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Impact of Implant Developers on Published Outcome and Reproducibility of Cohort-Based Clinical Studies in Arthroplasty
Gerold Labek, MD1; Daniel Neumann, MD2; Mark Agreiter, MD1; Reinhard Schuh, MD1; Nikolaus Böhler, MD3
1 Department of Orthopaedic Surgery, Innsbruck Medical University, Anichstrasse 35, 6020 Innsbruck, Austria. E-mail address for G. Labek: gerold.labek@efort.org
2 Orthopedic University Clinic, PMU Salzburg, Muellner Hauptstrasse 48, 5020 Salzburg, Austria
3 Department of Orthopaedic Surgery, General Hospital Linz, Krankenhausstrasse 9, A-4020 Linz, Austria
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Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

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Investigation performed at Innsbruck Medical University, Innsbruck, Orthopedic University Clinic, PMU Salzburg, Salzburg, and General Hospital Linz, Linz, Austria

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Dec 21;93(Supplement 3):55-61. doi: 10.2106/JBJS.K.01108
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Abstract

Background: 

The reproducibility of the results of cohort-based clinical studies of arthroplasty procedures by the average orthopaedic surgeon is a major issue involving the quality of the scientific literature. We compared the results of a comprehensive literature analysis with data from national arthroplasty registries to examine the influence of arthroplasty implant inventors on the outcomes published in peer-reviewed journals.

Methods: 

A structured review of the literature published in MEDLINE-listed journals was performed. A comparison of the average revision rates in the identified studies (adjusted for the number of arthroplasty cases and the duration of follow-up) with the registry data was then conducted.

Results: 

Seventeen of the analyzed arthroplasty implants were developed in the United States. Studies by the developers of these implants often had a substantial influence on the published outcome. For approximately 50% of the implant systems analyzed, the average revision rate derived by combining all published studies showed a statistically significant and clinically relevant deviation from the revision rate derived from the arthroplasty registry data, which reflected the outcome in the average patient. For the majority of implants for which the revision rate calculated from the published clinical studies was very low compared with the rate calculated from the registry data, the developing institution accounted for 39% to 100% of the published outcome data for the implant. In contrast, the published results were usually reproducible in clinical practice if <25% of the published data were reported by the developers. Three of the nine arthroplasty implants developed in Europe showed a significant and clinically relevant difference between the revision rate derived from only the studies published by the developers and the rate calculated from the registry data. However, because of the considerably greater amount of data from independent studies that was typically available for the European implants than for the American implants, studies by the developer that deviated significantly from the registry data could usually also be identified as outliers by a meta-analysis of all published studies. A high proportion of the published data involving three of the European implants was reported by the inventors, but comparison with the registry data revealed that the average published revision rates for two of these three implants were reproducible in clinical practice.

Conclusions: 

The published results of the clinical studies involving many of the arthroplasty implants, especially implants developed in the United States, were highly influenced by reports from the center that developed the implant. This often had a substantial effect on the reproducibility of the outcome data. There appeared to be relevant differences between the medical research systems in Europe and the United States that also affected the reproducibility and applicability of the results for the average surgeon. Registry data can contribute substantial added value to an informed discussion of arthroplasty outcomes.

