Vitamin E-enriched medium cross-linked polyethylene in total knee arthroplasty (VIKEP): clinical outcome, oxidation profile, and wear analysis in comparison to standard polyethylene-study protocol for a randomized controlled trial.

BACKGROUND: The gliding surface of total knee endoprostheses is exposed to high loads due to patient weight and activity. These implant components are typically manufactured from ultra-high molecular weight polyethylene (UHMWPE). Crosslinking of UHMWPE by ionizing radiation results in higher wear resistance but induces the formation of free radicals which impair mechanical properties after contact with oxygen. Medium-crosslinked UHMWPE enriched with vitamin E (MXE) provides a balance between the parameters for a sustainable gliding surface, i.e., mechanical strength, wear resistance, particle size, and oxidation stability. Therefore, a gliding surface for knee endoprostheses made up from this material was developed, certified, and launched. The aim of this study is to compare this new gliding surface to the established predecessor in a non-inferiority design. METHODS: This multicenter, binational randomized controlled trial will enroll patients with knee osteoarthritis eligible for knee arthroplasty with the index device. Patients will be treated with a knee endoprosthesis with either MXE or a standard gliding surface. Patients will be blinded regarding their treatment. After implantation of the devices, patients will be followed up for 10 years. Besides clinical and patient-related outcomes, radiological data will be collected. In case of revision, the gliding surface will be analyzed biomechanically and regarding the oxidative profile. DISCUSSION: The comparison between MXE and the standard gliding surface in this study will provide clinical data to confirm preceding biomechanical results in vivo. It is assumed that material-related differences will be identified, i.e., that the new material will be less sensitive to wear and creep. This may become obvious in biomechanical analyses of retrieved implants from revised patients and in radiologic analyses. TRIAL REGISTRATION: ClinicalTrials.gov, NCT04618016. Registered 27 October 2020, https://clinicaltrials.gov/study/NCT04618016?term=vikep&checkSpell=false&rank=1 . All items from the World Health Organization Trial Registration Data Set can be found in Additional file 1.

Systematic Comparison of IgM and IgG ABO Antibody Titers by Using Tube and Gel Card Techniques and its Relevance for ABO-Incompatible Kidney Transplantation.

BACKGROUND: Although the determination of the ABO antibody titers is necessary for the decision-making in ABOincompatible (ABOi) kidney transplantations, various methods for the determination of the ABO antibody titers are being used. However, the absence of uniform standards makes their comparability far more difficult. Two of the most commonly used methods are the tube method and the gel card method. In this study, we systematically investigate to what extent these two methods affect the result of ABO antibody titers. METHODS: ABO antibodies were determined from plasmas of 90 donors (30 individuals each with blood group A, B, and O). Seven further donors with blood group A, B, and AB provided erythrocytes for the testing. A total of 360 ABO antibody titers were determined; 180 tests for each method, each with 90 determinations of immunoglobulin G (IgG) and immunoglobulin M (IgM) antibody titers. In addition, we also made a differentiation by blood groups to find out if and to what extent the blood groups have an impact on the results. RESULTS: Our analysis shows that the choice of method has a highly significant (p < 0.0001) impact on the titer level of the ABO antibodies. The median values of ABO antibody titers determined by using the gel card method are two titer steps lower than the titers, which are determined when using the tube method. Moreover, our data shows that there are major differences in the ABO antibody titer level among the blood groups, regardless of the choice of methods. CONCLUSIONS: We consider changing to the gel card method for determining the ABO antibody titers as a simple and effective way to achieve a standardized and uniform method. Here, too, the clinicians should be provided with sufficient information by the laboratories, in order to draw the right consequence from this change, while considering all the relevant data. As a consequence of this study, the transplant center of the University of Hamburg-Eppendorf paired a change from tube to gel card regarding the ABO antibody titer determination of ABOi kidney transplantations with an intensification of the preoperative target titer from ≤ 1:8 to ≤ 1:4.