Wrist Replacement Flashcards
What 2 types of wrist prostheses are there?
flexible hinge
total wrist
What is the main indication for wrist replacement?
pain from OA/RA
What surgical option is typically used instead of arthroplasty in a younger patient with high functional demands?
arthrodesis
why is the DRUJ considered separately?
its primary function is supination and pronation
How many tendons cross the wrist joint?
24
Which bone is the centre of rotation of the wrist located in? What consideration is made in replacement operations as a result?
capitate
the prostheses are precisely positioned so as to protect as much natural motion as possible and ensure better balance between extensors and flexors
How much flexion extension is there in the wrist? adduction-abduction?
80-90 flexion
70-80 extension
35 adduction
15-20 abduction
What wrist movement is particularly important to activities of daily living, resulting in a certain position of fixation in arthrodesis?
extension
the wrist will be set between 20 and 30 degrees of extension in arthrodesis
describe the radoiocarpal joint
condyloid joint
greater radius of curvature for abduction-adduction than for flexion-extension
What is important about the positioning of the tendons through the carpal tunnel?
maintains close proximity to the centre of rotation and thus reduces the moment arm
Describe the flexible hinge prosthesis for the wrist
proximal and distal stem with a barrel shaped midsection
one stem inserted into the medullary canal of the distal radius and the other in the 3rd metacarpal through the partially resected capitate
it is a resection arthroplasty with interposition of a rubber spacer (barrel)
over time new ligamentous systems develop over it and the stems are not fixed, allowing movement in and out of the canals
What material is the flexible hinge prosthesis made from?
high performance silicone elastomer (rubber)
What are grommets used for and what are they made from?
how successful are they?
improve durability by protecting it form sharp bone edges
titanium
similar outcome with or without
What percentage of flexible wrist prostheses have been found to tear on sharp bony edges?
20%
Describe the Mueli TWR
two prongs inserted into the 2nd and 3rd metacarpals
twin pronged radial component
polyethylene ball fixed to the radial component which articulates with the distal component
What is a disadvantage of the Mueli prosthesis?
it relies on adequate and proper soft tissue balance to prevent undesirable rotary motion
Name two advantages of the Mueli ball and socket design
avoids rotational failures
stress on anchorages are reduced because impingement can occur only at the extremes of motion
Describe the Voltz Prosthesis
metacarpal component with a single stem inserted into the third metacarpal
a single stem radial component
polyethylene cup mounted on the radial component and articulates with the metacarpal component
which normal wrist articulation does the Voltz prosthesis replicate?
the radoiocarpal joint
Why did patients with TWRs go on to develop ulnar deviation?
centre of rotation was placed to radially resulting in excessive pull form the ulnar tendons
What are 2 main problems of total wrist replacement?
stem loosening
stress shielding
What is the most frequently indicated hand joint replacement?
Name the two possible types
MCP replacement
flexible hinge
total MCP
what shape of joint is the MCP?
condyloid - ovoid head of the metacarpal and eliptic cavity of the proximal phalanx base
What structures contribute to stabilising the MCP joint?
jont capsule
collateral ligaments
fibrocartilagenous palma r plate
muscle tendons
