RESUMEN
PURPOSE: The aim of this experimental study was to compare the ability of polyurethane cushions of three arbitrary selected thicknesses to minimize vibrations transmitted from the wheelchair to its user. METHODS: Measurements were made during passive motion on five different surfaces often found in public spaces. Two tests were carried out during the measurements. In the first test, the sensor was located directly on the surface of the wheelchair seat. In the second test, a polyurethane cushion was placed on the seat, on which the measuring sensor was then placed. RESULTS: The study showed that regardless of the surface on which the wheelchair user moves, the threshold defined in the ISO standard for frequencies in the range of 4-40 Hz was exceeded. However, thanks to the use of polyurethane cushions, vibration damping was visible for frequencies ranging from 10 to 40 Hz. The impact of the user's weight on the magnitude of the perceived vibrations was also observed. CONCLUSIONS: Studies show that wheelchair users are exposed to whole body vibration that can negatively affect their health. Cushions made of polyurethane seem to be a promising solution to reduce whole body vibration in the frequency range that is burdensome and harmful to human health.
Asunto(s)
Vibración , Silla de Ruedas , Humanos , Poliuretanos , Modalidades de Fisioterapia , Diseño de EquipoRESUMEN
PURPOSE: Research efforts summarised in this study were a part of preliminary investigation to evaluate the impact of pregnant women's exposure to vibrations generated by public transport system when using. METHODS: The assessment of the problem and discomfort for pregnant women, caused by the public transportation is based on a questionnaire including questions relating to the women's subjective feelings on well-being or discomfort when exposed to vibration during the ride in passenger cars or when using means of public transport. In the second stage of investigation, vibrations transmitted onto a sitting person during the tram or car ride were measured. RESULTS: The survey shows that when travelling on a tram the women complained mostly of digestive or neurological disorders, during the car ride they suffered most acutely from digestive disorders, sensed enhanced foetus movements and reported problems with the osteoarticular system. Amplitude-frequency characteristics of the investigated vehicle types reveal that vibration amplitudes registered during the ride in a motor vehicle are higher than on tram (in the analysed frequency range). Furthermore, vibration accelerations in the z-axis direction registered during the tram ride exceed the vibration discomfort threshold, particularly for the 1/3 octave bands 5 and 6.3 Hz. These are frequency ranges corresponding to resonance frequencies of vital organs in the abdominal cavity (4.5-10 Hz). CONCLUSIONS: Correlating these results with frequencies reported in literature associated with subjective human responses to vibration, shows that pregnant women using public transport are likely to suffer from a variety of ailments caused by vibrations generated during the ride.
Asunto(s)
Emociones , Transportes , Vibración , Adolescente , Adulto , Femenino , Humanos , Embarazo , Encuestas y Cuestionarios , Adulto JovenRESUMEN
Restoration of mandible discontinuity defects continues as a challenge for maxillofacial surgeons. Despite the development of algorithms for reconstruction plates fixation and autogenous grafting techniques, complications are still encountered including screw loosening, bone resorption or delayed/incomplete union. The aim of the study was to analyze the possibility of obtaining bone union in the aspect of biomechanical conditions of two mandible reconstructions using an autogenous iliac crest bone graft stabilized with a reconstruction plate, and to attempt to predict patient outcomes based on strength parameters obtained by the finite element analysis. The authors of the present paper were trying to determine to what extent the reconstruction model and changes occurring in hard tissues of the bone and autogenous graft (simulated by changes in material properties) might help predict individual patient courses. The effort of reconstruction plates was defined using the values of the von Mises stress (σHMH) while the effort of bones was determined based on the values of strain intensity εint. The results of the above mentioned simulations are presented in the form of bar graphs and strain/stress distribution maps. Our strength analyses indicate that uncomplicated healing of grafts fixed with reconstruction plates requires that the initial loading of the stomatognatic system should not result in strain intensity exceeding 20-40 [×10â»4]. This range of strain intensity evokes an increase in the mineral phase. The state of nonunion between the mandibular bone and the graft might result from prolonged periods of insufficient loading of the mandible during treatment.
Asunto(s)
Análisis de Elementos Finitos , Mandíbula/cirugía , Reconstrucción Mandibular , Adulto , Fenómenos Biomecánicos , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Mandíbula/diagnóstico por imagen , Mandíbula/fisiopatología , Persona de Mediana Edad , Radiografía , Estudios Retrospectivos , Estrés MecánicoRESUMEN
The paper presents an analysis of the distribution of dislocations in the case of fixation of a mandible low subcondylar fracture. Three types of elements have been used for fixation: NiTi shape-memory staples, miniaturized titanium plates and the Synthes compression plate, also called the Synthes zygomatic plate. The analysis was conducted using the finite element method. The degree of the mobility of the fractures was analysed as well as the tendency towards their separation on the basis of value analysis and the distribution of dislocation areas. The results obtained allowed a preliminary assessment of predicted healing effects and the possibility of being able to predict developing complications after osteosynthesis with the use of the elements analysed.