Biomech of Knee & tkr knee

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Biomech of Knee & tkr knee

  1. 1. BIOMECHANICS OF NORMAL & REPLACED KNEE
  2. 2. BIOMECHANICS KNEE :Force closed mechanism HIP :Self closed mechanism
  3. 3. The Axis Of Lower Limb •Vertical Axis •Mechanical Axis •Anatomical Axis of Femur •Anatomical Axis of Tibia
  4. 4. Tibio-Femoral Motion •Flexion – Extension •Abduction – Adduction •Internal – External Rotation
  5. 5. Instantaneous centre of motion FLEXION - EXTENSION
  6. 6. Instantaneous center pathway FLEXION - EXTENSION
  7. 7. Sliding/Rocking
  8. 8. FLEXION - EXTENSION Sliding/Rocking of femur
  9. 9. Gliding/Rolling
  10. 10. FLEXION - EXTENSION Gliding/Rolling of femur
  11. 11. FLEXION - EXTENSION Knee glides & Slides Rocks & Rolls!
  12. 12. ROTATION OF KNEE •Screw home movement •Rotation increases as knee is flexed •Arc ranges 30 – 60
  13. 13. Abduction - Adduction •Normal angulation of 7 Degrees with knee extended •Motion permitted by cruciate and collaterals •No movement in flexion
  14. 14. Flexion 40 0 40Extension HS FF HO TO
  15. 15. Flexion - Extension •Sit & Rise from a chair 90 -110 degrees
  16. 16. Flexion - Extension •Descending stairs 90 degrees
  17. 17. Flexion - Extension •Ascending stairs 82 degrees
  18. 18. Int – Ext Rotation •Normal 30-60 Degrees •13 degrees in normal walking •More in stair walking •More on rough ground walking
  19. 19. Loads Applied to Knee •3X - in Level Walking •4X – in Stair Climbing •Area of Contact is less in Flexion •Medial side bears more weight
  20. 20. STABILITY •Surface geometry •Muscles crossing the joint •Ligaments and capsule •Menisci
  21. 21. SURFACE GEOMETRY Femur is convex Tibia is concave medially Tibia is convex laterally Tibial eminence aids in stability
  22. 22. •Resists deforming force •Resists slow forces •Increase joint compression •Increase stability MUSCLES
  23. 23. •Resists motion •Resists translatory movement •Resists excessive rotation LIGAMENTS
  24. 24. •Joint conformity •Varus valgus stability •Resists translation MENISCUS
  25. 25. IDEAL KNEE • Extends fully & achieves excellent stability • Flexes beyond 110 & still retains stability • Gliding and sliding occurs simultaneously • Allows more rotation as knee flexes • Articular contact maximum throughout range
  26. 26. • Reduplicate the function of menisci • Reduplicate the function of cruciates • Achieve excellent ligament balance • Have anatomic femur & tibial surface IDEAL KNEE
  27. 27. RESTORATION OF MECHANICAL AXIS
  28. 28. RESTORATION OF MECHANICAL AXIS Perpendicular to the Mechanical & Anatomical axis of the Tibia
  29. 29. BIOMECHANICS OF TKR Should none, one or both cruciate ligaments be sacrificed
  30. 30. ACL & PCL SACRIFICED • Conforming concave surface of tibia producing inherent stability • Long term results from HSS still remains the gold standard
  31. 31. • Limited knee motion • Tibial component subluxated posteriorly • Stair climbing was difficult TOTAL CONDYLAR DESIGNS
  32. 32. TOTAL CONDYLAR DESIGNS
  33. 33. RETAIN THE PCL • PCL roll back in flexion • Roll back needs flat tibial surface
  34. 34. ROLL BACK WITH PCL
  35. 35.  More arc of motion  Intact PCL prevents post subluxation of tibia  Stability is increased  Decreased interface stresses  Shear forces are well tolerated RETAIN THE PCL
  36. 36. • Proprioception is better • Retention of PCL helps in maintaining the joint line RETAIN THE PCL
  37. 37. Why surgeon sacrifices PCL? • Minimum tibial resection • Easier surgical technique • Easier correction of deformity
  38. 38. PCL SUBSTITUTING KNEE • Spine & Cam mechanism • Produces roll back • Prevents posterior subluxation
  39. 39. • Anterior tibial subluxation not prevented • Does not substitute collaterals • Posterior slope in tibia necessary PCL SUBSTITUTING KNEE
  40. 40. PCL SUBSTITUTING KNEE
  41. 41. PCL SUBSTITUTING KNEE • Bad for valgus knee • Wear of spine • Bone loss
  42. 42. Can we substitute the PCL by ultra congruent insert ? PCL SUBSTITUTING KNEE
  43. 43. PCL SUBSTITUTING KNEE • Patellectomy • Old PCL injury • Over release of PCL • Inflammatory conditions ?
  44. 44. MENISCAL BEARING KNEE • ACL, PCL retaining • PCL retaining
  45. 45. ROTATING PLATFORM KNEE • Cruciate sacrificing • Spin off • Undersurface wear
  46. 46. FEMUR • Anatomic • Decrease radius of curvature posteriorly
  47. 47. EXTERNAL ROTATION OF FEMUR
  48. 48. EXTERNAL ROTATION OF FEMUR
  49. 49. EXTERNAL ROTATION OF FEMUR
  50. 50. TIBIAL TRAY • Concave conforming • No rotation in extension • Intercondylar eminence to prevent translocation • Anterior Posterior margin equal height
  51. 51. •Anatomic TIBIAL TRAY
  52. 52. PATELLA
  53. 53. PATELLA
  54. 54. Recent thoughts… • Adductor moment • Rotatory arthritis of knee (RAK) • Does tibia really slope posteriorly?
  55. 55. Adductor Moment
  56. 56. Rotatory Arthritis of Knee • Deformities in Knee are triplanar – frontal, saggital & coronal • ACL ‘s role • Soft tissue involvement
  57. 57. Posterior slope of tibia

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