Wrist Replacement

Question 1

What 2 types of wrist prostheses are there?

Answer 1

flexible hinge

total wrist

Question 2

What is the main indication for wrist replacement?

Answer 2

pain from OA/RA

Question 3

What surgical option is typically used instead of arthroplasty in a younger patient with high functional demands?

Answer 3

arthrodesis

Question 4

why is the DRUJ considered separately?

Answer 4

its primary function is supination and pronation

Question 5

How many tendons cross the wrist joint?

Answer 5

24

Question 6

Which bone is the centre of rotation of the wrist located in? What consideration is made in replacement operations as a result?

Answer 6

capitate

the prostheses are precisely positioned so as to protect as much natural motion as possible and ensure better balance between extensors and flexors

Question 7

How much flexion extension is there in the wrist? adduction-abduction?

Answer 7

80-90 flexion
70-80 extension
35 adduction
15-20 abduction

Question 8

What wrist movement is particularly important to activities of daily living, resulting in a certain position of fixation in arthrodesis?

Answer 8

extension

the wrist will be set between 20 and 30 degrees of extension in arthrodesis

Question 9

describe the radoiocarpal joint

Answer 9

condyloid joint

greater radius of curvature for abduction-adduction than for flexion-extension

Question 10

What is important about the positioning of the tendons through the carpal tunnel?

Answer 10

maintains close proximity to the centre of rotation and thus reduces the moment arm

Question 11

Describe the flexible hinge prosthesis for the wrist

Answer 11

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

Question 12

What material is the flexible hinge prosthesis made from?

Answer 12

high performance silicone elastomer (rubber)

Question 13

What are grommets used for and what are they made from?

how successful are they?

Answer 13

improve durability by protecting it form sharp bone edges

titanium

similar outcome with or without

Question 14

What percentage of flexible wrist prostheses have been found to tear on sharp bony edges?

Answer 14

20%

Question 15

Describe the Mueli TWR

Answer 15

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

Question 16

What is a disadvantage of the Mueli prosthesis?

Answer 16

it relies on adequate and proper soft tissue balance to prevent undesirable rotary motion

Question 17

Name two advantages of the Mueli ball and socket design

Answer 17

avoids rotational failures

stress on anchorages are reduced because impingement can occur only at the extremes of motion

Question 18

Describe the Voltz Prosthesis

Answer 18

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

Question 19

which normal wrist articulation does the Voltz prosthesis replicate?

Answer 19

the radoiocarpal joint

Question 20

Why did patients with TWRs go on to develop ulnar deviation?

Answer 20

centre of rotation was placed to radially resulting in excessive pull form the ulnar tendons

Question 21

What are 2 main problems of total wrist replacement?

Answer 21

stem loosening

stress shielding

Question 22

What is the most frequently indicated hand joint replacement?

Name the two possible types

Answer 22

MCP replacement

flexible hinge
total MCP

Question 23

what shape of joint is the MCP?

Answer 23

condyloid - ovoid head of the metacarpal and eliptic cavity of the proximal phalanx base

Question 24

What structures contribute to stabilising the MCP joint?

Answer 24

jont capsule
collateral ligaments
fibrocartilagenous palma r plate
muscle tendons