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  • 1. Artificial Knee Studies
    Zimmerman Reed, PLLP
  • 2. NexGen CR Problems
    NexGen LPS-Flex Problems
    NexGen Standard v. NexGen High Flex
    NexGen MIS Problems
  • 3. Problems with the NexGen CR Flex
    Dr. Berger Study
  • 4. Dr. Richard A. Berger
    Assistant Professor, Rush University Medical Center
    Degree in mechanical engineering from MIT
    Revolutionized hip and knee replacement surgery by developing a minimally invasive method of replacing knee joints
    Full Disclosure: currently being investigated by the DOJ
    Dr. Craig Della Valle
    Assistant Professor, Rush University Medical Center
    Board Certified - Orthopaedic Surgery
    Awarded the Hip Society's Frank Stinchfield Award for his research
    New York Times – The “Berger Study” AuthorsNew York Times June 19, 2010
  • 5.
    • From 2002 to 2008 Dr. Berger was a consultant for Zimmer, training physicians on Zimmer’s Minimally Invasive Surgery (“MIS”) technique
    In 2005, Dr. Berger implanted the NexGen CR-Flex Porous into 125 patients
    Over the next year, Dr. Berger found his patients reported uncommon pain relating to their NexGen knee
    Berger Study Background
  • 6. In early 2006, Dr. Berger’s follow-up care revealed X-rays showing lines in some patients where the implant met the thigh bone, an indication that the device
    was loose and had not fused
    Several of the loose knees
    eventually required early
    knee revision surgery
    Berger Study Background
  • 7. As a result of the 2005-2006 experience, Dr. Berger, along with Dr. Della Valle, set up a study of 100 patients who received the NexGen CR-Flex Porous Knee
    Berger Study
  • 8.
    • Dr. Berger’s and Dr. Della Valle’s presented their results at American Academy of Orthopaedic Surgeons Conference in March 2010
    • 9. Failure rate resulting in revision surgery reached 9%
    • 10. Actual number of complications could be much higher as many patients (36%) showed signs of loosening but had not yet reached the level of revision surgery
    Berger’s Study Findings:
  • 11. “This component is still commercially available but should not be used for any patient.” 
    Dr. Richard A. Berger
    Rush Medical Center
    Former Zimmer Consultant
    Dr. Berger’s Conclusion:
  • 12. Problems with the NexGen LPS Flex
  • 13. High incidence of loosening of the femoral component in legacy posterior stabilized-flex total knee replacement
    H.S. Han, et al, Journal of Bone and Joint Surgery – British Edition, Vol 89-B, No. 11, Nov. 2007- Korea
    Study Demographics:
    47 patients
    72 knees
    44 women and 3 men
    All NexGen LPS-Flex - no standard LPS
    Study Goal: Analysis of high-flexion design for evidence of aseptic loosening and related pain
    Han Study (2007)
  • 14. Patients did get better flexion then regular Total Knee Replacement (“TKR”) designed knees
    111-165 degrees of knee flexion in LPS-Flex knee
    Versus 110-120 degree of flexion in general TKA
    BUT aseptic loosening was found at a higher rate in the LPS-Flex than regular TKR knees
    38% of the knees (27) were loose
    at mean follow-up of 32 months
    21% of the knees (15) were revised
    at mean of 23 months
    Han Study (2007) Study Results
  • 15. Han Study (2007) – Specific Findings
    All loosening at femoral component which migrated into a position of increased flexion
    (i.e. additional flexion emanated from the fact that the knee was loose)
    “Several [physicians] have expressed concern that relatively small gains in maximum knee flexion achieved by making changes in the design may substantially reduce the stability of the prosthesis and increase the stresses on the component.”
    “[W]e have not previously experienced such a high rate of early loosening for any design of TKR.”
  • 16. Are High Flexion Activities after High-Flex Total Knee Replacement Safe?
