Axially rigid steerable needle with compliant active tip control.

Steerable instruments allow for precise access to deeply-seated targets while sparing sensitive tissues and avoiding anatomical structures. In this study we present a novel omnidirectional steerable instrument for prostate high-dose-rate (HDR) brachytherapy (BT). The instrument utilizes a needle with internal compliant mechanism, which enables distal tip steering through proximal instrument bending while retaining high axial and flexural rigidity. Finite element analysis evaluated the design and the prototype was validated in experiments involving tissue simulants and ex-vivo bovine tissue. Ultrasound (US) images were used to provide visualization and shape-reconstruction of the instrument during the insertions. In the experiments lateral tip steering up to 20 mm was found. Manually controlled active needle tip steering in inhomogeneous tissue simulants and ex-vivo tissue resulted in mean targeting errors of 1.4 mm and 2 mm in 3D position, respectively. The experiments show that steering response of the instrument is history-independent. The results indicate that the endpoint accuracy of the steerable instrument is similar to that of the conventional rigid HDR BT needle while adding the ability to steer along curved paths. Due to the design of the steerable needle sufficient axial and flexural rigidity is preserved to enable puncturing and path control within various heterogeneous tissues. The developed instrument has the potential to overcome problems currently unavoidable with conventional instruments, such as pubic arch interference in HDR BT, without major changes to the clinical workflow.

Comportamento biomecânico de caninos desgastados por atrição frente a diferentes técnicas restauradoras / Canine guide reconstruction with diferente technics: influence on biomechanics properties

O objetivo do estudo foi avaliar o comportamento mecânico de materiais restauradores utilizados na reabilitação da guia canino. O estudo foi dividido em uma etapa in sílico e outra in vitro. Dez modelos 3D de dentes caninos hígidos foram obtidos por engenharia reversa e utilizados como Grupo Controle (n = 10) para o teste in sílico por meio da análise por elementos finitos (FEA). Um desgaste incisal de 2 mm foi simulado em cada amostra 3D e reabilitado com restauração incisal direta de resina composta (Grupo IRC, n = 10) e indireta de cerâmica (Grupo IC, n = 10). Os mesmos modelos também receberam, além do desgaste incisal, um preparo vestibular para faceta laminada, restaurados com os mesmos materiais, compondo os Grupos FRC (faceta de resina composta, n = 10) e FC (faceta cerâmica, n = 10). Os modelos foram exportados para um software de engenharia assistida por computador (CAE) e as geometrias foram transformadas em malhas de elementos tetraédricos, consideradas sólidas, isotrópicas, homogêneas e lineares. Uma carga de 100 N foi aplicada simulando a desoclusão pelo canino para análise mecânica estrutural dinâmica. A deformação total foi mensurada e a tensão máxima principal foi usada como critério de falha. Com base nos resultados da avaliação in sílico, dois tipos de restauração foram selecionados para a fase in vitro, onde realizou-se um ensaio mecânico de fadiga para análise do desgaste. Trinta dentes caninos hígidos foram distribuídos em três grupos: Controle (n = 10), IRC (n = 10) e FC (n = 10). As amostras foram submetidas ao ensaio de fadiga em cicladora mecânica com deslizamento de 2 mm por 240.000 ciclos, carga de 49 N e 4 Hz de frequência, imersas em água em temperatura ambiente. A cada 60.000 ciclos as amostras foram moldadas e seus modelos escaneados para avaliação da quantidade de desgaste através da técnica de correlação por imagem digital, quantificando a perda de estrutura a cada intervalo. As técnicas restauradoras com resina composta sofreram maior deformação total, tendo a cerâmica um comportamento semelhante ao dente hígido. A probabilidade de falha no movimento de desoclusão foi menor na cerâmica. Para o desgaste, não houve diferença significante entre grupos experimentais até 180.000 ciclos. Aos 240.000 ciclos, a resina composta apresentou maior desgaste que a cerâmica (p = 0,02). Todos os grupos provocaram desgaste em seus antagonistas, mas não houve diferença significante entre eles (p < 0,05). Dentro das limitações deste estudo, pode-se concluir que os laminados cerâmicos apresentaram menor desgaste, deformação e probabilidade de falha na restauração da guia canino. Ainda, a anatomia do dente e o tipo de restauração influenciaram o comportamento dos materiais(AU)

