Carpal Instability
Chris Oliver FRCS (Orth) DM Royal Infirmary of Edinburgh http://www.orthopaedic.ed.ac.uk c.w.oliver@ed.ac.uk
Definition Carpal Instability ?
carpal injury where loss of normal alignment of the carpal bones develops “inability to bear physiological load” with an associated loss of normal carpal alignment carpal dysfunction
Key Issue ~ Carpal Instability
“instability” versus “malalignment”
Key Issue ~ Carpal Instability
static versus dynamic
kinetic versus kinematic
Epidemiology Carpal Instability
10% of all carpal injuries result in instability
Aetiology ~ Carpal Instability
variable congenital trauma
after “sprain” fracture+/- dislocation end stage of mal or non-union
rheumatoid arthritis neoplastic
Pathomechanics Carpal Instability
intercalated segment
lunate is in state of dynamic balance scaphoid induced to flex under compressive load and induces flexion force on lunate triquetral inherently prefers to extend and induces extension force on lunate dynamic balance interrupted, lunate follows unbalanced force
Instability Patterns
Classification
Complex Amadio (1991) dissociative carpal Instability CID non-dissociative instability CIND
complex carpal instability CIC
adaptive carpal instability CIA
Groups CID
carpal instability dissociative Instability due to loss of linkage between individual carpal bones bones of same row short ligaments Includes DISI and VISI
Unstable scaphoid non-union
Proximal CID DISI pattern of carpal malalignment volar wedge shaped graft
Groups CIND
nondissociative carpal instability dysfunction between rows longer ligaments instability at radiocarpal or midcarpal joints
Groups CIC
carpal instability complex CID & CIND perilunate dislocation instabilities not otherwise classifiable
Groups CIA
adaptive carpal instability instability not in wrist malunited wrist #
Treatment of Carpal Instability
no single treatment (Larsen 1995) chronicity constancy aetiology location direction pattern
Proximal Dissociative Carpal Instability
unstable scaphoid non-union scapholunate dissociation lunotriquetral dissociation
Unstable Scaphoid Malunion
proximal scaphoid # follows unconstrained lunate and triquetrum and rotates into extension DISI zigzag radiolunatocapitate alignment
treat the scaphoid fracture Most common
Scapholunate Instability
complete disruption of SL ligament scaphoid rotates around the radiocapitate ligaments repair dorsal portion of SL interosseous membrane stabilise with K wires two months
Chronic SL instability
degenerative changes midcarpal fusion with resection of scaphoid SLAC procedure
Intermediate SL dissociation
no degenerative changes fusion scaphoid-trapezium-trapezoid fuse midcarpal joint arthroscopic repair
Lunotriquetral dissociation
dissociative VISI loss of ulnar support from triquetral lunate flexes palmar flexion of lunate less common acute repair late lunotriquetral arthrodesis
Dissociative Distal Carpal Instability CID
very rare
rupture of transverse ligaments, distal row axial radial, axial ulnar, axial-radial-ulnar repair/fuse
Non-dissociative radiocarpal instability
dorsally malunion of distal radius
not a true carpal instability
adaptive
corrective osteotomy
Other Carpal Instabilities
midcarpal non-dissociative instability
soft tissue reconstructions
combined radiocarpal and midcarpal
CLIP capito-lunate
carpal instability complex
failed treatment for perilunate dislocation
Reference
The treatment of wrist instability
ICL - JBJS(b) ~ July 97 Garcia-Elias 684-690
End