biomech of knee & tkr knee
TRANSCRIPT
BIOMECHANICSOF
NORMAL &
REPLACED KNEE
BIOMECHANICSOF
NORMAL &
REPLACED KNEE
BIOMECHANICSBIOMECHANICS
KNEE :Force closed mechanism
HIP :Self closed mechanism
The Axis Of Lower Limb
The Axis Of Lower Limb
•Vertical Axis•Mechanical Axis•Anatomical Axis of Femur
•Anatomical Axis of Tibia
•Vertical Axis•Mechanical Axis•Anatomical Axis of Femur
•Anatomical Axis of Tibia
Tibio-Femoral Motion
Tibio-Femoral Motion•Flexion – Extension
•Abduction – Adduction
•Internal – External Rotation
•Flexion – Extension
•Abduction – Adduction
•Internal – External Rotation
Instantaneous centre of motion
Instantaneous centre of motion
FLEXION - EXTENSIONFLEXION -
EXTENSION
Instantaneous center pathway
Instantaneous center pathway
FLEXION - EXTENSIONFLEXION -
EXTENSION
Sliding/RockingSliding/Rocking
FLEXION - EXTENSIONFLEXION -
EXTENSION
Sliding/Rocking of femurSliding/Rocking of femur
Gliding/Rolling
FLEXION - EXTENSIONFLEXION -
EXTENSION
Gliding/Rolling of femur
FLEXION - EXTENSIONFLEXION -
EXTENSION
Knee glides & SlidesRocks & Rolls!
Knee glides & SlidesRocks & Rolls!
ROTATION OF KNEEROTATION OF KNEE
•Screw home
movement
•Rotation increases
as knee is flexed
•Arc ranges 30 – 60
•Screw home
movement
•Rotation increases
as knee is flexed
•Arc ranges 30 – 60
Abduction - AdductionAbduction - Adduction•Normal angulation
of 7 Degrees with knee extended
•Motion permitted by cruciate and collaterals
•No movement in flexion
•Normal angulation of 7 Degrees with knee extended
•Motion permitted by cruciate and collaterals
•No movement in flexion
FlexionFlexion40
0
40ExtensionExtension
HS
FFFF
HO
TOTO
Flexion - ExtensionFlexion - Extension
•Sit & Rise from a chair90 -110 degrees
•Sit & Rise from a chair90 -110 degrees
Flexion - ExtensionFlexion - Extension
•Descending stairs 90 degrees•Descending stairs 90 degrees
Flexion - ExtensionFlexion - Extension
•Ascending stairs 82 degrees•Ascending stairs 82 degrees
Int – Ext RotationInt – Ext Rotation
•Normal 30-60 Degrees
•13 degrees in normal walking
•More in stair walking•More on rough
ground walking
•Normal 30-60 Degrees
•13 degrees in normal walking
•More in stair walking•More on rough
ground walking
Loads Applied to Knee
Loads Applied to Knee
•3X - in Level Walking•4X – in Stair Climbing•Area of Contact is less in Flexion•Medial side bears more weight
•3X - in Level Walking•4X – in Stair Climbing•Area of Contact is less in Flexion•Medial side bears more weight
STABILITYSTABILITY• Surface geometry• Muscles
crossing the joint
• Ligaments and capsule
• Menisci
• Surface geometry• Muscles
crossing the joint
• Ligaments and capsule
• Menisci
SURFACE GEOMETRYSURFACE
GEOMETRY
Femur is convexTibia is concave mediallyTibia is convex laterally
Tibial eminence aids in stability
Femur is convexTibia is concave mediallyTibia is convex laterally
Tibial eminence aids in stability
•Resists deforming force
•Resists slow forces
•Increase joint compression
•Increase stability
•Resists deforming force
•Resists slow forces
•Increase joint compression
•Increase stability
MUSCLES
MUSCLES
•Resists motion
•Resists translatory movement
•Resists excessive rotation
•Resists motion
•Resists translatory movement
•Resists excessive rotation
LIGAMENTSLIGAMENTS
•Joint conformity
•Varus valgus stability
•Resists translation
•Joint conformity
•Varus valgus stability
•Resists translation
MENISCUSMENISCUS
IDEAL KNEEIDEAL 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
• 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
• Reduplicate the function of menisci
• Reduplicate the function of cruciates
• Achieve excellent ligament balance
• Have anatomic femur & tibial surface
• Reduplicate the function of menisci
• Reduplicate the function of cruciates
• Achieve excellent ligament balance
• Have anatomic femur & tibial surface
IDEAL KNEEIDEAL KNEE
RESTORATION OF MECHANICAL AXISRESTORATION OF MECHANICAL AXIS
RESTORATION OF MECHANICAL AXISRESTORATION OF MECHANICAL AXIS
Perpendicular to the Mechanical & Anatomical axis of the Tibia
Perpendicular to the Mechanical & Anatomical axis of the Tibia
BIOMECHANICS OF TKR
BIOMECHANICS OF TKR