The purpose of this study was to evaluate the mechanical behavior of materials restorative used in rehabilitation of canine guide. The study was divided in two parts in silico and in vitro test. Ten 3D models of sound canine teeth were obtained by reverse engineering technique and used as Control Group (n = 10) to in silico test by finite elements analysis (FEA). A 2 mm wear were simulated in each 3D sample and restored according to restorative material; Group IRC (Incisal Composite Resin, n=10) and Group IC (Incisal Ceramic, n = 10). Laminate preparations were modeled and restored with the same materials, Group FRC (Laminate Composite Resin, n=10) and Group FC (Laminate Ceramic, n = 10). All models were exported to Computer Aided Engineering (CAE) software, the geometries were meshed with tetrahydric elements and all contacts were considered perfectly bonded. The load simulated the canine guide (100 N) and the assembly was constrained at the bottom surface to run a structural mechanic dynamic analysis. The Total Deformation was measured and Maximum Principal Stress was used as failure criteria. Thirty sound canine tooth were divided in three groups to in vitro test; Control (n = 10), IRC (n = 10) and FC (n = 10). The samples were subjected to the fatigue test in a wear machine for 240.000 cycles, load of 49 N, frequency of 4 Hz, sliding distance of 2 mm in water at room temperature. The samples were molded every 60.000 cycles and their models scanned to evaluate wear by digital image correlation. Composite resin groups showed higher total deformation and ceramic groups had a more similar behavior to the control group. The probability of failure was lower for the ceramic in the canine guidance. For wear, there was no significant difference between groups up to 180.000 cycles. After 240.000 cycles, the wear was greater in the IRC group (p = 0,02). The wear of the antagonists was not statistically different between groups. Within the limitations of this study, it can be concluded that the ceramic laminates showed less wear, deformation and probability of failure in restoring of the canine guide. In addition, anatomy of the tooth and type of restoration influenced the behavior of the materials(AU)

Numerical simulation of transapical off-pump mitral valve repair with neochordae implantation.

BACKGROUND: Transapical off-pump mitral valve (MV) repair is a novel minimally-invasive surgical technique, allowing to correct mitral regurgitation (MR) caused by chordae tendineae rupture. While numerical simulation of the MV structure has proven to be useful to evaluate the effects of the MV surgical repair techniques, no numerical simulation studies on the outcomes of transapical MV repair have been done up to now. OBJECTIVE: The purpose of this study is to evaluate the transapical MV repair using finite element modeling and to determine the effect of the neochordal length on the function of the prolapsing MV. METHODS: The reconstruction of the MV geometry based on the patient-specific data was performed. In order to simulate prolapse, chordae inserted into the middle segment of the posterior leaflet (P2) were ruptured. A total of four virtual transapical repairs using neochordae of different length were performed. The function of the MV before and after virtual repairs was simulated. RESULTS: The evaluation of the effect of the neochordal length on post-repair MV function showed that the length of the implanted neochordae has a significant impact on the correction of MR caused by chordae tendineae rupture. CONCLUSIONS: The presented results can improve the understanding of the effects of transapical MV repair.

Efeito da graduação do módulo elástico na vida útil e resistência de restaurações cerâmicas / Effect of the elastic modulus graduation on the useful life and resistance of ceramic restorations