    Kang, S., Journal of Bone and Joint Surgery, British Edition, Vol 92-B, Issue SUPP_II, 322
    Study Demographics:
    72 knees were implanted
    All were NexGen LPS-Flex
    Study Goal: Determine the factors contributing to the high rate of aseptic loosening in LPS-Flex knees
    Kang Study (2008)
  • 17. At a mean of 32 months, 27cases (38%) had shown the radiological findings of aseptic looseningaround the femoral components
    At a mean of 32 months, 15 cases (21%) had beenrevised for the progression of component loosening and pain
    Kang (2008) Results
  • 18. Three- to six-year follow-up results after high-flexion total knee arthroplasty: can we allow passive deep knee bending?
    Cho, SD et al., Journal of Bone and Joint Surgery - British Volume, Vol 92-B, Issue SUPP_I, 131
    Study Demographics:
    218 knees
    All with NexGen LPS-Flex
    166 patients (22 males, 144 females)
    Followed up for more than 3 years after TKA
    Study Goals: Evaluate clinical and radiological follow up results of NexGen LPS-Flex
    Cho Study (2010)
  • 19. While NexGen LPS-flex Knee satisfactorily improved ROM, it was associated with a relatively high incidence of early loosening of the femoral components
    Indications of loosening were visible on radiographs of 30 knees (13.8%)
    The mean time to loosening was 24 months
    Eventually 7 knees required revision surgery (3.2%)
    The mean time to final revision surgery was 49 months
    Cho Study (2010) Results
  • 20. High Flex v. Standard
    Flexion and Range of Motion
  • 21. Postoperative evaluation of the NexGen Legacy posterior stabilized LPS flex implants
    Allen, DG, et al., La SocieteInternationale de Chiragie Orthopedic et de Traumalologic/La SocieteInternationale de Recherche Orthopedic et de Traumalological, XXII World Congress, San Diego 2002:542
    Study Goal: Compared range of motion between patients implanted with the LPS knee and the LPS-Flex knee
    Found no difference between the two replacement knees in regards to range of motion
    Allen Study (2002)
  • 22. Range of motion of standard and high-flexion posterior stabilized total knee prostheses: a prospective randomized study
    Kim, YH, et al., Journal of Bone and Joint Surgery, American Edition, 2005; 87:1470-1475
    Study Demographics:
    2 men
    48 women
    Each receiveda standard LPS prosthesis in one knee and a LPS high-flexion prosthesis in the other knee.
    Study Goal: to compare the ranges of motion associated with standard andhigh-flexion posterior stabilized total knee prostheses in patientsmanaged with simultaneous bilateral total knee arthroplasty
    Kim Study (2005)
  • 23. Authors found no difference between the eventual flexion of the two types of implanted knees
    The knees with the standard LPS prosthesis had a mean range of motion of 135.8
    The knees with the LPS-flex prosthesis had a mean range of motion of 138.6
    Kim Study (2005) Results
  • 24. High Flexion Knee Designs: More Hype than Hope? In the Affirmative
    Ritter, M., Journal of Arthroplasty, 21(4), Supp. 1 (2006)
    Study Demographics:
    4727 Total Knee Replacements
    Various ages and genders
    Using Biomet knee
    Study Goal: Evaluated the range of motion after 4727 TKA
    Ritter Study (2006)
  • 25. Range of motion after a TKA is dependant primarily upon preoperative range of motion; not device design
    High-Flex designs may increase knee instability and possible wear
    Ritter Study (2006) Conclusions
  • 26. Range of flexion after primary TKA: the effect of soft tissue release and implant design.
    Amed, I, et al., Orthopedics, 2009 Nov; 32(11): 811.
    Study reported no difference in range of movement between standard and high flexion variants of the NexGen LPS implants in a randomized controlled study.
    Amed Study (2009)
  • 27. Clinical and radiological results of high flex total knee arthroplasty: a 5 year follow-up.
    D. Wohlrab et al., Arch Orthop Trauma Surg (2009) (Germany)
    Study Demographics:
    30 patients received a LPS-Flex knee
    30 received a LPS knee
    Study Goal: Compare the clinical outcome and radiological results after TKR using a high flex design versus a standard design
    Wohlrab Study (2009)
  • 28. Wohlrab Study (2009) ResultsLimited to no advantage of using a high flex knee instead of a regular knee at the end of a 5 year period.
