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Milosev I.,Jozef Stefan Institute | Milosev I.,Orthopaedic Hospital Valdoltra
Electrochimica Acta | Year: 2012

CoCrMo orthopaedic alloy was oxidized potentiostatically in various simulated physiological solutions in order to reveal differences in the composition, thickness and structure of the surface layers formed as a function of solution composition. X-ray photoelectron spectroscopy, combined with angle-resolved measurements and depth profiling, was used for the purpose. The following simulated physiological solutions were used: (1) 0.9% NaCl, (2) simulated Hanks physiological solution containing various inorganic salts, (3) simulated Hanks physiological solution containing an aliquot of synovial fluid retrieved at a primary operation, and (4) minimum essential medium containing various inorganic salts, amino acids and vitamins. No significant differences between alloy treated in these solutions were observed after oxidation in the passive region; the oxide films are a few nanometres thick and, except in NaCl solution, contain a small amount of calcium phosphate. After oxidation at a potential in the transpassive range, however, the oxide thickness increases considerably due to incorporation of cobalt and molybdenum oxides. Further, the concentration of calcium phosphate increases. The layers formed in minimum essential medium and Hanks solution containing synovial fluid comprise nitrogen and carbon containing species. The addition of synovial fluid significantly affects the behaviour in Hanks solution. © 2012 Elsevier Ltd.

Vengust R.,University of Ljubljana | Mihalic R.,Orthopaedic Hospital Valdoltra | Turel M.,University of Ljubljana
European Spine Journal | Year: 2010

We report a case of 73-year-old man with massive hyperostosis of the cervical spine associated with diffuse idiopathic skeletal hyperostosis (DISH), resulting in dysphagia, hoarseness and acute respiratory insufficiency. An emergency operation was performed, which involved excision of osteophytes at the level of C6-C7, compressing the trachea against enlarged sternoclavicular joints, also affected by DISH. Approximately 3 years later, the patient sustained a whiplash injury in a low impact car accident, resulting in a C3-C4 fracture dislocation, which was not immediately diagnosed because he did not seek medical attention after the accident. For the next 6 months, he had constant cervical pain, which was growing worse and eventually became associated with dysphagia and dyspnoea, ending once again in acute respiratory failure due to bilateral palsy of the vocal cords. The patient underwent a second operation, which comprised partial reduction and combined anteroposterior fixation of the fractured vertebrae. Twenty months after the second operation, mild hoarseness was still present, but all other symptoms had disappeared. The clinical manifestations, diagnosis and treatment of the two unusual complications of DISH are discussed. © Springer-Verlag 2009.

Trost Z.,University of Ljubljana | Trebse R.,Orthopaedic Hospital Valdoltra | Prezelj J.,University of Ljubljana | Komadina R.,General and Teaching Hospital Celje | And 2 more authors.
Bone | Year: 2010

Genetic factors influencing the pathogenesis of osteoporosis are still largely unknown. We employed genome-wide gene expression approach in order to discover novel genes involved in the pathogenesis of osteoporosis. To this end, primary cultures of osteoblasts isolated from osteoporotic and non-osteoporotic human bone tissue samples were prepared. One thousand six hundred six genes were found to be differentially expressed, indicating increased demand for protein synthesis and decreased cell proliferation rate in osteoblasts from osteoporotic tissue as compared to osteoblasts from non-osteoporotic tissue. At first, top four genes, based on the microarray data and potential role in bone metabolism, were further studied in bone tissue samples of 55 patients. PTN and COL15A1 were both downregulated in osteoporotic bone tissue (6.2- and 3.4-fold, respectively, both p < 0.05), while IBSP and CXCL2 were both upregulated (5.7-fold, p < 0.05, and 2.1-fold, p > 0.05). Further biostatistical analysis of the microarray data by gene set enrichment analysis suggested oxidative stress may have an important part in the pathogenesis of osteoporosis. Thus, secondly, we tested it by an in vitro assay on human osteosarcoma cell line cells treated with hydrogen peroxide. After 72 h of treatment with 500 μM hydrogen peroxide, the upregulation of the same genes involved in the response to oxidative stress as on the microarrays was observed: MT1G (metallothionein 1G, 22.1-fold, p < 0.05), TXNRD1 (thioredoxin reductase 1, 3.7-fold, p < 0.05), AOX1 (aldehyde oxidase 1, 24.5-fold, p < 0.05) and GSR (glutathione reductase, 4.7-fold, p < 0.05). Our results present a novel list of genes and metabolic pathways that may be associated with the pathogenesis of osteoporosis. PTN, CXCL2, COL15A1, IBSP, AOX1, MT1G, GSR and TXNRD1 are candidate genes for further studies in the assessment of the genetic susceptibility to osteoporosis. In addition, differences in protein synthesis, cell proliferation rate and response to oxidative stress may also be involved in the pathogenesis of osteoporosis. © 2009 Elsevier Inc. All rights reserved.

