Wyniki wyszukiwania - Biblioteka Nauki

1

Validation of computer models of an artificial hip joint

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Okrajni J. , Plaza M. , Ziemba S.

Archives of Materials Science and Engineering

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2007

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tom Vol. 28, nr 5

305-308

EN

Purpose: Problems of the modelling of the surgical cement behaviour during implantation have been presented in the paper. The purpose was to validate the FEM model describing the temperature fields in the bone during the surgery treatment. Design/methodology/approach: The physical laboratory modelling has been used to perform validation of the model that makes it possible to predict the temperature influence on the bone tissue during polymerization process. Findings: Due to its non-invasive nature, the computer models' validation method applied in the study seems to be the right solution for the research on surgical procedures of endoprosthesis implantation. However, a particular emphasis should be placed on a correct selection of thermophysical properties of the designed laboratory models. Relying on the calculations and research results, similar local values of maximum temperatures were obtained. Practical implications: The computer modelling methods presented in the paper together with the analytical approach are of great importance to both forecasting the implants' behaviour during a surgical procedure and in their operational conditions, as well as in the selection and modification process of surgical cements' material properties. The analysis carried out makes it possible to determine the location of zones most threatened with an adverse effect of an elevated temperature. They are located in the vicinity of the top of the endoprosthesis stem. Originality/value: The work presents the own method of validation of the FEM model used for heat flow modelling.

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Przepływ ciepła w warstwie cementu chirurgicznego z dodatkiem cząstek AL203

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Okrajni J. , Ziemba S. , Stumpf J.

Inżynieria Materiałowa

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2007

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tom Vol. 28, nr 2

73-78

PL

Opis zjawiska przepływu ciepła w warstewce cementu chirurgicznego i możliwości ograniczenia niekorzystnego wpływu cementu na organizm człowieka wymaga dokładnego poznania procesu polimeryzacji w ujęciu termodynamicznym. Szczególne znaczenie ma przy tym zagadnienie opisu źródła ciepła będącego efektem reakcji chemicznej, którego czasowe charakterystyki decydują o intensywności oddziaływania polimeru na organizm. Praca koncentruje się na opisie źródłowego pola temperatury w warstewce cementu chirurgicznego. Przedstawiono w niej wyniki pomiarów umożliwiających wyznaczenie charakterystyk wewnętrznego źródła ciepła w cemencie. W pracy wyznaczono rozkład temperatury w płycie dla różnych wartości współczynnika wyrównywania temperatury. Wykonano pomiary temperatury cementu polimeryzującego pomiędzy dwiema ściankami drewnianych foremek w kąpieli wodnej o temperaturze 37 °C. Wyznaczono wpływ domieszki A1203 na właściwości cieplne kompozytu PMMA + A1203 oraz na temperaturę maksymalną w procesie polimeryzacji. Opracowany model procesu przepływu ciepła pozwala ocenić kierunek zmian spowodowany dodatkami komponentów, oraz oszacować wartość temperatury maksymalnej dla danego ich udziału objętościowego. Praca wskazuje na potrzebę dalszych badań zjawiska przepływu ciepła w warstewce cementu chirurgicznego.

EN

A description of the heat flow phenomenon in a surgical cement layer and of the chance to reduce the disadvantageous influence of surgical cement on the human organism (Fig. 1) requires in-depth understanding of the polymerization process from the thermodynamic point of view. The problem of a description of the heat source, being the effect of a chemical reaction, is of particular importance, since its time characteristics determine the intensity of polymer influence on the human organism. This paper focuses on the description of the source temperature field in a surgical cement film. The results of measurements (Fig. 2, 3) are presented which allow the determination of the characteristics of the internal heat source in cement (Fig. 4). The paper discribes temperature distribution in a plate, determined for different values of temperature diffusivity coefficient. The temperature field modelling results are presented in Fig. 5+7. Temperature measurements were made of the cement located between thin wooden plates in water bath of a temperature of 37 °C (Fig. 8,9). Data concerning the thermal properties of PMMA and A1203 admixture are gathered in (Table 1). The influence has been determined of the A1203 admixture on the thermal properties of the PMMA + A1203 composite (Table 2). The maximum temperature of the cement layer has been determined as the function of the A1203 admixture (Fig. 10). The heat flow model developed enables the evaluation of the direction of changes caused by addition of components as well as the estimation of the maximum temperature of the cement during polymerization.

