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

PURPOSE: The purpose of this study was the simulation of the implantation of intrastromal corneal-ring segments for patients with keratoconus. The aim of the study was the prediction of the corneal curvature recovery after this intervention. METHODS: Seven patients with keratoconus diagnosed and treated by implantation of intrastromal corneal-ring segments were enrolled in the study. The 3D geometry of the cornea of each patient was obtained from its specific topography and a hyperelastic model was assumed to characterize its mechanical behavior. To simulate the intervention, the intrastromal corneal-ring segments were modeled and placed at the same location at which they were placed in the surgery. The finite element method was then used to obtain a simulation of the deformation of the cornea after the ring segment insertion. Finally, the predicted curvature was compared with the real curvature after the intervention. RESULTS: The simulation of the ring segment insertion was validated comparing the curvature change with the data after the surgery. Results showed a flattening of the cornea which was in consonance with the real improvement of the corneal curvature. The mean difference obtained was of 0.74 mm using properties of healthy corneas. CONCLUSIONS: For the first time, a patient-specific model of the cornea has been used to predict the outcomes of the surgery after the intrastromal corneal-ring segments implantation in real patients.

• Klíčová slova
• Biomechanical simulation, Cornea, Intrastromal ring segments, Keratoconus,
• MeSH
• analýza metodou konečných prvků MeSH
• biomechanika MeSH
• keratokonus chirurgie   MeSH
• lidé MeSH
• mechanické jevy * MeSH
• počítačové modelování podle konkrétního pacienta * MeSH
• protézy a implantáty * MeSH
• rohovka chirurgie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

PURPOSE OF THE STUDY: 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 endplate 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.

• MeSH
• biologické modely * MeSH
• biomechanika MeSH
• krční obratle patofyziologie   MeSH
• lidé MeSH
• osteofytóza páteře patofyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články 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.

• Klíčová slova
• Computer simulation, Countermovement jump, Physical functional performance, Squat jump,
• 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

The molecular level of the functional structure of the contractile apparatus of cross-striated muscle has been mapped out almost minutely. Most authors accept the basic principles of the theory of sliding filaments and the theory of operation of molecular generators of force which, of course, are progressively updated by integrating new knowledge. The idea of the model delineated below does not contradict these theories, for it refers to another level of the system's hierarchy. The definition of the system, hereafter referred to Ideal Sarcomere (IS), takes into account the fact that, during isotonic contraction, a large number of not wholly independently working sarcomeres and molecular generators of force is active in a synergistic way. The shortening velocity of isotonically contracting IS is determined by the relation between quantities conveying different tasks of active generators of force and the influence of the system parameters. Although IS is derived from simple axiomatic predicates, it has properties which were not premediated in defining the system and which, in spite of this, correspond to some properties of the biological original. The equations of the system allow us to calculate the shortening velocity of 'isotonic contraction' and other variables and parameters and show, inter alia, an alternative way to derive and interpret the relations stated in Hill's force-velocity equation. The simulation results indicate that the macroscopic manifestations of isotonic contraction may be also contingent on the properties of the cooperating system of the multitude of sarcomeres, which also constitutes one part of the functional structure of muscle.

