Wrist Kinematics Flashcards
What is the carpal height ratio?
It is the distance defined from the base of the third metacarpal to the distal subchondral bone of the radius divided
by the length of the third metacarpal. The normal ratio is 0.54±0.03.
What are the main muscles primarily responsible for wrist motion?
They include the flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis longus and brevis, and extensor carpi ulnaris (ECU).
What is the only muscle that inserts into the carpus?
Flexor carpi ulnaris attaches into the pisiform.
How many degrees of freedom are their pertaining to wrist range of motion?
There are 6 degrees of freedom: flexion, extension, radial deviation, ulnar deviation, pronation, and supination.
What is the intercalated segment within the wrist?
The proximal row (scaphoid, lunate, and triquetrum) is the intercalated segment within the wrist. The bones of the proximal row are less tightly bound together than the distal row and there is approximately three times more motion between the scaphoid and lunate compared to the lunotriquetral joint.
During wrist flexion, the bones of the proximal row go into flexion and ulnar deviation whereas with wrist extension, they go into extension and radial deviation. Similar motion is noted within the distal carpal row albeit with less radial and ulnar deviation as noted with the proximal carpal row during wrist extension and flexion, respectively.
