EndoLab GmbH

Weissenburg in Bayern, Germany

EndoLab GmbH

Weissenburg in Bayern, Germany
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Grupp T.M.,Aesculap AG | Grupp T.M.,Ludwig Maximilians University of Munich | Giurea A.,University of Vienna | Miehlke R.K.,Rhine Main Center for Joint Diseases | And 6 more authors.
Acta Biomaterialia | Year: 2013

The objective of the present study was to evaluate the biotribological behaviour, in terms of wear and particle release, of bushings and flanges made of carbon fibre reinforced poly-ether-ether-ketone (CFR-PEEK) in articulation with a zirconium nitride (ZrN) multilayer surface coating in a rotating hinge knee system. For the bushings of the rotational and flexion axles and the medial and lateral flanges, a CFR-PEEK with 30% polyacrylonitrile fibre content was used in a new bearing combination with ZrN. In vitro wear simulation was performed for patients with metal ion hypersensitivity, using a new rotating hinge knee design with a ZrN surface articulation in comparison with the clinically established cobalt-chromium version. For the bushings and flanges made of CFR-PEEK subjected to wear simulation, the volumetric wear rates were 2.3 ± 0.48 mm3 million-1 cycles in articulation to cobalt-chromium as reference and 0.21 ± 0.02 mm3 million -1 cycles in the coupling with ZrN, a 10.9-fold decrease. The released CFR-PEEK particles were comparable in size and shape for the coupling to cobalt-chromium and ZrN with most of the particles in a size range between 0.1 and 2 μm. The study reveals comparable low wear and no macroscopic surface fatigue in a new rotating hinge knee design with highly congruent flanges and axles bushings made of CFR-PEEK articulating to a ZrN multilayer surface coating. Favourable wear behaviour of the newly introduced CFR-PEEK/ZrN coupling in comparison with the clinically established CFR-PEEK/cobalt-chromium articulation was found. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Pourzal R.,University of Duisburg - Essen | Catelas I.,University of Ottawa | Theissmann R.,University of Duisburg - Essen | Kaddick C.,EndoLab GmbH | Fischer A.,University of Duisburg - Essen
Wear | Year: 2011

Biological effects of wear products (particles and metal ions) generated by metal-on-metal (MoM) hip replacements made of CoCrMo alloy remain a major cause of concern. Periprosthetic osteolysis, potential hypersensitivity response and pseudotumour formation are possible reactions that can lead to early revisions. To accurately analyse the biological response to wear particles from MoM implants, the exact nature of these particles needs to be characterized. Most previous studies used energy-dispersive X-ray spectroscopy (EDS) analysis for characterization. The present study used energy filtered transmission electron microscopy (TEM) and electron diffraction pattern analysis to allow for a more precise determination of the chemical composition and to gain knowledge of the crystalline structure of the wear particles.Particles were retrieved from two different test rigs: a reciprocating sliding wear tribometer (CoCrMo cylinder vs. bar) and a hip simulator according to ISO 14242-1 (CoCrMo head vs. CoCrMo cup). All tests were conducted in new born calf serum (30 g/l protein content). Particles were retrieved from the test medium using a previously published enzymatic digestion protocol.Particles isolated from tribometer samples had a size of 100-500nm. Diffraction pattern analysis clearly revealed the lattice structure of strain induced hcp e{open}-martensite. Hip simulator samples revealed numerous particles of 15-30nm and 30-80nm size. Most of the larger particles appeared to be only partially oxidized and exhibited cobalt locally. The smallest particles were Cr2O3 with no trace of cobalt. It optically appeared that these Cr2O3 particles were flaking off the surface of larger particles that depicted a very high intensity of oxygen, as well as chromium, and only background noise of cobalt. The particle size difference between the two test rigs is likely related to the conditions of the two tribosystems, in particular the difference in the sample geometry and in the type of sliding (reciprocating vs. multidirectional).Results suggest that there may be a critical particle size at which chromium oxidation and cobalt ionization are accelerated. Since earlier studies have shown that wear particles are covered by organic residue which may act as a passive layer inhibiting further oxidation, it would suggest that this organic layer may be removed during the particle isolation process, resulting in a change of the particle chemical composition due to their pyrophoric properties. However, prior to being isolated from the serum lubricant, particles remain within the contact area of head and cup as a third-body. It is therefore possible that during that time, particles may undergo significant transformation and changes in chemical composition in the contact area of the head and cup within the tribological interface due to mechanical interaction with surface asperities. © 2011 Elsevier B.V.