Should none, one or both cruciate ligaments be sacrificed
Should none, one or both cruciate ligaments be sacrificed
ACL & PCL SACRIFICEDACL & PCL
SACRIFICED• Conforming
concave surface of tibia producing inherent stability
• Long term results from HSS still remains the gold standard
• Conforming concave surface of tibia producing inherent stability
• Long term results from HSS still remains the gold standard
• Limited knee motion• Tibial component
subluxated posteriorly• Stair climbing was
difficult
• Limited knee motion• Tibial component
subluxated posteriorly• Stair climbing was
difficult
TOTAL CONDYLAR DESIGNS
TOTAL CONDYLAR DESIGNS
TOTAL CONDYLAR DESIGNS
TOTAL CONDYLAR DESIGNS
RETAIN THE PCLRETAIN THE PCL
• PCL roll back in flexion
• Roll back needs flat tibial surface
• PCL roll back in flexion
• Roll back needs flat tibial surface
ROLL BACK WITH PCLROLL BACK WITH PCL
More arc of motion Intact PCL prevents post
subluxation of tibia Stability is increased Decreased interface
stresses Shear forces are well
tolerated
More arc of motion Intact PCL prevents post
subluxation of tibia Stability is increased Decreased interface
stresses Shear forces are well
tolerated
RETAIN THE PCLRETAIN THE PCL
• Proprioception is better
• Retention of PCL helps in
maintaining the joint line
• Proprioception is better
• Retention of PCL helps in
maintaining the joint line
RETAIN THE PCLRETAIN THE PCL
Why surgeon sacrifices PCL?
Why surgeon sacrifices PCL?
• Minimum tibial resection • Easier surgical technique• Easier correction of
deformity
• Minimum tibial resection • Easier surgical technique• Easier correction of
deformity
PCL SUBSTITUTING KNEE
PCL SUBSTITUTING KNEE
• Spine & Cam mechanism
• Produces roll back
• Prevents posterior subluxation
• Spine & Cam mechanism
• Produces roll back
• Prevents posterior subluxation
• Anterior tibial subluxation not prevented
• Does not substitute collaterals
• Posterior slope in tibia necessary
• Anterior tibial subluxation not prevented
• Does not substitute collaterals
• Posterior slope in tibia necessary
PCL SUBSTITUTING KNEE
PCL SUBSTITUTING KNEE
PCL SUBSTITUTING KNEE
PCL SUBSTITUTING KNEE
PCL SUBSTITUTING KNEE
PCL SUBSTITUTING KNEE• Bad for valgus knee
• Wear of spine
• Bone loss
• Bad for valgus knee
• Wear of spine
• Bone loss
Can we substitute the PCL by ultra congruent insert ?
Can we substitute the PCL by ultra congruent insert ?
PCL SUBSTITUTING KNEEPCL SUBSTITUTING KNEE
PCL SUBSTITUTING KNEEPCL SUBSTITUTING KNEE• Patellectomy
• Old PCL injury
• Over release of PCL
• Inflammatory conditions ?
• Patellectomy
• Old PCL injury
• Over release of PCL
• Inflammatory conditions ?
MENISCAL BEARING KNEE
MENISCAL BEARING KNEE
• ACL, PCL retaining• PCL retaining
• ACL, PCL retaining• PCL retaining
ROTATING PLATFORM KNEE
ROTATING PLATFORM KNEE
• Cruciate sacrificing
• Spin off
• Undersurface wear
• Cruciate sacrificing
• Spin off
• Undersurface wear
FEMURFEMUR• Anatomic• Decrease
radius of curvature posteriorly
• Anatomic• Decrease
radius of curvature posteriorly
EXTERNAL ROTATION OF FEMUR
EXTERNAL ROTATION OF FEMUR
EXTERNAL ROTATION OF FEMUR
EXTERNAL ROTATION OF FEMUR
EXTERNAL ROTATION OF FEMUR
EXTERNAL ROTATION OF FEMUR
TIBIAL TRAYTIBIAL TRAY
• Concave conforming
• No rotation in extension
• Intercondylar eminence to prevent translocation
• Anterior Posterior margin equal height
• Concave conforming
• No rotation in extension
• Intercondylar eminence to prevent translocation
• Anterior Posterior margin equal height
•Anatomic•Anatomic
TIBIAL TRAYTIBIAL TRAY
PATELLAPATELLA
PATELLAPATELLA
Recent thoughts…Recent thoughts…• Adductor moment• Rotatory arthritis
of knee (RAK)• Does tibia really
slope posteriorly?
• Adductor moment• Rotatory arthritis
of knee (RAK)• Does tibia really
slope posteriorly?
Adductor MomentAdductor Moment
Rotatory Arthritis of KneeRotatory Arthritis of Knee
• Deformities in Knee are triplanar – frontal, saggital & coronal
• ACL ‘s role• Soft tissue involvement
• Deformities in Knee are triplanar – frontal, saggital & coronal
• ACL ‘s role• Soft tissue involvement
Posterior slope of tibiaPosterior slope of tibia