• MeSH
• biofyzika MeSH
• biofyzikální jevy MeSH
• biologické modely * MeSH
• biomechanika MeSH
• isotonická kontrakce fyziologie   MeSH
• lidé MeSH
• počítačová simulace MeSH
• sarkomery fyziologie   MeSH
• techniky in vitro MeSH
• termoregulace fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The aim of the experiment was to compare the mechanical properties of intact spinal segment with impaired intervertebral disc and impaired intervertebral disc fixed by TSLP (Thoracolumbar Spine Locking Plate). METHODS AND RESULTS: Spinal specimens were taken from domestic swine. A total of 8 test mechanical states (intact, impaired and fixed) were modeled and the mechanical properties, expressed by the value of moment of couple necessary to twist the specimen at tensile force F = 200 N and the value of moments necessary for extension straining, were determined. The study was based on in vitro biomechanical testing of the TSLP plate used to stabilize the front thoracolumbar column of spinal segments taken from a pig. The plate was used for monosegmental fixation. The disc was cut by scalpel to simulate the Type A injury to front spinal column. In each state (intact, impaired or fixed), specimens were subjected to a tension load of prescribed force and, then, twisted by a given angle. Subsequently, extension load of intact, impaired and impaired & fixed segment was measured. Statistical evaluation verified the hypothesis of the different behavior of intact, impaired and fixed specimens - both for tension & torsion load and extension load. The analyses did not indicate different mechanical behavior of intact and fixed specimens. In other words, monosegmental fixation of both impaired and intact specimens by TSLP Synthes implant will lead to similar mechanical behavior of these specimens. Further, we found that intact and fixed specimens show non-symmetric behavior at positive and negative twisting angles. This was not observed for impaired specimens. CONCLUSION: Several stabilization systems were developed to stabilize the front thoracolumbar spinal column. Surgery of the anterior column of injured spine should restore the correct position of the spine, ensure decompression of vertebral canal when neural structures are compressed, and stabilize the spine to allow immediate loading and mobilization of the patient. The aim of this study was to compare mechanical properties of intact spinal segment, impaired spinal segment and impaired spinal segment stabilized by TSLP Synthes implant. The problems were solved by experimental modeling using a testing machine that simulated loads for several mechanical states of the spinal segment. Favorable mechanical properties of TSLP Synthes fixator were demonstrated. The experimental results will be used for subsequent computational modeling of the spinal segment in all experimentally solved states.

• MeSH
• bederní obratle chirurgie   MeSH
• biomechanika MeSH
• hrudní obratle chirurgie   MeSH
• kostní destičky * MeSH
• meziobratlová ploténka * MeSH
• nemoci páteře patofyziologie   chirurgie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

Abdominal aortic aneurysm (AAA) disease, the local enlargement of the infrarenal aorta, is a serious condition that causes many deaths, especially in men exceeding 65 years of age. Over the past quarter of a century, computational biomechanical models have been developed towards the assessment of AAA risk of rupture, technology that is now on the verge of being integrated within the clinical decision-making process. The modeling of AAA requires a holistic understanding of the clinical problem, in order to set appropriate modeling assumptions and to draw sound conclusions from the simulation results. In this article we summarize and critically discuss the proposed modeling approaches and report the outcome of clinical validation studies for a number of biomechanics-based rupture risk indices. Whilst most of the aspects concerning computational mechanics have already been settled, it is the exploration of the failure properties of the AAA wall and the acquisition of robust input data for simulations that has the greatest potential for the further improvement of this technology.

• Klíčová slova
• abdominal aortic aneurysm, modeling, ruptuer risk assessment, vascular biomechanics,
• MeSH
• aneurysma břišní aorty * MeSH
• aorta abdominalis MeSH
• biomechanika MeSH
• hodnocení rizik MeSH
• klinická relevance MeSH
• lidé MeSH
• mechanický stres MeSH
• modely kardiovaskulární MeSH
• ruptura aorty * MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

This work concerns a biomechanical study aiming to ascertain the optimal type of joint resection when performing a joint arthrodesis. A 3-dimensional digital model of the first metatarsophalangeal joint including the entire first metatarsal bone and proximal phalanx using CT scans of the forefoot was created. Using this computer model, 4 types of resections; ball-and-socket, flat-on-flat, wedge 90°, and wedge 100° were simulated. Parameters measured using this model were the force necessary to separate the 2 fused surfaces, the surface area of the resected surfaces and the shortening of the first ray. By measuring the reactive force necessary to separate the phalanx from the first metatarsal, the 90° wedge resection was found to be the most stable, with comparable results in the case of the 100° wedge resection. Wedge resections are also more favorable when comparing the shortening of the first ray. Wedge resections, though being more technically difficult to perform prove to be the most stable for metatarsophalangeal joint-1 arthrodesis using this model.

