Wrist joint replacement Flashcards
what are the two types of wrist joint prosthesis
flexible hinge
total wrist
when is arthrodesis the preferred option?
when only the radiocarpal joint is affected
what is the primary function of the distal radioulnar joint
forearm supination and pronation
where is the overall composite motion thought to be centred in the wrist
a fixed point on the capitate
in arthrodesis what position is the wrist set
20 to 30 degrees of extension
what type of joint is the radoiocarpal joint
condyloid
what is the normal ROM of the wrist joint
80-90 flexion
70-80 extension
35 adduction
15-20 abduction
what is different about the radius of the natural radoiocarpal joint and that of a replacement
naturally there is a greater radius of curvature for abduction-adduction than f-e»_space; more stability in a-a plane. this isn’t reproduced in a replacement making it difficult to maintain stability in the a-a plane
what is important about maintaining the flexor tendons close to the axis of rotation of the wrist
decreases their moment about the wrist joint
what makes up a flexible hinge prosthesis and what material is it constructed of
prox and diet stem + barrel shaped midsection
silicone elastomer (rubber)
with or without titanium bone liners (grommets)
what are the 3 parts of the Meuli prosthesis
distal component with prongs inserted into the 2nd and 3rd metacarpals
twin pronged radial component
polyethylene ball
disadvantage of the ball and socket design
relies on adequate soft tissue balance to prevent unwanted rotary motion
what type of deformities do many patients develop with both Meuli and Voltz designs and why
ulnar deviation due to the prosthetic centre of rotation aligning more radially than the normal wrist’s centre of rotation»_space; increased moment arms of the ulnar wrist tendons
how is wrist rotation prevented in the Meuli prosthesis?
relies upon surrounding soft tissues
what normal wrist articulation does the Voltz prosthesis resemble?
radoiocarpal (larger radius of curvature for a-a)