Figures in this Article
    The applicability of the results of cohort-based clinical studies to the general population has long been a topic of controversy. Untoward events resulting from both pharmaceuticals and medical devices continue to occur, and in some cases serious problems are not recorded until years after product launch. The analgesic Vioxx, which provoked cardiovascular side effects, and the ASR hip replacement system, which was recalled by the manufacturer in 2009 and 2010, are impressive examples that affected a large number of patients and caused high costs to the health-care system for the treatment of subsequent effects.
    The reproducibility of the results of clinical studies in routine patient treatment is also a matter of interest for the regulatory bodies that are responsible for ensuring maximum patient safety. Cohort-based clinical studies comprise an essential part of the medical literature on which the decisions of these regulatory bodies are based.
    The participants in the European Union's EUPHORIC (EUropean Public Health Outcome Research and Indicators Collection) project proposed a methodology to allow comparison between different health outcome data sets. During the validation phase, analysis of data pertaining to a sample of arthroplasty implant systems revealed considerable differences between the revision rates published in clinical studies and the rates derived from high-quality arthroplasty registries, which reflect the outcome of treatment of an average patient.
    As a result of these findings, the European Federation of National Associations of Orthopaedics and Traumatology (EFORT, http://www.efort.org) and the European Arthroplasty Register (EAR) initiated a multinational project to expand the analysis and evaluation of arthroplasty implants globally. All arthroplasty implant systems for which usable data were available from appropriate registries worldwide were analyzed, and a structured literature search of clinical studies of arthroplasty outcomes was performed.
    Comparison with the registry data revealed that the published revision rates for approximately 50% of the individual implants were classified as outliers because they were not reproducible in typical clinical practice (at least three times higher or at least three times lower, with the difference being statistically significant)1. The data from the literature search also provided information on the extent to which the clinical trials performed by the developer of each arthroplasty implant had influenced the published outcome. For the majority of implants with a published outcome that was not reproducible in clinical practice, the reports from the implant developer accounted for a large proportion of the data involving the implant that had been published worldwide2-7.
    The aim of the present report was to provide a descriptive summary of the results for all of the arthroplasty implants that were examined, particularly with respect to the reproducibility of the results and the differences between published data for implants developed in Europe and in the United States.
    Published data regarding each individual implant were collected by comprehensive web-based research involving a search of the literature indexed by PubMed2-7, followed by a manual literature search and direct requests to the manufacturer for literature.
    The corresponding arthroplasty registry data were obtained from the most recent annual reports that were available from all national registries that met the Type A.1.1.1.1 criteria in the EAR/EUPHORIC classification (Table I). National registries were identified with use of the registry summary page of the EFORT web portal (http://www.efort.org/education/registers.aspx), the links from this web page to the individual registry web sites, and a search of the Internet performed by entering the search term “arthroplasty register” in the Google search engine.
     
