Assessment of Thermal Osteonecrosis during Bone Drilling Using a Three-Dimensional Finite Element Model.

Bone drilling is a common procedure used to create pilot holes for inserting screws to secure implants for fracture fixation. However, this process can increase bone temperature and the excessive heat can lead to cell death and thermal osteonecrosis, potentially causing early fixation failure or complications. We applied a three-dimensional dynamic elastoplastic finite element model to evaluate the propagation and distribution of heat during bone drilling and assess the thermally affected zone (TAZ) that may lead to thermal necrosis. This model investigates the parameters influencing bone temperature during bone drilling, including drill diameter, rotational speed, feed force, and predrilled hole. The results indicate that our FE model is sufficiently accurate in predicting the temperature rise effect during bone drilling. The maximum temperature decreases exponentially with radial distance. When the feed forces are 40 and 60 N, the maximum temperature does not exceed 45 °C. However, with feed forces of 10 and 20 N, both the maximum temperatures exceed 45 °C within a radial distance of 0.2 mm, indicating a high-risk zone for potential thermal osteonecrosis. With the two-stage drilling procedure, where a 2.5 mm pilot hole is predrilled, the maximum temperature can be reduced by 14 °C. This suggests that higher feed force and rotational speed and/or using a two-stage drilling process could mitigate bone temperature elevation and reduce the risk of thermal osteonecrosis during bone drilling.

Local thermal effect of power-on setting on monopolar coagulation: a three-dimensional electrothermal coupled finite element study.

A three-dimensional (3-D) electrothermal coupled finite element (FE) model was used to simulate and analyze the effects of the electrosurgical power-on setting on the temperature distribution and thermal damage in biological tissue during coagulation. The discussed parameters include the power-on-off durations, contact distance between the electrosurgical blade and tissue surface, and inclination angle of the blade during cutting. The results indicate that under the condition of a constant input electrical energy, the maximal temperature decreased when the power-on time was shortened and the power-off (pause) duration was increased. The two contact distances between the blade and tissue (0 and 0.25 mm) did not show a significant temperature difference; however, the tissue temperature increased with increasing blade inclination angle. We concluded that using a normal cut angle and set at a multiple shorter-time power-on with intermittent power-off operation procedure can reduce the risk of thermal damage during monopolar electrosurgery.

Can NT-proBNP Levels Be an Early Biomarker of Reduced Left Ventricular Ejection Fraction in Preterm Infants?

Background/Objective: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a cardiac natriuretic hormone that cardiomyocytes release in response to ventricular stretch. It helps with the diagnosis of heart failure in adults, but this application in preterm infants has rarely been reported. This study aimed to evaluate whether NT-proBNP could be used for the early detection of reduced cardiac ejection fraction in preterm infants and the optimal timing for NT-proBNP assessment. Design/Methods: This prospective, single-center, observational study enrolled all preterm infants with NT-proBNP measurements from October 2014 to February 2022. They underwent echocardiographic examinations within 48 h of the NT-proBNP measurements. Reduced left ventricular ejection fraction was defined as below 60%. Receiver operator characteristic (ROC) curves were generated to assess the optimal NT-proBNP cutoff point for the early prediction of reduced cardiac ejection fraction. Results: A total of 68 preterm infants were enrolled, with a total of 134 NT-proBNP measurements being available for analysis. Reduced left ventricular ejection fraction was present in seven infants (10.3%) due to various underlying diseases. The NT-proBNP cutoff level for detecting reduced left ventricular ejection fraction was 9248 pg/mL, with 71.4% sensitivity and 60.8% specificity; the area under the curve was 0.623 (95% CI: 0.487~0.760). The threshold for the optimal postnatal age for applying NT-proBNP to detect reduced left ventricular ejection fraction was >2 days of life (AUC: 0.682; 95% CI: 0.518~0.845), with 70% sensitivity and 67.1% specificity. Conclusions: Although the NT-proBNP levels declined dramatically after birth, a NT-proBNP serum level of 9248 pg/mL might be helpful for the early detection of reduced ejection fraction in preterm infants, and the optimal age for detection was after 2 days of life.

Effects of Kinesio taping on forearm supination/pronation performance fatigability.

