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

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Axes of Motion

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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

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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

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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

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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

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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

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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