    Anchor for tracking jumpAnchor for jumpTABLE I  Rating of Large Data Sets According to the EFORT/EAR Classification**
    Aim/PurposeConformity between aim of data collection and aim of evaluationCoverageData collectionConformity of data set for assessment
    Outcome (A)Data collection performed for the specific purpose of evaluation (1)Nationwide (1)Comprehensive (1)Representative (1)
    Process (B)Data collection not performed for the specific purpose of evaluation (2)Regional (2)Incomprehensive (2)Not representative (2)
    Structure (C)Local (3)Sample-based (3)
    Anchor for Jump*Based on the final report of the European Union's EUPHORIC Project. EFORT = European Federation of National Associations of Orthopaedics and Traumatology, and EAR = European Arthroplasty Register.
    The inclusion criteria for published clinical studies were unambiguous identification of the implant, a revision rate that either was stated or could be unambiguously calculated from the reported data, and publication in English or German in a MEDLINE-listed, peer-reviewed journal. Tens of thousands of articles were reviewed, and >1000 were included in the analysis.
    The inclusion criteria for national registry reports were revision rates that either were stated or could be unambiguously calculated from the reported data, documentation of at least 90% of the applicable arthroplasties, and information describing the data validation performed by the register. The registries for Sweden, Denmark, Finland, Australia, and New Zealand met these criteria. However, data were not available for all implants from all of these countries. For total ankle arthroplasty, comparable data were available from published studies from Sweden, New Zealand, and Norway and were also included8-10.
    The primary outcome variable analyzed was the revision rate per 100 observed component-years, which was calculated with use of a standardized methodology This form of the revision rate is an adaption of well-known calculations expressing the number of complications in terms of the number of years of exposure to a risk; such calculations have been used to describe the correlation between tobacco use and lung cancer11, and their use was introduced in the arthroplasty field by Australia's National Joint Replacement Registry. The calculations in the present study were performed according to the guidelines published in the Australian registry's annual reports12. The method, which is also routinely used by the New Zealand Joint Registry, allows for the summing of data involving different durations of follow-up into one value. The weighting process takes into account not only the number of cases but also the duration of follow-up.
    All data were summarized with use of a standardized methodology1-7. The developers (or groups of developers) of twenty-six implant systems were identified as definitely being based in the United States (seventeen) or in continental Europe (nine). To be identified as the developer of an arthroplasty implant, an individual had to be clearly named in either the manufacturer's documentation or at least one publication regarding the implant in a MEDLINE-listed scientific journal. In the latter case, the developer either had to be listed as one of the authors of the publication or had to have the same academic affiliation as the authors of the study.
    Confidence intervals calculated with use of the Microsoft Excel-based Circulator software (version 4; University of Adelaide, Adelaide, Australia) were used to assess statistical significance.
    Analysis of the published data according to the region of implant origin revealed relevant differences between implants developed in the United States and those developed in Europe. For the implants developed in the United States, 48.2% of the primary cases and 47.1% of the observed component-years that were reported were reported by authors with the same affiliation as the implant developer. In contrast, for the implants developed in continental Europe, 10.2% of the cases and 15.9% of the observed component-years were reported by authors with the same affiliation as the developer.
    The differences between the two regions became even more apparent when implants for which the developer could not be clearly determined were excluded from the comparison. When only implants with an identifiable developer in the United States were analyzed, the data for 57.2% of all primary and revision cases and 52.1% of all observed component-years were reported by authors with the same affiliation as the developer. However, only 37.6% of the revisions were reported by such authors. For implants with an identifiable developer in continental Europe, authors with the same affiliation as the developer reported 13.8% of the cases and 20.6% of the observed component-years, as well as 11.3% of the revisions, which is only slightly lower than the corresponding percentage for primary arthroplasties.
    Most studies by implant developers in the United States were published fairly soon after market launch and represented short or medium-term follow-up, whereas studies by implant developers in Europe were more likely to represent long-term studies follow-up. For implants developed in the United States, the mean duration of follow-up (weighted according to the numbers of cases) was 8.38 years in published studies by the developers and 10.48 years in independent studies. For implants developed in Europe, the mean duration of follow-up was 11.84 years in studies by developers and 7.29 years in independent studies.
    Analysis revealed that the difference between the revision rate calculated from the published clinical studies and the revision rate calculated from the registry data, which served as a benchmark, was both statistically significant and clinically relevant for eight of the seventeen implant systems developed primarily in the United States—i.e., the outcome was not reproducible in daily patient care to a clinically relevant extent. For two of these implants, no revisions were reported in the studies by the group of developers, so they were classified as outliers1. For two other implant systems (the Buechel-Pappas total ankle arthroplasty system and the cementless Taperloc stem), the calculated revision rate (expressed in terms of observed component-years to take into account the duration of follow-up) was more than ten times greater for the arthroplasty registry data than that for the studies published by the developer. This implies that less than one-tenth of the revisions documented in the registries were also documented in the records of the centers at which these two implants were developed. In both cases, the revision rate calculated from the studies performed by the developers was also considerably lower than the revision rate calculated from the registry data for all implants of the same general type, which provided another indication that the results of the published studies by the developers of the implant must be considered to be an outlier2,4,5,13.
    The number of published cases varied considerably among the implants systems. In one case, the AGC total knee system, the number of reported primary implantations exceeded 30,000, and >75% of these were reported by the group associated with the implant inventor4. A similar situation was also observed for the Genesis II system, although the number of patients and the percentage were somewhat lower. The cumulative number of published cases for these implants is so large that multiple reports involving the same patient population would appear to exist, but such an abundance of data is likely to affect the assessment of the implant concerned even if the data and discussion are redundant.
    For all of the implants for which exceptionally good average results were published, the developers reported an extraordinarily high share of the total number of observed component-years, ranging from 39.2% to 100%. In contrast, the published results were usually reproducible in clinical practice if <25% of the published data were reported by the developers (Table II).
     
