Carpal Instability: an overview

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Carpal Instability an overview

• Abdelsalam EidAssistant Professor of Orthopaedic
  Surgery.
• Zagazig University

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Wrist Stabilizers

• Complex interlocking shapes
• Intrinsic and extrinsic ligaments
• Extrinsic ligaments
• Volar stronger than dorsal
• Intrinsic ligaments
• Important 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

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Kinematics

• Center of rotation head of capitate

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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
  highposition 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

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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

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Definition Carpal Instability

• Carpal malalignment caused by injury or disease

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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.

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Carpal instability terminology

• dynamic
• Neg Xrayve stress testing e.g.Watsonve
  cineradiography
• static
• ve plain films
• Degenerative
• Secondary
• Kienbocks SNAC

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Normal wrist
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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 -gt repair/ Chronic -gtfuse

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Dorsal Intercalated SegmentInstability
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Volar Intercalated SegmentInstability
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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

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Scapholunate Instability

• complete disruption of SL ligament
• scaphoid flexes
• lunate and triquetrum rotate into extension
• DISI
• Recent -gt Open and repair dorsal portion of SL
  interosseous lig.
• stabilise with K wires two months

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Scapholunate Instability
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Chronic SL instability

• degenerative changes
• SLAC
• 4 corner fusion with resection of scaphoid
• PRC

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Lunotriquetral dissociation

• dissociative VISI
• Lunate loses support from triquetrum
• palmar flexion of lunate with the scaphoid
• less common
• acute -gt repair
• late -gt lunotriquetral arthrodesis

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Groups ...CIND

• nondissociative carpal instability
• dysfunction between rows
• instability at radiocarpal or midcarpal joints

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Non-dissociative radiocarpal instability

• dorsal malunion of distal radius
• not a true carpal instability
• adaptive
• corrective osteotomy

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Groups CIC

• carpal instability complex
• CID CIND
• perilunate dislocation
• instabilities not otherwise classifiable

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Perilunate Dislocation

• Still missed in ER
• Ttt of choice open reduction repair of
  ligaments/bones
• Dorsal and volar approach
• Late fusion or PRC

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Thank you.