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    Item type:Publication, Access status: without files ,
    Pre-clinical assessment of the in vivo behaviour of non-articulating Interfaces between implant components concerning the consequences of micro motion or corrosion processes : test methodology, and requirements for testing and characterization of implant modularities
    (EFORT, 2023-05)
    Kretzer, Jan Philippe
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    Grupp, Thomas M.
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    Kaddick, Christian
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    Mayer, Richard T.
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    Morlock, Michael
    Question: Modularities / interfaces How can the in vivo behaviour of interfaces between implant components (e.g. head-conus-connection, not articulation partners) be assessed pre-clinically, for example concerning the consequences of micro motion or corrosion processes? 1. Which test methods concerning modularities / corrosion / performance in vivo/in vitro do exist? 2. Which aspects cannot be covered by the current test methods? 3. Which are the requirements for the testing / the characterization of implant modularities and what needs to be considered? Summary / Recommendation: Test methods concerning modular interfaces are available (e.g. ASTM F1875) and they are frequently used in short- or long-term applications. By mechanically loading the interfaces, several outcome variables like electrochemical parameters or the amount of lost material are assessed. Furthermore, some studies focus on the analysis of interface micro motions. Nevertheless, in the past, clinically relevant failure modes regarding modular connections were not completely predictable by these testing methods. Current research has pointed out the importance of an appropriate test fluid and the addition of pH lowering additives or corrosion enhancing supplements such as H2O2, FeCl3 or HCl are of interest and should be considered in pre-clinical testing. To evaluate the fretting and fatigue performance of modular connections the addition of bovine calf serum to the test fluid should be considered. Furthermore it appears to be advisable to perform long-term tests and to gain quantitative information about the amount and composition of the degraded material.
    Publicationtype: Research Report
      12
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    Item type:Publication, Access status: without files ,
    Endurance habitual and peak loads in hip and knee arthroplasty : review and summary of aspects to be considered
    (EFORT, 2023-05)
    Morlock, Michael
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    Kretzer, Jan Philippe
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    Schierjott, Ronja A.
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    Traina, Francesco
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    Larrainzar-Garijo, Ricardo
    Question: Mechanical component testing How can be established from a clinical perspective that the implant will withstand the endurance habitual and peak loads that must reasonably be expected (i.e. single implant parts as well as complete arthroplasty combination)? Summary/Recommendation: Presently catastrophic implant failure as the origin of clinical failure is rare as long as the implant is loaded according to its designed purpose, especially with respect to the load transfer between implant and bone. Aspects to be considered are: • The execution of established and standardized pre-clinical testing methods for the determination of strength and endurance properties are the essential basis for successful pre-clinical assessment. These have to be performed under physiological conditions (i.e. considering the pH-value in the body and potential corrosion processes, especially for implants with interfaces such as modular implants – see also Consensus Statement 13: Modularities / Interfaces) and worst-case size combinations (e.g. based on FEA). • The combination matrix for implant systems (size range of component 1 compatible with size range of component 2) has to be respected in the clinical application to avoid failure due to overloading (e.g. for TKA components to find suitable size combinations and avoid failure of PE inserts due to mechanical overloading). • Systematic analysis of retrieved implants from clinical studies and specific cases (even if the reason for retrieval was not mechanical failure, the retrievals could be analyzed for potential signs of fatigue) • Careful analysis of registry results (especially for combinations) and their association with patient characteristics and the respective results from pre-clinical testing. • If implants are used in a mix&match combination, which is typically not tested pre-clinically, the potential influence of this combination on overall survival is difficult to assess since frequently not both manufacturers are notified of adverse events. This is one more justification for public registries.
    Publicationtype: Research Report
      46
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    Item type:Publication, Access status: with files ,
    Explant analysis and implant registries are both needed to further improve patient safety
    (The British Editorial Society of Bone & Joint Surgery, 2022-05-31)
    Morlock, Michael
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    Gomez-Barrena, Enrique
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    Wirtz, Dieter Christian
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    Hart, Alister
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    Kretzer, Jan Philippe
    In the early days of total joint replacement, implant fracture, material problems and wear presented major problems for the long-term success of the operation. Today, failures directly related to the implant comprise only 2–3% of the reasons for revision surgeries, which is a result of the material and design improvements in combination with the standardization of pre-clinical testing methods and the post-market surveillance required by the legal regulation. Arthroplasty registers are very effective tools to document the long-term clinical performance of implants and implantation techniques such as fixation methods in combination with patient characteristics. Revisions due to implant failure are initially not reflected by the registries due to their small number. Explant analysis including patient, clinical and imaging documentation is crucial to identify failure mechanisms early enough to prevent massive failures detectable in the registries. In the past, early reaction was not always successful, since explant analysis studies have either been performed late or the results did not trigger preventive measures until clinical failures affected a substantial number of patients. The identification of implant-related problems is only possible if all failures are reported and related to the number of implantations. A system that analyses all explants from revisions attributed to implant failure is mandatory to reduce failures, allowing improvement of risk assessment in the regulatory process.
    Publicationtype: Journal Article
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