Stiehl Jb. Is Ps Needed In Tka

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Stiehl Jb. Is Ps Needed In Tka

  1. 1. Is Posterior Stabilized Needed in TKA James B. Stiehl, MD Medical College of Wisconsin Milwaukee, Wisconsin
  2. 2. Posterior Stabilized Advantages and Problems <ul><li>Enforced femoral rollback </li></ul><ul><li>Greater range of motion </li></ul><ul><li>Greater extensor mechanism lever </li></ul><ul><li>Optimal for more difficult deformity </li></ul><ul><li>Requires tight gap stability and correct prosthetic alignment </li></ul><ul><li>Not good for high contact (Innex, LCS) </li></ul><ul><li>Spine/Cam source of wear </li></ul>
  3. 3. KINEMATICS OF TOTAL KNEE ARTHROPLASTY <ul><li>Posterior Femorotibial Contact in Extension </li></ul><ul><li>Paradoxical Anterior Contact Translation </li></ul><ul><li>Lateral Condyle Liftoff </li></ul><ul><li>ACL Deficient Kinematics </li></ul><ul><ul><ul><ul><ul><li>Stiehl, et.al JBJS(B)1995 </li></ul></ul></ul></ul></ul>
  4. 4. INVIVO FLUROROSCOPY Lat condyle, normal Lateral Condyle PCR-TKA
  5. 5. Fluoroscopic Kinematic Analysis of TKA: Conclusions <ul><li>Exaggerated and abnormal motions such as greater medial AP sliding TYPICAL!! </li></ul><ul><li>Rotation can be up to 10 ° Internal/External </li></ul><ul><li>Condylar Liftoff up to 3-4 mm in “good” TKA </li></ul><ul><li>Frontal plane translation important, confirms multidirectional sliding on polyethylene </li></ul><ul><li>TKA Design and Clinical Performance must accommodate these biomechanical parameters!! </li></ul><ul><li>Kinematics are SURGEON SPECIFIC!! </li></ul>
  6. 7. What About Wear in Mobile Bearings? <ul><li>206 LCS MB vs 619 Fixed Bearings </li></ul><ul><li>M B had less delamination, cold flow and abrasion(p<.01 </li></ul><ul><li>MB ususally oxidized poly </li></ul><ul><li>MB measured wear estimated at .05 mm/year </li></ul><ul><ul><ul><ul><li>Collier,Mayor,2002 </li></ul></ul></ul></ul>
  7. 8. LCS Failure at 6 years Pitting, small med,lat Deep Knee Bend Gait +6mm -7mm +14 °
  8. 9. Forward Body Lean on Stairs <ul><li>Extensor Moment Weakness in TKA: </li></ul><ul><li> 19% Posterior Cruciate Sacrifice </li></ul><ul><li> 15 % Posterior Cruciate Retention </li></ul><ul><li> 12% Posterior Cruciate Substitution </li></ul><ul><ul><ul><ul><ul><li>Mahoney, Jl Arthroplasty,1994 </li></ul></ul></ul></ul></ul>
  9. 10. Extensor Mechanism Power Curve
  10. 11. Anterior Femorotibial Translation in TKA <ul><li>Anterior translation decreases levering effect of the patella </li></ul><ul><li>Occurs with posterior cruciate retention </li></ul><ul><li>PS 4-5 mm rollback reduces </li></ul>
  11. 12. Mechanics of Joint Line Elevation: PCR vs PS <ul><li>PS: elevation of joint line 5-7mm </li></ul><ul><li>PCR: slight elevation of joint line, anterior translation causes significant PF contact elevation </li></ul><ul><li>Outcome: ???Wash </li></ul><ul><ul><ul><li>Stiehl, J of Arthroplasty 2001 </li></ul></ul></ul>
  12. 13. Contact Stress and High Flexion <ul><li>Morra, et.al. 135  Flexion, 3100N- 32MPa </li></ul><ul><li>Chapman, et.al. 90  to 135  , 3600N- 22 to 36MPa </li></ul><ul><li>Morra, et.al. Spine/Cam articulation, 279N - 32 MPa </li></ul><ul><li>Nakayama, et.al. Spine/Cam articulation, 500 N, 90  to 150  flexion- 22-34MPa </li></ul><ul><li>Polyethylene fails at 30 Mpa </li></ul><ul><li>???? Realistic For Invivo Loading </li></ul>
  13. 14. Active vs Passive Range of Motion in TKA <ul><li>Weight bearing flexion < Passive flexion in Normal, PCR, PS (P<.045) </li></ul><ul><li>Active Flexion: Normal-135°; PCR-103°;PS-113° </li></ul><ul><li>PS > PCR Active Weight Bearing (P<.025) </li></ul><ul><ul><ul><ul><li>Dennis, et.al., Jl Arthroplasty,1998 </li></ul></ul></ul></ul>
  14. 15. Balanced Flexion Gap <ul><li>Posterior condylar reference (0° ER): 120° Preop to 100° Postop </li></ul><ul><li>Posterior condylar reference (~3° ER): 115° Preop to 112° Postop </li></ul><ul><ul><ul><li>Laskin, et.al., Jl Arthroplasty, 1995 </li></ul></ul></ul><ul><li>Tibia Cut First ??? </li></ul>
  15. 16. PS for Deformity 7  Varus 16  Varus 16  Varus 0  Varus
  16. 17. Case: 52 YO Female Severe Distal Femur Fracture with 10 ° Varus Deformity; Flexion
  17. 19. Final Result: Free Navigation Mechanical Axis: 0 ° !!!
  18. 20. Final Result: Free Navigation