Milosev I.,Jozef Stefan Institute | Milosev I.,Orthopaedic Hospital Valdoltra | Kapun B.,Jozef Stefan Institute
Materials Science and Engineering C | Year: 2012

The effect of surface treatment - boiling in water and thermal oxidation at temperatures up to 600 °C - on the corrosion behavior of Nitinol was investigated in simulated Hanks physiological solution using electrochemical polarization methods. Morphological and compositional properties of the modified surfaces were analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy and Auger electron spectroscopy depth profiling. Surface preparation - grinding or polishing - is shown to have a decisive role in the degree of improvement of corrosion properties by surface treatments. Low temperature treatments like boiling in water and thermal oxidation at 100°C resulted in the formation of oxide layers only a few nanometers thick, and composed mainly of TiO 2 and a small amount of NiO. These layers are well able to protect the underlying Nitinol substrate. Up to 500°C, surface preparation directly determines the thickness of the oxide scale, as a 20-fold difference in thickness is observed between ground and polished samples. At higher temperatures, the oxide thickness was similar for the two samples. A multilayer structure is observed at all temperatures investigated. The outermost layer at the oxide/air interface is composed of TiO 2 and NiO, while the interior of the oxide scale is composed exclusively of TiO 2. Oxide layers formed by thermal oxidation at elevated temperatures also improve the corrosion characteristics of Nitinol, especially for polished substrates. © 2011 Elsevier B.V. All rights reserved.

Milosev I.,Jozef Stefan Institute | Milosev I.,Orthopaedic Hospital Valdoltra | Kapun B.,Jozef Stefan Institute
Materials Science and Engineering C | Year: 2012

The corrosion behaviour of Nitinol alloy containing nearly equi-atomic composition of nickel and titanium and its constituent metals (nickel and titanium) was investigated in simulated Hanks physiological solution (pH value 7.5) and pH modified simulated Hanks physiological solution (pH values 4.5 and 6.5) and by electrochemical method of anodic potentiodynamic polarization at 37°C. In this chloride-rich medium the corrosion stability of Nitinol is limited by the susceptibility to localized corrosion and is in that sense more similar to nickel than to titanium. The corrosion stability of Nitinol is strongly dependent on the surface preparation - grinding, polishing or chemical etching. Whereas a ground surface is not resistant to localized corrosion, polished and chemically etched surfaces are resistant to this type of corrosion attack. The reasons for this behaviour were investigated through metallurgical, topographical and chemical properties of the surface as a function of surface preparation. For that purpose, scanning electron microscopy combined with chemical analysis, confocal microscopy and X-ray photoelectron spectroscopy were used. The surface roughness decreased in the following order: chemically etched > ground > polished surface. Besides differences in topography, distinct differences in the chemical composition of the outermost surface are observed. Ground, rough surfaces comprised mainly titanium oxides and small amounts of nickel metal. Chemically etched and, especially, polished surfaces are composed of a mixture of titanium, nickel and titanium oxides, as studied by angle resolved X-ray photoelectron spectroscopy. These results emphasize the importance of detailed investigation of the metal surface since small differences in surface preparation may induce large differences in corrosion stability of material when exposed to corrosive environments. © 2011 Elsevier B.V. All rights reserved.

Topolovec M.,Orthopaedic Hospital Valdoltra | Milosev I.,Orthopaedic Hospital Valdoltra | Milosev I.,Jozef Stefan Institute
Journal of Arthroplasty | Year: 2014

We present a retrospective evaluation of 1369 hip arthroplasties performed using the Bicon-Plus cups and SL-Plus stems, differing only in the bearing combination. Four bearing combination groups were used: metal-on-polyethylene (MoP) group with 587 hips, ceramic-on-polyethylene (CoP) group with 161 hips, metal-on-metal (MoM) group with 322 hips and ceramic-on-ceramic (CoC) group with 299 hips. The mean follow-up was 11.5. years (4.1 to 15.0). Radiological evaluation was performed on implants failed due to aseptic loosening. The survival for prosthesis with revision for any reason at ten years was 96.1% (95% confidence interval (CI) 94.3 to 97.9) for MoP, 98.1% (CI 95.9 to 100) for CoP, 90.2% (CI 86.8 to 93.6) for MoM, and 95.6% (CI 93.0 to 98.2) for CoC. Survival for aseptic loosening was also determined. © 2014 Elsevier Inc.

Rak M.,University of Primorska | Barlic-Maganja D.,University of Primorska | Kavcic M.,Institute of Public Health Koper | Trebse R.,Orthopaedic Hospital Valdoltra | And 2 more authors.
FEMS Microbiology Letters | Year: 2013

Diagnosis of prosthetic joint infection with culture technique can be problematic since the causative agent(s) are not possible to cultivate in all cases. Molecular methods had been evaluated in many studies but their inclusion in routine diagnostics is still controversial. The purpose of our prospective study was to compare the diagnostic accuracy of broad-range (BR)-PCR and culture technique. Intraoperative samples of periprosthetic tissue were retrieved in 67 patients undergoing revision arthroplasty. Samples were analyzed with culture technique, immunohistochemistry and BR 16S rRNA gene PCR. Bacteria in PCR-positive samples were identified using two different methods: direct sequencing of PCR products and specific TaqMan assays. In 63 cases, full concordance was found between BR-PCR and culture technique. Specific TaqMan assays failed to identify bacteria in four culture- and BR-PCR-positive cases and therefore had a lower sensitivity in comparison with BR-PCR. Molecular methods detected bacteria with the same accuracy as culture; however, identification of bacteria was inferior to culture. Further development of species-recognition techniques is required to improve identification of causative microorganisms. © 2013 Federation of European Microbiological Societies.

