Unit 5c: Wrist Joint Replacement Flashcards
What are the 2 types of wrst joint prosthesis?
Flexible hinge
Total wrist
What operation is used if only the radiocarpal joint is affected?
Arthrodesis (especially for younger patients)
How many tendons cross the wrist?
24
What is the primary function of the distal radioulnar joint?
Forearm supination and pronation
How does disease of the distal radioulnar joint affect replacement?
If diseased around 1cm of the distal ulna is excised and the remaining distal ulna is carefully stabilised with soft tissues
Where is the composite motion of the wrist centred?
On a fixed point on the capitate
What is the normal range of motion of the wrist?
80-90 flexion
70-80 extension
35 adduction
15-20 abduction
What range of motion is generally satisfcatory for activities of daily living?
10 flexion
35 extension
What position is the wrist set at during arthrodesis?
20-30 extension
What type of joint is the radiocarpal joint?
Condyloid joint
In which movement does the radiocarpal joint provide more stability?
Abduction-adduction
In which movement does the radiocarpal joint have a greater arc of motion?
Flexion-extension
Why does a ball-and-socket type wrist joint have issues with stability?
Does not have radiocarpal joint but instead has a reduced radius of curvature for ab/adduction making it difficult to maintain stability
What is the basic design of a flexible hinge prosthesis?
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
What is the flexble hinged prosthesis made of?
Silicone elastomer (rubber) - with or without titanium bone liners
What is the purpose of the silicone rubber spacer in flexible hinge prosthesis?
Helps to maintain adequate joint space and overall wrist alignment
What is the benefit of the flexible hinged prosthesis?
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
What long terms problems have been found with flexible hinge prostheses?
Radiographic deterioration
Torn on the bone edges of the medullary canal
Subside into radius, crapus or both
Describe the 3 parts of the Meuli prosthesis
Distal component (eccentric prongs that are inserted into the second and third metacarpals)
Twin pronged radial component
Polyethylene ball
What is the disadvantage of the ball-and-socket design of the Meuli prosthesis?
It relies on adequate and proper sot tissue balance to prevent undesirable rotatory motion
What are the advantages of the ball-and-socket Meuli prosthesis
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
What are the 3 parts of the Voltx prosthesis
Metacarpal component (singe stem that is inserted into the 3rd metacarpal)
Single-stem radial component
Polyethylene cup
What is the range of motion of the Voltz prosthesis?
90 flexion-extension
50 abduction-adduction
What problem did pateints develop with the original Meuli and Voltz designs?
Ulnar deviation
What caused ulnar deviation in the original Meuli and Voltz designs?
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
How do the early follow up results for total wrist prostheses compare to those of flexible prostheses?
Similar in terms of pain relief and maintenance of pre-op range of motion
Is loosening more frequent with the Meuli or Voltz design?
Higher incidence of stem loosening in the Meuli
What improvement was made to the Voltz design and gave more positive results in terms of bone resorption?
Change to single stem