    Anchor for tracking jumpAnchor for jumpTABLE II  Published Data Regarding Implants Designed in the United States
    ImplantNo. of Primary Procedures in All Clinical StudiesNo. of Revisions in All Clinical StudiesNo. of Component-Years Observed in All Clinical StudiesRevisions per 100 Observed Component-Years in All Clinical StudiesRatio of Revision Rates in Registries and Clinical Studies by DeveloperPercentage of Primary Procedures Reported by DeveloperPercentage of Revisions Reported by DeveloperPercentage of Observed Component-Years Reported by Developer
    Optetrak total knee arthroplasty448122830.04Infinity**74.78081.43
    Pinnacle cup4201480.00Infinity**100Not applicable100
    Buechel-Pappas total ankle arthroplasty5173631521.1414.29*57.2541.6758.63
    Taperloc stem cementless19293616,1440.2210.81**44.5311.1139.19
    Corail stem214225070.085.24**68.6910067.42
    AML cementless stem5772359920.384.74**62.4317.3967.61
    AGC total knee arthroplasty30,596571310,8720.184.15**85.9377.2679.86
    Genesis II total knee arthroplasty15,04913695,4330.143.70**47.5147.7945.89
    Agility TAA6828229172.812.4331.9623.1754.37
    Harris-Galante cup735239368,4810.572.2231.4616.7924.37
    CONSERVE PLUS total hip arthroplasty202314010,1341.381.4796.2495.8296.95
    LCS total knee arthroplasty14,196863162,2710.531.115.676.955.56
    Natural-Knee total knee arthroplasty15146810,8470.631.0991.8810097.17
    P.F.C. total knee arthroplasty14,36361788,0900.700.647.214.384.03
    Miller-Galante unicompartmental knee arthroplasty4492936390.805.2027.176.9024.98
    Duracon total knee arthroplasty4721335370.371.4823.7338.4617.10
    Kinemax total knee arthroplasty188713216,0220.822.7527.7213.6445.70
    Anchor for Jump*Significant and clinically relevant difference between the revision rate in published clinical trials and the rate in the registries.
    Significant and clinically relevant differences were also found between the revision rate of the Miller-Galante unicompartmental knee implant calculated from the data reported by the developers1 and the rates calculated from both the registry data and the independent clinical studies. However, because the developers reported only about one-quarter of the observed component-years and the revision rate calculated from the independent studies was close to the registry benchmark, the revision rate calculated from all published studies did not differ significantly from the value calculated from the registry data.
    The developers of the Kinemax system accounted for 27.7% of the primary arthroplasties, 45.7% of the observed component-years, and 13.6% of the revision arthroplasties reported in clinical studies. The revision rate calculated from the studies by the developers was 5.4 times lower than the rate calculated from independent studies and 2.75 times lower than the rate calculated from the registry data. The difference between the rate reported by the developers and the registry value is only just within the limit that is explicable by differences in normal determinants of the revision rate such as patient selection and surgeon expertise. The average revision rate calculated from the independent studies, however, exceeded the value calculated from the registry data, which explains the large deviation between the studies by the developers and the independent studies.
    Only two groups of developers from the United States, those including Aaron Hofmann (developer of the Natural-Knee system) and Harlan Amstutz (CONSERVE PLUS), were responsible for a high proportion of the published outcome data involving the implant1 and reported well-reproducible data involving the revision rate.
    A comparative analysis of revision rates was possible for nine implants that were developed in Europe. The difference between the revision rate calculated from studies performed at the developer's hospital and the rate calculated from the arthroplasty registry data was significant and clinically relevant for three of these implants. The publications authored by the developers of the STAR total ankle arthroplasty system and of the LINK unicompartmental knee arthroplasty system differed significantly from the weighted average in the meta-analysis, whereas the independent studies concerning these implants did not differ significantly from the registry data that represented the benchmark value. The LINK unicompartmental data set is, however, dominated by a single German-language study from 199114.
    Spotorno only published a single small study of the acetabular cup that he developed1. Since this study represented <5% of the observed component-years in the literature on this implant, it had no substantial influence on a meta-analysis of the published revision rates for the implant. There was no significant or clinically relevant difference between the revision rate calculated from the independent studies and the rate calculated from the registry data.
    In addition to the LINK unicompartmental knee implant, two other implants had a very high percentage of published outcome data that were reported by the developers. However, these data sets exhibited no conspicuous deviations from the registry data and may therefore be assumed to be reproducible in typical patient treatment (Table III).
     