BACKGROUND: Repetitive exertion in supination/pronation could increase the risk of forearm diseases due to fatigue. Kinesio taping (KT) is a physical therapy technique that decreases muscle tone and musculoskeletal disorders (MSDs) risk. Many assumptions about taping have been made and several studies have considered the taping applications; however, the effect of KT on strength and fatigue of the forearm supination/pronation remains unclear. The purpose of this study was to evaluate the effect of KT on forearm performance fatigability. METHODS: A screwing test was constructed to measure the forearm force loss and screwing efficiency during repetitive supination/pronation. Data from 18 healthy adults who underwent both KT and no taping (NT) sessions were used to investigate the forearm strength change in terms of grip force (GF), driving torque (DT), and push force (PF). The maximal isometric forces before and after the screwing test and force decreasing rate (efficiency) during screwing were evaluated to assess the performance fatigability in KT and NT conditions. RESULTS: A statistically significant force loss (FL) in maximal isometric GF (p = 0.039) and maximal isometric DT (p = 0.044); however, no significant difference was observed in maximal isometric PF (p = 0.426) between NT and KT. KT provides greater screwing efficiency than NT. CONCLUSIONS: KT could not improve FL in the maximal muscle strength of the forearm in healthy subjects. KT on the forearm was associated with a lesser decline in DT efficiency than NT, implying that KT could decrease the loss rate of muscle strength and delay the development of fatigue; however, the KT did not yield improvements in PF while performing screwing tasks.

Assessment of heat generation and risk of thermal necrosis during bone burring by means of three-dimensional dynamic elastoplastic finite element modelling.

During bone burring, the heat generated due to friction at the bone-burr interface may cause thermal damage to the bone. Therefore, it is necessary to assess bone temperature distribution around a burring site and identify high-risk regions for thermal necrosis due to bone burring. In this study, a three-dimensional (3-D) dynamic elastoplastic finite element model for the burring process was developed and experimentally validated to investigate the influence of burring parameters (rotational speeds: 3,000, 10,000, 15,000 and 60,000 rpm; feed rates: 0.5, 0.9, 1.5 and 3.0 mm/s) on heat generation and evaluate the risk region for thermal necrosis. Calculated bone temperatures were compared with experimental values and found to be in good agreement with them. The analytical results demonstrated a linear relationship between the burring time and friction energy. In addition, the friction energy increased with the bone temperature. The high-risk thermal necrosis zone was measured from the edge of burring (y-direction) at feed rates of 0.5, 0.9, 1.5 and 3.0 mm/s and was found to be 7.8, 7.3, 6.6 and 5.5 mm, respectively. When the burr rotational speed increased from 3,000 to 60,000 rpm, the high-risk zone for thermal necrosis increased from 4.5 to 8.1 mm. We concluded that both the friction energy and the bone temperature increased in proportion with the burr rotational speed. Reducing burr rotational speeds and/or increasing feed rates may decrease the rise in bone temperature, thus decreasing the potential for thermal necrosis near the burring site. Our model can be used to select the optimal surgery parameters to minimise the risk of thermal necrosis due to bone burring and to assist in the design of optimal orthopaedic drill handpieces.

Assessment of thermal necrosis risk regions for different bone qualities as a function of drilling parameters.

BACKGROUND AND OBJECTIVE: During bone drilling, the heat generated by friction depends directly on bone quality and surgical parameters. Excessive bone temperatures may cause thermal necrosis around the pilot hole, weaken the purchase of inserted screws, and in turn reduce the stability of screw fixation. A few studies have addressed the key parameters of drilling, such as the rotation speed of the drill-bit, feed force (axial force), feed rate, tool type, and tip geometry of drill-bits. Nevertheless, in the literature, information on the relationship between bone quality and thermally affected regions is still lacking. This study employed a three-dimensional dynamic elastoplastic finite element model to evaluate the influence of surgical parameters on the bone temperature elevation and assess the risk region of thermal necrosis for different bone qualities as a function of drilling parameters. METHODS: To ascertain the heat generation rate and the high-risk region of thermal necrosis, the effects of bone quality, feed rate, feed force, and drill-bit diameter on the bone temperature elevation were explained using a three-dimensional dynamic elastoplastic finite element model, which was validated through experimental measurements. RESULTS: The bone temperature was affected by the drilling parameters; the maximum temperature was attained at the junction of cancellous and cortical bones. The bone temperature increased with cortical bone thickness, bone density, and drill-bit diameter, and it decreased with the drilling speed and feed force. CONCLUSIONS: The present model could assess the risk region of thermal necrosis by accurately analyzing the bone temperature elevation for various bone qualities, feed forces, and feed rates. The bone temperature increased with the bone mineral density and cortical bone thickness. The highest bone temperature and maximum necrosis region were found near the junction of cortical and cancellous bones. Increasing the drilling speed or feed force can minimize the bone temperature elevation and the risk range of thermal necrosis.

