Unit 5b: Elbow Joint Replacement

Question 1

What are the primary and secondary indications for elective replacement of the elbow joint?

Answer 1

Primary = pain relief 
Secondary = restoration of stability

Question 2

What condition to most patients for elective elbow replacement suffer from?

Answer 2

Rheumatoid arthritis

Question 3

What are the primary functions of the elbow?

Answer 3

Allow positioning of the hand in space

Allow the forearm to act as a lever

Question 4

What are the 3 articulations of the elbow?

Answer 4

Humeroulnar (trochleo-ulnar)
Humeroradial (radiocapitellar)
Proximal radioulnar

Question 5

What magnitude of loads are carried by the elbow in dynamic activities?

Answer 5

As high as 6x body weight

Question 6

Which articulation carries the major part of the load at the elbow?

Answer 6

Humeroulnar articulation

Question 7

What is the angulation of the forearm in relation to the upper arm in full extension?

Answer 7

10 - 15 degrees of valgus angulation

Question 8

What is the angulation of the forearm in relation to the upper arm at full flexion?

Answer 8

A few dgrees of valgus or varus angulation

Question 9

Why do uniaxial hinge prostheses give rise to excessive shearing forces at the bone-cement interface?

Answer 9

As coronal plane angle between the upper arm and forearm is not fixed but varies

Question 10

How may degrees of flexion does a normal elbow joint allow?

Answer 10

140 degrees

Question 11

What range of flexion is needed at the elbow for normal daily activities?

Answer 11

30 - 130 degrees

Question 12

What is the normal range of pronation and supination of the forearm?

Answer 12

70 pronation

80 supination

Question 13

What range of pronation and supination is needed for most activities of daily living?

Answer 13

50 pronation

50 supination

Question 14

What structures are important in stability of the elbow joint?

Answer 14

Anterior capsule

Medial and lateral collateral ligaments

Question 15

Which structure is most important for stability in flexion?

Answer 15

Medial collateral ligament

Question 16

What effect does removal of the radial head have on stability mechanisms in the elbow?

Answer 16

Medial collateral must resist all valgus loads entirely

Question 17

Why is shoulder replacement given priority over elbow replacements?

Answer 17

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

Question 18

What is the basic design of first generation total elbow prostheses?

Answer 18

Single axis hinges (also called “constrained” or “hinged”)

Question 19

Example of 3 first generation prostheses

Answer 19

Dee
McKee
Stanmore

Question 20

What were the 3 cobalt chrome parts of the Dee prosthesis?

Answer 20

Humeral component
Ulnar component
(Both curved tofit the medullary cavities of the humerus and ulna)
Axis pin

Question 21

What was the range of motion of the Dee prosthesis?

Answer 21

0 - 150 degrees of flexion (though not always achieved)

Question 22

How was the Dee prosthesis fixated?prosthesis

Answer 22

PMMA bone cement with additional keying points using metal buttons at the base of the humeral stem and undersurface of the ulnar platform

Question 23

What caused long term loosening of the Dee and other first generation prostheses?

Answer 23

The restricted single-axis motion forced upon the elbow by the prosthesis - unnatural motion causes excessive shearing forces at the bone-cement interface

Metal wear debris was also a contributing factor

Loss of bone stock

Question 24

What long term implications does loss of bone stock have?

Answer 24

When a prosthesis fails it is extremely difficult to salvage the joint

Question 25

What are the 2 main types of second generation prostheses?

Answer 25

Semi-constrained metal-to-polyethylene hinge types Unconstrained metal-to-polyethylene hinge types

Question 26

What is a recent variation of the two main types of second generation total elbow prostheses?

Answer 26

Resurfacing the radial head

Question 27

What are the 3 parts of a semi-constrained elbow joint replacement?

Answer 27

Humeral component Ulnar component Hinged-like metal-to-polyethylene articulation

Question 28

What are examples of semi-constrained elbow joint replacements?

Answer 28

Pritchard-Walker Coonrad Tri-Axial

Question 29

Why are semi-constrained elbow replacements sometimes referred to as "sloppy-hinge" prostheses?

Answer 29

They are essentially hinge-like in appearance and function but allow varying degrees of side-to-side laxity

Question 30

Describe the Tri-Axial prosthesis

Answer 30

Semi-constrained design | Loose fitting metal-to-polyethylene hinged articulation with long humeral and ulnar metal stems

Question 31

In which condition did the Tri-Axial prosthesis prove most successful?

Answer 31

Rheumatoid arthritis

Question 32

What is the aim behind unconstrained elbow joint replacements?

Answer 32

Resurface the lower end of the humerus and the olecranon to reproduce the anatomical structure

Question 33

To achieve full stability in an unconstrained replacement what must remain intact?

Answer 33

Collateral ligaments

Question 34

Name 3 examples of unconstrained elbow replacements

Answer 34

Ewald (capitellocondylar) Kudo Souter-Strathclyde

Question 35

What makes up the Souter-Strathclyde prosthesis?

Answer 35

``` Humeral resurfacing (Vitallium) Ulnar resurfacing (HDP) ```

Question 36

How does the unconstrained design compare to the semi-constrained design in terms of outcomes?

Answer 36

Rates of dislocation slightly higher than semi-constrained Rates of aseptic loosening generally lower than semi-constrained

Question 37

What is the theoretical benefits of resurfacing the radial head?

Answer 37

Benefits of load-transmission stability that are afforeded by the humeroradial articulation

Question 38

What are the 3 components of the Pritchard elbow replacement?

Answer 38

Metal humeral component Ulnar component (metal stemmed base and polyethylene spacer which replaces the articulating surface of the ulna) Radial component (metal stemmed base and polyethylene spacer which replaces the articulating surfaces of the radius)

Question 39

What has caused variable results with designs that resurface the radial head?

Answer 39

Difficulties in balancing the 3 articulations at the time of operation