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Wrist Biomechanics and Carpal Instability

Wrist Biomechanics and Carpal Instability. Wrist Biomechanics. Anatomy Kinematics Force transmission. Anatomy. 8 bones Complex interlocking shapes Intrinsic and extrinsic ligaments. Wrist ligaments. Wrist ligaments. Volar stronger than dorsal

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Wrist Biomechanics and Carpal Instability

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  1. Wrist Biomechanicsand Carpal Instability MUN ORTHOPEDICS

  2. Wrist Biomechanics • Anatomy • Kinematics • Force transmission MUN ORTHOPEDICS

  3. Anatomy • 8 bones • Complex interlocking shapes • Intrinsic and extrinsic ligaments MUN ORTHOPEDICS

  4. MUN ORTHOPEDICS

  5. Wrist ligaments MUN ORTHOPEDICS

  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 MUN ORTHOPEDICS

  7. Kinematics • Three axes of motion • FEM 90 – 70 degrees • Flex/ext split between radiocarpal & midcarpal • RUD 20 – 50 degrees • PSM 90 – 90 degrees MUN ORTHOPEDICS

  8. Axes of Motion MUN ORTHOPEDICS

  9. Kinematics • Rows • Columns (Navarro) • Oval ring • Longitudinal columns (Weber) • “Link Joint” MUN ORTHOPEDICS

  10. Link Joint MUN ORTHOPEDICS

  11. Kinematics • Rows • 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 MUN ORTHOPEDICS

  12. MUN ORTHOPEDICS

  13. Kinematics • Center of rotation : head of capitate MUN ORTHOPEDICS

  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 MUN ORTHOPEDICS

  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 MUN ORTHOPEDICS

  16. Force Transmission • Principal force transmission is through capitate lunate and proximal pole of scaphoid • 75% radius 25% ulna MUN ORTHOPEDICS

  17. Classification of Carpal Instability • CID (dissociative) • DISI • VISI • CIND (non-dissociative) • Radiocarpal,Midcarpal,Ulnar transloc’n • CIC (complex) • Perilunate Dislocation MUN ORTHOPEDICS

  18. Progressive periLunate Instability • Stage I – scapholunate instability • Stage II – capitate dislocation • Stage III – triquetral dislocation • Stage IV – lunate dislocation • Spectrum of injury MUN ORTHOPEDICS

  19. PLI MUN ORTHOPEDICS

  20. Mechanism of injury • Impact on thenar side of wrist causes hyperextension , ulnar deviation and intercarpal supination • Progressive damage around lunate • Bony or ligamentous MUN ORTHOPEDICS

  21. Normal wrist MUN ORTHOPEDICS

  22. Volar Intercalated SegmentInstability MUN ORTHOPEDICS

  23. Dorsal Intercalated SegmentInstability MUN ORTHOPEDICS

  24. Gilula lines MUN ORTHOPEDICS

  25. Carpal Angles MUN ORTHOPEDICS

  26. Carpal Height • L2/L1 = 0.54 • New ratio L2/capitate = 1.57 MUN ORTHOPEDICS

  27. Scapholunate Instability • Most common form • Rarely diagnosed acutely • Local tenderness • Scaphoid shift(Watson) • Associated with other injuries eg distal radius MUN ORTHOPEDICS

  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 MUN ORTHOPEDICS

  29. Scapholunate Instability:Radiographs • Scapholunate gap >2mm • Foreshortened scaphoid • Cortical ring sign • Taliesnik,s “V” sign • Lack of parallelism? MUN ORTHOPEDICS

  30. Scapholunate Instability MUN ORTHOPEDICS

  31. DISI MUN ORTHOPEDICS

  32. Scapholunate Instability MUN ORTHOPEDICS

  33. MUN ORTHOPEDICS

  34. MUN ORTHOPEDICS

  35. Scapholunate Instability:Treatment • Acute (0-3 wks) : open repair vs arthroscopically-assisted PCP x 8wks • Chronic (>4 wks) : repair + reconstruction • STT • Blatt • SLC MUN ORTHOPEDICS

  36. Scapholunate instability MUN ORTHOPEDICS

  37. Acute repair SLIL MUN ORTHOPEDICS

  38. Blatt Capsulodesis MUN ORTHOPEDICS

  39. STT Fusion MUN ORTHOPEDICS

  40. STT Arthrodesis MUN ORTHOPEDICS

  41. Scapholunate Instability:Arthrosis • SLAC • PRC • Arthrodesis • RSL MUN ORTHOPEDICS

  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 MUN ORTHOPEDICS

  43. VISI MUN ORTHOPEDICS

  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 MUN ORTHOPEDICS

  45. Lesser and Greater arcs MUN ORTHOPEDICS

  46. Perilunate Dislocation MUN ORTHOPEDICS

  47. Perilunate repair MUN ORTHOPEDICS

  48. Ulnar Translocation • Rare • Difficult to treat • Non-traumatic causes : RA,Madelung’s MUN ORTHOPEDICS

  49. Ulnar Translocation MUN ORTHOPEDICS

  50. MUN ORTHOPEDICS

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