Evaluation of the parameters affecting bone temperature during drilling using a three-dimensional dynamic elastoplastic finite element model.

A three-dimensional dynamic elastoplastic finite element model was constructed and experimentally validated and was used to investigate the parameters which influence bone temperature during drilling, including the drill speed, feeding force, drill bit diameter, and bone density. Results showed the proposed three-dimensional dynamic elastoplastic finite element model can effectively simulate the temperature elevation during bone drilling. The bone temperature rise decreased with an increase in feeding force and drill speed, however, increased with the diameter of drill bit or bone density. The temperature distribution is significantly affected by the drilling duration; a lower drilling speed reduced the exposure duration, decreases the region of the thermally affected zone. The constructed model could be applied for analyzing the influence parameters during bone drilling to reduce the risk of thermal necrosis. It may provide important information for the design of drill bits and surgical drilling powers.

Effects of implant drilling parameters for pilot and twist drills on temperature rise in bone analog and alveolar bones.

This study concerns the effects of different drilling parameters of pilot drills and twist drills on the temperature rise of alveolar bones during dental implant procedures. The drilling parameters studied here include the feed rate and rotation speed of the drill. The bone temperature distribution was analyzed through experiments and numerical simulations of the drilling process. In this study, a three dimensional (3D) elasto-plastic dynamic finite element model (DFEM) was proposed to investigate the effects of drilling parameters on the bone temperature rise. In addition, the FE model is validated with drilling experiments on artificial human bones and porcine alveolar bones. The results indicate that 3D DFEM can effectively simulate the bone temperature rise during the drilling process. During the drilling process with pilot drills or twist drills, the maximum bone temperature occurred in the region of the cancellous bones close to the cortical bones. The feed rate was one of the important factors affecting the time when the maximum bone temperature occurred. Our results also demonstrate that the elevation of bone temperature was reduced as the feed rate increased and the drill speed decreased, which also effectively reduced the risk region of osteonecrosis. These findings can serve as a reference for dentists in choosing drilling parameters for dental implant surgeries.

High Sensitivity C Reactive Protein (hs-CRP) in Adolescent and Young Adult Patients with History of Kawasaki Disease.

BACKGROUND: For children with a history of Kawasaki disease (KD), low grade inflammation was generally reported to be associated with persistent coronary artery lesions (CAL). However, this association has not been clearly demonstrated to hold true in KD adolescents and young adults (10-25 years of age). METHODS: We enrolled 104 subjects into our study, who were separated into the following 3 groups and controls: 1): 22 KD patients with angiography-confirmed CAL which persisted for an average of 12.5 years after onset of KD; 2) 38 KD patients with regressed aneurysms; 3) 44 KD patients without any coronary complications from the disease onset; and 4) 31 age-matched (18.7 ± 1.88 years old) healthy controls. Plasma levels of high-sensitivity C reactive protein (hs-CRP) were measured for all participants. RESULTS: Plasma levels of hs-CRP were significantly higher in KD patients than in the controls, regardless of their coronary severity. However, there was no significant difference in hs-CRP levels among KD patients with different severities of CAL. Of the candidate risk factors of elevated hs-CRP such as body mass index, gender, coronary severity, and levels of high-density lipoprotein-cholesterol, linear regression analysis showed the only independent predictor of hs-CRP levels was BMI (ß = 0.306, p = 0.01), rather than patient grouping (p = 0.091). CONCLUSIONS: Our study found that levels of hs-CRP are significantly higher in adolescent and young adult patients with a history of KD, compared with age-matched controls. Low grade inflammation may play a minor role when KD patients enter into adulthood. body mass index (BMI), rather than coronary severity, was independently associated with the elevation of hs-CRP levels, one of biomarkers for further cardiovascular event. Therefore, ongoing control and management of BMI may be one of beneficial strategies that can be employed to help avoid elevation of hs-CRP levels in KD patients. KEY WORDS: Adolescents; High sensitivity-C reactive protein; Kawasaki disease; Young adult.

Coronary Diameters in Taiwanese Children Younger than 6 Years Old: Z-Score Regression Equations Derived from Body Surface Area.

