Elbow Replacement

Question 1

Describe a first generation elbow replacement

Answer 1

simple uniaxial hinges

Dee prosthesis

Question 2

What is the main indication for elbow replacement?

Answer 2

pain relief

secondary - stability restoration

Question 3

What 3 articulations make up the elbow?

Answer 3

humeroulnar
humeroradial
proximal radioulnar

Question 4

To what degree of valgus is the forearm positioned while in anatomical position?

Answer 4

10-15 degrees

Question 5

What problem does the slight valgus angulation of the forearm cause fo uniaxial prostheses?

Answer 5

uniaxial prostheses maintain the same coronal plane as the upper arm which gives rise to excessive shearing forces at the bone-cement interface and subsequent loosening

Question 6

What ROM is required for the elbow to perform activities of daily living?

Answer 6

30-130 flexion

50 supination/pronation

Question 7

What provides stability at the elbow joint?

Answer 7

congruence of surfaces

soft tissues

Question 8

In flexion, which elbow ligament provides most stability (50+%)

Answer 8

medial collateral ligament

Question 9

Why is it important to preserve soft tissues at the elbow?

Answer 9

much stability is conferred from surrounding ligaments, muscles and joint capsules

Question 10

How is loading on the elbow dependent in some ways on the stiffness of the shoulder joint?

Answer 10

If a patient with a total elbow replacement and a stiff shoulder joint attempts internal or external rotation of the arm, the stiffness at the shoulder will increase the rotational stresses at the bone-cement interface of the elbow replacement.

Question 11

What two main problems are seen in uniaxial hinged elbow prostheses?

Answer 11

loosening of parts

requirement of removal of a large amount of bone stock

Question 12

In the early metal-metal prostheses designed by Dee, what was a contributory factor to loosening?

Answer 12

constraint to uniaxial motion creates large shear forces at the bone-cement interface

high volume of wear debris

Question 13

What two groups can second generation prostheses be divided into?

Answer 13

semiconstrained

unconstrained

Question 14

Describe semi constrained elbow replacements

Answer 14

stemmed humeral and ulnar components
hinge-like metal-polyethylene articulation.

varying degree of side-to-side laxity but essentially hinge-like in appearance and function

Question 15

What are semi constrained prostheses sometimes called?

Answer 15

sloppy hinges

Question 16

In what situation are semi constrained prostheses more useful?

Answer 16

some soft tissue insufficiency and some lost bone stock

Question 17

Name an example of a semi constrained prosthesis

Answer 17

Tri-axial

Question 18

Describe unconstrained elbow replacements

Answer 18

resurfaced lower end of humerus and olecranon to reproduce anatomical structure

vitallium humeral component

HDP ulnar component

Question 19

What is required for full stability in unconstrained prostheses?

Answer 19

collateral ligaments intact

Question 20

What is the supposed benefit of radial head resurfacing?

Answer 20

load transmission stability conferred by the humeroradial articulation

Question 21

What is the Ewald prosthesis sometimes known as?

Answer 21

capitellocondylar

Question 22

Name some examples of unconstrained prostheses

Answer 22

Ewald
Kudo
Souter-Strathclyde

Question 23

Describe a Pritchard elbow replacement

Answer 23

the metal humeral component which replaces the articulating surfaces of the trochlea
and capitellum

the ulnar component, consisting of a metal stemmed base and polyethylene spacer, which replaces the articulating surface of the ulna

the radial component, consisting of a metal stemmed base and polyethylene spacer, which replaces the articulating surfaces of the radius.

Question 24

What is an advantage of using spacers?

Answer 24

various thicknesses can be selected so that surgeons can select optimum size for joint stability

Question 25

how do semi constrained prostheses differ from first generation hinged prostheses?

Answer 25

they have “sloppy” hinges with varying degrees of side-to-side laxity.