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Povzetek: In this paper, we present the mechanisms of premature fracture of modular neck stems in two case studies: (I) when the neck and stem are both made of the same Ti6Al4V alloy, and (II) when the neck and stem are made from two different alloys, CoCrMo and Ti6Al4V alloy. Our study integrates two orthopedic patients who have undergone primary uncemented THA for usual indications in two orthopedic centers (Community Health Centre and University Medical Centre). Both centers are part of the national public health care system. Both surgeries were performed by two skilled orthopedic surgeons with more than 10 years of experience in THA. The survivorship of the modular neck of cast CoCrMo alloy was 24 months. The survivorship of the modular neck from Ti6Al4V alloy was 84 months. Multivariate analyses were performed to assess the differences in the fretting, corrosion, and fatigue of the two prematurely failed modular neck stems: stereo light microscopy (SLM), scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). Patient demographic information, including sex, age, body mass index, survivorship of implants, and reason for the revision, was collected from medical records. We found that fretting and fatigue occurred on both neck-stem retrievals due to additional galvanic corrosion, but the CoCrMo/Ti6Al4V alloy system suffered more corrosion due to additional galvanic corrosion and fractured earlier than the Ti6Al4V/Ti6Al4V metal alloy system. Both metallic alloy systems used in this application are known to be highly corrosion-resistant, but the bio-tribo-corrosion processes need to be understood in detail and characterized so that appropriate improvements in design and materials can be made.
Ključne besede: total hip arthroplasty, modular neck, Ti6Al4V alloy, CoCrMo alloy, corrosion
Objavljeno v DiRROS: 07.02.2024; Ogledov: 257; Prenosov: 134
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Ključne besede: tungsten, tungsten carbide, interface, microstructure, fusion energy
Objavljeno v DiRROS: 07.02.2024; Ogledov: 158; Prenosov: 85
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Ključne besede: endoprosthesis failure, corundum, cytokines, reactive oxygen species, lipid droplets
Objavljeno v DiRROS: 02.02.2024; Ogledov: 222; Prenosov: 85
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Povzetek: The hematopoietic stem cell (HSC) niche undergoes detrimental changes with age. The molecular differences between young and old niches are well studied and understood; however, young and old niches have not yet been extensively characterized in terms of morphology. In the present work, a 2D stromal model of young and old HSC niches isolated from bone marrow was investigated using light and scanning electron microscopy (SEM) to characterize cell density after one, two, or three weeks of culturing, cell shape, and cell surface morphological features. Our work is aimed at identifying morphological differences between young and old niche cells that could be used to discriminate between their respective murine HSC niches. The results show several age- specific morphological characteristics. The old niches differ from the young ones in terms of lower cell proliferating capacity, increased cell size with a flattened appearance, increased number of adipocytes, and the presence of tunneling nanotubes. In addition, proliferating cell clusters are present in the young niches but not in the old niches. Together, these characteristics could be used as a relatively simple and reliable tool to discriminate between young and old murine HSC niches and as a complementary approach to imaging with specific cellular markers.
Ključne besede: bone marrow, hematoopetic stem cell niche, aging, adipocytes, scanning electron microscopy
Objavljeno v DiRROS: 26.01.2024; Ogledov: 231; Prenosov: 112
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Povzetek: Purpose. Most published grading systems of soft tissue sarcomas (STS) are somewhat subjective and it seems that there is no definite consensus among experts which of them is the most effective. The aim of this study was to collect data from practicing pathologists and to get some insight in the practice of STS grading. Subjects. A questionnaire was sent to 135 pathologists chosen randomly. Results. There were 88 responders from 30 countries from 5 continents. Most responders (85%) grade STS, more frequently in Europe than in non-European countries. Three-grade system is preferred by both European and non-European pathologists, who use it in almost 77% and 67%,respectively. They apply the criteria set by FNCLCC in 37.3%, by NCI in 24%, by Broders in 12% and by Markhede in 1.4%. In Europe, FNCLCC system is the most widely used. Beside classical histological criteria, other modern methods are applied by more than one half of the responders. Immunohistochemical evaluation of proliferation markers is the method most widely used, followed by molecular markers and DNA flow cytometry. Conclusion.The results of our study indicate that most pathologists consider histologic grade of STS as a valuable, however not completely satisfactory predictor of a patients survival.
Objavljeno v DiRROS: 25.01.2024; Ogledov: 196; Prenosov: 43
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