3

Wpływ domieszki tytanu na właściwości fizykochemiczne cementu chirurgicznego

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Balin A. , Ziemba S. , Myalski J. , Toborek J.

Inżynieria Biomateriałów

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2006

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tom R. 9, nr 58-60

60-62

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Metodyka oceny przepływu ciepła w zabiegach protezoplastyki

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Ziemba S. , Jasik A. , Plaza M.

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tom Vol. 10, no. 69-72

99-101

5

Description of heat flow in a surgical cement layer

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Okrajni J. , Ziemba S. , Stumpf J.

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tom Vol. 8, nr 2

135-142

EN

The hip joint alloplasty is one of the surgical treatments often performed in clinics and in traumaorthopaedic departments of hospitals. The popular method for connecting pelvis and femoral component with a bone during alloplasty is the use of a thin surgical cement layer. During a surgery, thermal properties of the cement, e.g., high polymerization temperature, appear to be harmful. The understanding of thermodynamic phenomena occurring during polymerization process is necessary to limit harmful cement influence on human body. Thus the description of the heat release due to chemical reactions is especially important. The paper deals mainly with the description of the heat source and temperature field in the surgical cement layer. Characteristics of the heat source in the cement were described. The temperature distributions in the cement layers at different values of thermal diffusivity coefficient were presented.

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Computer modelling of the heat flow in surgical cement during endoprosthesoplasty

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Okrajni J. , Plaza M. , Ziemba S.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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tom Vol. 20, nr 1-2

311-314

EN

Purpose: The problem of the modelling of the surgical cement behavior during implantation has been presented in the paper. The purpose was to find the proper model describing the temperature fields in the bone during the surgery treatment. Design/methodology/approach: Computer modelling has been used to predict the temperature influence on the bone tissue during polymerization process. Findings: During orthopaedic surgical procedures with the use of methyl polymethacrylate surgical cements, the temperature sometimes reaches 80 degrees centigrade, which causes atrophy of the bone tissue. The process occurs locally, since it depends on both the amount of polymerization heat generated during the reaction and on the heat exchange conditions at cement-bone tissue and bone cement - implant boundaries. Striving to better understand the above-mentioned phenomena through a model approach, models were developed under the study to calculate temperature distributions in the bone and in implant components during the procedure of endoprosthesis stem implantation. Calculations were made for different cement layer thickness variants and for different amount of cement concentrated around the top of the stem. The characteristics of temperature changes with time in different points of the bone and cement have been determined and temperature distributions in bone and cement for selected instants of time have been worked out. Practical implications: The analysis carried out makes it possible to determine the location of areas most threatened with an adverse effect of an elevated temperature. In each case, they are located in the vicinity of the top of the endoprosthesis stem. These conclusion together with obtained data should be important for the surgeons during surgical operation. Originality/value: The work presents the own method of heat flow modelling during the polymerization of surgical cements. The results of the own method of the heat source characteristic description has been shown as well.

7

Examination of heat flow in a model of the biomechanical prosthesis-cement-bone system

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Balin A. , Ziemba S. , Plaza M. , Myalski J. , Toborek J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2006

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tom z. 26

29-34

EN

Under the study, a stand has been designed and made for examining the temperature of PMMA-based (methyl polymethacrylate) surgical cement polymerization in conditions corresponding to the conditions of its implantation into an organism. A Weller endoprosthesis was implanted in a bone model made of resin by means of Palacos R-40 cement. The temperature of polymerizable cement was measured in different points at the border of its contact with the bone model.