Grupp T.M.,Aesculap AG | Grupp T.M.,Ludwig Maximilians University of Munich | Saleh K.J.,University of Illinois at Springfield | Mihalko W.M.,University of Tennessee | And 5 more authors.
Journal of Biomechanics | Year: 2013

The objective of our study was to examine the effect of biphaseal AP translation and IE rotation restraint, using a system defined specifically for posterior stabilised knee designs, on wear, kinematics and particle release in comparison to linear motion restraint as required by the established ISO 14243-1:2002(E) protocol. In the ISOlinear groups, an AP motion restraint of 30. N/mm and an IE rotation restraint of 0.6. Nm/° were applied in the knee wear simulation. In the ISOgap biphaseal groups with PCL sacrificing implants, the restraining AP force was zero in a ±2.5. mm range with, externally, a constant of 9.3. N/mm applied proportionally to the AP translation of the tibia plateau, whereas the restraining IE torque was zero in a ±6° range with, externally, a constant of 0.13. Nm/° applied proportionally to the IE rotation of the tibia plateau. Using the ISOgap biphaseal protocol on a posterior stabilised knee design, we found an increase of 41% in AP translation and of 131% in IE rotation, resulting in a 3.2-fold higher wear rate compared to the results obtained using the ISOlinear protocol. Changes in AP translation and IE rotation ligament motion restraints have a high impact on knee joint kinematics and wear behaviour of a fixed bearing posterior stabilised knee design. © 2012 Elsevier Ltd.


Morlock M.M.,TU Hamburg - Harburg | Bishop N.,TU Hamburg - Harburg | Kaddick C.,EndoLab GmbH
Orthopade | Year: 2011

Replacement of the hip joint has become an exceptionally successful procedure since the inauguration of the low friction principle by Charnley. Aseptic osteolysis and joint dislocation have been addressed by the development of wear-optimized materials and the introduction of larger heads. As an increase in head diameter against polyethylene causes wear increase, larger hard-on-hard bearings were introduced, which exhibit reduced wear and reduced dislocation risk with increasing head diameter. These findings were derived from standard simulator testing, not sufficiently considering the risk of fluid film breakdown under adverse conditions, which can cause a dramatic increase in wear and friction proportional to the head diameter. Such adverse conditions can occur clinically in patients due to several factors and have caused the presently observed unexpected problems with these new designs. Standardized preclinical testing has to be viewed as a minimum requirement but certainly not as a guarantee for the clinical success of new materials and designs even if the testing is adapted to the current patient requirements, which is presently not the case. The future of tribology lies in the prevention of adverse conditions in patients, the improvement and optimized use of proven existing materials and not in the use of new materials. © 2011 Springer-Verlag.


Fohr P.,TU Munich | Hautmann V.,EndoLab GmbH | Prodinger P.,TU Munich | Pohlig F.,TU Munich | And 2 more authors.
Orthopade | Year: 2012

Articular cartilage repair methods, in particular scaffold-based autologous chondrocyte implantation, are already in clinical use. In the coming years, the European guidelines on human cell-based medicinal products by the European Medical Agency (EMA) will extend today's quality control mechanisms by additional structural analyses. As articular cartilage has complex biphasic and viscoelastic mechanical properties, a high-performance material test system is required and has already been implemented. To characterize the recovery of cartilage and cartilage replacement materials, it is necessary to measure the dynamic recovery profile. A measurement system for an application like this requires an axis acceleration of more then 50 m/s 2. Furthermore, the test system needs custom-made components to fix the biological specimen while testing. A software package consisting of a graphical user interface and an axis controller leads to highly reproducible tests. The software makes use of a position and velocity controller as well as a force controller at kilohertz speed. While using the high performance force controller it is possible to apply static and dynamic loading profiles that are independent from position or speed set points and signals. © 2012 Springer-Verlag Berlin Heidelberg.


