Unit 5c: Wrist Joint Replacement

Question 1

What are the 2 types of wrst joint prosthesis?

Answer 1

Flexible hinge

Total wrist

Question 2

What operation is used if only the radiocarpal joint is affected?

Answer 2

Arthrodesis (especially for younger patients)

Question 3

How many tendons cross the wrist?

Answer 3

24

Question 4

What is the primary function of the distal radioulnar joint?

Answer 4

Forearm supination and pronation

Question 5

How does disease of the distal radioulnar joint affect replacement?

Answer 5

If diseased around 1cm of the distal ulna is excised and the remaining distal ulna is carefully stabilised with soft tissues

Question 6

Where is the composite motion of the wrist centred?

Answer 6

On a fixed point on the capitate

Question 7

What is the normal range of motion of the wrist?

Answer 7

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

Question 8

What range of motion is generally satisfcatory for activities of daily living?

Answer 8

10 flexion

35 extension

Question 9

What position is the wrist set at during arthrodesis?

Answer 9

20-30 extension

Question 10

What type of joint is the radiocarpal joint?

Answer 10

Condyloid joint

Question 11

In which movement does the radiocarpal joint provide more stability?

Answer 11

Abduction-adduction

Question 12

In which movement does the radiocarpal joint have a greater arc of motion?

Answer 12

Flexion-extension

Question 13

Why does a ball-and-socket type wrist joint have issues with stability?

Answer 13

Does not have radiocarpal joint but instead has a reduced radius of curvature for ab/adduction making it difficult to maintain stability

Question 14

What is the basic design of a flexible hinge prosthesis?

Answer 14

Proximal and distal stem with a barrel-shaped midsection

Prox stem - medullary canal of distal radius
Dist stem - inserted into 3rd metacarpal through partiall resected capitate

Question 15

What is the flexble hinged prosthesis made of?

Answer 15

Silicone elastomer (rubber) - with or without titanium bone liners

Question 16

What is the purpose of the silicone rubber spacer in flexible hinge prosthesis?

Answer 16

Helps to maintain adequate joint space and overall wrist alignment

Question 17

What is the benefit of the flexible hinged prosthesis?

Answer 17

After a period of time a new capsulo-ligamentous system develops around the midsection

The stems are not fixed into bone so during motion the implant not only articulates through the flexible midsection but the stems slide in and out of the intramedullary canals

Question 18

What long terms problems have been found with flexible hinge prostheses?

Answer 18

Radiographic deterioration

Torn on the bone edges of the medullary canal

Subside into radius, crapus or both

Question 19

Describe the 3 parts of the Meuli prosthesis

Answer 19

Distal component (eccentric prongs that are inserted into the second and third metacarpals)

Twin pronged radial component

Polyethylene ball

Question 20

What is the disadvantage of the ball-and-socket design of the Meuli prosthesis?

Answer 20

It relies on adequate and proper sot tissue balance to prevent undesirable rotatory motion

Question 21

What are the advantages of the ball-and-socket Meuli prosthesis

Answer 21

Avoids the possibility of rotational filures of the prosthesis

Stresses on the anchorage of the distal and radial components are reduced because impingement can occur only at the extremes of motion

Question 22

What are the 3 parts of the Voltx prosthesis

Answer 22

Metacarpal component (singe stem that is inserted into the 3rd metacarpal)

Single-stem radial component

Polyethylene cup

Question 23

What is the range of motion of the Voltz prosthesis?

Answer 23

90 flexion-extension

50 abduction-adduction

Question 24

What problem did pateints develop with the original Meuli and Voltz designs?

Answer 24

Ulnar deviation

Question 25

What caused ulnar deviation in the original Meuli and Voltz designs?

Answer 25

Increased moment arms of the ulnar wrist tendons caused by the siting of the prosthetic centre of rotation radial to the normal wrist’s centre of rotation

Question 26

How do the early follow up results for total wrist prostheses compare to those of flexible prostheses?

Answer 26

Similar in terms of pain relief and maintenance of pre-op range of motion

Question 27

Is loosening more frequent with the Meuli or Voltz design?

Answer 27

Higher incidence of stem loosening in the Meuli

Question 28

What improvement was made to the Voltz design and gave more positive results in terms of bone resorption?

Answer 28

Change to single stem