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Biomechanical comparison of a transiliac internal fixator and two iliosacral screws in transforaminal sacral fractures: a finite element analysis

Salasek M., Jansova M., Křen J., Pavelka T., Weisova D.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 1

39--49

EN

Purpose: Vertically unstable sacral transforaminal fractures can be stabilized with a transiliac internal fixator (TIFI) or two iliosacral screws (IS). This study was designed to compare stiffness between TIFI and IS. Methods: Using CT images finite element model of the pelvis was developed. Denis II type fracture was simulated and fixed either with TIFI or two IS. The sacral base was loaded vertically (250–500 N), displacement magnitudes on medial and lateral fracture surface and the maximum bone stress were calculated. The intact pelvis was used as a reference. Stiffness was determined by linear regression of load and displacement, computed stiffness ratio %. The von Mises stress was expressed as % ratio, evaluation of colour mapping was made. Results: The mean stiffness ratio medially in TIFI was 75.22%, in IS 46.54% ( p = 0.00005), laterally in TIFI 57.88%, in IS 44.74% ( p = 0.03996). The von Mises stress ratio of TIFI was 139.27%, of IS 565.35% ( p < 0.00001). Conclusions: Significantly higher stiffness and lower stress were found in TIFI model. TIFI provides a lower risk of over-compression of the fracture line in comparison with IS. TIFI thus exhibits superiority for fixation of transforaminal fractures, particularly with comminutive zone.

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Patellar tracking in the total knee joint replacement model with patellar retinaculum

Jansova M., Kren J., Pokorny J., Koudela K., Koudela K.

Modelling and Optimization of Physical Systems

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2011

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z. 10

29--34

EN

The study aims to identify the key points affecting the patello-femoral joint stability and stress pressure distribution. The finite element model of the knee joint with structures supplying patellar retinaculum is used. The femoral component is rotated along the mechanical axis for 5 degrees both medially and laterally. The stress pressure distribution is analyzed within patello-femoral joint during gait cycle.

CS

Cilem teto prace je urćeni klicovych faktom, ktere ovlivnuji stabilitu patelo-femoralniho kloubniho spojeni. Dalśim cilem je urćeni rozłożeni napeti v tomto spojeni. Pro uvedenou analyzu je poużit drive definovany konećneprvkovy model kolenniho kloubu doplnćny o patelarni retinaculum. Pfidany dalsi ćtyfi vazy ćesky, dva vazy k femuru a dva vazy k tibii. Pfi analyze je kondylar twist uhel nulovy a tibialni plato nahrady je polożeno kolmo na mechanickou osu nohy (fyziologicky spravne nasazena totalni kolenni nahrada). Femoralni ćast nahrady je potom otaćena kołem mechanicke osy o 5 stupnu jak v medialnim, tak i v lateralnim smeru. Nakonec je provedena analyza rozłożeni napeti na patelofemoralnim kloubu behem chuze.

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Patellar tracking in the total knee joint replacement model

Jansova M., Kren J., Pokorny J., Koudela K., Koudela Jr. K.

Modelling and Optimization of Physical Systems

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2010

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z. 9

37--40

EN

The study aims to identify the key points that affect the patello-femoral joint stability and stress distribution. The finite element model of the knee joint is used. The femoral component is rotated along the mechanical axis for 5 degrees both medially and laterally. The stress pressure distribution is analyzed within patello-femoral joint during gait cycle.

CS

Tato práce si klade za cíl urćeni klíćových faktorů ovlivňujících stabilitu patelo-femorálního kloubniho spojení a rozloženi napěti v tomto spojení. Je použit konečně-prvkový model kolenního kloubu. Femorální část náhrady je otáčena kołem mechanické osy o 5 stupňů jak mediálně tak laterálně. Nakonec je provedena analýza rozložení napětí na patelo-femorálním kloubu během chůze.