Focused examination for carpal instability including scapholunate dissociation, lunotriquetral instability, DRUJ instability, and provocative testing for dynamic instability patterns.
Carpal instability examination requires understanding the complex carpal ligament anatomy and different instability patterns. Examiners expect you to perform Watson's test correctly, understand the difference between DISI and VISI patterns, and assess the DRUJ systematically.
High-Yield Exam Summary
Intrinsic Ligaments (Between Carpal Bones):
Extrinsic Ligaments (Radius/Ulna to Carpus):
Carpal Rows:
DISI vs VISI Patterns:
DISI (Dorsal Intercalated Segment Instability):
VISI (Volar Intercalated Segment Instability):
Scapholunate Instability:
Lunotriquetral Instability:
DRUJ Instability:
Scapholunate instability
Painful clunk or click as scaphoid subluxates dorsally, or apprehension
Scapholunate ligament injury - scaphoid shifts dorsally due to lack of ligamentous restraint
Ability to detect true positives
Ability to exclude false positives
Watson's Test Interpretation:
SL ligament integrity
Increased translation, pain, or crepitus between scaphoid and lunate
Scapholunate ligament injury or disruption
Ability to detect true positives
Ability to exclude false positives
SL instability screening
Dorsal wrist pain over SL interval
Scapholunate injury (ECRB and ECRL load the scaphoid during finger extension)
Ability to detect true positives
Ability to exclude false positives
Lunotriquetral ligament integrity
Increased laxity, painful crepitus, or click
Lunotriquetral ligament injury
Ability to detect true positives
Ability to exclude false positives
LT instability
Pain at LT interval, click
LT ligament pathology
Ability to detect true positives
Ability to exclude false positives
LT interval assessment
Point tenderness at LT interval
LT ligament injury (nonspecific but helpful localizing sign)
Ability to detect true positives
Ability to exclude false positives
DRUJ stability
Increased dorsal-volar translation compared to contralateral wrist
DRUJ instability (TFCC and/or radioulnar ligament injury)
Ability to detect true positives
Ability to exclude false positives
DRUJ Testing Positions:
Test in all three positions and compare with contralateral side!
DRUJ instability
Ulnar head springs back up like piano key
Dorsal DRUJ instability (dorsal subluxation of ulna)
Ability to detect true positives
Ability to exclude false positives
TFCC integrity
Ulnar-sided wrist pain
TFCC pathology (tear, degeneration)
Ability to detect true positives
Ability to exclude false positives
TFCC and LT assessment
Point tenderness at fovea
TFCC tear at foveal attachment or LT injury
Ability to detect true positives
Ability to exclude false positives
Midcarpal instability
Painful clunk as proximal row shifts from VISI to neutral
Midcarpal instability (extrinsic ligament laxity)
Ability to detect true positives
Ability to exclude false positives
Types:
Clinical Features:
| finding | view | value | indicates |
|---|---|---|---|
| SL Widening | PA | Greater than 3mm (Terry Thomas sign) | SL dissociation |
| Scaphoid Ring Sign | PA | Cortical ring from flexed scaphoid | SL dissociation |
| SL Angle | Lateral | Greater than 70° (DISI) | SL ligament injury |
| SL Angle | Lateral | Less than 30° (VISI) | LT ligament injury |
| Capitolunate Angle | Lateral | Greater than 30° | Carpal instability |
| DRUJ Widening | PA or CT | Asymmetric compared to contralateral | DRUJ instability |
| condition | location | mechanism | keyTest | imaging |
|---|---|---|---|---|
| SL Dissociation | Dorsoradial wrist | FOOSH | Watson's test +ve | SL gap greater than 3mm, DISI |
| LT Instability | Ulnar wrist | FOOSH, rotation | LT ballottement | VISI pattern |
| DRUJ Instability | Distal RU joint | DR fracture, trauma | Ballottement, piano key | DRUJ widening on CT |
| Midcarpal Instability | Central/ulnar | Laxity | Midcarpal shift | May need dynamic views |
| Scaphoid Fracture | Snuffbox | FOOSH | Snuffbox tenderness | Scaphoid views/MRI |
| TFCC Tear | Ulnar wrist | Rotation, load | Fovea sign, press test | MR arthrogram |
"35-year-old woman presents 3 months after a fall on outstretched hand with persistent dorsal wrist pain and clicking."
High-Yield Exam Summary