[Comparison of Explanted UHMWPE Hip Replacement Components of Various Manufacturers after 10 Years in vivo]. / Porovnání explantovaných UHMWPE komponent náhrady kycelního kloubu ruzných výrobcu po 10 letech in vivo.

PURPOSE OF THE STUDY Considered to be one of the most common causes of aseptic loosening of endoprostheses is the THA failure due to the wear of articulating components, UHMWPE in particular. The purpose of this study is to verify, in terms of oxidative damage and other parameters, the differences between the UHMWPE implants made by various manufacturers explanted for aseptic loosening with the same life span in vivo. MATERIAL AND METHODS In the period 2010-2015, a total of 21 THA articulating components (cups) made of Ultrahigh molecular weight polyethylene by seven different manufacturers were explanted. For each manufacturer, three UHMWPE cups with the same life span (10-12 years after the primary implantation) were evaluated. The damage to the examined joint replacements was described in complexity using three different criteria, namely independently by three evaluators - experienced orthopaedic surgeons. The evaluated criteria were the following: degree of osteolysis determined based on the preoperative radiographs, wear rate of the explanted UHMWPE component, and extent of perioperatively detected granuloma. Oxidative damage and other structural characteristics of explanted cups were studied by means of infrared spectroscopy and microhardness testing. The correlation between the clinical orthopaedic assessment and oxidative damage were statistically processed. RESULTS Strong correlations between the oxidative damage and crystallinity, strong correlations between all types of orthopaedic assessments, negligible correlations between trans-vinylene index and all the other quantities, and moderate correlations between the oxidative damage and clinical evaluation were identified. It was confirmed by experimental measurement that the observed high oxidative damage, resulting in increased crystallinity, manifested itself also in micromechanical properties of the material at the respective site of the THA articulating component. DISCUSSION The discussion includes the comparison of correlations of individual quantities as well as potential effects on the differences in values of components made by individual manufacturers. The values are related to the data in literature and generally accepted claims. CONCLUSIONS At the time of failure almost all the components showed severe or even critical oxidative damage that strongly correlated with the overall clinical evaluation of the damage to the implant. This confirmed that the oxidative degradation is one of the main causes of THA failure. Key words: UHMWPE, oxidation index, crystallinity, THA failure, wear.

Thermoplastic starch composites with TiO2 particles: Preparation, morphology, rheology and mechanical properties.

Composites of thermoplastic starch (TPS) with titanium dioxide particles (mTiO2; average size 0.1µm) with very homogeneous matrix and well-dispersed filler were prepared by a two-step method, including solution casting (SC) followed by melt mixing (MM). Light and scanning electron microscopy confirmed that only the two-step procedure (SC+MM) resulted in ideally homogeneous TPS/mTiO2 systems. The composites prepared by single-step MM contained non-plasticized starch granules and the composites prepared by single-step SC suffered from mTiO2 agglomeration. Dynamic mechanical measurements showed an increase modulus with increasing filler concentration. In TPS containing 3wt.% of mTiO2 the stiffness was enhanced by >40%. Further experiments revealed that the recommended addition of chitosan or the exchange of mTiO2 for anisometric titanate nanotubes with high aspect ratio did not improve the properties of the composites.

[Analysis of Oxidative Damage to Components Removed from Beznoska/Poldi Total Hip Replacements]. / Analýza oxidacního poskození explantovaných komponent náhrady kycelního kloubu Beznoska/Poldi.

UNLABELLED: PURPOSE OF THE STUDY Ultrahigh molecular weight polyethylene (UHMWPE) is today the most frequently used bearing surface in total joint replacements (TJR) because of its properties, i.e., excellent biocompatibility, good mechanical and tribological performance and high wear resistance. UHMWPE liners are the most loaded TJR components and, therefore, their properties are decisive for TJR longevity. This study had three objectives: 1) to evaluate the oxidative degradation of explanted UHMWPE components; 2) to look for a statistically significant relationship between the extent of oxidative degradation and the durability of joint replacements; and 3) to investigate whether the durability of a TJR was related to the type of sterilisation used in manufacture. MATERIAL AND METHODS The study included 26 acetabular components obtained at revision arthroplasty between 2004 and 2013 from patients in whom a Beznoska/Poldi total hip replacement was used in the period from 1977 to 2002. The average age of the patients at the time of primary implantation was 57.9 years, the average longevity of the components removed was 18.63 years (range, 6.9 to 27.9 years). Samples of worn out and unworn areas from explanted components were processed in a three-step procedure in order to finally obtain 2-mm microtome sections. These were studied by infrared microspectroscopy. Oxidative damage to UHMWPE was determined as the oxidation index (OI); radiation damage to UHMWPE during sterilization was evaluated as the transvinylene index (VI); oxidation-induced changes in the polymer structure and its properties were characterised as the crystallinity index (CI); and local changes in mechanical properties due to oxidative degradation were assessed as microhardness (MH). Spearman's correlation coefficient and the Wilcoxon two-sample test were used for statistical analysis. RESULTS The OI values (average and maximum) in both worn out and unworn surface areas were related to component longevity. The difference between the oxidation index of ruptured components and that of the other components was statistically significant. Significant differences were also found between the average and maximum OI values of worn out areas and those of unworn surfaces. The relationship between the average oxidation index in both the unworn and worn out areas of UHMWPE components and the longevity of cracked components was statistically significant. DISCUSSION Our results show that the OI values obtained by microspectroscopy correlated with both the microscopic damage and the longevity of UHMWPE liners and the correlation was statistically significant also in relation to the longevity of total replacements. Relationships amongst OI, VI, CI and MH values as well as their relation to failure and longevity of total replacements are discussed. CONCLUSIONS It can be concluded that infrared microspectroscopic measurement of OI values is a simple and fast method to characterise UHMWPE liners. In addition, the IR spectra also show other supplementary characteristics, such as VI and CI indices. These values provide information on the quality of various UHMWPE types currently used in TJR surgery. The types of UHMWPE which exhibit high oxidative degradation should be avoided in clinical practice due to increased risk of early TJR failure. Responsible orthopedic surgeons should be aware of this fact and, if possible, collaborate with an independent, noncommercial laboratory in order to evaluate the quality of various UHMWPE liners used in their hospitals. KEY WORDS: UHMWPE, oxidation, total joint replacement, infrared spectroscopy, microhardness.