BIOMECHANICS OF KNEE AND
IMPLANT DESIGN
KINEMATICS OF KNEE
VARYING TRANSVERSE AXIS OF KNEE
EACH GAIT CYCLE
• Flexion and extension -70 * swing
20 * stance
• Abduction and adduction 10 *
• internal and external rot...
NORMAL POST TRANSLATION OF KNEE IN
FLEXION
• Medial condyle = 2mm
• Lateral condyle = 21 mm
• Medial based pivoting of the...
• MA is 3 degrees
of valgus from
vertical axis of
body.
• AA is in 6 * of
valgus from MA
•9 degrees of
valgus vertical axi...
• The tibial articular surface is in 3* of varus.
• The distal femur is in 9* of valgus
• So in order to get the neutral m...
• Proximal tibial cut is perpendicular to the
mechanical axis
• Posterior condylar axis is 3*
• In order to create a recta...
PATELLO FEMORAL JOINT
Q ANGLE
JOINT REACTION FORCE
• It’s the force experienced by the trochlea due
to posterior displacement of the patella
during flex...
EVOLUTION OF KNEE PROSTHESIS
• Interpositional
• Mold arthroplasty
• Hinged knee implants- they did not account
for the co...
ARGUMENTS IN FAVOUR PCL RETAINING
• > range of motion with effective femoral roll-
back
• restraint to translational displ...
PCL substituting design the displacement must
be resisted by the prosthetic articular
geometry
↓
Inc stress on the prosthe...
GAIT
• SYMMETRICAL GAIT more so in stair climbing
• PCL substituting
1. decreased knee flexion
2. tendency to lean forward...
• The patella to the joint line is less altered with
PCL-R
• Improved patello-femoral joint function
• Patellar clunk synd...
ARGUMENTS IN FAVOUR PCL SUBSTITUTION
• PCL is diseased with arthritis and contracture
• Technically surgery is less demand...
Biomechanics  of knee and implant design
Biomechanics  of knee and implant design
Biomechanics  of knee and implant design
Biomechanics  of knee and implant design
Biomechanics  of knee and implant design
Biomechanics  of knee and implant design
Biomechanics  of knee and implant design
Upcoming SlideShare
Loading in...5
×

Biomechanics of knee and implant design

1,224

Published on

0 Comments
3 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
1,224
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
105
Comments
0
Likes
3
Embeds 0
No embeds

No notes for slide

Biomechanics of knee and implant design

  1. 1. BIOMECHANICS OF KNEE AND IMPLANT DESIGN
  2. 2. KINEMATICS OF KNEE
  3. 3. VARYING TRANSVERSE AXIS OF KNEE
  4. 4. EACH GAIT CYCLE • Flexion and extension -70 * swing 20 * stance • Abduction and adduction 10 * • internal and external rotation - 10 to 15* • 67* flexion for swing phase • 83* flexion for climbing stairs • 90* flexion for descending stairs • 93* flexion for rise from chair
  5. 5. NORMAL POST TRANSLATION OF KNEE IN FLEXION • Medial condyle = 2mm • Lateral condyle = 21 mm • Medial based pivoting of the knee • In flexion - tibia undergoes internal rotation • In extension - tibia undergoes ext rotation
  6. 6. • MA is 3 degrees of valgus from vertical axis of body. • AA is in 6 * of valgus from MA •9 degrees of valgus vertical axis of body.
  7. 7. • The tibial articular surface is in 3* of varus. • The distal femur is in 9* of valgus • So in order to get the neutral mechanical axis in TKR we insert the femoral component in 5-7* of valgus.
  8. 8. • Proximal tibial cut is perpendicular to the mechanical axis • Posterior condylar axis is 3* • In order to create a rectangular flexor space the femoral component should be in 3* ER
  9. 9. PATELLO FEMORAL JOINT
  10. 10. Q ANGLE
  11. 11. JOINT REACTION FORCE • It’s the force experienced by the trochlea due to posterior displacement of the patella during flexion • JRF increases with flexion • Normal ADL it is 2-5 times • Squatting and 120* flexion 8 times
  12. 12. EVOLUTION OF KNEE PROSTHESIS • Interpositional • Mold arthroplasty • Hinged knee implants- they did not account for the complex knee motion. • Bi-compartmental prosthesis- 1. Gunston- polycentric knee
  13. 13. ARGUMENTS IN FAVOUR PCL RETAINING • > range of motion with effective femoral roll- back • restraint to translational displacement • more symmetrical gait. • less bone resection • improved function of the patellofemoral joint • proprioceptive role of the PCL
  14. 14. PCL substituting design the displacement must be resisted by the prosthetic articular geometry ↓ Inc stress on the prosthesis ↓ Inc stress transfer to the bone cement interphase
  15. 15. GAIT • SYMMETRICAL GAIT more so in stair climbing • PCL substituting 1. decreased knee flexion 2. tendency to lean forward in a quadriceps- sparing posture • Contradicting studies both in favor of and against PCL retaining.
  16. 16. • The patella to the joint line is less altered with PCL-R • Improved patello-femoral joint function • Patellar clunk syndrome with PCL-S.
  17. 17. ARGUMENTS IN FAVOUR PCL SUBSTITUTION • PCL is diseased with arthritis and contracture • Technically surgery is less demanding • No problems related to a too loose or a too tight PCL • Better deformity correction • No problems with excess femoral rollback • Less polyethylene wear.
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×