the cup

Question 4

What material normally makes up the acetabular component?

Answer 4

HDP

Question 5

How does a metal backing plate assist in stress management?

Answer 5

evens stresses and reduces stress concentrations

not found in practice

Question 6

name some important features in acetabular cup design

Answer 6

size of femoral head and cup

metal backing plate

thickness of HDP layer

outer dimension of the acetabulum

positioning of the acetabular cup (more centrally)

Question 7

How can cup loosening occur?

Answer 7

mechanical over stressing

biological reaction to ingress of HDP particles

Question 8

how does HDP wear cause bone resporption?

Answer 8

hip fragments come into contact with bone

tissue reaction to the HDP causes bone resorption

HDP migrates long the interface causing further resorption

Question 9

How does centralisation of the cup help?

Answer 9

reduces the moment arm and therefore reduces the hip joint load

Question 10

What disadvantages does centralisation of the cup have?

Answer 10

the prosthesis is mounted on softer weaker bone

deepened cup leads to earlier impingement of the femoral neck on the rim of the acetabulum - limiting motion and increasing risk of dislocation as the head is prised from the socket.

Question 11

What is the failure rate before 10 years in hip replacements?

Answer 11

10%

Question 12

What happens first in most cases: Loosening or wear out?

Answer 12

loosening

Question 13

What is the process of replacing a hip prosthesis called?

Answer 13

revision arthroplasty

Question 14

If the revision process is completed in one step what is this called?

Answer 14

exchange arthroplasty

Question 15

Why is revision extra difficult to achieve?

Answer 15

loss of bone by the osteolytic resorption process

Question 16

What are the complications of revision surgery?

Answer 16

high failure rate

wheelchair existence

death from complications of difficult surgery