Unit 5b: Elbow Joint Replacement Flashcards
What are the primary and secondary indications for elective replacement of the elbow joint?
Primary = pain relief Secondary = restoration of stability
What condition to most patients for elective elbow replacement suffer from?
Rheumatoid arthritis
What are the primary functions of the elbow?
Allow positioning of the hand in space
Allow the forearm to act as a lever
What are the 3 articulations of the elbow?
Humeroulnar (trochleo-ulnar)
Humeroradial (radiocapitellar)
Proximal radioulnar
What magnitude of loads are carried by the elbow in dynamic activities?
As high as 6x body weight
Which articulation carries the major part of the load at the elbow?
Humeroulnar articulation
What is the angulation of the forearm in relation to the upper arm in full extension?
10 - 15 degrees of valgus angulation
What is the angulation of the forearm in relation to the upper arm at full flexion?
A few dgrees of valgus or varus angulation
Why do uniaxial hinge prostheses give rise to excessive shearing forces at the bone-cement interface?
As coronal plane angle between the upper arm and forearm is not fixed but varies
How may degrees of flexion does a normal elbow joint allow?
140 degrees
What range of flexion is needed at the elbow for normal daily activities?
30 - 130 degrees
What is the normal range of pronation and supination of the forearm?
70 pronation
80 supination
What range of pronation and supination is needed for most activities of daily living?
50 pronation
50 supination
What structures are important in stability of the elbow joint?
Anterior capsule
Medial and lateral collateral ligaments
Which structure is most important for stability in flexion?
Medial collateral ligament
What effect does removal of the radial head have on stability mechanisms in the elbow?
Medial collateral must resist all valgus loads entirely
Why is shoulder replacement given priority over elbow replacements?
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
What is the basic design of first generation total elbow prostheses?
Single axis hinges (also called “constrained” or “hinged”)
Example of 3 first generation prostheses
Dee
McKee
Stanmore
What were the 3 cobalt chrome parts of the Dee prosthesis?
Humeral component
Ulnar component
(Both curved tofit the medullary cavities of the humerus and ulna)
Axis pin
What was the range of motion of the Dee prosthesis?
0 - 150 degrees of flexion (though not always achieved)
How was the Dee prosthesis fixated?prosthesis
PMMA bone cement with additional keying points using metal buttons at the base of the humeral stem and undersurface of the ulnar platform
What caused long term loosening of the Dee and other first generation prostheses?
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
What long term implications does loss of bone stock have?
When a prosthesis fails it is extremely difficult to salvage the joint
What are the 2 main types of second generation prostheses?
Semi-constrained metal-to-polyethylene hinge types
Unconstrained metal-to-polyethylene hinge types
What is a recent variation of the two main types of second generation total elbow prostheses?
Resurfacing the radial head
What are the 3 parts of a semi-constrained elbow joint replacement?
Humeral component
Ulnar component
Hinged-like metal-to-polyethylene articulation
What are examples of semi-constrained elbow joint replacements?
Pritchard-Walker
Coonrad
Tri-Axial
Why are semi-constrained elbow replacements sometimes referred to as “sloppy-hinge” prostheses?
They are essentially hinge-like in appearance and function but allow varying degrees of side-to-side laxity
Describe the Tri-Axial prosthesis
Semi-constrained design
Loose fitting metal-to-polyethylene hinged articulation with long humeral and ulnar metal stems
In which condition did the Tri-Axial prosthesis prove most successful?
Rheumatoid arthritis
What is the aim behind unconstrained elbow joint replacements?
Resurface the lower end of the humerus and the olecranon to reproduce the anatomical structure
To achieve full stability in an unconstrained replacement what must remain intact?
Collateral ligaments
Name 3 examples of unconstrained elbow replacements
Ewald (capitellocondylar)
Kudo
Souter-Strathclyde
What makes up the Souter-Strathclyde prosthesis?
Humeral resurfacing (Vitallium) Ulnar resurfacing (HDP)
How does the unconstrained design compare to the semi-constrained design in terms of outcomes?
Rates of dislocation slightly higher than semi-constrained
Rates of aseptic loosening generally lower than semi-constrained
What is the theoretical benefits of resurfacing the radial head?
Benefits of load-transmission stability that are afforeded by the humeroradial articulation
What are the 3 components of the Pritchard elbow replacement?
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)
What has caused variable results with designs that resurface the radial head?
Difficulties in balancing the 3 articulations at the time of operation