    Anchor for tracking jumpAnchor for jumpTABLE III  Published Data Regarding Implants Designed in Continental Europe
    ImplantNo. of Primary Procedures in All Clinical StudiesNo. of Revisions in All Clinical StudiesNo. of Component-Years Observed in All Clinical StudiesRevisions per 100 Observed Component-Years in All Clinical StudiesRatio of Revision Rates in Registries and Clinical Studies by DeveloperPercentage of Primary Procedures Reported by DeveloperPercentage of Revisions Reported by DeveloperPercentage of Observed Component-Years Reported by Developer
    LINK unicompartmental knee arthroplasty**327617146,8230.3711.4039.5012.8755.27
    CLS Spotorno cup38339031,3870.299.057.801.114.76
    STAR total ankle arthroplasty**123314956762.634.6314.926.0419.94
    Allofit cup467524730.202.5917.5640.0033.49
    BiCONTACT stem12641710,7900.162.1143.2088.2466.49
    HINTEGRA total ankle arthroplasty403259752.561.94100100100
    CLS Spotorno stem923313348,3610.281.843.252.264.24
    Alloclassic stem857619457,4450.340.877.6314.436.83
    Müller stem cemented655126645,3150.590.591.883.012.55
    Anchor for Jump*Significant and clinically relevant difference between the revision rate in published clinical trials and the rate in the registries.
    The greater number of cases included in the registries than in other data sources such as published clinical trials suggests that registry data are distinctly superior to such other data sources. For the implants analyzed in this study that were developed in the United States, published clinical studies worldwide reported on a total of 92,310 primary and 3142 revision arthroplasties. In contrast, registries from the included small and medium-sized countries contained a total of 250,353 primary and 6730 revision arthroplasties for exactly the same implants. Thus, the number of arthroplasty cases available from the selected, high-quality registries was nearly three times greater than the number available in published studies worldwide.
    For the implants that were developed in Europe, a total of 34,836 primary and 1050 revision arthroplasties were reported in clinical studies. For the same implants, 23,400 primary and 656 revision arthroplasties were recorded in the included registries.
    The comparative analysis revealed that the developers of an arthroplasty implant generally accounted for a high proportion of the literature published on that implant. For most studies worldwide, the extent to which the revision rate in a published study by the developers was replicated in typical clinical practice was similar to that in independent studies.
    Whereas the basic data published on approximately 50% of the implants developed in the United States were not reproducible to a statistically significant and clinically relevant extent in typical clinical practice, as indicated by a comparison with registry data, publications on implants developed in continental Europe provided a much more realistic view of the revision rate to be expected.
    A number of implant developers in the United States reported a high proportion of the published data on patient outcomes related to the implant. These developers predominantly reported revision rates that were not reproducible in routine patient treatment. This was often not readily detectable in a conventional literature analysis because of an absence of sufficient data from independent clinical studies for comparison. Most of the studies that featured extraordinarily good outcomes were published in two journals. Furthermore, the average revision rates calculated from the independent studies published in these two journals were also conspicuously lower than those calculated from the registry data, even for implants for which the vast majority of the total data was reported by the developers1.
    It is important to critically analyze why such a large proportion of the published outcome data for arthroplasty implants developed in the United States has come from the developers of the implant. Implant developers may not be representative of the average orthopaedic surgeon who uses the implant; since they have focused on the subject for years, they can be assumed to have high personal expertise. The development of instruments and implants always proceeds in the context of a specific background of individual preferences and local requirements. Since these factors should apply to all prestigious implant developers, and since these factors should have a great impact on the revision rate that is achieved, this raises the question of why this phenomenon of elevated success rates does not apply to the clinical series reported by all implant developers. Another factor that may lead to an increased revision rate is the use of the implant for nonconventional patient indications by the developer. The crucial question—why a large majority of the developers whose studies dominated the publications on their implant achieved outstanding revision rates that could not be reproduced in independent clinical studies or in registries—cannot be answered conclusively on the basis of the data available. It is reasonable to assume that the underlying causes are complex and multiple. However, the data clearly indicated that these outstanding revision rates had a relevant impact on the published results and represented a systematic bias.
    Similar findings were not observed for the majority of the implants developed in Europe. Although the revision rates reported by a few groups of developers differed conspicuously from the rates calculated from the registry data, most of these reports were recognizable as outliers even in a conventional meta-analysis since sufficient data from independent studies were available for comparison. Also, even when a developer in Europe was responsible for a high proportion of the literature published regarding the implant, the published results usually appeared to be trustworthy when the usual determinants of the revision rate in arthroplasty surgery were considered.
    The average duration of follow-up for arthroplasty implants developed in Europe was longer in studies authored by the developers than in independent studies.
    Although the results of clinical trials by implant developers in the United States were typically very positive, it is not possible to fully establish whether, or to what extent, this affected the sales success of the implant on the basis of the data available. However, the cumulative sales of the implants developed in the United States were more than twice as high as the sales of European implants in the countries in Europe and Oceania that were included in the registry reports.
    The range of variation in arthroplasty revision rates among individual hospitals in a country is relatively wide, with deviations of a factor of four from the national average1,2. There is ample room for quality improvement in arthroplasty surgery. Although clinical studies alone do not represent a reliable tool for individual decisions in patient care, high-quality registry data can provide substantial additional value for outcome research and the assessment of published results of arthroplasty surgery.
    Labek  G; QoLA Study Group. Quality of publications regarding the outcome of revision rate after arthroplasty. Final report of the QoLA Project presented at the EFORT Congress 2011 in Copenhagen. 2011.  http://www.ear.efort.org/downloads/E-Book_QoLA%20Project_Final%20Report_EFORT%20Copenhagen%202011.pdf. Accessed 2011 Aug 19.
     
