Stiehl Jb. Design Factors Influencing Rom In Tka

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  • 1. Design Factors Influencing Range of Motion in TKA James B. Stiehl, MD Medical College of Wisconsin Milwaukee, Wisconsin
  • 2. Factors Determining ROM in TKA
    • Preoperative ROM and body habitus
    • Prior surgery or trauma
    • Surgical technique
    • Postoperative pain and scarring problems
    • Prosthetic Design
    130
  • 3. Patient Factors: Obesity
    • Flexion > 120°; 7% obese
    • Flexion 101° to 119°; 28% obese
    • Flexion < 100°; 78% obese
        • Shoji,et.al. Orthopaedics, 1990
    • Flexion>130  Kinemtics Driven by Thigh Contact
  • 4. Active vs Passive Range of Motion in TKA
    • Weight bearing flexion < Passive flexion in Normal, PCR, PS (P<.045)
    • Active Flexion: Normal-135°; PCR-103°;PS-113°
    • PS > PCR Active Weight Bearing (P<.025)
          • Dennis, et.al., Jl Arthroplasty,1998
  • 5. Balanced Flexion Gap
    • Posterior condylar reference (0° ER): 120° Preop to 100° Postop (PCR)
    • Posterior condylar reference (~3° ER): 115° Preop to 112° Postop (PS)
        • Laskin, et.al., Jl Arthroplasty, 1995
  • 6. Tibia Cut First Surgical Technique
    • Anterior Femoral Cortical Reference
    • Flexion Space: Tension Adjustment
    • Distal Femoral Cut Last
    • Standard Revision Arthroplasty Method
  • 7. Kinematic “Conflict”, circa 2007
    • Absent ACL Causes Loss of “Rollback”
    • True for Unicondylar, Bicruciate, Cruciate Retaining, and “Total Condylar” Rotating Platform
    • Anterior Translation exaggerated by Flexion Laxity
    • ? Effect of Joint Line Elevation, but may tend to tighten extensor mechanism
    • PS drives “roll back” and higher flexion
            • Dennis, et.al., Knee Society, 2003
  • 8. LCS Design Issues for ROM
    • Neutral to Anterior Starting Position
    • Early “Rollback” for BCR, PCR, and RP
    • “ Slide Forward” seen in deep flexion in virtually all cases (120  Limit)
    • Lack ACL Function
        • Stiehl, et.al. “LCS Moble Bearing TKA”,2002, Springer
  • 9. LCSPS Design Flaws
  • 10. LPS High Flex TKA
    • Posterior Stabilized Design: “ROLLBACK”
    • Augmented Posterior Condyles: + 2MM
    • Patellar Cutout to prevent impingment
    • Spine/Cam: Low contact point, Higher spine, Extended articulation posterior
  • 11. LPS Design Considerations Longer Cam; Posterior Condyle 2mm > LPS High Flex LPS
  • 12. Patellar Impingement Impingement LPS LPS High Flex
  • 13. LPS High Flex Mobile ROM
    • 102 TKA; Age 66 ave.(43 to 80); Wt- 72 Kg ( 36 to 110)
    • Varus Deformity: Ave 9 ° (Range 4° to 20°)
    • Valgus Deformity: Ave 6°(Range 1° to 11°)
    • Postop Femorotibial Angle: 2° Valgus (Range 1° to 5°)
    • Preoperative Flexion: 120° ( 90° to 140°)
    • Postoperative Flexion: 131° (90° to 150°)
            • Argenson, et.al., ISK Fall Meeting, 2003
  • 14. Literature Review: PS vs PS Flex <.05 135  120  50 Weeden, et.al. =0.41 138  135  50* Kim, et.al. <.05 138  126  50 Huang, et.al. <.05 129  124  180 Bin, et.al. SD PS High Flex PS N Author
  • 15. Kinematics of LPS High Flex
    • Cadaver Test: (n=13)
    • Quads force 400 N; Hamstring force 200 N
    • Spine/Cam engagement: 80  to 135 
    • Soft Tissues Active >135 
    • Medial Rollback: 2.3 mm
    • Lateral Rollback: 3.2 mm
          • Li, et.al. JBJS 86A: 1721
  • 16. Kinematics of LPS High Flex
    • 20 Subjects; invivo fluoroscopy
    • Weight Bearing Deep Knee Bend:125 
    • Average 4.4 millimeters Rollback
    • Average 4.9  Internal Rotation
          • Argenson, et.al. J Biomechanics 38: 277, 2005
  • 17. LPS High Flex Mobile Results 150 ° Passive Flexion
  • 18. LPS High Flexion Sitting 9 Inch Stool, >135 ° Flexion
  • 19. LPS High Flex- Down Stairs
  • 20. LCS Versus LPS High Flex in Passive Flexion Left- LPS High Flex- 115  Right- LCS - 105 
  • 21. What Do I Tell My Patients?
    • Preoperative Range of Motion of 90 ° probably improves 15-25°
    • Stair function, sitting, and exercycle requires > 110° Flexion
    • Certain patients have painful knees and will not improve (about 1 of 20)
    • LPS High Flex, properly done, may flex 130° to 140° in many cases!!
    • This may be best in patients over 65-70.
  • 22. Is There A Liabilty to High Flexion in TKA
    • Yes, Yes, and YES!!!
    • The mechanical forces in high flexion are EXTREME, 40-60 mPascals on Poly
    • Forces may exaggerate post wear and potential failure
    • Chronic synovitis and anterior knee pain seem to be more common in these patients. (Now AVOID Patella resurface)
  • 23. CONCLUSION
    • PostOP Flexion is multifactorial
    • Surgical Technique and Design are important
    • PS Option Best in Low Demand; ??? High forces on poly in flexion
    • LPS High Flex offers predictably higher flexion!!
  • 24.  
  • 25. Detrimental Kinematics Of A Flat on Flat Condylar TKA Stiehl, CORR, 1999 Medial Condyle Lateral Condyle
  • 26. LPS High Flex on Stairs
  • 27. Functional Outcome after TKA
    • 67 ° Swing phase of gait
    • 83° Ascend stairs
    • 93° Rise from seated position
    • 100° Average PCR TK(Dennis)
    • 110° Average MB TKA(Stiehl,et.al.)
    • 115° Average PS TKA
    • 125° Average PS Extended condyle
  • 28. LPS High Flex Walking
  • 29. LCS PS Mobile Bearing TKA
  • 30. Clinical Experience With LCSPS (Stiehl)
    • 1998-1999
    • Early Range of Motion  in ~25% (115 ° to 135 °) vs RP
    • Nontraumatic hemarthrosis- over 20%
    • 8 of 110 revised to standard RP insert under 2 year FU
    • 2 Femoral Loose!!