Carpal Instability: Carpal Instability: an overviewan overview
Abdelsalam EidAbdelsalam EidAssistant Professor of Orthopaedic Assistant Professor of Orthopaedic
Surgery.Surgery.
Zagazig UniversityZagazig University
Abdelsalam Eid, Zagazig University
Abdelsalam Eid, Zagazig University
Wrist Stabilizers
Complex interlocking shapesIntrinsic and extrinsic ligaments
Extrinsic ligamentsVolar stronger than dorsal
Intrinsic ligamentsImportant 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
KinematicsWhat 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
Pathomechanics Carpal Instability
intercalated segment lunate is in state of dynamic balancescaphoid 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
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.
MUN ORTHOPEDICS
Carpal instability terminology
dynamic Neg Xray;+ve stress testing e.g.Watson:
+ve cineradiographystatic
+ve plain filmsDegenerativeSecondary
Kienbock’s ; SNAC
Abdelsalam Eid, Zagazig University
Normal wrist
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
Abdelsalam Eid, Zagazig University
Dorsal Intercalated SegmentInstability
Abdelsalam Eid, Zagazig University
Volar Intercalated SegmentInstability
Scaphoid Nonunion
proximal scaphoid pole follows unconstrained lunate and triquetrum and rotates into extension ( hump back deformity)
DISItreat the scaphoid N UMost 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
MUN ORTHOPEDICS
Scapholunate Instability
Chronic SL instability
degenerative changes
SLAC 4 corner fusion with
resection of scaphoidPRC
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Lunotriquetral dissociation
dissociative VISILunate loses support
from triquetrumpalmar flexion of lunate
with the scaphoid less common acute -> repair late -> lunotriquetral
arthrodesisAbdelsalam Eid, Zagazig
University
Groups ...CIND
nondissociative carpal instabilitydysfunction 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
adaptivecorrective osteotomy
Abdelsalam Eid, Zagazig University
Groups CIC
carpal instability complexCID & CIND
perilunate dislocation instabilities not otherwise classifiable
Abdelsalam Eid, Zagazig University
Abdelsalam Eid, Zagazig University
Perilunate Dislocation
Still missed in ERTtt of choice : open
reduction & repair of ligaments/bones
Dorsal and volar approach
Late: fusion or PRC
Thank you.
Abdelsalam Eid, Zagazig University