    Labek  G;  Frischhut  S;  Schlichtherle  R;  Williams  A;  Thaler  M. Outcome of the cementless Taperloc stem: a comprehensive literature review including arthroplasty register data. Acta Orthop.  2011;82:143-8.[PubMed][CrossRef]
     
    Labek  G;  Sekyra  K;  Pawelka  W;  Janda  W;  Stöckl  B. Outcome and reproducibility of data concerning the Oxford unicompartmental knee arthroplasty: a structured literature review including arthroplasty registry data. Acta Orthop.  2011;82:131-5.[PubMed][CrossRef]
     
    Schuh  R;  Dorninger  G;  Agreiter  M;  Boehler  N;  Labek  G. Validity of published outcome data concerning Anatomic Graduated Component total knee arthroplasty: a structured literature review including arthroplasty register data. Int Orthop.   2011 Apr 13. [Epub ahead of print]
     
    Labek  G;  Herrmann  K;  Schlichtherle  R;  Williams  A;  Agreiter  M. Outcome and reproducibility of published data concerning total ankle arthroplasty. Foot Ankle Int.  2011;32:740-5.[PubMed][CrossRef]
     
    Labek  G;  Liebensteiner  M;  Williams  A;  Thaler  M;  Stöckl  B. Impact of patellar resurfacing on the revision rate in total knee arthroplasty. Eur Orthop Traumatol.  2010;1:95-101.[CrossRef]
     
    Janda  W;  Hübl  M;  Stöckl  B;  Thaler  M;  Labek  G. Performance of the Zweymüller total hip arthroplasty system: a literature review including arthroplasty register data. Eur Orthop Traumatol.  2010;1:9-15.[CrossRef]
     
    Hosman  AH;  Mason  RB;  Hobbs  T;  Rothwell  AG. A New Zealand National Joint Registry review of 202 total ankle replacements followed for up to 6 years. Acta Orthop.  2007;78:584-91.[PubMed][CrossRef]
     
    Fevang  BT;  Lie  SA;  Havelin  LI;  Brun  JG;  Skredderstuen  A;  Furnes  O. 257 ankle arthroplasties performed in Norway between 1994 and 2005. Acta Orthop.  2007;78:575-83.[PubMed][CrossRef]
     
    Henricson  A;  Skoog  A;  Carlsson  A. The Swedish Ankle Arthroplasty Register: an analysis of 531 arthroplasties between 1993 and 2005. Acta Orthop.  2007;78:569-74.[PubMed][CrossRef]
     
    Doll  R;  Hill  AB. Lung cancer and other causes of death in relation to smoking; a second report on the mortality of British doctors. Br Med J.  1956;2:1071-81.[PubMed][CrossRef]
     
    Australian Orthopaedic Association.  Annual Report 2010. http://www.dmac.adelaide.edu.au/aoanjrr/publications.jsp?section=reports2010. Accessed 2011 Jul 7.
     
