In unicompartmental replacement surgery, there are a wide variety of commercially available unicompartmental prostheses, and the consistency of the contact surface between the common liner and the femoral prosthesis could impact the stress distribution in the knee after replacement in different ways. Medial tibial plateau fracture and liner dislocation are two common forms of failure after unicompartmental replacement. One of the reasons is the mismatch in the mounting position of the unicompartmental prosthesis in the knee joint, which may lead to failure. Therefore, this paper focuses on the influence of the shape of the contact surface between the liner and the femoral prosthesis and the mounting position of the unicompartmental prosthesis on the stress distribution in the knee joint after replacement. Firstly, a finite element model of the normal human knee joint was established, and the validity of the model was verified by both stress and displacement. Secondly, two different shapes of padded knee prosthesis models (type A and type B) were developed to simulate and analyze the stress distribution in the knee joint under single-leg stance with five internal or external rotation mounting positions of the two pads. The results showed that under a 1 kN axial load, the peak contact pressure of the liner, the peak ACL equivalent force, and the peak contact pressure of the lateral meniscus were smaller for type A than for type B. The liner displacement, peak contact pressure of the liner, peak tibial equivalent force, and peak ACL equivalent force were the smallest for type A at 3° of internal rotation in all five internal or external rotation mounting positions. For unicompartmental replacement, it is recommended that the choice of type A or type B liner for prosthetic internal rotation up to 6° should be combined with other factors of the patient for comprehensive analysis. In conclusion, the results of this paper may reduce the risk of liner dislocation and medial tibial plateau fracture after unicompartmental replacement, providing a biomechanical reference for unicompartmental prosthesis design.
There are two main types of fluid in bone tissue: blood and interstitial fluid. The metabolism of cells mainly relies on the microenvironment of the interstitial fluid. Researches of osteonal fluid seepage behavior based on the microstructure of bone tissue have become a hot point. The aim of the present research work is to assess the effect of blood pressure oscillation on the osteonal interstitial fluid seepage behavior. We established finite element osteon models for a hollow and that considering blood pressure oscillation, respectively, with COMSOL Multiphysics software in order to compare their fluid flow behavior under the axial loading. The results predicted that the interstitial fluid pressure field was enlarged considering the blood pressure oscillation, while the velocity filed changed little. Specifically, the increase of blood pressure oscillatory amplitude could result in the increase of osteonal interstitial fluid pressure, while the blood pressure oscillatory frequency had limited effects on the osteonal pore fluid pressure. Moreover, the blood pressure oscillatory amplitude and frequency had no effect on the osteonal interstitial fluid velocity. The finite element model can be used for the study of the poroelastic behaviors of the osteon under non-axisymmetric loads and microcracks, and can also be a new way to study the mechanism of bone mechanotransduction and electromechanotransduction.
ObjectiveTo study the method of rapid and accurate measurement of body temperature in dense population during the coronavirus disease 2019 pandemic.MethodsFrom January 27th to February 8th, 2020, subjects were respectively measured with two kinds of non-contact infrared thermometers (blue thermometer and red one) to measure the temperature of forehead, neck, and inner side of forearm under the conditions of 4–6℃ (n=152), 7–10℃ (n=103), and 11–25℃ (n=209), while the temperature of axillary was measured with mercury thermometer under the same conditions. Taking the mercury thermometer temperature as the gold standard, the measurement results with non-contact infrared thermometers were compared.ResultsAt 7–10℃, there was no statistical difference among the forehead temperatures measured by the two non-contact infrared thermometers and the axillary temperature (P>0.05); there was no difference among the temperature measured by blue thermometer on forehead, neck, and inner side of forearm (P>0.05); no difference was found between the temperature measured by the red thermometer on forehead and inner side of forearm (P>0.05), while there was statistical difference between the temperatures measured by the red thermometer on forehead and neck (P<0.05). Under the environment of 11−25℃, there was no statistical difference among the forehead temperatures measured by the two infrared thermometers and the axillary temperature (P>0.05); the difference between the temperatures of forehead and inner side of forearm measured by the blue thermometer was statistically significant (P<0.05), while no difference appeared between the forehead and neck temperatures measured by the blue thermometer (P>0.05); there was no statistical difference among the temperatures of three body regions mentioned above measured by the red thermometer (P>0.05). According to the manual, the allowable fluctuation range of the blue thermometer was 0.3℃, and that of the red one was 0.2℃. The mean differences in measured values between different measured sites of the two products were within the allowable fluctuation range. Therefore, the differences had no clinical significance in the environment of 7–25℃. Under the environment of 4–6℃, the detection rate of blue thermometer was 2.2% and that of the red one was 19.1%.ConclusionsThere is no clinical difference between the temperature measured by mercury thermometer and the temperature measured by temperature guns at 7–10 or 11–25℃, so temperature guns can be widely used. In order to maintain the maximum distance between the measuring and the measured persons and reduce the infection risk, it is recommended to choose the inner forearm for temperature measurement. Under the environment of ambient temperature 4–6℃, the detection rate of non-contact electronic temperature gun is low, requiring taking thermal measures for the instrument.