O objetivo deste estudo foi avaliar a distribuição de tensão, resistência, confiabilidade e vida útil de diferentes configurações cerâmicas dispostas em multicamadas, compostas por materiais cerâmicos de módulos de elasticidade distintos, comparando-as a modelos monocamadas. Para o delineamento dos modelos teórico e experimental, foram utilizadas as cerâmicas usinadas, com respectivos módulos elásticos: Feldspática (F): 64 GPa; dissilicato de lítio (L): 95 GPa; Zircônia tetragonal policristalina parcialmente estabilizada por ítrio (Y): 209,3 GPa. No estudo teórico foi utilizada a análise de elementos finitos, e foram desenhados dois modelos em 3D de um primeiro molar superior num software CAD para simular uma restauração monolítica (espessura: 1,5 mm) e uma restauração multicamadas (3 camadas cerâmicas de 0,4 mm + 2 camadas de cimento de 0,15 mm, totalizando de 1,5 mm de espessura). Foram preconizados 3 grupos monolíticos: F, L e Y; e 5 grupos multicamadas: FLY (F + L + Y), FFY (F + F + Y), LLY (L + L + Y), LFY (L + F + Y); YLF (Y + L + F), correspondente ao modelo bioinspirado. Foi aplicada uma carga de 150 N em três áreas de contato na fossa central e a tensão máxima principal (MPS) foi calculada em cada camada. O pico de tensão obtido (MPa) em cada camada de cada grupo foi: F: 10,55; Y: 18,48; L: 12,26; LFY: 25,58/3,96/26,82; LLY: 22,07/7,18/24,04; FFY: 22,58/6,26/28,99; FLY: 20,11/9,68/24,98; YLF: 39,44/7,18/5,42. Desta forma, foi possível constatar que a gradação do módulo elástico, com maior E externamente e menor E na região mais interna, proporcionou menor tensão nas camadas internas da restauração. Com o objetivo de validar os achados, foi proposto o modelo experimental simplificado, no qual foram utilizados discos cerâmicos de espessuras 0,3 mm e 1,5 mm. Os discos de 0,3 mm foram dispostos em 4 camadas, cimentados com cimento químico (Multilink N), e os discos de 1,5 mm não receberam nenhum tratamento, de modo que a espessura final dos espécimes fossem 1,5 mm (±0,15 mm). Foram obtidos 6 grupos: F (F: monolítico de 1,5 mm); L (L: monolítico de 1,5 mm); LLFF (L + L + F + F); FFLL (F + F + L + L); YLFF (Y + L + F + F); YLLF (Y + L + L + F). A carga para a fratura foi obtida através do ensaio de flexão biaxial (n=10; 1000 kgf, velocidade 1,0 mm/min) até a ocorrência de falha. Os dados foram analisados através de ANOVA-1 fator e comparações múltiplas de Tukey (5%). O ensaio de flexão biaxial foi também simulado através da análise de elementos finitos para identificar a tensão de tração gerada em cada camada dos grupos. O limite de fadiga (100.000 ciclos; 20 Hz) foi determinado através do método de escada (staircase). A análise de fratura foi realizada através de estereomicroscópio e microscopia eletrônica de varredura. Os resultados mostraram valores de carga para a fratura (N) seguindo a ordem: L (592,88 ± 73,78)D > FFLL (319,78 ± 43,59)C > YLLF (246,75 ± 24,89)B > F (167,13 ± 9,84)A > YLFF (166,51 ± 15,24) A > LLFF (165,46 ± 22,75)A ; e limite de resistência à fadiga (N): L (310,92 ± 26.73)F > FFLL (190,17 ± 8.32)E > F (106,21 ± 2.81)D > YLLF (96,48 ± 5.73)C > YLFF (89,56 ± 2.38)B > LLFF (77,23 ± 6.33)A . Ocorreram falhas em todos os grupos, sendo o local de origem na superfície de tração, coincidente com o local de maior tensão de tração analisado pelo método dos elementos finitos. Desta forma, concluiu-se que o modelo teórico evidenciou melhor desempenho de restaurações bioinspiradas, entretanto, no modelo experimental, a resistência do conjunto foi guiada pelo material na região de tração e a interface adesiva foi um fator limitante, com necessidade de se desenvolver uma estrutura bioinspirada de forma homogênea para validar os achados do modelo teórico(AU)

