Ana Laura Puente Reyna

Metal ion and particle release of cobalt chrome in total hip arthroplasty has been shown to induce metal hypersensitivity, adverse local tissue reactions and systemic ion related diseases. The purpose of our study was to analyze the metal ion release barrier function of a cemented zirconium nitride (ZrN) multilayer coated hip stem subjected to an axial sinusoidal load of 3.875 kN for 10 million cycles in a completely cemented and well settled condition. An uncoated cobalt chromium alloy stem was tested in the tribo-system with the surrounding bone cement mantle for reference values of a clinically established material. Moreover, the ZrN coated hip stems were also tested under the worst-case scenario of debonding from the bone cement mantle and with high micro-motions due to toggling against the cement mantle to challenge the ZrN multilayer coating. Ion concentration comparison analysis showed a substantial reduction in the release of cobalt, chromium and molybdenum in the ZrN coated stems against the uncoated version, even during the worst-case scenario of high micro-motion by a severe implant debonding from the cement mantle.

Patients undergo total knee arthroplasty (TKA) at younger ages with the expectation that the devices will perform well over two to three decades. During this time, the ultra-high molecular weight polyethylene (UHMWPE) bearing material properties of the implant may change due to aging induced by radiation and oxygen diffusion or other effects. Vitamin E or other antioxidants are promoted since several years to improve the oxidation resistance of UHMWPE. To compare the effectivity of these substances against established materials, a six weeks aging process was used and the chemical, mechanical and bio-tribological properties were analysed. Highly crosslinked and two weeks aged UHMWPE served as a reference for the currently established aging standards and virgin UHMWPE was aged for six weeks to separate the effects of crosslinking and vitamin E blending. Six weeks artificially aging changed the chemical, mechanical and bio-tribological properties of cross-linked UHMWPE significantly compared to only two weeks artificially aging, leading to cracks and delamination during the highly demanding activities wear test. The degradative effect of extended aging was also observed for virgin UHMWPE. These observations are in good accordance to retrieval findings. Minor changes on the chemical properties were observed for the cross-linked UHWMPE blended with vitamin E without impact on the mechanical and bio-tribological properties.

This study aims to evaluate and compare the properties of a biomedical clinically established zirconium nitride (ZrN) multilayer coating prepared using two different techniques: pulsed magnetron sputtering and cathodic arc deposition. The investigation focuses on the crystalline structure, grain size, in-vitro oxidation behaviour and tribological performance of these two coating techniques. Experimental findings demonstrate that the sputter deposition process resulted in a distinct crystalline structure and smaller grain size compared to the arc deposition process. Furthermore, in vitro oxidation caused oxygen to penetrate the surface of the sputtered ZrN top layer to a depth of 700 nm compared to 280 nm in the case of the arc-deposited coating. Finally, tribological testing revealed the improved wear rate of the ZrN multilayer coating applied by sputter deposition.

The purpose of the study was to compare the mechanical properties, oxidation and wear resistance of a vitamin E blended and moderately crosslinked polyethylene for total knee arthroplasty (MXE) in comparison with clinically established polyethylene materials.The following polyethylene materials were tested: CPE (30 kGy e-beam sterilized), XLPE (75 kGy gamma crosslinked @ 100°C), ViXLPE (0.1 % vitamin E blended, 80 kGy e-beam crosslinked @ 100°C), and MXE (0.1 % vitamin E blended polyethylene, 30 kGy gamma sterilized). For the different tests, the polyethylene materials were either unaged or artificially aged for two or six weeks according to ASTM F2003-02.The oxidation index was measured based on ASTM F2102 at a 1 mm depth. Small punch testing was performed based on ASTM F2977. Mechanical properties were measured on unaged materials according to ASTM D638.Wear simulation was performed on a load controlled 3 + 1 station knee wear simulator (EndoLab GmbH, Thansau, Germany) capable of reproducing loads and movement of highly demanding activities (HDA) as well as ISO 14243-1 load profiles. The load profiles were applied for 5 million cycles (mc) or delamination of the polyethylene components. Medium size AS e.motion^® PS Pro (Aesculap AG, Tuttlingen, Germany) femoral and tibial components with a ZrN-multilayer surface, as well as Columbus^® CR cobalt-chrome alloy femoral and tibial components were tested. Particle analysis was performed on the serum samples of the ISO 14243-1 wear simulations based on ISO 17853:2011 and ASTM F1877.The analysis of the mechanical properties show that moderately crosslinked polyethylene (MXE) might be a superior material for total knee arthroplasty applications [Schwiesau et al. 2021]. The addition of vitamin E in a moderately crosslinked polyethylene prevented its oxidation, kept its mechanical characteristics, and maintained a low wear, even under a HDA knee wear simulation.

предыдущие исследования были посвящены износу тыльной поверхности кратковременно имплантированных вкладышей в сравнении со вкладышами, тестируемыми in vitro, в течение равного количества времени. в результате были продемонстрированы сравнимые результаты в обеих группах, при этом не было отмечено существенного износа тыльной поверхности вследствие микроподвижности. Цель исследования — получить данные об общем износе (артикулирующей поверхности и тыльной поверхности) полиэтиленовых вкладышей, стабилизированных 0,1% витамином е, которые блокировали за счет пресс-фит посадки в шероховатой титановой внутренней поверхности чашки. условия моделирования износа составляли 200 миллионов циклов движений тазобедренного сустава. Материал и методы. для оценки степени повреждения тыльной поверхности вкладышей использовали полуколичественный метод. степень износа сочленяющихся поверхностей определяли с использованием 3d координатно-измерительного прибора. Результаты. общий средний показатель износа тыльной поверхности вкладышей составил 22,00±2,59, максимальный общий показатель составил 147 после 5 млн циклов. авторы наблюдали увеличение среднего показателя до 31,92±5,57 через 10 млн циклов, при этом, дальнейшего увеличения показателей через 15 и 20 млн циклом не отмечали. контрольные вкладыши (подверженные только аксиальной нагрузке) продемонстрировали схожие показатели и модели износа как вкладыши, подверженные моделированию износа (аксиальная нагрузка и движение). небольшие царапины, нанесенные во время установки и удаления вкладышей, были четко видны в области фиксации, при этом значимого абразивного истирания не было отмечено. всегда были видны риски на выпуклой поверхности вкладышей. скорость износа сочленяющихся поверхностей составила 7 мкм/год. Выводы. Результаты исследования продемонстрировали, что основной объем износа тыльной стороны вкладышей происходит в процессе их установки и удаления, нежели в период функционирования протеза. Более того, объем износа артикулирующей поверхности был идентичен объему износа, который отмечали in vivo при кратко- и среднесрочной имплантации вкладышей из кросс-линк полиэтилена с высокими поперечными связями без или с добавлением витамина е.