    Labek  G;  Thaler  M;  Janda  W;  Agreiter  M;  Stöckl  B. Revision rates after total joint replacement: cumulative results from worldwide joint register datasets. J Bone Joint Surg Br.  2011;93:293-7.[PubMed][CrossRef]
     
    Nieder  E. [Sled prosthesis, rotating knee and hinge prosthesis: St. Georg model and ENDO-model. Differential therapy in primary knee joint arthroplasty]. Orthopade.  1991;20:170-80.  German.[PubMed]
     

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    Anchor for tracking jumpAnchor for jumpTABLE I  Rating of Large Data Sets According to the EFORT/EAR Classification**
    Aim/PurposeConformity between aim of data collection and aim of evaluationCoverageData collectionConformity of data set for assessment
    Outcome (A)Data collection performed for the specific purpose of evaluation (1)Nationwide (1)Comprehensive (1)Representative (1)
    Process (B)Data collection not performed for the specific purpose of evaluation (2)Regional (2)Incomprehensive (2)Not representative (2)
    Structure (C)Local (3)Sample-based (3)
    Anchor for Jump*Based on the final report of the European Union's EUPHORIC Project. EFORT = European Federation of National Associations of Orthopaedics and Traumatology, and EAR = European Arthroplasty Register.
    Anchor for tracking jumpAnchor for jumpTABLE II  Published Data Regarding Implants Designed in the United States
    ImplantNo. of Primary Procedures in All Clinical StudiesNo. of Revisions in All Clinical StudiesNo. of Component-Years Observed in All Clinical StudiesRevisions per 100 Observed Component-Years in All Clinical StudiesRatio of Revision Rates in Registries and Clinical Studies by DeveloperPercentage of Primary Procedures Reported by DeveloperPercentage of Revisions Reported by DeveloperPercentage of Observed Component-Years Reported by Developer
    Optetrak total knee arthroplasty448122830.04Infinity**74.78081.43
    Pinnacle cup4201480.00Infinity**100Not applicable100
    Buechel-Pappas total ankle arthroplasty5173631521.1414.29*57.2541.6758.63
    Taperloc stem cementless19293616,1440.2210.81**44.5311.1139.19
    Corail stem214225070.085.24**68.6910067.42
    AML cementless stem5772359920.384.74**62.4317.3967.61
    AGC total knee arthroplasty30,596571310,8720.184.15**85.9377.2679.86
    Genesis II total knee arthroplasty15,04913695,4330.143.70**47.5147.7945.89
    Agility TAA6828229172.812.4331.9623.1754.37
    Harris-Galante cup735239368,4810.572.2231.4616.7924.37
    CONSERVE PLUS total hip arthroplasty202314010,1341.381.4796.2495.8296.95
    LCS total knee arthroplasty14,196863162,2710.531.115.676.955.56
    Natural-Knee total knee arthroplasty15146810,8470.631.0991.8810097.17
    P.F.C. total knee arthroplasty14,36361788,0900.700.647.214.384.03
    Miller-Galante unicompartmental knee arthroplasty4492936390.805.2027.176.9024.98
    Duracon total knee arthroplasty4721335370.371.4823.7338.4617.10
    Kinemax total knee arthroplasty188713216,0220.822.7527.7213.6445.70
    Anchor for Jump*Significant and clinically relevant difference between the revision rate in published clinical trials and the rate in the registries.
    Anchor for tracking jumpAnchor for jumpTABLE III  Published Data Regarding Implants Designed in Continental Europe
    ImplantNo. of Primary Procedures in All Clinical StudiesNo. of Revisions in All Clinical StudiesNo. of Component-Years Observed in All Clinical StudiesRevisions per 100 Observed Component-Years in All Clinical StudiesRatio of Revision Rates in Registries and Clinical Studies by DeveloperPercentage of Primary Procedures Reported by DeveloperPercentage of Revisions Reported by DeveloperPercentage of Observed Component-Years Reported by Developer
    LINK unicompartmental knee arthroplasty**327617146,8230.3711.4039.5012.8755.27
    CLS Spotorno cup38339031,3870.299.057.801.114.76
    STAR total ankle arthroplasty**123314956762.634.6314.926.0419.94
    Allofit cup467524730.202.5917.5640.0033.49
    BiCONTACT stem12641710,7900.162.1143.2088.2466.49
    HINTEGRA total ankle arthroplasty403259752.561.94100100100
    CLS Spotorno stem923313348,3610.281.843.252.264.24
    Alloclassic stem857619457,4450.340.877.6314.436.83
    Müller stem cemented655126645,3150.590.591.883.012.55
    Anchor for Jump*Significant and clinically relevant difference between the revision rate in published clinical trials and the rate in the registries.

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