Trebse R.,Orthopaedic Hospital Valdoltra
HIP International | Year: 2012

Infection is becoming the most important as well as the most devastating mechanism of prosthetic joint failure. The incidence is increasing because the absolute number of patients operated is increasing and because more often very sick, debilitated and immunocompromised patients are operated. The trend reveals a further increase in the years to come. Diagnosis may be very easy in case of high grade processes, but also extremely difficult in some other instances. Misdiagnosing infection leads to repeated early failures that are distressing for patients as well as surgeons. To avoid failures related to misdiagnosed prosthetic joint infections a step-wise algorithm of action is proposed and the diagnostic strength of the steps discussed. The key point is to select potential candidates to define the probability of an ongoing infection and then to select the tools to strengthen the suspicion. Further procedures are based on the analysis of the pseudo-synovial fluid obtained by aspiration. Diagnostic conclusions form the basis for treatment decisions. © 2012 Wichtig Editore.

Milosev I.,Orthopaedic Hospital Valdoltra | Kovac S.,Orthopaedic Hospital Valdoltra | Trebse R.,Orthopaedic Hospital Valdoltra | Levasic V.,Orthopaedic Hospital Valdoltra | Pisot V.,Orthopaedic Hospital Valdoltra
Journal of Bone and Joint Surgery - Series A | Year: 2012

Background: To improve the long-term performance of hip prostheses, alternative bearings with metal-on-metal (MoM) and ceramic-on-ceramic (CoC) couples have been introduced. Although currently the results from the use of these bearings are in the midterm stage, there have been few comparative studies of these different bearings. Methods: From 2000 to 2002, 487 total hip replacements were performed with use of a BICON-PLUS acetabular cup and an SL-PLUS femoral stem (Plus Orthopedics, Rotkreuz, Switzerland, now Smith & Nephew Orthopaedics). The patients were divided into three groups according to the type of bearing that was used: an MoM group (sixty-nine prostheses), a metal-on-polyethylene (MoP) group (200 prostheses), and a CoC group (218 prostheses). Patient demographic data and data with regard to revision operations were evaluated from the hospital computer database. The mean follow-up period was 8.5 years (range, 6.9 to 10.5 years). Patient activity was assessed with use of the University of California at Los Angeles activity scale. Results: The mean patient age was sixty years at the time of the index arthroplasty in the MoM and CoC groups, and seventy-one years in the MoP group. Based on a scale of ten, the mean postoperative activity level was six in the CoC group, five in the MoM group, and four in the MoP group. Survival at ten years with regard to revision for any reason was 0.984, 0.956, and 0.879 for the MoP, CoC, and MoM groups, respectively. When revision for any reason was considered as the end point, survival of the MoM bearings was significantly worse than that of the MoP bearings (p = 0.005). Survival at ten years with regard to revision for aseptic loosening was 0.995, 0.990, and 0.894 for the MoP, CoC, and MoM groups, respectively. When revision for aseptic loosening was considered as the end point, survival of the MoM group was significantly worse than that of either the MoP group (p = 0.001) or the CoC group (p = 0.003). Conclusions: When comparing two groups of patients of similar mean age and mean activity level undergoing total hip arthroplasty with the use of alternative bearings, CoC bearings had better survival than did MoM bearings at the ten-year follow-up; the difference was significant when revision for aseptic loosening was defined as a failure. However, neither the CoC nor the MoM alternative bearings provided improved midterm results when compared with the results of the conventional MoP bearings. For older, less active patients, traditional metal-on-polyethylene bearings are the appropriate choice. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence. Copyright © 2012 by The Journal of Bone and Joint Surgery, Incorporated.

Milosev I.,Orthopaedic Hospital Valdoltra
Pure and Applied Chemistry | Year: 2011

Prolongation of the average life expectancy and an active lifestyle in old age are related to the constant increase in the number of joint diseases that eventually require a surgical procedure. The diseased joint is replaced with a joint prosthesis, the functionality of the joint is recovered, and pain is reduced. In the last decade, the number of joint replacement operations has increased several times over and is expected to increase further. In order to enable patients to have a painless and active lifestyle, it is necessary to develop materials that are long-lasting in vivo. Metallic biomaterials must exhibit high corrosion and wear resistance. In vitro research on materials under simulated physiological conditions is presented. These experiments are complemented by examples from clinical practice performed in collaboration with orthopedic surgeons. Morphological and chemical changes in the material during the course of in vivo performance are related to processes of wear and corrosion. The local and systemic consequences of these processes in the human body are presented. © 2010 IUPAC.

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