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