Elbow Replacement Flashcards
Describe a first generation elbow replacement
simple uniaxial hinges
Dee prosthesis
What is the main indication for elbow replacement?
pain relief
secondary - stability restoration
What 3 articulations make up the elbow?
humeroulnar
humeroradial
proximal radioulnar
To what degree of valgus is the forearm positioned while in anatomical position?
10-15 degrees
What problem does the slight valgus angulation of the forearm cause fo uniaxial prostheses?
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
What ROM is required for the elbow to perform activities of daily living?
30-130 flexion
50 supination/pronation
What provides stability at the elbow joint?
congruence of surfaces
soft tissues
In flexion, which elbow ligament provides most stability (50+%)
medial collateral ligament
Why is it important to preserve soft tissues at the elbow?
much stability is conferred from surrounding ligaments, muscles and joint capsules
How is loading on the elbow dependent in some ways on the stiffness of the shoulder joint?
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.
What two main problems are seen in uniaxial hinged elbow prostheses?
loosening of parts
requirement of removal of a large amount of bone stock
In the early metal-metal prostheses designed by Dee, what was a contributory factor to loosening?
constraint to uniaxial motion creates large shear forces at the bone-cement interface
high volume of wear debris
What two groups can second generation prostheses be divided into?
semiconstrained
unconstrained
Describe semi constrained elbow replacements
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
What are semi constrained prostheses sometimes called?
sloppy hinges
In what situation are semi constrained prostheses more useful?
some soft tissue insufficiency and some lost bone stock
Name an example of a semi constrained prosthesis
Tri-axial
Describe unconstrained elbow replacements
resurfaced lower end of humerus and olecranon to reproduce anatomical structure
vitallium humeral component
HDP ulnar component
What is required for full stability in unconstrained prostheses?
collateral ligaments intact
What is the supposed benefit of radial head resurfacing?
load transmission stability conferred by the humeroradial articulation
What is the Ewald prosthesis sometimes known as?
capitellocondylar
Name some examples of unconstrained prostheses
Ewald
Kudo
Souter-Strathclyde
Describe a Pritchard elbow replacement
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.
What is an advantage of using spacers?
various thicknesses can be selected so that surgeons can select optimum size for joint stability