Haider H.,University of Nebraska Medical Center | Kaddick C.,EndoLab GmbH
Journal of ASTM International | Year: 2012

Some well-known mobile bearing designs have had truly excellent long-term clinical results. Their lower constraint and ability for some self-alignment might have helped reduce the shear forces and torques transmitted to the prosthesis-bone interface, thereby lowering the risk of loosening. However, the most commonly assumed benefit of mobile bearings is the reduction in wear due to less contact stress and reduced cross shear. In a rotating platform, wear can be reduced because the rolling/sliding motion is separated from the transverse rotational motion, which reduces cross-shear. Although it has not been categorically proven clinically, such lower wear expectations with mobile bearings might have influenced the thinking of some total knee replacement (TKR) designers and test engineers. This paper amalgamates in vitro TKR wear results from two separate laboratories (in Nebraska and Germany) to present the largest data set ever published on wear, across the widest variety of fixed and mobile bearing TKR designs. Many hundreds of TKR samples were tested with largely similar methodologies using the ISO 14243-1 force-control method. These tests covered 133 different fixed and mobile bearing designs and materials, in total (bicondylar) and unicompartmental forms, and of a wide range of sizes. Clear differences in wear resulted with known superior bearing materials. This illustrates how sensitive and capable of discriminating between low and high wearing implants the force-control wear testing methodology is. However, between both labs, and across all tests, no statistically significant differences were found in wear overall between fixed and mobile bearings. Therefore, the wear of mobile bearing knees is not necessarily less than that of fixed bearings. In both, it depends on the detailed design and materials of the TKR. Testing appears to be necessary with all implant designs, regardless of the history of clinically successful predicates of seemingly similar generic design. Copyright © 2012 by ASTM International.


Hintner M.,EndoLab GmbH | Kaddick C.,EndoLab GmbH | Usbeck S.,CeramTec GmbH | Scheuber L.,CeramTec GmbH | Streicher R.M.,CeramTec GmbH
Seminars in Arthroplasty | Year: 2012

Revision surgery for fractured ceramic components in total hip arthroplasty (THA) potentially leaves small ceramic fragments in the joint capsule, and the fragments might become embedded in polyethylene (PE) acetabular liners. The purpose of this study was to determine the wear behavior of metal femoral ball heads and ceramic femoral ball heads tested with highly cross-linked and conventional polyethylene liners in the presence of ceramic debris. A worst-case scenario, assuming embedding of ceramic fragments in the PE liner, contamination of the test environment with third-body ceramic debris and continuous subluxation, was simulated in vitro. High wear rates were found for metal femoral ball heads, being 1,010 times higher when compared to ceramic femoral ball heads tested with XPE liners and 560 times higher when compared to ceramic femoral ball heads tested with PE liners. The test results indicate the use of ceramic femoral ball heads for revision surgery in the presence of ceramic fragments. © 2012 Elsevier Inc..


