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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

2015

Vol. 17, no. 1

39--49

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.

Photometry of LED sources

Škoda J., Baxant P., Krbal M., Sumec S., Pavelka T.

Przegląd Elektrotechniczny

2013

R. 89, nr 6

341--344

In this article each luminous intensity curve of LED sources, measured in different photometric distances were compared. It also compares the luminous efficacy, luminance and illuminance provided with LED sources compared to fluorescent sources. It also compares the energy demands of different sources to achieve equivalent illumination.

W artykule porównano rozsyły światłości diod świecących, mierzone w różnych odległościach fotometrowania. Również porównano skuteczności świetlne, luminancje i natężenia oświetlenia uzyskane od źródeł LED w odniesieniu do wyników uzyskanych dla świetlówek. Również porównano charakterystyki energetyczne różnych źródeł w celu osiągnięcia równoważnego natężenia oświetlenia.