  19. 21. Level 4 Outcome Data <ul><li>Non-randomized Control Retrospective Outcome Studies (??Designer) </li></ul><ul><li>Literature Review: </li></ul><ul><ul><li>10-23 Year Follow-up </li></ul></ul><ul><ul><li>4-13% Revision Rate </li></ul></ul><ul><ul><li>Survivorship Rates: 85% to 95% </li></ul></ul><ul><ul><li>No advantage: PS, CR, Measured Resection, Tibia Cut First, etc </li></ul></ul><ul><ul><li>Most studies lack Control Group, Statistical Power or careful study design, >80% followup, etc. </li></ul></ul>
  20. 22. Swedish Arthroplasty Register <ul><li>1988-1997 </li></ul><ul><li>Cumulative Revision Rate: 1%/Year </li></ul><ul><li>Average Age 71; 69% Women </li></ul><ul><li>Diagnosis: Age 72 for OA; 66 for RA </li></ul><ul><li>Revision: Loosening-41%; Sepsis-9.9%; Instability- 5.7% </li></ul><ul><li>????? PS, CR, CS </li></ul><ul><ul><ul><ul><ul><li>Robertson, et.al. Acta Orthop Scand, 2001 </li></ul></ul></ul></ul></ul>
  21. 23. Osteolysis in PS TKA <ul><li>105 PS TKA’s, 5-8 year followup </li></ul><ul><li>Modular Base Plates </li></ul><ul><li>Osteolysis found in 16% </li></ul><ul><li>Two revisions were found to have backsided wear and tibial post wear due to impingement </li></ul><ul><ul><ul><ul><li>O’Rourke, et.al. JBJS 84A: 1362 </li></ul></ul></ul></ul>
  22. 24. Tibial Post Wear in PS TKA <ul><li>23 TKA Revisions of PS TKA </li></ul><ul><li>Median followup 3.5 years ( 2.3 to 107 mo) </li></ul><ul><li>40% had Post Deformation, Adhesive Wear, Burnishing </li></ul><ul><li>Wear: Medial, lateral and anterior surfaces </li></ul><ul><li>Two failures due to post failure </li></ul><ul><ul><ul><ul><li>Puloski, Rorabeck, et.al. JBJS 83A: 390 </li></ul></ul></ul></ul>
  23. 25. Recommendations for TKA <ul><li>Implant Design: LCS RP vs LPS High Flex </li></ul><ul><li>Surgical Technique: Tibia Cut First </li></ul><ul><li>Goals: 0  Mechanical Axis; <3  Gaps </li></ul><ul><li>Mobile Bearing: High Performance, Healthy and Under Age 65 </li></ul><ul><li>PS: Offers better flexion; easier in cases with deformity! Best option for patient over age 70 </li></ul>
  24. 27. LCS Rotating Platform vs Posterior Stabilized 3D Analysis <ul><li>Invivo Weight Bearing Fluoroscopy </li></ul><ul><li>10 Patients </li></ul><ul><li>Automated 3D Computer Model Fitting </li></ul><ul><li>Medial/Lateral Condyle Sagital Plane Evaluation </li></ul>
  25. 28. LCS ROTATING PLATFORM <ul><li>Average position midline during stance phase gait </li></ul><ul><li>Deep Knee Bend: 0 ° to 60°- Medial 1.2 mm anterior; Lateral 4.0 mm posterior 60° to 90° - Medial 1.2 mm anterior; Lateral 1.0 mm anterior </li></ul>Gait Deep Knee Bend
  26. 29. LCSPS ROTATE PLATFORM <ul><li>Gait: Positions are constant from stance to swing phase </li></ul><ul><li>DKB: Medial condyle –0.5 mm to –2.5 mm Lateral condyle -0.6 mm to –6.5 mm </li></ul>Gait Deep Knee Bend
  27. 30. LCS RESULTS: CONDYLAR LIFTOFF <ul><li>80% Significant Liftoff (0.75 mm) </li></ul><ul><li>50% Liftoff - Heelstrike, 66% , Toeoff </li></ul><ul><li>50% Medial and Lateral Condyle Liftoff </li></ul><ul><li>Greatest Medial Liftoff: 2.12 mm </li></ul><ul><li>Greatest Lateral Liftoff: 3.53 mm </li></ul><ul><ul><ul><ul><ul><li>Stiehl, Jl Arthroplasty 1999 </li></ul></ul></ul></ul></ul>
  28. 31. Coronal Plane Liftoff <ul><li>LPS High Flex- 6  </li></ul><ul><li>Insall design allows both liftoff and medial translation </li></ul><ul><li>LCS PS- fixed with 2  of liftoff and minimal medial translation </li></ul>
  29. 32. Disadvantages: PS High Flex <ul><li>??? Anterior Knee Pain (?Unresurface, Gender) </li></ul><ul><li>??? Increased Polyethylene Contact Stress in High Flexion </li></ul><ul><li>??? Chronic effect of asymetrical loads on late loosening </li></ul><ul><li>Designs: posterior femoral condyle extension, patellar tendon cut out, posterior tibia flat, must not have anterior tibial impingement, ??? Poor for mobile bearing </li></ul>
  30. 33. Posterior Stabilized Disadvantages <ul><li>Wear: Spine/Cam </li></ul><ul><ul><li>Rotational Mismatch (needs mobile) </li></ul></ul><ul><ul><li>Limb mal-alignment </li></ul></ul><ul><ul><li>Ligamentous instability </li></ul></ul><ul><ul><li>Limited area contact from design </li></ul></ul><ul><li>Joint Line Elevation </li></ul><ul><li>??? Ligament Stretching over time </li></ul><ul><ul><ul><ul><li>Callaghan </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Rorabeck </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Hamelynck </li></ul></ul></ul></ul>

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