The aim of this study was to evaluate the strength, reliability and useful life of different ceramic configurations arranged in multilayers, composed of ceramic materials with different elastic moduli, comparing them to monolayer models. For the design of the theoretical and experimental models, machined ceramics were used, with respective elastic modulus: feldspathic (F), 64 GPa; lithium disilicate (L), 95 GPa; and Yttrium-partially stabilized tetragonal zirconia (Y-TZP) (Y), 209.3 GPa. In the theoretical study it was used the Finite Element Analyses, Two 3D upper first molar models were generated in CAD software in order to simulate monolayer (1.5 mm thickness) and multilayer restorations (3 ceramic layers of 0.4 mm + 2 cement layers of 0.15 mm, with a final thickness of 1.5 mm. The following groups were obtained: Monolithic groups: F, L and Y; Multilayer groups: FLY (F + L + Y), FFY (F + F + Y), LLY (L + L + Y), LFY (L + F + Y); and a Bioinspired Multilayer group: YLF (Y + L + F). Maximum principal stress (MPS) was calculated on each layer through a load of 150 N in three contact areas in the central fossa. The tensile strength peaks (MPa) were F: 10.55, Y: 18.48, L: 12.26, LFY: 25.58/3.96/26.82, LLY: 22.07/7.18/24.04, FFY: 22.58/6.26/28.99, FLY: 20.11/9.68/24.98 and YLF: 39.44/7.18/5.42. F and L ceramics did not prevent stress dissipation in the inner layers, and Y provided a decrease in tensile stress in the inner layers when used in the outermost layer in ZLF group. Multilayer ceramics with a larger external E modulus and a smaller internal modulus provided less stress in the innermost layers of the restoration. To validate these findings an experimental simplified model was preconized in order to obtain discs of 0.3 mm and 1.5 mm thickness. The 0.3 mm discs were arranged in 4 layers cemented with chemical cement (Multilink N), and the 1.5 mm discs were not treated, in such a way that the final thickness of all specimens was 1.5 mm (± 0.15 mm). The following 6 groups were obtained: F (F: monolithic); L (L: monolithic); LLFF (L + L + F + F); FFLL (F + F + L + L); YLFF (Y + L + F + F); YLLF (Y + L + L + F). The loads to fracture were obtained using the biaxial flexure strength test (1000 kgf, 1 mm/min) until failure and data were analyzed using ANOVA-1 way and Tukey's multiple comparisons (5%). The biaxial bending test was also simulated through finite element analysis (FEA) to identify the tensile stress generated at each layer of the groups. Mean flexural fatigue limits (100,000 cycles; 20 Hz) were determined under stair case approach. The fracture analysis was performed by stereomicroscope and scanning electron microscopy. The load to fracture (N) were obtained as follow L (592,88 ± 73,78)D > FFLL (319,78 ± 43,59)C > YLLF (246,75 ± 24,89)B > F (167,13 ± 9,84)A > YLFF (166,51 ± 15,24)A > LLFF (165,46 ± 22,75)A ; and the fatigue limit (N): L (310,92 ± 26.73)F > FFLL (190,17 ± 8.32)E > F (106,21 ± 2.81)D > YLLF (96,48 ± 5.73)C > YLFF (89,56 ± 2.38)B > LLFF (77,23 ± 6.33)A . All the groups presented failures and the origin were located at the tension region of the discs, as encountered in FEA. Thus, it was concluded that the theoretical model showed better performance of bioinspired restorations, however, in the experimental model the material under tension was mandatory for the resistance of the restoration, the adhesive interface negatively influenced the biomechanical behavior of the multilayer structures and there is a need to develop a homogeneous bio-inspired structure to validate the findings of the theoretical model(AU)

Distribuição de tensões em um modelo tridimensional de canino e pré-molares superiores sob diferentes carregamentos oclusais: análise pelo método de elementos finitos / Stress distribution in a three-dimensional model of canine and premolars superiors under different occlusal loads: analysis by finite element method

O objetivo desse estudo foi analisar, por meio do Método de Elementos Finitos, a distribuição de tensões na estrutura dentária, no ligamento periodontal (LP) e no osso alveolar em um modelo tridimensional do canino (23), primeiro (24) e segundo pré-molares superiores (25) submetidos à ação de cargas axiais e oblíquas. Além disso, objetivou-se avaliar a influência do ponto de contato proximal na distribuição das tensões no modelo de três dentes (M1), comparado a um modelo unitário do 24 (M2). As propriedades mecânicas bem como as condições de contorno e carregamento foram determinadas no programa de elementos finitos Ansys®. Cargas axiais e oblíquas foram aplicadas nas seguintes simulações: C1) Carga axial nos contatos A e B no dente 24; C2) Contato excêntrico no dente 24; C3) Carga oblíqua de 45N, com inclinação de 45o no contato A do dente 24; C4) Carga oblíqua de 45N, com inclinação de 45o no contato B do dente 24; C5) Cargas axiais simultâneas, de 70N na ponta de cúspide do dente 23, 90N nos contatos A e B do dente 24 e de 105N nos contaos A e B do dente 25. Para estimar a possibilidade de falha no esmalte, as tensões máximas principais foram analisadas e deformações máximas e mínimas principais foram analisadas no LP e no osso alveolar, sendo que ambos foram comparados a valores encontrados em outros estudos com metodologia similar. Em C1, a distribuição de tensões foi mais favorável para as estruturas dente-LP-osso, com picos de tensões semelhantes em M1 e M2. Em C2, tensões deslocaramse para apical, devido ao contato entre os dentes 24 e 23 em M1; os picos de tensões foram maiores em M1 do que em M2 no esmalte e no osso e o inverso ocorreu na dentina e no LP. Em C3, tensões de tração concentraram-se na região cervical do esmalte e na furca do dente 24; os picos das tensões no esmalte, osso e LP foram menores em M1 comparado a M2, mas na dentina ocorreu o contrário (M1>M2). Em C4, ocorreu o maior pico de tensão de tração no esmalte, tensões de tração concentraram-se na furca do dente 24; esmalte e dentina comportaram-se de forma similar (M1>M2) e osso e LP também (M1˂M2). Em C5, tensões de tração se concentraram no osso alveolar do dente 23. Os contatos proximais em M1 permitiram a distribuição das tensões de forma mais homogênea para o LP e osso que em M2. Exceto em C1, a distribuição de tensões no esmalte cervical, na dentina, no LP e no osso alveolar diferiram em um modelo unitário comparado a um de três dentes, devido à presença dos contatos proximais.

