Biomechanical simulation
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One of the least known conditions of the lumbar spine in terms of biomechanics is spondylolisthesis which causes many serious consequences for the patient. This research aimed to perform a mechanical analysis of the origins of spondylolisthesis and its impact on the biomechanics of the lumbar section of the spine. Within the framework of this study, a physiologically model of the lumbar spine was created in the MADYMO software. In the next stage a slip of vertebra L4 was simulated by means of a controlled forward displacement of the vertebral body of vertebra L4. 10 variants of spondylolisthesis (W1–W10) of different degrees were subjected to a biomechanical evaluation. In maximum bending of the physiological spine at an angle of 27° the value of the shear force amounted to 1.9 kN, while for the spine affected by spondylolisthesis with slip grade W9 at the maximum bending of 34° the shear force amounted to 5.5 kN. It was observed that the lumbar spine with the simulated spondylolisthesis had greater mobility in comparison with the physiological spine, which was shown by maximum bending angles (physiological 27°, W9 34°).
The aim of this study was to simulate different types of cervical vertebra loading and to find out whether mechanical stress would concentrate in regions known in clinical practice as predilection sites for osteophyte formation. The objective was to develop a theoretical model that would elucidate clinical observations concerning the predilection site of bone remodelling in view of the physiological changes inside the cervical vertebral body. MATERIAL AND METHODS A real 3D-geometry of the fourth cervical vertebra had been made by the commercially available system ATOS II. This is a high-resolution measuring system using principles of optical triangulation. This flexible optical measuring machine projects fringe patterns on the surface of a selected object and the pattern is observed with two cameras. 3D coordinates for each camera pixel were calculated with high precision and a polygon mesh of the object's surface was further generated. In the next step an ANSYS programme was used to calculate strains and stresses in each finite element of the virtual vertebra. The applied forces used in the experiment corresponded in both magnitude and direction to physiological stress. Mechanical loading in neutral position was characterized by a distribution of 80% mechanical stress to the vertebral body and 10% to each of the zygoapophyseal joints. Hyperlordotic loading was simulated by 60% force transfer to the vertebral body end-plate and 20% to each of the small joint while kyphotic loading involved a 90% load on the vertebral body end-plate and 5% on each facet. RESULTS Mechanical stress distribution calculated in a neutral position of the model correlated well with bone mineral distribution of a healthy vertebra, and verified the model itself. The virtual mechanical loading of a vertebra in kyphotic position concentrated deformation stress into the uncinate processes and the dorsal apophyseal rim of the vertebral body. The simulation of mechanical loading in hyperlordosis, on the other hand, shifted the region of maximum deformation into the articulation process of the Z-joint. All locations are known as areas of osteophyte formation in degenerated cervical vertebrae. DISCUSSION AND CONCLUSIONS The theoretical model developed during this study corresponded well with human spine behaviour in terms of predilection sites for osteodegenerative changes, as observed in clinical practice. A mathematical simulation of mechanical stress distribution in pre-operative planning may lead to the optimisation of post-operative anatomical relationship between adjacent vertebrae. Such improvement in our surgical practice may further reduce the incidence of degenerative changes in adjacent motion segments of the cervical spine and possibly also lead to better subjective and clinical results after cervical spine reconstruction.
A pathological disorder of human penile function, known as Peyronie's disease, is characterized by the formation of plaque particles within the tunica albuginea. The plagues in the shape of rigid plate form in the scars as a result of the imperfect healing process. Due to high stiffness, plagues are the source of pain and anomalous deformations during erectile penis function. The authors simulate the biomechanical behavior of the penile structure by a 3D finite element model. The numerical model is based on the real geometrical shape and the tissue structure with consideration of large nonlinear deformations. The penile erection is modeled by the initial strains imposed on the corpus cavernosa. The stress analysis is performed in a case study of various plague locations. The Peyronie's syndrome manifested by the penis angular deviation simulated by the analysis is compared with the clinical data. The computational simulations provide a rational explanation for the clinical observations on patients. The objective is to apply the proposed modeling approach for the development and validation of treatment methods based on the application of shock waves.
