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Artificial Knee Studies
Zimmerman Reed, PLLP
NexGen CR Problems
NexGen LPS-Flex Problems
NexGen Standard v. NexGen High Flex
NexGen MIS Problems
Introduction
Problems with the NexGen CR Flex
Dr. Berger Study
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
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
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 completely
Several of the loose kneeseventually required early knee revision surgery
Berger Study Background
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
Dr. Berger’s and Dr. Della Valle’s presented their results at American Academy of Orthopaedic Surgeons Conference in March 2010
Failure rate resulting in revision surgery reached 9%
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:
“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:
Problems with the NexGen LPS Flex
Loosening
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)
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
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.”
Han Study (2007) – Specific Findings
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)
At a mean of 32 months, 27 cases (38%) had shown the radiological findings of aseptic loosening around the femoral components
At a mean of 32 months, 15 cases (21%) had been revised for the progression of component loosening and pain
Kang (2008) Results
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)
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
High Flex v. StandardFlexion and Range of Motion
Postoperative evaluation of the NexGen Legacy posterior stabilized LPS flex implants◦ Allen, DG, et al., La Societe Internationale de Chiragie
Orthopedic et de Traumalologic/La Societe Internationale 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)
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 received a 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 and high-flexion posterior stabilized total knee prostheses in patients managed with simultaneous bilateral total knee arthroplasty
Kim Study (2005)
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
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)
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
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)
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)
Flexion Measurement High Flex Knee Regular Knee
Post Op 108.5 ⁰ 105.67 ⁰
3 months 122.5 ⁰ 107.33 ⁰
3 years 112.14 ⁰ 109.14 ⁰
5 years 116.74 ⁰ 117.5 ⁰
Wohlrab Study (2009) Results
Limited to no advantage of using a high flex knee instead of a regular knee at the end of a 5 year period.
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)
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
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)
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
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)
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
Problems with MIS Tibial
Loosening and Revision
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
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
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
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
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
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