  • 29. Comparison Between Standard and High-Flexion Posterior-Stabilized Rotating-Platform Mobile-Bearing Total Knee Arthroplasties
    Choi, WC et al., Journal of Bone and Joint Surgery, American Edition, 2010; 92:2634-42
    Study Demographics:
    85 knee replacements using a standard prostheses design
    85 knee replacements using a high-flexion prostheses design
    Study Goal: Compare the outcomes of standard and high-flexion posterior stabilizing TKR
    Choi Study (2010)
  • 30. Showed no significant differences between standard and high flexion posterior stabilized mobile bearing total knee prostheses
    Average maximal flexion for the standard design was 128⁰
    Average maximal flexion for the high-flex design was 130⁰
    Choi Study (2010) Results
  • 31. Does the new generation of high-flex knee prostheses improve the post-operative range of movement?
    Mehin, R., Journal of Bone and Joint Surgery, British Edition, Vol. 92-B, Issue 10, 1429-1434
    Study Type: Metadata analysis of already published articles regarding standard TKR design and high-flex TKR design
    Study Goal: Determine whether the high-flex knee prostheses provide increased movement over standard knee prostheses design
    Mehin Study (2010)
  • 32. Analysis suggests that high-flex knee prostheses do not increase the post-operative maximum knee flexion compared with traditional implants
    The weighted mean difference between the range of flexion between a standard design and a high-flex design was 2.1⁰
    “Not only is [the difference] not statistically significant, but more importantly it is not clinically significant. Additional flexion of 2⁰
    . . . has no functional advantage to the patient.”
    Mehin Study (2010) Results
  • 33. Comparison of standard and gender-specific posterior-cruciate-retaining high flexion total knee replacements: a prospective, randomized study
    Kim, YH, et al., Journal of Bone and Joint Surgery, British Edition, 2010 May, 92(5): 639-45
    Study Demographics:
    85 women
    Received LPS-Flex design in one knee and gender-specific LPS-Flex design in the other knee
    Study Goal: Compare clinical and radiographic results in patients receiving a LPS-Flex or gender specific LPS-Flex prostheses
    Kim Study (2010)
  • 34. Study found no difference in clinical and radiological results in female patients undergoing standard and gender-specific variants of the NexGen LPS-Flex prosthesis
    Kim Study (2010) Results
  • 35. Problems with MIS Tibial
    Loosening and Revision
  • 36. Presented by Dr. Steven H Weeden and Dr. Steven Boyd Ogden
    Podium Presentation: Early Loosening of MIS Tibial Implants in Primary TKA
    From 2005 to 2007 the authors performed 403 TKAs with a Zimmer MIS tibial component
    Study Demographics:
    All procedures were performed with a MIS technique, PS articulation, and cement
    22 replacements did not have the modular stem component
    381 replacements included a stem component
    American Academy of Orthopaedic Surgeons Conference in March 2010
  • 37. The study reports a higher than expected rate of early loosening in cemented primary TKA with an MIS tibial component
    The average time to diagnosis of loosening in this study is 2.6 yrs
    The overall loosening rate was 5.2% (21 tibias of the 403)
    Early Loosening of MIS Tibial Implants
  • 38. Of the MIS Tibias placed without a stem component, 5 tibias out of 22 failed (24%)
    Of the MIS tibias placed with a stem component, 16 tibias out of 381 failed (4.2%)
    Early Loosening of MIS Tibial Implants specifics
  • 39. The doctors recommendation: “the use of an MIS tibia without the use of a modular stem is not recommended secondary to a high rate of early loosening in primary TKA.”
    Early Loosening of MIS Tibial Implants continued
  • 40. Early Aseptic Loosening with Precoated Low Profile Tibial Component: A Case Study
    Foran, J.R.H., et al, Journal of Arthroplasty, published online January 14, 2011
    Authors performed TKAs in 460 patients using the NexGen MIS Tibial Component
    Authors experienced early loosening of the tibial component
    The average time to diagnosis of loosening was 17 months
    In addition, several additional patients show radiographic signs of pending failure
    Foran Case Study
  • 41. Based on their experience with early aseptic loosening of the MIS Tibial Component, the authors report they will discontinue further use until the etiology of the high failure rate is able to be determined
    Foran Case Study: Specific conclusions