BACKGROUND: The measurements of coronary diameters, usually obtained by 2-dimentsional echocardiography, play important roles oin the management and follow-up of Kawasaki disease (KD). However, in Taiwan, domestic normgrams and a Z-score calculator for coronary artery diameters are still not available. METHODS: Echocardiography was performed on 412 healthy children younger than 6 years of age. The appropriate exponential regression model was fitted to correspond with body surface area (BSA). The computed Z-scores of all subjects were also tested for normal distribution. RESULTS: Using the model ln (measurement) = ß1 + ß2 × ln (BSA), the adjusted R(2) values were 0.611 and 0.484 for the models of the left main coronary artery (LMCA) and the right (RCA), respectively. Analysis of computed Z-score distribution showed acceptable goodness of fit for a normal distribution [p = 0.90 (LMCA); p = 0.17 (RCA)]. CONCLUSIONS: We have established reference ranges for the coronary artery diameters in Taiwanese children younger than 6 years of age. The regression equations and Z-score calculators for the LMCA and RCA provide an objective determination of coronary dilatation in a large population, which is important for the care and medical management of KD patients in Taiwan. KEY WORDS: Coronary diameter; Kawasaki disease; Taiwan; Z-score.

Distribution of micromotion in implants and alveolar bone with different thread profiles in immediate loading: a finite element study.

PURPOSE: To detect the differences in the distribution of micromotion within implants and alveolar bone with different implant thread designs during immediate loading. MATERIALS AND METHODS: A three-dimensional finite element model with contact elements was used to simulate the contact behavior between the implant and alveolar bone. Implants with four different thread designs were created: Acme (trapezoidal) thread (AT), buttress thread (BT), square thread (ST), and a standard V-thread (VT). To simulate immediate loading, the model was designed without osseointegration between the implant and alveolar bone. A load of 300 N was applied axially to the model, and the micromovements were measured. RESULTS: The maximum micromotion values of the ST, AT, VT, and BT models were 8.53, 9.57, 11.00, and 15.00 µm, respectively. All micromotion was located near the interface of cortical and cancellous bone. Different thread designs showed different distribution of micromotion during loading. This indicates that initial stability in immediate loading may be affected by thread design. CONCLUSION: The ST profile showed the most favorable result in the study. An implant with an ST profile might provide the best primary stability in an immediate loading situation.

A sensing element based on a bent and elongated grooved polymer optical fiber.

An experimental and numerical investigation is performed into the power loss induced in grooved polymer optical fibers (POFs) subjected to combined bending and elongation deformations. The power loss is examined as a function of both the groove depth and the bend radius. An elastic-plastic three-dimensional finite element model is constructed to simulate the deformation in the grooved region of the deformed specimens. The results indicate that the power loss increases significantly with an increasing bending displacement or groove depth. Specifically, the power loss increases to as much as 12% given a groove depth of 1.1 mm and a bending displacement of 10 mm. Based on the experimental results, an empirical expression is formulated to relate the power loss with the bending displacement for a given groove depth. It is shown that the difference between the estimated power loss and the actual power loss is less than 2%.

Optical performance of symmetrical and asymmetrical Y-branch couplers for plastic optical fibers.

The excess loss and output optical power ratio of symmetrical and asymmetrical Y-branch couplers for plastic optical fibers (POFs) are studied in this work. A ray-tracing model for the Y-branch coupler is derived to investigate the effect of coupling parameters on its optical performance. The coupling parameters, namely coupling angle, axial displacement, and refractive index of filling medium between the emitting-end and receiving-end POFs, are studied. The simulated and measured results indicate that the coupling efficiency is sensitive to all these coupling parameters. A minimum excess loss of approximately 0.83 dB is observed for the symmetrical Y-branch coupler. It is found that both the excess loss and the output power ratio are increased with the increase of the refractive index of the filling medium and the total coupling angle (α+ß) for the asymmetrical Y-branch coupler. The experimental results indicate that the maximum output power ratio P1∶P2 is found to be 3.8∶1 for excess loss of less than 2.8 dB for the asymmetrical Y-branch coupler.

Power loss characteristics of a sensing element based on a polymer optical fiber under cyclic tensile elongation.

In this study, power losses in polymer optical fiber (POF) subjected to cyclic tensile loadings are studied experimentally. The parameters discussed are the cyclic load level and the number of cycles. The results indicate that the power loss in POF specimens increases with increasing load level or number of cycles. The power loss can reach as high as 18.3% after 100 cyclic loadings. Based on the experimental results, a linear equation is proposed to estimate the relationship between the power loss and the number of cycles. The difference between the estimated results and the experimental results is found to be less than 3%.

Plastic optical fiber displacement sensor based on dual cycling bending.

In this study, a high sensitivity and easy fabricated plastic optical fiber (POF) displacement sensor is proposed. A POF specimen subjected to dual cyclic bending is used to improve the sensitivity of the POF displacement sensor. The effects of interval between rollers, relative displacement and number of rollers on the sensitivity of the displacement sensor are analyzed both experimentally and numerically. A good agreement between the experimental measurements and numerical calculations is obtained. The results show that the interval between rollers affects sensitivity most significantly than the other design parameters. Based on the experimental data, a linear equation is derived to estimate the relationship between the power loss and the relative displacement. The difference between the estimated results and the experimental results is found to be less than 8%. The results also show that the proposed POF displacement sensor based on dual cyclic bending can be used to detect displacement accurately.

Knockdown of the aryl hydrocarbon receptor attenuates excitotoxicity and enhances NMDA-induced BDNF expression in cortical neurons.

NMDA receptors play dual and opposing roles in neuronal survival by mediating the activity-dependent neurotrophic signaling and excitotoxic cell death via synaptic and extrasynaptic receptors, respectively. In this study, we demonstrate that the aryl hydrocarbon receptor (AhR), also known as the dioxin receptor, is involved in the expression and the opposing activities of NMDA receptors. In primary cultured cortical neurons, we found that NMDA excitotoxicity is significantly enhanced by an AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin, and AhR knockdown with small interfering RNA significantly reduces NMDA excitotoxicity. AhR knockdown also significantly reduces NMDA-increases intracellular calcium concentration, NMDA receptor expression and surface presentation, and moderately decreases the NMDA receptor-mediated spontaneous as well as miniature excitatory post-synaptic currents. However, AhR knockdown significantly enhances the bath NMDA application- but not synaptic NMDA receptor-induced brain-derived neurotrophic factor (BDNF) gene expression, and activating AhR reduces the bath NMDA-induced BDNF expression. Furthermore, AhR knockdown reveals the calcium dependency of NMDA-induced BDNF expression and the binding activity of cAMP-responsive element binding protein (CREB) and its calcium-dependent coactivator CREB binding protein (CBP) to the BDNF promoter upon NMDA treatment. Together, our results suggest that AhR opposingly regulates NMDA receptor-mediated excitotoxicity and neurotrophism possibly by differentially regulating the expression of synaptic and extrasynaptic NMDA receptors.

Power losses in deformed graded-index polymer optical fibers.

We investigate the power losses in bent and elongated graded-index polymer optical fibers (GI POFs). The variations of power losses in deformed GI POFs for various radii of curvature and elongations are measured. A simple tensile test result is used to calculate the average plastic energy density (APED) in a deformed GI POF at various elongations. The results indicate that the APED accumulated in a deformed GI POF can be considered as a key index to study the power loss in POF. Based on the experimental results, a curve-fitted equation is proposed to estimate the power loss using the APED for various radii of curvature. The maximum difference between the proposed equation and the experimental results is less than 3% for the deformed GI POFs.

Power losses in bent and elongated polymer optical fibers.

This study performs experimental and numerical investigations into the power losses induced in bent, elongated polymer optical fibers (POFs). The theoretical analysis is based on a three-dimensional elastic-plastic finite-element model and makes the assumption of a planar waveguide. The finite-element model is used to calculate the deformation of the elongated POFs such that the power loss can be analytically derived. The effect of bending on the power loss is examined by considering seven different bend radii ranging from 10 to 50 mm. The results show that bending and elongation have a significant effect on the power loss in POFs. The contribution of skew rays to the overall power loss in bent, elongated POFs is not obvious at large radii of curvature but becomes more significant as the radius is reduced.

Effect of Electrical Contact on the Contact Residual Stress of a Microrelay Switch.

This paper investigates the effect of electrical contact on the thermal contactstress of a microrelay switch. A three-dimensional elastic-plastic finite element model withcontact elements is used to simulate the contact behavior between the microcantilever beamand the electrode. A model with thermal-electrical coupling and thermal-stress coupling isused in the finite element analysis. The effects of contact gap, plating film thickness andnumber of switching cycles on the contact residual stress, contact force, plastic deformation,and temperature rise of the microrelay switch are explored. The numerical results indicatethat the residual stress increases with increasing contact gap or decreasing plating filmthickness. The results also show that the residual stress increases as the number of switchingcycles increases. A large residual stress inside the microcantilever beam can decrease thelifecycle of the microrelay.