Plantar Shear Research Articles

A cross sectional pilot study utilising STrain Analysis and Mapping of the Plantar Surface (STAMPS) to measure plantar load characteristics within a healthy population

BackgroundNo in-shoe systems, measuring both components of plantar load (plantar pressure and shear stress) are available for use in patients with diabetes. The STAMPS (STrain Analysis and Mapping of the Plantar Surface) system utilises digital image correlation (DIC) to determine the strain sustained by a deformable insole, providing a more complete understanding of plantar shear load at the foot-surface interface. Research questionsWhat is the normal range and pattern of strain at the foot-surface interface within a healthy population as measured by the STAMPS system? Is STAMPS a valid tool to measure the effects of plantar load? MethodsA cross-sectional study of healthy participants was undertaken. Healthy adults without foot pathology or diabetes were included. Participants walked 20 steps with the STAMPS insole in a standardised shoe. Participants also walked 10 m with the Novel Pedar® plantar pressure measurement insole within the standardised shoe. Both measurements were repeated three times. Outcomes of interest were global and regional values for peak resultant strain (SMAG) and peak plantar pressure (PPP). ResultsIn 18 participants, median peak SMAG and PPP were 35.01 % and 410.6kPa respectively. The regions of the hallux and heel sustained the highest SMAG (29.31 % (IQR 24.56–31.39) and 20.50 % (IQR 15.59–24.12) respectively) and PPP (344.8kPa (IQR 268.3 – 452.5) and 279.3kPa (IQR 231.3–302.1) respectively). SMAG was moderately correlated with PPP (r= 0.65, p < 0.001). Peak SMAG was located at the hallux in 55.6 % of participants, at the 1st metatarsal head (MTH) in 16.7 %, the heel in 16.7 %, toes 3–5 in 11.1 % and the MTH2 in 5.6 %. SignificanceThe results demonstrate the STAMPS system is a valid tool to measure plantar strain. Further studies are required to investigate the effects of elevated strain and the relationship with diabetic foot ulcer formation.

New Perspectives on Foot Segment Forces and Joint Kinetics-Integrating Plantar Shear Stresses and Pressures with Multi-segment Foot Modeling.

The role of the many small foot articulations and plantar tissues in gait is not well understood. While kinematic multi-segment foot models have increased our knowledge of foot segmental motions, the integration of kinetics with these models could further advance our understanding of foot mechanics and energetics. However, capturing and effectively utilizing segmental ground reaction forces remains challenging. The purposes of this study were to (1) develop methodology to integrate plantar pressures and shear stresses with a multi-segment foot model, and (2) generate and concisely display key normative data from this combined system. Twenty-six young healthy adults walked barefoot (1.3m/s) across a pressure/shear sensor with markers matching a published 4-segment foot model. A novel anatomical/geometric template-based masking method was developed that successfully separated regions aligned with model segmentation. Directional shear force plots were created to summarize complex plantar shear distributions, showing opposing shear forces both between and within segments. Segment centers of pressure (CoPs) were shown to be primarily stationary within each segment, suggesting that forward progression in healthy gait arises primarily from redistributing weight across relatively fixed contact points as opposed to CoP movement within a segment. Inverse dynamics-based normative foot joint moments and power were presented in the context of these CoPs to aid in interpretation of tissue stresses. Overall, this work represents a successful integration of motion capture with direct plantar pressure and shear measurements for multi-segment foot kinetics. The presented tools are versatile enough to be used with other models and contexts, while the presented normative database may be useful as a baseline comparison for clinical work in gait energetics and efficiency, balance, and motor control. We hope that this work will aid in the advancement and availability of kinetic MSF modeling, increase our knowledge of foot mechanics, and eventually lead to improved clinical diagnosis, rehabilitation, and treatment.

A wearable three-axis force sensor based on deep learning technology for plantar measurement

A challenge in the measurement of plantar shear stress measurement is the absence of wearable and comfortable monitoring devices. In this paper, a wearable three-axis force sensor based on end-to-end deep learning technology is developed for plantar shear stress monitoring. The sensor can convert the three-axis stress it experiences into image signals through the deformation of the pattern layer embedded in the elastomeric probe. These images and three-axis stresses are fed into a convolution neural network for training, establishing a mapping relationship between images and three-axis forces. The prepared sensor has the advantages of small size (1.62 cm3), light weight (1.68 g), and flexibility, which make it possible to form a sensor array in the shoe without affecting the comfort of the wearer. By synchronizing with an action camera, the sensor array can provide real-time three-axis stress in different plantar regions for each frame of motions such as walking, running, playing football or basketball. This work contributes to the advancement of gait analysis, the clinical diagnosis of foot diseases, and the evaluation of athletic training.