• Klíčová slova
• biomechanical, fusion, hallux rigidus, joint resection, metatarsophalangeal joint arthrodesis, technique, union,
• MeSH
• artrodéza MeSH
• hallux rigidus * MeSH
• hallux valgus * MeSH
• lidé MeSH
• metatarzální kosti * diagnostické zobrazování   chirurgie   MeSH
• metatarzofalangeální kloub * diagnostické zobrazování   chirurgie   MeSH
• palec nohy * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

This study aimed to introduce a procedure for determining the bilinear elastic moduli (E1 and E2) of the periodontal ligament for a mathematical tooth model to analyse stress in the mandible. The bone and tooth morphology were scanned from a dry skull and an extracted intact tooth, respectively, and reconstructed in a three-dimensional finite element model. The model showed good agreement with previously reported in vivo premolar movement when an E1 for the first phase tooth movement of 0.05 MPa and an E2 for the second phase of 8.0 MPa with ε(12) of 0.075 were adopted. The mandible model analysis indicated that a remarkably high maximum compressive stress in the cervical cortical bone and the tensile stress in areas of masticatory muscle attachment were found. Future stress analyses using a jaw model may follow the process of determination of bilinear moduli to enhance accurate simulation with less calculation time.

• MeSH
• analýza metodou konečných prvků * MeSH
• biologické modely MeSH
• biomechanika MeSH
• hrot zubního kořene anatomie a histologie   MeSH
• lidé MeSH
• mandibula anatomie a histologie   fyziologie   MeSH
• mechanický stres MeSH
• modul pružnosti MeSH
• musculus masseter anatomie a histologie   fyziologie   MeSH
• musculus pterygoideus anatomie a histologie   fyziologie   MeSH
• musculus temporalis anatomie a histologie   fyziologie   MeSH
• odontometrie MeSH
• periodontální vaz fyziologie   MeSH
• počítačová simulace * MeSH
• počítačové zpracování obrazu metody   MeSH
• pohyb MeSH
• premolár anatomie a histologie   fyziologie   MeSH
• processus alveolaris anatomie a histologie   fyziologie   MeSH
• síla skusu MeSH
• zobrazování trojrozměrné metody   MeSH
• zubní kořen anatomie a histologie   MeSH
• zubní korunka (anatomie) anatomie a histologie   MeSH
• zubní lůžko anatomie a histologie   fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Ankle fractures are complex injuries with variable prognoses that depend upon many factors. The aim of the treatment is to restore the ankle joint biomechanical stability with maximum range of motion. Most ankle fractures are fibular fractures, which have a typical oblique fracture line in the distal fibula located in the area of the tibiofibular syndesmosis. The aim of this study was to simulate numerically several fixation techniques of the distal fibular fractures, evaluate their stability, determine their impact on surrounding tissue load, and correlate the results to clinical treatment experience. The following three models of fibular fracture fixation were used: (a) plate fixation with three screws attached above/below and lag screws, (b) plate fixation with two screws attached above/below and lag screws, and (c) three lag screws only. All three fracture fixation models were analyzed according to their use in both healthy physiological bone and osteoporotic bone tissue. Based on the results of Finite Element Analysis for these simulations, we found that the most appropriate fixation method for Weber-B1 fibular fractures was an unlocked plate fixation using six screws and lag screws, both in patients with physiological and osteoporotic bone tissue. Conversely, the least appropriate fixation method was an unlocked plate fixation with four screws and lag screws. Although this fixation method reduces the stress on patients during surgery, it greatly increased loading on the bone and, thus, the risk of fixation failure. The final fixation model with three lag screws only was found to be appropriate only for very limited indications.

• MeSH
• analýza selhání vybavení MeSH
• biologické modely * MeSH
• fibula zranění   patofyziologie   chirurgie   MeSH
• fraktury kotníku patofyziologie   chirurgie   MeSH
• kostní destičky * MeSH
• lidé MeSH
• mechanický stres MeSH
• pevnost v tahu MeSH
• pevnost v tlaku MeSH
• počítačová simulace MeSH
• protézy - design MeSH
• tření MeSH
• vnitřní fixace fraktury přístrojové vybavení   metody   MeSH
• výsledek terapie MeSH
• zatížení muskuloskeletálního systému MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH