Simulation of Orbital Fractures Using Experimental and Mathematical Approaches: A Pilot Study.

This contribution gives basic information about the mechanical behavior of the facial part of the human skull cranium, i.e., the splanchnocranium, associated with external loads and injuries caused mainly by brachial violence. The main areas suffering from such violence include the orbit, frontal, and zygomatic bones. In this paper, as a first approach, brachial violence was simulated via quasi-static compression laboratory tests, in which cadaveric skulls were subjected to a load in a testing machine, increasing till fractures occurred. The test skulls were also used for research into the dynamic behavior, in which experimental and numerical analyses were performed. A relatively high variability in forces inducing the fractures has been observed (143-1403 N). The results lay the basis for applications mainly in forensic science, surgery, and ophthalmology.

Design and Behavior of Lightweight Flexible Structure with Spatial Pattern Reducing Contact Surface Fraction.

Flexible structures are increasingly important in biomedical applications, where they can be used to achieve adaptable designs. This paper presents a study of the design and behavior of 3D-printed lightweight flexible structures. In this work, we focus on the design principles and numerical modelling of spatial patterns, as well as their mechanical properties and behavior under various loads. Contact surface fraction was determined as the ratio of the surface area of the printed pattern to the surface area of the entire curved surface. The objective of this work is to design a spatial pattern reducing contact surface fraction and develop a non-linear numerical model evaluating the structure's stiffness; in addition, we aimed to identify the best design pattern with respect to its stiffness:mass ratio. The experimental verification of the numerical model is performed on 3D-printed prototypes prepared using the Selective Laser Sintering (SLS) method and made of Nylon-Polyamide 12. The obtained results provide insights into designing and optimizing lightweight external biomedical applications such as prostheses, orthoses, helmets, or adaptive cushions.

Simplified Numerical Model for Determining Load-Bearing Capacity of Steel-Wire Ropes.

Steel-wire rope is a mechanical component that has versatile uses and on which human lives depend. One of the basic parameters that serve to describe the rope is its load-bearing capacity. The static load-bearing capacity is a mechanical property characterized by the limit static force that the rope is able to endure before it breaks. This value depends mainly on the cross-section and the material of the rope. The load-bearing capacity of the entire rope is obtained in tensile experimental tests. This method is expensive and sometimes unavailable due to the load limit of testing machines. At present, another common method uses numerical modeling to simulate an experimental test and evaluates the load-bearing capacity. The finite element method is used to describe the numerical model. The general procedure for solving engineering tasks of load-bearing capacity is by using the volume (3D) elements of a finite element mesh. The computational complexity of such a non-linear task is high. Due to the usability of the method and its implementation in practice, it is necessary to simplify the model and reduce the calculation time. Therefore, this article deals with the creation of a static numerical model which can evaluate the load-bearing capacity of steel ropes in a short time without compromising accuracy. The proposed model describes wires using beam elements instead of volume elements. The output of modeling is the response of each rope to its displacement and the evaluation of plastic strains in the ropes at selected load levels. In this article, a simplified numerical model is designed and applied to two constructions of steel ropes, namely the single strand rope 1 × 37 and multi-strand rope 6 × 7-WSC.

Evaluation of breast stiffness pathology based on breast compression during mammography: Proposal for novel breast stiffness scale classification.

Breast cancer is diagnosed through a patient's Breast Self-Examination (BSE), Clinical Breast Examination (CBE), or para-clinical methods. False negativity of PCM in breast cancer diagnostics leads to a persisting problem associated with breast tumors diagnosed only in advanced stages. As the tumor volume/size at which it becomes invasive is not clear, BSE and CBE play an exceedingly important role in the early diagnosis of breast cancer. The quality and effectiveness of BSE and CBE depend on several factors, among which breast stiffness is the most important one. In this study, the authors present four methods for evaluating breast stiffness pathology during mammography examination based on the outputs obtained during the breast compression process, id est, without exposing the patient to X-Ray radiation. Based on the subjective assessment of breast stiffness by experienced medical examiners, a novel breast stiffness classification was designed, and the best method of its objective measurement was calibrated to fit the scale. Hence, this study provides an objective tool for the identification of patients who, being unable to perform valid BSE, could benefit from an increased frequency of mammography screening. Dum vivimus servimus.

Cost analysis of early rehabilitation after stroke in comprehensive cerebrovascular centres in the Czech Republic.

