Shore hardness is a more representative measurement of bulk tissue biomechanics than of skin biomechanics.

To support the effective use of Shore hardness (SH) in research and clinical practice this study investigates whether SH should be interpreted as a measurement of skin or of bulk tissue biomechanics. A 3D finite element model of the heel and a validated model of a Shore-00 durometer were used to simulate testing for different combinations of stiffness and thickness in the skin and subcutaneous tissue. The results of this numerical analysis showed that SH is significantly more sensitive to changes in skin thickness, relatively to subcutaneous tissue, but equally sensitive to changes in the stiffness of either tissue. Indicatively, 25% reduction in skin thickness (0.3 mm thickness change) or in subcutaneous tissue thickness (5.9 mm thickness change), reduced SH by 7% or increased SH by 2% respectively. At the same time, 25% reduction in skin stiffness (10.1 MPa change in initial shear modulus) or of subcutaneous tissue (4.1 MPa change in initial shear modulus) led to 11% or 8% reduction in SH respectively. In the literature, SH is commonly used to study skin biomechanics. However, this analysis indicates that SH quantifies the deformability of bulk tissue, not of skin. Measurements of skin thickness are also necessary for the correct interpretation of SH

Rocker outsole shoes and margin of stability during walking: a preliminary study

Rocker outsole shoes are commonly prescribed to diabetic patients to redistribute peak plantar pressures at high risk areas such as forefoot thereby decreasing risks of plantar ulceration. However, there are evidences of postural destabilizing effect of the rocker outsole shoes. Patients with diabetes, particularly those suffering from neuropathy, are at a higher risk of falling. Then, beside primary role of rocker outsole in offloading, it is essential to explore the effect of the rocker outsole on postural stability of these patients. The smaller base of support (BOS) of the rocker outsoles due to their specific geometry has been previously mentioned as a threat to postural stability. Margin of stability (MOS) appeared to be an appropriate method for measuring postural stability during walking by considering the dynamicity of BOS in its equation. MOS is defined as the distance between the velocity adjusted position of the centre of mass (COM) and the boundaries of the BOS which constantly changes during walking. Then, this study proposes how we can use MOS concept to investigate the impact of the rocker outsoles on dynamic stability. In this study the kinematic data from a single subject with diabetic neuropathy was used to explain the efficiency of the methodology. Conclusive results are expected after carrying out systematic tests using a statistically representative sample size.This project is funded by Iran University of Medical Sciences (IR.IUMS.REC. 1395.9211503202).info:eu-repo/semantics/publishedVersio

A Finite Element Analysis of foot with hammer toe deformity during walking

This is the author accepted manuscript. The final version is available from the International Society of Biomechanics via the link in this recordA three-dimensional finite element model of a diabetic neuropathic foot with hammer toe deformity was constructed. The geometry of the FE model was formed based on segmentation and reconstruction of MRI images. A multi-body musculoskeletal simulation based on 3D gait analysis was carried out for predicting six muscle forces. Validation of the derived muscle forces were performed using EMG. FE simulations were run at five stages of stance phase of gait. The derived muscle forces and measured GRFs during gait were added to the model as boundary conditions. The validation of FE results indicated a good agreement between simulated plantar pressures (PP) against the measured values from pressure plate. The analyses showed that the presence of hammer toe causes stress concentration on metatarsals. However, the stress concentration seems to shift from the 5th metatarsal to the 3rd metatarsal as the gait progresses from early stance to toe-off

Associating ground magnetometer observations with current or voltage generators

A circuit analogy for magnetosphere‐ionosphere current systems has two extremes for drivers of ionospheric currents: ionospheric electric fields/voltages constant while current/conductivity vary—the “voltage generator”—and current constant while electric field/conductivity vary—the “current generator.” Statistical studies of ground magnetometer observations associated with dayside Transient High Latitude Current Systems (THLCS) driven by similar mechanisms find contradictory results using this paradigm: some studies associate THLCS with voltage generators, others with current generators. We argue that most of this contradiction arises from two assumptions used to interpret ground magnetometer observations: (1) measurements made at fixed position relative to the THLCS field‐aligned current and (2) negligible auroral precipitation contributions to ionospheric conductivity. We use observations and simulations to illustrate how these two assumptions substantially alter expectations for magnetic perturbations associated with either a current or a voltage generator. Our results demonstrate that before interpreting ground magnetometer observations of THLCS in the context of current/voltage generators, the location of a ground magnetometer station relative to the THLCS field‐aligned current and the location of any auroral zone conductivity enhancements need to be taken into account.Key PointsConductivity and location assumptions used to interpret ground magnetic perturbations yield conflicting resultsHigh‐latitude currents associated with voltage generators may instead be associated with current generators, and vice versaWithout better constraints on conductivity/station location relative to currents, conflicts will not be resolvedPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138366/1/jgra53632.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138366/2/jgra53632_am.pd

An investigation of the ankle contact forces in a foot with hammer toe deformity. A comparison of patient-specific approaches using finite element modeling and musculoskeletal simulation