Evaluation of in-shoe plantar pressure and shear during walking for diabetic foot ulcer prevention.

To investigate reliability and changes of in-shoe plantar pressure and shear during walking at three cadences with two insole designs. This was a precursor to the investigation of plantar loading in people with diabetes for potential foot ulcer prevention. A sensorised insole system, capable of measuring plantar pressure and shear at the heel, fifth metatarsal head (5MH), first metatarsal head (1MH) and hallux, was tested with ten healthy participants during level walking. Reliability was evaluated, using intra-class correlation coefficient (ICC), while varying the cadences and insole types. Percentage changes in pressure and shear relative to values obtained at self-selected cadence with a flat insole design were investigated. Mean±standard deviation of maximum pressure, medial-lateral and anterior-posterior shear of up to 380±24kPa, 46±2kPa and -71±4kPa, respectively, were measured. The ICC in ranges of 0.762-0.973, 0.758-0.987 and 0.800-0.980 were obtained for pressure, anterior-posterior and medial-lateral shear, respectively. Opposite anterior-posterior shear directions between 5MH and 1MH (stretching), and between 1MH and hallux (pinching) were observed for some participants. Increasing cadence increased pressure and anterior-posterior shear (by up to +77%) but reduced medial-lateral shear at the heel and hallux (by up to -34%). Slower cadence increased anterior-posterior shear (+114%) but decreased medial-lateral shear (-46%) at the hallux. The use of a flexible contoured insole resulted in pressure reduction at the heel and 5MH but an increase in anterior-posterior shear at the heel (+69%) and hallux (+75%). The insole system demonstrated good reliability and is comparable to reported pressure-only systems. Pressure measurements were sensitive to changes in cadence and insole designs in ways that were consistent with the literature. However, our plantar shear showed localised shear changes with cadences and insoles for the first time, as well as stretching and pinching effects on plantar tissue. This opens new possibilities to investigate plantar tissue viability, loading characteristics and orthotic designs aimed towards foot ulcer prevention.

Getting Ready for Foot Care Certification: Implementing Off-loading Interventions to Prevent or Manage Injury.

Getting Ready for Foot Care Certification: Implementing Off-loading Interventions to Prevent or Manage Injury.

Integration of reginal shear measurements at the foot-ground interface during routine balance assessment of the elderly population

BackgroundForce-plate posturography offers a convenient way for quantitative assessment of postural stability in the elderly. However, studies focusing on routine balance assessment have usually not taken reginal shear distributions (i.e., arising from horizontal forces) into consideration. Research question(1) Does plantar shear distribution differ between young and elderly subjects during upright standing? (2) How do the maximum plantar shear forces vary at different regions of the foot? MethodsThe new reginal shear measurement (RSM) method can simultaneously capture the three-dimensional force distributions at regional plantar sites while subjects maintaining standing balance. The feasibility of the proposed method in characterizing the magnitude and distribution of plantar shear forces was tested in thirty-two normal young and nineteen elderly subjects. Statistical analysis was performed using the independent samples t-test for both the continuous and ordinal variables. ResultsFor regional AP shear forces, statistically significant differences were found between the two groups for the toe region of the right foot and the midfoot of both feet. For ML shear distributions, statistically significant differences were found at nearly all plantar sites expect for the hallux and lateral metatarsal. The maximum increase in ML shear forces occurred in the toe region of the right foot, where the peak shear values were 113.16% higher than those of the young subjects. The peak ML shear occurred in the midfoot were averagely 83.19% and 70.57% higher in the elderly’s left and right feet, respectively. SignificanceThe RSM method may offer unique solutions to identify functional decline in postural control of the elderly. The plantar shear pattern has potential to become an important parameter in evaluating one’s balance performance during upright standing.