- Publikační typ
- časopisecké články MeSH
Úvod: Cílem studie byla laboratorní „in vitro“ modelace zatížení defektu předního sloupce páteře ošetřeného transpedikulární fixací na kadaverozním preparátu a jeho biomechanické měření. Materiál a metoda: Celkem byly získány 4 kadaverozní modely hrudní páteře v rozsahu Th3-L2. Anatomická preparace byla provedena se zachováním základních kostních a vazivových struktur. Pro vlastní měření byly připraveny celkem 3modely, celkem 1 preparát byl ošetřen transpedikulární instrumentací 1+1 a celkem 2 preparáty ošetřeny instrumentací 2+2. V průběhu vlastního měření a kalibrace přístroje byl na úrovni Th6/7 proveden vlastní defekt předního sloupce resekcí meziobratlové ploténky. Pro vlastní měření byl využit testovací systém MTS 858,2 Mini Bionix v sestavě s víceosým simulátorem. K měření deformací fixace byl použit extenzometr MTS s pracovním rozsahem +/- 0,4 mm. Z tuhostních charakteristik jednotlivých pohybů je možné odečíst základní parametry měřeného vzorku tj. neutrální zóna, elastická zóna, rozsah pohybu soustavy. Výsledky: Hodnocení tuhosti soustavy fl./ext. a dukce po vytvoření defektu předního sloupce páteře dochází k progresi nárůstu hodnocených parametrů bez ohledu na vzorek nebo typ montáže s výslednou směrovou asymetrií ve směru převahy extenze proti flexi a jednotlivých směrů dukce. V hodnocení napětí na fixačních tyčích vykazuje také nárůst napětí po provedení defektu předního sloupce páteře. Z hlediska absolutních hodnot je nejméně zatížena instrumentace vzorku 1+1. Diskuze: Z vyhodnocení napětí na fixačních tyčích je možné interpretovat dva obecné závěry. Prvním výsledkem je zvýšení napětí na spojovací tyči konstrukce po destabilizaci páteře, druhým závěrem je nezanedbatelná asymetrie výsledných hodnot na pravé a levé tyči. V tuhostních charakteristikách vzorku se v celém rozsahu zatížení nevyskytují žádné skokové změny tuhosti, které by ukazovaly k možnému selhání konstrukce.
Introduction: The aim of the biomechanical study was laboratory „in-vitro“ testing and measurement of spinal column axial loading. The biomechanical simulation tested the thoracolumbar spinal cadaver with anterior column defect instrumented by the transpedicular fixation. Material and method: The study group (4 spinal cadavers Th3-L2) were anatomically prepared in the anatomy lab conserving the bone, disc and ligament structures and subsuquently instrumented by the transpedicular fixation. There were 2groups (2 + 2 cadavers), the first group were transpediculary instrumented 1+1 segment and the second by 2+2 segments. One spinal cadaver from the first group was unable for the final biomechanical testing, because of spinal deformity, rest 3 cadavers were finally measured. The proper biomechanical testing, were done on the testing system MTS 858,2 Mini-Bionix with extensometr MTS, tested the axial loading of spinal column (flexion, extension, duction) with parametric results of total range of motion, neutral, elastic zone a rod deformation. The anterior column defects were done during the proper testing by the disc Th6/7 resection. Results: There were progression in all assessed parametres /range of motion, elastic, neutral zone, rod deformation) with considerable asymetry direction in extension to flexion and duction in spinal column loading with anterior defect. The rod deformation decrease with extent of transpedicular instrumentation. Discussion: The range of motion (elastic zone, neutral zone) and instrumentation rod strain in the measured system (spinal cadaver) increase in plane asymetry in the spinal column with anterior defect. The rigidity of the spinal transpedicular instrumentation (rod deformation) increase continuously without any skip transmutations and there is no risk factor of possible loosening of constructions in calibrated conditions.
- Klíčová slova
- celkový rozsah pohybu, elastická zóna, instantní centrum rotace, neutrální zóna,
- MeSH
- biomechanika MeSH
- design vybavení MeSH
- interní fixátory MeSH
- lidé MeSH
- mrtvola MeSH
- ortopedické fixační pomůcky MeSH
- páteř chirurgie patofyziologie MeSH
- poranění páteře chirurgie MeSH
- testování materiálů metody přístrojové vybavení MeSH
- zatížení muskuloskeletálního systému MeSH
- Check Tag
- lidé MeSH
- MeSH
- biomechanika * MeSH
- dospělí MeSH
- experimenty na lidech MeSH
- kraniocerebrální traumata etiologie MeSH
- lidé MeSH
- mladý dospělý MeSH
- násilí MeSH
- počítačová simulace MeSH
- rány a poranění * etiologie MeSH
- soudní lékařství * MeSH
- statistika jako téma MeSH
- teoretické modely MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
During vertical jump evaluations in which jump height is estimated from flight time (FT), the jumper must maintain the same body posture between vertical takeoff and landing. As maintaining identical posture is rare during takeoff and landing between different jump attempts and in different individuals, we simulated the effect of changes in ankle position from takeoff to landing in vertical jumping to determine the range of errors that might occur in real-life scenarios. Our simulations account for changes in center of mass position during takeoff and landing, changes in ankle position, different subject statures (1.44-1.98 m), and poor to above-average jump heights. Our results show that using FT to estimate jump height without controlling for ankle position (allowing dorsiflexion) during the landing phase of the vertical jump can overestimate jump height by 18% in individuals of average stature and performing an average 30 cm jump or may overestimate by ≤60% for tall individuals performing a poor 10 cm jump, which is common for individuals jumping with added load. Nevertheless, as assessing jump heights based on FT is common practice, we offer a correction equation that can be used to reduce error, improving jump height measurement validity using the FT method allowing between-subject fair comparisons.
- MeSH
- biomechanika fyziologie MeSH
- dospělí MeSH
- hlezenní kloub fyziologie MeSH
- kotník fyziologie MeSH
- lidé MeSH
- mladý dospělý MeSH
- počítačová simulace MeSH
- pohyb fyziologie MeSH
- postura těla * fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
