Chapter 24 - Carpal Instability Flashcards
Which extrinsic wrist ligaments are stronger palmar or dorsal
palmar
palmar radiocarpal ligaments
- radioscaphoid ligament (aka radial collateral ligament)
- radioscaphoicapitate (RSC): connects to the waist of the scaphoid (serves as a point of rotation for the scaphoid), limits the ulnar translation of the carpus
- long radiolunate: helps limit ulnar translation of the carpus
- short radiolunate: controls lunate position
- radioscapholunate: vascular conduit - NOT a true ligament
Palmar ulnocarpal ligaments
- ulnolunate: aattaches to the palmar radioulnar ligament and lunate
- ulnocapitate: attaches to ulnar head - most palmar ligament
- ulnotriquetral: attaches to palmar radioulnar ligament and the triquetrum
Dorsal radiocarpal ligament
also called the dorsal radiotriquetral ligament
- passes from the dorsal rim of the distal radius to the lunate and the triquetrum, fibers insert onto the lunotriquetral interosseous ligament
- can be associated with both volar and dorsal intercalated segment instabilities
Scapholunate interosseous ligament
consists of dorsal, palmar, and interosseous portions - the DORSAL portion of this ligament is the strongest
- provides a FLEXION force on the lunate
Lunotriqutral interosseous ligament
consists of volar, dorsal, and interosseous portions - the VOLAR portion of this ligament is the strongest
- provides a EXTENSION force on the lunate
injury to what palmar wrist ligament causes ulnar translation of the carpus?
Radioscaphocapitate
Scapholunate interoseous ligament - what portion is the thickest/strongest?
Dorsal - disruption leads to disi deformity
Lunotriquetral interosseous ligament - what portion is the thinkest/strongest?
Palmar - disruption leads to visi deformity
with neutral ulnar variance, what percent of axial load is transmitted via the radius vs the ulna
8-% vs 20%
DISI (etiology and diagnosis)
Most commonly 2/2 SLIL injury - causes the lunate to extend with wrist flexion, diagnoses with a SL angle >60 -70, capitolunate/radiolunate angle > 15-30
VISI (etiology and diagnosis)
less common than DISI, 2/2 LTIL disruption (can even be from ulnar impaction, results in lunate flexing with MC flexion, SL angle <30
Perilulate dislocation - forces that cause the dislocation
wrist extension with ulnar deviation and supination
what ligament typically stays intact in a perilunate dislocation?
short rdiolunate ligament
describe the mayfield classification of perilunae injuries
I: SL dissociation/scaphoid fracture, SLIL, and RSC injuries (can causes DISI)
II: lunocapitate dislocation, space of porier torn VOLARLY -> capitate dislocates DORSALLY
III: lunotriquetral disruption/triquetrum fracture - failure of the LTIL, can cause VISI
IV: lunate dislocation from the lunate fossa - disruption of the DRC ligament (short radiolunate remains INTACT)(capitate falls proximally)
SLAC etiology
Untreated SL injury with associated DISI - lunate dorsiflexion and capitate flexion leads to an incongruous MC joint
SLAC stages
I: Radioscaphoid arthritis at the radial styloid
II: degen changes of the entire radioscaphoid articulation (scaphoid fossa, and styloid)
III: radioscaphoid and capitolunate changes
IV: pan carpal changes
Watson scaphoid shift test
wrist moves from ulnar deviation and extension to radial deviation and flexion with pressure applied to the palmar scaphoid tubercle, pain elicited as the scaphoid grinds over the dorsal lip of the radius, and when you release your thumb, the scaphoid will fall back into place palmarly feeling a clunk
XR view for SL injury
AP (rather than PA), with slight supination, and ulnar deviation