The internal forces and stresses in the tissue are important as they are linked to the risk of mechanical trauma and injuries. Despite their value, the internal stresses and forces cannot be directly measured in-vivo. A previously validated 3D finite element model (FEM) was constructed using Magnetic Resonance Imaging (MRI) of a person with diabetes and hammer toe deformity. The foot model simulated at five different instances during the stance phase of gait. The internal stress distribution on the talus that was obtained using the FEM simulation, was used to calculate the joint reaction force at the ankle joint. In addition, the musculoskeletal model (MSM) of the participant with hammer toe foot was developed based on the gait analysis and was used to determine the muscle forces and joint reactions. The result showed that the vertical reaction forces obtained from the FEM and MSM follow a similar trend through the stance phase of gait cycle and are significantly correlated ( R=0.99 ). The joint reaction forces obtained through the two methods do not differ for the first 25% of the gait cycle, while the maximum difference was ∼0.7 Body weight that was observed at 50% of the stance phase. Clinical Relevance: Finite element modeling and musculoskeletal simulation can shed light on the internal forces at the ankle in pathological conditions such as hammer toe. The similarities and differences observed in the joint reaction forces calculated from the two methods can have implications in assessing the effect of clinical interventions

Using Copper-Doped Mesoporous Bioactive Glass Nanospheres to Impart Anti-Bacterial Properties to Dental Composites

Experimental dental resin composites containing copper-doped mesoporous bioactive glass nanospheres (Cu-MBGN) were developed to impart anti-bacterial properties. Increasing amounts of Cu-MBGN (0, 1, 5 and 10 wt%) were added to the BisGMA/TEGDMA resin matrix containing micro- and nano-fillers of inert glass, keeping the resin/filler ratio constant. Surface micromorphology and elemental analysis were performed to evaluate the homogeneous distribution of filler particles. The study investigated the effects of Cu-MBGN on the degree of conversion, polymerization shrinkage, porosity, ion release and anti-bacterial activity on S. mutans and A. naeslundii. Experimental materials containing Cu-MBGN showed a dose-dependent Cu release with an initial burst and a further increase after 28 days. The composite containing 10% Cu-MBGN had the best anti-bacterial effect on S. mutans, as evidenced by the lowest adherence of free-floating bacteria and biofilm formation. In contrast, the 45S5-containing materials had the highest S. mutans adherence. Ca release was highest in the bioactive control containing 15% 45S5, which correlated with the highest number of open porosities on the surface. Polymerization shrinkage was similar for all tested materials, ranging from 3.8 to 4.2%, while the degree of conversion was lower for Cu-MBGN materials. Cu-MBGN composites showed better anti-bacterial properties than composites with 45S5 BG

Prevalence, awareness and risk factors of hypertension in a large cohort of Iranian adult population

Background: There is considerable variation in hypertension prevalence and awareness, and their correlates, across different geographic locations and ethnic groups. We performed this cross-sectional analysis on data from the Golestan Cohort Study (GCS). Methods: Enrollment in this study occurred in 2004-2008, and included 50 045 healthy individuals from Golestan Province in northeastern Iran. Hypertension was defined as a SBP at least 140 mmHg, a DBP at least 90 mmHg, a prior diagnosis of hypertension, or the use of antihypertensive drugs. Potential correlates of hypertension and its awareness were analyzed by logistic regression adjusted for sex, age, BMI, place of residence, literacy, ethnicity, physical activity, smoking, black and green tea consumption and wealth score. Results: Of the total cohort participants, 21 350 (42.7) were hypertensive. Age-standardized prevalence of hypertension, using the 2001 WHO standard world population, was 41.8 (95 confidence interval: 38.3-45.2). Hypertension was directly associated with female sex, increased BMI, Turkmen ethnicity, and lack of physical activity, and inversely associated with drinking black tea and wealth score. Among hypertensive patients, 46.2 were aware of their disease, 17.6 were receiving antihypertensive medication, and 32.1 of the treated patients had controlled hypertension. Hypertension awareness was greater among women, the elderly, overweight and obese patients, and those with a higher wealth score. Conclusion: Hypertension is highly prevalent in rural Iran, many of the affected individuals are unaware of their disease, and the rate of control by antihypertensive medications is low. Increasing hypertension awareness and access to health services, especially among less privileged residents are recommended. © Lippincott Williams and Wilkins

Increased exposure to loading is associated with decreased plantar soft tissue hardness in people with diabetes and neuropathy

Aims Literature indicates that altered plantar loading in people with diabetes could trigger changes in plantar soft tissue biomechanics which, in turn, could affect the risk for ulceration. To stimulate more research in this area, this study uses in vivo testing to investigate the link between plantar loading and tissue hardness. Methods Tissue hardness and plantar pressure distribution were measured for six plantar areas in 39 people with diabetes and peripheral neuropathy. Results Spearman correlation analysis revealed that increased pressure time integral at the 1st metatarsal-head region (r = -0.354, n = 39, P = 0.027) or at the heel (r = -0.378, n = 39, P = 0.018) was associated with reduced hardness in the same regions. After accounting for confounding parameters, generalised estimating equations analysis also showed that 10% increase in pressure time integral at the heel was associated with ≈ 1 unit reduction in hardness in the same region. Conclusions For the first time, this study reveals that people with diabetes and neuropathy who tend to load their feet more heavily also tend to have plantar soft tissues with lower hardness. The observed difference in tissue hardness is likely to affect the tissue’s vulnerability to overload injury. More research will be needed to explore the implications of the observed association for the risk of ulceration