The direction, type and magnitude of loads on the oclusal surface and also the characteristics of the support structures determines the stress distribution. The aim of this study was to analyze, by the finite element method, the stress distribution on the first superior premolar, in a tridimensional (3D) model subjected to various types of loadings considering the enamel anisotropic or isotropic. The geometric modeling was performed based on a computed tomography (CT) scan. The mechanical properties as well as the loading conditions determined by the Abaqus® finite element program. Axial and oblique loads were applied on the occlusal surface of the first superior premolar in the following conditions: I) 30N axial load applied simultaneously on the occlusal contacts A and B and in the mesial marginal ridge, totaling 90N; II) 90N axial load in the mesial longitudinal edge of the lingual cusp, simulating eccentric contact; III) 45N oblique load with a 45o inclination on theocclusal contact A; IV) 45N oblique load with a 45o inclination on the occlusal contact B. To estimate the possibility of failure in the simulated structures, the maximum principal stress were analyzed and compared to known tensile strength values of the tissues studied. The results showed compression stress on the side in which the load was applied and tensile stress on the opposite side. Tensile stress concentrates mainly in the cervical region of the tooth and in the alveolar insertion bone. Anisotropic models revealed areas of tensile stress concentration smaller than the isotropic models. It was concluded that the isotropic 3D models were suitable for analyzing the stress distribution in teeth, because they are less complex models to build and produced similar results compared to the anisotropic models. The cervical enamel seems to be more susceptible to fracture because of the largest stress concentration on this area, associated with its composition and anatomical characteristics

Biomecânica da união dente-implante com plataforma restauradora reduzida, sistema de retenção tipo cone morse e roscas quadradas: uma análise por elementos finitos / Biomechanics of tooth-implant union with restorative platform reduced, restraint system morse cone type and square threads: a finite element analysis

Objetivou-se, a partir do Método dos Elementos Finitos, avaliar a biomecânica da união dente-implante e implante-implante, além de estabelecer uma análise qualitativa com achados fotoelásticos prévios. Foram planejados quatro modelos tridimensionais: dois Modelos Teste (dentes unidos a implantes) e dois Modelos Controle (a mesma condição, porém implanto suportada). Os implantes (ANKYLOS® - Dentsply) apresentaram conexão cônica, roscas quadradas e pilares Switching. Suas dimensões, ângulos externos e pilares protéticos foram obtidos a partir de um projetor de perfil. Já, dentes e próteses, a partir da visão direta, tiveram suas formas externas construídas em plataforma CAD (SOLIDSWORKS). O suporte alveolar foi configurado como um retângulo (68/30/15 mm). Todos os pilares foram posicionados no suporte alveolar, conforme os modelos físicos pré-existentes, gerando modelos sólidos. O ligamento periodontal consistiu de uma camada de 0,25 mm de espessura em poliéter (Impregum Soft, 3M Espe). Os modelos de dentes foram produzidos em dentina, pilares e implantes em titânio puro, próteses em liga Níquel-Cromo (Ni-Cr), e o suporte alveolar em resina fotoelástica (Araldite® - Produtos Químicos Ciba S/A do Brasil). As propriedades da resina foram obtidas por meio de ensaio de tração. Carga pontual, vertical e estática, de 150 N, foi aplicada. Os resultados destes ensaios evidenciaram menor concentração de tensão no aspecto cervical de implantes do grupo teste. Ao se confrontar tais achados com os fotoelásticos anteriormente obtidos, foi possível estabelecer uma relação direta entre as áreas mais solicitadas para os modelos de prótese fixa (PF) de três elementos. Concluiu-se que, para as condições estudadas ¿ conexão cônica, roscas quadradas e restauração com Plataforma Switching ¿, unir dentes a implantes parece ser uma terapia clínica viável, sugerindo, inclusive, ser mais favorável que a união de implantes entre si. Além disso, a partir da afinidade positiva entre os achados das duas técnicas, pôde-se considerar validados os modelos matemáticos de prótese fixa de três elementos

