Carpal Instability: an overview
Abdelsalam Eid
Assistant Professor of Orthopaedic
Surgery.
Zagazig University
Abdelsalam Eid, Zagazig
University
Wrist Stabilizers
Complex interlocking shapes
Intrinsic and extrinsic ligaments
Extrinsic ligaments
Volar stronger than dorsal
Intrinsic ligaments
Important interosseous ligaments are SLIL and LTIL
Abdelsalam Eid, Zagazig
University
Axes of Motion
Abdelsalam Eid, Zagazig
University
Kinematics
Rows
Proximal and Distal with scaphoid as a bridge
Motion within and between rows
Columns
Central(flex/ext) lunate,capitate,hamate
Lateral (longitudinal stability)
scaphoid,trapezoid,trapezium
Medial (rotation) triquetrum
Abdelsalam Eid, Zagazig
University
Kinematics
Center of rotation : head of capitate
Abdelsalam Eid, Zagazig
University
Force Transmission
Principal force transmission is through
capitate lunate and proximal pole of
scaphoid
75% radius 25% ulna
Abdelsalam Eid, Zagazig
University
Kinematics
What happens when the wrist moves
 Radial deviation : scaphoid flexes “pulling” lunate into palmar
flexion
 Ulnar deviation : scaphoid extends pulling lunate into dorsiflexion
 Triquetrohamate helicoid joint
 Ulnar deviation : hamate rotates into “low” position distal causing
the triquetrum to dorsiflex pulling lunate into dorsiflexion
 Radial deviation : : hamate rotates into “high”position proximal
causing the triquetrum to palmar flex pulling lunate into palmar
flexion
 So in conclusion, in radial deviation the proximal row flexes and in
ulnar deviation it extends
Abdelsalam Eid, Zagazig
University
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
Abdelsalam Eid, Zagazig
University
Abdelsalam Eid, Zagazig
University
Definition~ Carpal Instability
Carpal malalignment caused by injury
or disease
Abdelsalam Eid, Zagazig
University
Classification of Carpal
Instability
 CID (dissociative)
DISI
VISI
 CIND (non-dissociative)
Radiocarpal,Midcarpal,Ulnar translocation
 CIC (complex)
Perilunate Dislocation
 CIA (adaptive)
instability not in carpus
malunited wrist fr.
Abdelsalam Eid, Zagazig
University
Carpal instability terminology
dynamic
Neg Xray;+ve stress testing e.g.Watson:+ve
cineradiography
static
 +ve plain films
Degenerative
Secondary
Kienbock’s ; SNAC
MUN ORTHOPEDICS
Normal wrist
Abdelsalam Eid, Zagazig
University
Groups ...CID
 carpal instability dissociative
 Instability due to loss of linkage between individual carpal bones
 bones of same row
 short ligaments
 Proximal Dissociative Carpal Instability (DISI and VISI)
 unstable scaphoid non-union
 scapholunate dissociation
 lunotriquetral dissociation
 Distal Dissociative Carpal Instability CID
 very rare
 rupture of ligaments of distal row
 Acute -> repair/ Chronic ->fuse
Abdelsalam Eid, Zagazig University
Dorsal Intercalated Segment
Instability
Abdelsalam Eid, Zagazig
University
Volar Intercalated Segment
Instability
Abdelsalam Eid, Zagazig
University
Scaphoid Nonunion
proximal scaphoid pole follows unconstrained
lunate and triquetrum and rotates into
extension ( hump back deformity)
DISI
treat the scaphoid N U
Most common
Abdelsalam Eid, Zagazig
University
Scapholunate Instability
 complete disruption of SL ligament
 scaphoid flexes
 lunate and triquetrum rotate into
extension
 DISI
 Recent -> Open and repair dorsal
portion of SL interosseous lig.
 stabilise with K wires two months
Abdelsalam Eid, Zagazig
University
Scapholunate Instability
MUN ORTHOPEDICS
Chronic SL instability
degenerative
changes
SLAC
4 corner fusion with
resection of scaphoid
PRC
Abdelsalam Eid, Zagazig
University
Lunotriquetral dissociation
dissociative VISI
Lunate loses support
from triquetrum
palmar flexion of
lunate with the
scaphoid
less common
acute -> repair
late -> lunotriquetral
Abdelsalam Eid, Zagazig
University
arthrodesis
Groups ...CIND
nondissociative carpal instability
dysfunction between rows

instability at radiocarpal or midcarpal
joints
Abdelsalam Eid, Zagazig
University
Non-dissociative radiocarpal
instability
dorsal malunion of
distal radius
not a true carpal
instability
adaptive
corrective osteotomy
Abdelsalam Eid, Zagazig
University
Groups CIC
carpal instability complex
CID & CIND
perilunate dislocation
instabilities not otherwise classifiable
Abdelsalam Eid, Zagazig
University
Perilunate Dislocation
Still missed in ER
Ttt of choice : open
reduction & repair of
ligaments/bones
Dorsal and volar
approach
Late: fusion or PRC
Abdelsalam Eid, Zagazig
University
Thank you.
Abdelsalam Eid, Zagazig
University