1. Wrist Biomechanics and Carpal Instability
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2. Wrist Biomechanics Anatomy Kinematics Force transmission
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3. Anatomy 8 bones Complex interlocking shapes
Intrinsic and extrinsic ligaments
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4. MUN ORTHOPEDICS

5. Wrist ligaments
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6. Wrist ligaments Volar stronger than dorsal
Double V shape with weak area ; space of Poirier
Important interosseous ligaments are SLIL and LTIL
Dorsal ligaments tend to converge on triquetrum
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7. Kinematics Three axes of motion FEM 90 – 70 degrees
Flex/ext split between radiocarpal & midcarpal
RUD – 50 degrees
PSM – 90 degrees
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8. Axes of Motion
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9. Kinematics Rows Columns (Navarro) Oval ring
Longitudinal columns (Weber)
“Link Joint”
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10. Link Joint
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11. Kinematics Rows Columns Proximal and Distal with scaphoid as a bridge
Motion within and between rows
Columns
Central(flex/ext) lunate,capitate,hamate
Lateral (mobile) scaphoid,trapezoid,trapezium
Medial (rotation) triquetrum
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13. Kinematics
Center of rotation : head of capitate
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14. Kinematics
Radial deviation : scaphoid flexes proximal pole goes dorsal “pulling” lunate into palmar flexion
Ulnar deviation : scaphoid extends proximal pole goes volar pulling lunate into dorsiflexion
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15. Kinematics Triquetrohamate helicoid joint
Ulnar deviation : “low” position distal and dorsiflexed pulling lunate into dorsiflexion
Radial deviation : “high”position proximal and palmar flexed pulling lunate into palmar flexion
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16. Force Transmission
Principal force transmission is through capitate lunate and proximal pole of scaphoid
75% radius 25% ulna
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17. Classification of Carpal Instability
CID (dissociative)
DISI
VISI
CIND (non-dissociative)
Radiocarpal,Midcarpal,Ulnar transloc’n
CIC (complex)
Perilunate Dislocation
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18. Progressive periLunate Instability
Stage I – scapholunate instability
Stage II – capitate dislocation
Stage III – triquetral dislocation
Stage IV – lunate dislocation
Spectrum of injury
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19. PLI
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20. Mechanism of injury
Impact on thenar side of wrist causes hyperextension , ulnar deviation and intercarpal supination
Progressive damage around lunate
Bony or ligamentous
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21. Normal wrist
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22. Volar Intercalated Segment Instability
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23. Dorsal Intercalated Segment Instability
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24. Gilula lines
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25. Carpal Angles
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26. Carpal Height L2/L1 = 0.54 New ratio L2/capitate = 1.57
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27. Scapholunate Instability
Most common form
Rarely diagnosed acutely
Local tenderness
Scaphoid shift(Watson)
Associated with other injuries eg distal radius
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28. Scapholunate Instability: Classification
Type 1 – dynamic
Neg Xray;+ve Watson:+ve cine
Type 2 – static
+ve plain films
Type 3 – degenerative
Type 4 – secondary
Kienbock’s ; SNAC
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29. Scapholunate Instability: Radiographs
Scapholunate gap >2mm
Foreshortened scaphoid
Cortical ring sign
Taliesnik,s “V” sign
Lack of parallelism?
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30. Scapholunate Instability
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31. DISI
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32. Scapholunate Instability
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35. Scapholunate Instability: Treatment
Acute (0-3 wks) : open repair vs arthroscopically-assisted PCP x 8wks
Chronic (>4 wks) : repair + reconstruction
STT
Blatt
SLC
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36. Scapholunate instability
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37. Acute repair SLIL
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38. Blatt Capsulodesis
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39. STT Fusion
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40. STT Arthrodesis
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41. Scapholunate Instability: Arthrosis
SLAC
PRC
Arthrodesis
RSL
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42. Triquetrolunate instabliity
Limited understanding of ulnar side
TL or TH ??
Ulnar pain post injury
Click
+ve ballottement test
Beware ulnar impaction syndrome
Conservative Rx; rarely need limited fusion
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43. VISI
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44. Perilunate Dislocation
Perilunate & Lunate are same basic injury
Still missed in ER
Rx of choice : open reduction & repair of ligaments/bones
Dorsal and volar approach
Late: fusion or PRC
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45. Lesser and Greater arcs
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46. Perilunate Dislocation
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47. Perilunate repair
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48. Ulnar Translocation Rare Difficult to treat
Non-traumatic causes : RA,Madelung’s
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49. Ulnar Translocation
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50. MUN ORTHOPEDICS

51. Carpal Instability: Unresolved Issues
Role of arthroscopy
Method of reconstruction SLIL eg bone-tendon-bone
Ulnar side pathomechanics
Role of MRI
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52. Grade III
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53. Grade IV
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