Schwiesau J.,Aesculap AG | Schilling C.,University of Stuttgart | Kaddick C.,EndoLab GmbH | Utzschneider S.,Ludwig Maximilians University of Munich | And 5 more authors.
Medical Engineering and Physics | Year: 2013

The objective of our study was the definition of testing scenarios for knee wear simulation under various highly demanding daily activities of patients after total knee arthroplasty. This was mainly based on a review of published data on knee kinematics and kinetics followed by the evaluation of the accuracy and precision of a new experimental setup. We combined tibio-femoral load and kinematic data reported in the literature to develop deep squatting loading profiles for simulator input. A servo-hydraulic knee wear simulator was customised with a capability of a maximum flexion of 120°, a tibio-femoral load of 5000. N, an anterior-posterior (AP) shear force of ±1000. N and an internal-external (IE) rotational torque of ±50. Nm to simulate highly demanding patient activities. During the evaluation of the newly configurated simulator the ability of the test machine to apply the required load and torque profiles and the flexion kinematics in a precise manner was examined by nominal-actual profile comparisons monitored periodically during subsequent knee wear simulation. For the flexion kinematics under displacement control a delayed actuator response of approximately 0.05. s was inevitable due to the inertia of masses in movement of the coupled knee wear stations 1-3 during all applied activities. The axial load and IE torque is applied in an effective manner without substantial deviations between nominal and actual load and torque profiles. During the first third of the motion cycle a marked deviation between nominal and actual AP shear load profiles has to be noticed but without any expected measurable effect on the latter wear simulation due to the fact that the load values are well within the peak magnitude of the nominal load amplitude. In conclusion the described testing method will be an important tool to have more realistic knee wear simulations based on load conditions of the knee joint during activities of daily living. © 2012 IPEM.


Kaddick C.,EndoLab GmbH | Blomer W.,Aesculap AG
Orthopade | Year: 2014

Background: Test standards are developed worldwide by extremely committed expert groups working mostly in an honorary capacity and have substantially contributed to the currently achieved safety standards in reconstructive orthopedics. Independent of the distribution and quality of a test specification, the specialist knowledge of the user cannot replace a well founded risk analysis and if used unthinkingly can lead to a false estimation of safety. Limits: The limits of standardization are reached where new indications or highly innovative products are concerned. In this case the manufacturer must undertake the time and cost-intensive route of a self-developed testing procedure which in the ideal case leads to a further testing standard. Conclusion: Test standards make a substantial contribution to implant safety but cannot replace the expert knowledge of the user. Tests as an end to themselves take the actual objectives of standardization to absurdity. © 2014 Springer-Verlag Berlin Heidelberg.


Grupp T.M.,Aesculap AG | Grupp T.M.,Ludwig Maximilians University of Munich | Yue J.J.,Yale University | Garcia R.,Aventura | And 5 more authors.
European Spine Journal | Year: 2015

Introduction: The objective of our in vitro study was to introduce a test method to evaluate impingement in lumbar spinal disc arthroplasty in terms of wear, contact pattern, metal ion concentration and particle release. Material and Method: Impingement wear simulation was performed on a 6-station spinal wear simulator (Endolab, Germany) on a lumbar spinal disc system (activ® L Aesculap AG, Germany) using four different protocols specific to impingement in flexion, in extension, in lateral bending and in combined flexion bending. Impingement contact stress is intentionally created by applying an angular displacement of +2° in addition to the intended range of motion in the impingement direction, whereas a bending moment of 8 Nm remains constant during the impingement phase (plateau). Results: An average volumetric wear rate of 0.67 mm3/million cycles was measured by impingement under flexion, of 0.21 mm3/million cycles under extension, of 0.06 mm3/million cycles under lateral bending and of 1.44 mm3/million cycles under combined flexion bending. The particle size distribution of the cobalt-chromium wear particles released by impingement in flexion (anterior), extension (posterior), lateral bending (lateral) and combined flexion bending (antero-lateral) revealed that most of the detected cobalt-chromium particles were in a size range between 0.2 and 2 µm. Conclusion: The impingement wear simulation introduced here proved to be suitable to predict in vivo impingement behaviour in regard to contact pattern seen on retrieved devices of the activ® L lumbar disc arthroplasty design in a pre-clinical test. © 2014, Springer-Verlag Berlin Heidelberg.

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