OBJECTIVES: The paper analyses real-world data on cost of treatment in patients after stroke hospitalized in early rehabilitation units within comprehensive stroke centres in the Czech Republic. This is the first study of the kind in the Czech Republic, while such information is extremely rare worldwide. Stroke treatment witnessed a dramatic development in the last years, when the main progress was due to establishment of specialized (comprehensive) stroke units incorporating also early rehabilitation. There is a general agreement among clinicians that early rehabilitation is beneficial for patients after stroke. METHODS: Costs of early rehabilitation after stroke were calculated by the micro-costing method alongside a pragmatic study in three Czech hospitals. Patients were transferred to specialized early rehabilitation units usually on 7th to 14th day after stroke onset and received four hours of interprofessional rehabilitation per day. RESULTS: The analysis of data collected during the prospective observational research of 87 patients proved significant differences between patients. The average costs of hospitalization were determined to be CZK 5,104 (EUR 194) per one day of intensive rehabilitation in seriously affected patients early after stroke. These costs differed significantly between hospitals (p-value < 0.001); the structure of direct costs was quite stable, though. About 60% of these costs were due to nursing and overhead, while no more than 15% were consumed by therapists. CONCLUSIONS: The treatment of patients after stroke in specialized stroke units proved to be beneficial for the patients increasing the number of those re-integrated in family and community life.

Study of Optimal Cam Design of Dual-Axle Spring-Loaded Camming Device.

The spring-loaded camming device (SLCD), also known as "friend", is a simple mechanism used to ensure the safety of the climber through fall prevention. SLCD consists of two pairs of opposing cams rotating separately, with one (single-axle SLCD) or two (dual-axle SLCD) pins connecting the opposing cams, a stem, connected to the pins, providing the attachment of the climbing rope, springs, which simultaneously push cams to a fully expanded position, and an operating element controlling the cam position. The expansion of cams is thus adaptable to allow insertion or removal of the device into/from a rock crack. While the pins, stem, operating element, and springs can be considered optimal, the (especially internal) shape of the cam allows space for improvement, especially where the weight is concerned. This paper focuses on optimizing the internal shape of the dual-axle SLCD cam from the perspective of the weight/stiffness trade-off. For this purpose, two computational models are designed and multi-step topology optimization (TOP) are performed. From the computational models' point of view, SLCD is considered symmetric and only one cam is optimized and smoothened using parametric curves. Finally, the load-bearing capacity of the new cam design is analyzed. This work is based on practical industry requirements, and the obtained results will be reflected in a new commercial design of SLCD.

Cost and cost-effectiveness of early inpatient rehabilitation after stroke varies with initial disability: the Czech Republic perspective.

The purpose of this prospective study was to determine whether the cost and cost-effectiveness of early rehabilitation after stroke are associated with the degree of initial disability. The data for cost calculations were collected by the bottom-up (micro-costing) method alongside the standard inpatient care. The total sample included 87 patients who were transferred from acute care to early rehabilitation unit of three participating stroke centers at the median time poststroke of 11 days (range 4-69 days). The study was pragmatic so that all hospitals followed their standard therapeutic procedures. For each patient, the staff recorded each procedure and the associated time over the hospital stay. The cost and cost-effectiveness were compared between four disability categories. The average cost of the entire hospitalization was CZK 114 489 (EUR 4348) with the daily average of CZK 5103 (EUR 194). The cost was 2.4 times higher for the immobile category (CZK/EU: 167 530/6363) than the self-sufficient category (CZK/EUR: 68 825/2614), and the main driver of the increase was the cost of nursing. The motor status had a much greater influence than cognitive status. We conclude that the cost and cost-effectiveness of early rehabilitation after stroke are positively associated with the degree of the motor but not cognitive disability. To justify the cost of rehabilitation and monitor its effectiveness, it is recommended to systematically record the elements of care provided and perform functional assessments on admission and discharge.

Modeling and Testing of Flexible Structures with Selected Planar Patterns Used in Biomedical Applications.

Flexible structures (FS) are thin shells with a pattern of holes. The stiffness of the structure in the normal direction is reduced by the shape of gaps rather than by the choice of the material based on mechanical properties such as Young's modulus. This paper presents virtual prototyping of 3D printed flexible structures with selected planar patterns using laboratory testing and computer modeling. The objective of this work is to develop a non-linear computational model evaluating the structure's stiffness and its experimental verification; in addition, we aimed to identify the best of the proposed patterns with respect to its stiffness: load-bearing capacity ratio. Following validation, the validated computational model is used for a parametric study of selected patterns. Nylon-Polyamide 12-was chosen for the purposes of this study as an appropriate flexible material suitable for 3D printing. At the end of the work, a computational model of the selected structure with modeling of load-bearing capacity is presented. The obtained results can be used in the design of external biomedical applications such as orthoses, prostheses, cranial remoulding helmets padding, or a new type of adaptive cushions. This paper is an extension of the conference paper: "Modeling and Testing of 3D Printed Flexible Structures with Three-pointed Star Pattern Used in Biomedical Applications" by authors Repa et al.