Loss of normal ligamentous and / or bony constraints of wrist




Overall alignment maintained by extrinsic and intrinsic  ligaments


1.  Intrinsic ligaments


Carpal bone to carpal bone

- support the lunate in a balanced position


A.  Scapho-lunate ligaments


SL ligament can be divided into three different zones

- dorsal ligamentous zone (structurally the most important)

- palmar ligamentous zone 

- proximal membranous fibrocartilaginous zone


B.  Luno-triquetral ligaments 

- also 3 components

- volar most strong


2.  Extrinsic Ligaments


Radius to carpus 

- obliquely oriented

- resist the tendency of the carpus to migrate ulnarly and palmarly


A.  Palmar extrinsic ligaments


A. Radioscaphocapitate ligament

B. Radiolunate ligament

C. Radioscapholunate ligament

- probably just a vascular fold

D. Ulnocarpal ligaments

E. Lunotriquetral ligament


Space of Poirier

- weak area of the palmar ligaments


B.  Dorsal Extrinsics


A. Dorsal radiotriquetral ligament / Dorsal radiocarpal ligament (DRC)

B. Dorsal radioulnar ligament

C. Triquetroscaphoid ligament / Dorsal intercarpal ligament (DIC)


No tendons attach to proximal row



- acess to dorsal carpus

- raise a radially based flap

- between radiotriquetral and triquetroscaphoid

- between DRC and DIC






Capitate is centre of rotation


Flexion / Extension

- 120o

- 50% midcarpal

- 50% radiocarpal


Radial / ulna deviation

- 60% midcarpal

- 40% radiocarpal


Radial deviation

- 20o

- proximal row and scaphoid flexes


Ulnar deviation

- 30o

- proximal row and scaphoid extends


Load transfer


Radius 80%

Ulna 20% (all via TFCC)




Division of the scapholunate ligament 

- allows the lunate to follow the triquetrum's unrestrained position of extension

- dorsal intercalated segmental instability pattern (DISI)

- scaphoid flexes, lunate extends


Lunotriquetral ligament disruption 

- allows the lunate to follow the scaphoid into its position of unrestrained flexion

- lunate flexes

- volar intercalated segmental instability pattern (VlSI)


Classification of Carpal Instabilities (Amadio)


I. Carpal instability dissociative (CID)


Transverse injury


Injury inter-osseous ligaments

- within the carpal rows

- disassociative rather than associative motion between the bones of each row


A.Dorsiflexion (DISI)

- scapholunate ligament injury


B. Palmar flexion (VISI)

- triquetrolunate injury


II. Carpal instability non-dissociative (CIND)


Transverse injury


Normal associative motion between the bones of each carpal row 

- the dissociation is between rows


A. Radiocarpal Dislocation


CIND Dislocated Radiocarpal Joint APDislocated Radiocarpal Joint lateral


Radiocarpal Dislocation CT 1Radiocarpal Dislocation CT 2Radiocarpal Dislocation CT 3


B. Midcarpal


C. Ulnar Translocation




Secondary to radial malunion

- treat with radial osteotomy if symptomatic


DISI CIND Secondary Radial Fracture




Secondary to ligamentous laxity

- non operative treatment

- no progression to OA


Whole proximal row is flexed

- lunate triangular

- scaphoid cortical ring sign

- no SL disassociation


III. Carpal instability complex (CIC)


Hyperextension injury


As the hand is forced into hyperextension

- ulnar deviation and intercarpal supination

- the ligamentous disruption


Mayfield Cadaver study 

- extend, ulna deviate, supinate


Stage 1 

- SL dissociation 


Stage 2

- CL dissociation 

- capitate dislocates


Stage 3

-  LT dissociation


Stage 4

-  Lunate dislocates




A. Perilunate Dislocation

1. Dorsal (10%)

2. Volar (90%)


B. Trans-scaphoid Perilunate


IV. Carpal instability longitudinal (axial)


Longitudinal injury


The carpus may also be disrupted in a longitudinal fashion, as opposed to the perilunate transverse pattern




A.  Axial Ulnar (AU)

B.  Axial Radial (AR)

C. Axial Ulnar-Radial (AUR) / Combined


These are severe injuries

- crush, blast or compression

- may be open injuries

- not a diagnostic dilemma


Usually wrist is split into two columns

- metacarpals follow their corresponding carpus




Deal with wounds and nerve / tendon injuries


K wire fixation


Greater and Lesser Arc Injuries


Greater arc injury

- fracture-dislocation of the scaphoid, capitate, hamate, triquetrum

- may include radial styloid


Lesser arc injury 

- a pure ligamentous injury

- around the lunate