Definition
Loss of normal ligamentous and / or bony constraints of wrist
Anatomy
Intrinsic ligaments
| Scapho-lunate ligaments | Luno-triquetral ligaments |
|---|---|
| 3 components | 3 components |
|
Dorsal - most important Palmar - thin Proximal membranous fibrocartilaginous zone
|
Volar strongest |
Extrinsic Ligaments
From radius to carpus
- no tendons attach to proximal row
- resist carpal subluxation volar / ulna
Space of Poirier - weak area of the palmar ligaments
| Palmar extrinsic ligaments | Dorsal extrinsic ligaments |
|---|---|
|
Radioscaphocapitate ligament Radiolunate ligament Radioscapholunate ligament Ulnocarpal ligaments Lunotriquetral ligament |
Dorsal radiocarpal ligament (DRC) - dorsal radiotriquetral ligament Dorsal intercarpal ligament (DIC) - triquetroscaphoid ligament Dorsal radioulnar ligament
|
Biomechanics
Center of rotation - capitate
Load transfer - Radius 80% / Ulna 20% (all via TFCC)
| Flexion / Extension | Radial deviation | Ulna deviation |
|---|---|---|
| 120o | 20o | 30o |
|
50% midcarpal 50% radiocarpal |
60% midcarpal 40% radiocarpal |
60% midcarpal 40% radiocarpal |
| Proximal row and scaphoid flexes | Proximal row and scaphoid extends |
Classification of Carpal Instabilities (Amadio)
| I: Carpal instability dissociative (CID) | II: Carpal instability non-dissociative (CIND) |
|---|---|
|
Injury inter-osseous ligaments within the carpal rows Disassociative motion between the bones of each row
|
Dissociation is between rows |
|
Dorsal intercalated segmental instability (DISI) - scapholunate ligament injury - dorsiflexion - scaphoid flexes and lunate extends
|
Radiocarpal dislocation Midcarpal dislocation Ulna translocation |
|
Volar intercalated segmental instability (VISI) - triquetrolunate ligament injury - lunate flexes |
CIND VISI - ligamentous laxity - proximal row flexed
|
| III. Carpal instability complex (CIC) | IV. Carpal instability longitudinal (axial) |
|---|---|
|
Hyperextension injury - perilunate dislocation (90% dorsal) - trans-scaphoid perilunate dislocation |
Longitudinal injuries - axial Ulnar (AU) - axial Radial (AR) - axial Ulnar-Radial (AUR) / Combined |
| Severe high velocity / blast injuries |