The goal of this study was to evaluate, from the Finite Element Method, the biomechanics of implant-tooth union and implant-implant and to establish a qualitative analysis with previous photoelastic findings. Four three-dimensional models were planned: two Test Models (teeth attached to implants) and two Control Models (the same condition, however implant supported). The implants (ANKYLOS® - Dentsply) showed conical connection, square threads and Switching pillars. Their dimensions, external angles and abutments were obtained from a profile projector. Already, teeth and dentures, from direct view, had their external forms built in CAD platform (SOLIDSWORKS). Alveolar support wasconfigured as a rectangle (68/30/15 mm). All the pillars were placed in the alveolar support, as the pre-existing physical models, generating solid models. The periodontal ligament consists of a layer of 0.25 mm thick in polyether (Impregum Soft, 3M Espe). The models of teeth trumped up of dentin, abutments and implants of pure titanium, prosthetics of Nickel-Chrome (Ni-Cr) alloy and alveolar support in photoelastic resin (Araldite® - Chemicals Ciba S/A of Brazil). The resin properties were obtained by traction tests. Punctual and vertical static load of 150 N was applied. The results of these tests showed lower concentration of tension in the cervical aspect of the test group implants. When comparing these findings with the photoelastic previously found, it was possible to establish a direct relation between the areas most requested for fixed prosthesis (FP) models of three elements. It was concluded that, for the studied conditions tapered connection, square threads and Platform Switching restoration , joining teeth implants seems to be a viable clinical therapy, suggesting, inclusive, to be more favorable than to join implants each other. Moreover, from the positive affinity between the findings of the two techniques, it was possible to consider validated the mathematical models of fixed prosthesis of three elements

Predicting revision risk for aseptic loosening of femoral components in total hip arthroplasty in individual patients--a finite element study.

Advances in surgical procedure, prosthesis design, and biomaterials performance have considerably increased the longevity of total joint replacements. Preoperative planning is another step in joint replacement that may have the potential to improve clinical outcome for the individual patient, but has remained relatively consistent for a long time. One means of advancing this aspect of joint replacement surgery may be to include predictive computer simulation into the planning process. In this article, the potential of patient-specific finite element analysis in preoperative assessment is investigated. Seventeen patient-specific finite element models of cemented Charnley reconstructions were created, of which six were early (<10 years) revisions. Creep was simulated using a Maxwell model, and fatigue damage was simulated using an anisotropic continuum damage formulation. Account was taken of the relationship between annual loading cycles and age, and stair-climbing loads were included using a walking to stair-climbing cycle ratio of 9:1. Simulations for the equivalent of 10 years of loading were performed. Accumulated damage, inducible displacement, and migration were computed. Five of the six early revisions had the highest migration indicating that migration could have been used to identify early failures of these prostheses. Resultant migration showed the most significant difference between the early revised and unrevised groups (p = 0.0024). Furthermore, this trend was apparent from 1 year postimplantation (p = 0.0052). This ability to differentiate early revisions shows that computational simulation of aseptic loosening in cemented prostheses could prove clinically useful in helping surgeons optimize the preoperative plan for individual patients.

[Computer stimulation of stress distribution in finite element models of the normal femur and after Weller, Centrament, Parhofer-Mönch type prosthesis implantation]. / Komputerowa symulacja rozkladów naprezen w modelach kosci udowej prawidlowej oraz po implantacji trzpieni typu Weller, Centrament i Parhofer-Mönch.

The paper presents an example of application of computerized analysis in the evaluation of the biomechanical reactions of the bone tissue after total hip replacement. Finite element models of the normal femur and femurs after Weller, Centrament and Parchofer-Monch type hip prosthesis implantation were constructed. Basing on these models, a comparative analysis of the stress patterns in all femurs was performed according to Pauwels' method. This study showed that total hip replacement leads to a redistribution and diminution of stress in the bone tissue, because of material disconformity of the prosthesis. The authors believe that the evolving virtual analytic tools used in simulations will in the future play a major role in reconstructive surgery.