Chapter 24 - Carpal Instability

Question 1

Which extrinsic wrist ligaments are stronger palmar or dorsal

Answer 1

palmar

Question 2

palmar radiocarpal ligaments

Answer 2

• 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

Question 3

Palmar ulnocarpal ligaments

Answer 3

• 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

Question 4

Dorsal radiocarpal ligament

Answer 4

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

Question 5

Scapholunate interosseous ligament

Answer 5

consists of dorsal, palmar, and interosseous portions - the DORSAL portion of this ligament is the strongest
- provides a FLEXION force on the lunate

Question 6

Lunotriqutral interosseous ligament

Answer 6

consists of volar, dorsal, and interosseous portions - the VOLAR portion of this ligament is the strongest
- provides a EXTENSION force on the lunate

Question 7

injury to what palmar wrist ligament causes ulnar translation of the carpus?

Answer 7

Radioscaphocapitate

Question 8

Scapholunate interoseous ligament - what portion is the thickest/strongest?

Answer 8

Dorsal - disruption leads to disi deformity

Question 9

Lunotriquetral interosseous ligament - what portion is the thinkest/strongest?

Answer 9

Palmar - disruption leads to visi deformity

Question 10

with neutral ulnar variance, what percent of axial load is transmitted via the radius vs the ulna

Answer 10

8-% vs 20%

Question 11

DISI (etiology and diagnosis)

Answer 11

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

Question 12

VISI (etiology and diagnosis)

Answer 12

less common than DISI, 2/2 LTIL disruption (can even be from ulnar impaction, results in lunate flexing with MC flexion, SL angle <30

Question 13

Perilulate dislocation - forces that cause the dislocation

Answer 13

wrist extension with ulnar deviation and supination

Question 14

what ligament typically stays intact in a perilunate dislocation?

Answer 14

short rdiolunate ligament

Question 15

describe the mayfield classification of perilunae injuries

Answer 15

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)

Question 16

SLAC etiology

Answer 16

Untreated SL injury with associated DISI - lunate dorsiflexion and capitate flexion leads to an incongruous MC joint

Question 17

SLAC stages

Answer 17

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

Question 18

Watson scaphoid shift test

Answer 18

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

Question 19

XR view for SL injury

Answer 19

AP (rather than PA), with slight supination, and ulnar deviation