Elbow Joint Replacement Flashcards
How are elbow joint replacements generally divided?
First generation
Second generation
What is the primary indication for elective replacement of the elbow joint?
Pain relief
What coniditon do most elective elbow replacement patients 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
(For many must also function as weight bearing)
What are the 3 articulations of the elbow joint?
Hemuroulnar (trochleo-ulnar)
Humeroradial (radiocapitellar)
Proximal radioulnar
Which articulation carries the ajor part of the load at the elbow?
Humeroulnar
In the anatomical position, what angulation is the forear in relation to the upper arm/
10 to 15 degrees of valgus angulation
What are the disadvantages of uniaxial hinge prostheses?
Maintain the same coronal plane angle between the upper arm and forearm - gives rise to excessive shearing forces at the bone cement interface - subsequent loosening
How much flexion does the elbow allow?
140 degrees
What range of flexion are most activities of daily living carried out at?
30 to 130 degrees of flexion
What is the range of pronation and supination of the frarm?
70 pronation
80 supination
What range of pronation and supination is needed for activities of daily living?
50 pronation
50 supination
What provides stability for the elbow joint?
Joint surfaces and soft tissues
Which three structures are particularly important in the stability of the elbow joint?
Anterior capsule
Medial and collateral ligaments
Which ligament provides over 50% of the joint stability when the elbow is flexed?
Medial collateral ligament
How does removal of the radial head affect stability?
Reduces joint congruity - medial collateral ligament must resist valgus loads entirely
How does the stiffness of the shoulder joint affect loadings on the elbow?
If stiff shoulder and attempt internal or external rotation the stiffness of the shoulder will increase the rotational stresses at the bone-cement interface (why shoulder should be replaced first
What are first generation elbow prostheses also known as?
“Constrained” or “hinged” designs
Give 3 examples of first generation elbow prostheses
Dee
McKee
Stanmore
Describe the Dee prosthesis
3 CoCr parts (humeral, ulnar and the axis pin)
Axis of rotation at right angles to the long axis
Possible 0 to 150 degrees flexion
Curved stems to fir the medullary cavities
Both stems convex anteriorly
Ulnar stem curved convex laterally (need right and eft sides)
Stems secured with PMMA cement and metal buttons
What problems were encountered long with first generation elbow prostheses?
Loosening (due to restricted single-axis motion - shearing forces at the bone-cement interface)
High amount of metal wear debris from the metal-on metal articulations (contributed to loosening
Loss of bone stock
What re the two main types of second generation total elbow prostheses?
Semiconstrained metal-to-polyethylene hinge types
Unconstrained metal-to-polyethylene resurface types
Examples of semiconstrained prostheses
Pritchard-Walker
Coonrad
Tri-Axial
What is the basic design of a semiconstrained elbow joint replacement
Stemmed humeral and ulnar components
Hinged-like metal-to-polyethylene articulation (“sloppy hinge”)
Why are semiconstrained more suitable than unconstrained types when there is some soft-tissue insufficiency?
Added stability
How much varus and valgus laxity does the tri-axial prosthesis allow?
Around 5 degrees varus
Around 6 degrees valgus
What magnitude of load is required to pull apart Tri-Axial prosthesis?
50N (unlikely to happen)
What is the principle of unconstrained elbow joint replacements?
Resurface lower end of the humerus and the olecranon - aim to reproduce anatomical structure to achieve normal elbow function and contribute to joint stability
Give 3 examples of unconstrained elbow prostheses
Ewald (capitellocondylar)
Kudo
Souter-Strathclyde
What are the 2 components of the Souter-Strathclyde prosthesis and what are they made of?
Humeral component - Vitallium
Ulnar component - HDP polyethylene
What is the success rate of the Souter-Strathclyde prosthesis?
Around 90% of patients achieve a good or excellent result
Examples of radial head resurfacingprostheses
Pritchard
Voltz
What are the 3 components of the Pritchard prosthesis
Metal humeral component (Replaces articulating surfaces of the trochlea and capitellum)
Ulnar component - metal stemmed base and polyethylene spacer (replaces articulating surface of the ulna)
Radial component - metal stemmed base and polyethylene spacer replaces articulating surfaces of the radius)
Why are polyethylene spacers supplied in various thicknesses?
So surgeons can select the correct size for optimum joint stability
Why are the Voltz and modified Capitellocondylar prostheses no longer recommended for use?
Unsatisfactory rates of loosening and dislocation
