Ankle Replacement 2

Question 1

What is one advantage of incongruent shapes?

Answer 1

less constraint in the movement, so that some horizontal movement is possible - could reduce load transmission to the bone-cement-prosthesis interfaces by transferring some to the soft tissues

Question 2

Name two types of incongruent ankle prostheses

Answer 2

trochlear (saddle)

convex-concave

Question 3

What are 3 problems with incongruent shapes?

Answer 3

higher rate of depth of wear than the congruent types

higher contact stresses due to lower contact area

less stability than congruent shapes due to greater freedom of movement

Question 4

List causes of failure of ankle replacement

Answer 4

aseptic loosening 
lateral or medial subluxation of the joint 
subsidence of the taller component 
impingement of the joint 
wound healing problems 
infection

Question 5

which type of replacement gives better wear resistance?

Answer 5

congruent

Question 6

Which ankle replacement design has the best results so far?

Answer 6

New Jersey LCS

Question 7

What is an advantage of using a meniscal bearing?

Answer 7

provides congruent bearing surfaces at the tibial and taller interfaces without the usual disadvantage of rigid transmission of media-lateral and rotational shear forces usually associated with constrained designs

Question 8

Do cemented or cementless designs seem to have better results?

Answer 8

cementless

Question 9

What advantage do meniscal bearings have over cylindrical bearings?

Answer 9

congruence (low wear) yet freedom of joint motion

Question 10

What trends are seen in modern ankle replacements?

Answer 10

towards meniscal bearings

towards cementless types