Plantar pressure measurement system based on piezoelectric sensor: a review

PurposePlantar force is the interface pressure existing between the foot plantar surface and the shoe sole during static or dynamic gait. Plantar force derived from gait and posture plays a critical role for rehabilitation, footwear design, clinical diagnostics and sports activities, and so on. This paper aims to review plantar force measurement technologies based on piezoelectric materials, which can make the reader understand preliminary works systematically and provide convenience for researchers to further study.Design/methodology/approachThe review introduces working principle of piezoelectric sensor, structures and hardware design of plantar force measurement systems based on piezoelectric materials. The structures of sensors in plantar force measurement systems can be divided into four kinds, including monolayered sensor, multilayered sensor, tri-axial sensor and other sensor. The previous studies about plantar force measurement system based on piezoelectric technology are reviewed in detail, and their characteristics and performances are compared.FindingsA good deal of measurement technologies have been studied by researchers to detect and analyze the plantar force. Among these measurement technologies, taking advantage of easy fabrication and high sensitivity, piezoelectric sensor is an ideal candidate sensing element. However, the number and arrangement of the sensors will influence the characteristics and performances of plantar force measurement systems. Therefore, it is necessary to further study plantar force measurement system for better performances.Originality/valueSo far, many plantar force measurement systems have been proposed, and several reviews already introduced plantar force measurement systems in the aspect of types of pressure sensors, experimental setups for foot pressure measurement analysis and the technologies used in plantar shear stress measurements. However, this paper reviews plantar force measurement systems based on piezoelectric materials. The structures of piezoelectric sensors in the measurement systems are discussed. Hardware design applied to measurement system is summarized. Moreover, the main point of further study is presented in this paper.

Plantar shear stress in the diabetic foot: A systematic review and meta-analysis.

Diabetic foot ulceration (DFU) is a multifactorial process involving undetected, repetitive trauma resulting in inflammation and tissue breakdown. Shear stress forms a major part of plantar load, the aim of this review is to determine whether elevated shear stress results in ulceration. A systematic review of the Ovid Medline, EMBASE, CINAHL and Cochrane library databases was performed. Studies involving patients with diabetes who underwent plantar shear stress assessment were included. The primary outcome was plantar shear stress in patients with diabetes who had a current/previous DFU compared with those with no prior ulceration. Meta-analysis was performed comparing shear stress between those with a current or previous DFU and those without, and those with diabetes and healthy controls. The search strategy identified 1461 potentially relevant articles, 16 studies met the inclusion criteria, involving a total of 597 patients. Comparing shear stress between the current/previous DFU group and those without: Standardised mean difference (SMD) 0.62 (95% CI -0.01 to 1.25), in favour of greater shear stress within the DFU group, p=0.05. Comparing shear stress between people with diabetes and healthy controls: 0.36 (95% CI -0.31 to 1.03), in favour of greater shear stress within the diabetes group, p=0.29. This review suggests that that patients with diabetes and a history of ulceration exhibit greater shear stress than their ulcer-free counterparts. This strengthens the premise that development of systems to measure shear stress may be helpful in DFU prediction and prevention.

Added body mass alters plantar shear stresses, postural control, and gait kinetics: Implications for obesity

Obesity is a growing global health concern. The increased body mass and altered mass distribution associated with obesity may be related to increases in plantar shear that putatively leads to physical functional deficits. Therefore, measurement of plantar shear may provide unique insights on the effects of body mass and body distribution on physical function or performance. 1) To investigate the effects of body mass and distribution on plantar shear. 2) To examine how altered plantar shear influences postural control and gait kinetics. 1) a weighted vest forward distributed (FV) would shift the center of pressure (CoP) location forward during standing compared with a weighted vest evenly distributed (EV), 2) FV would increase plantar shear spreading forces more than EV during standing, 3) FV would increase postural sway during standing while EV would not, and 4) FV would elicit greater compensatory changes during walking than EV. Twenty healthy young males participated in four different tests: 1) static test (for measuring plantar shear and CoP location without acceleration, 2) bilateral-foot standing postural control test, 3) single-foot standing postural test, and 4) walking test. All tests were executed in three different weight conditions: 1) unweighted (NV), 2) EV with 20% added body mass, and 3) FV, also with 20% added body mass. Plantar shear stresses were measured using a pressure/shear device, and several shear and postural control metrics were extracted. Repeated measures ANOVAs with Holms post hoc test were used to compare each metric among the three conditions (α = 0.05). FV and EV increased both AP and ML plantar shear forces compared to NV. FV shifted CoP forward in single-foot trials. FV and EV showed decreased CoP range and velocity and increased Time-to-Boundary (TTB) during postural control compared to NV. EV and FV showed increased breaking impulse and propulsive impulse compared to NV. In addition, EV showed even greater impulses than FV. While EV increased ML plantar shear spreading force, FV increased AP plantar shear spreading force during walking. Added body mass increases plantar shear spreading forces. Body mass distribution had greater effects during dynamic tasks. In addition, healthy young individuals seem to quickly adapt to external stimuli to control postural stability. However, as this is a first step study, follow-up studies are necessary to further support the clinical role of plantar shear in other populations such as elderly and individuals with obesity or diabetes.

The Associations between Rapid Strength Development and Muscle Stiffness in Older Population.

Background: Previous studies suggest that the capacity for rapid force production of ankle plantar flexors is essential for the prevention of falls in the elderly. In healthy young adults, there were significant associations between rate of force development and muscle stiffness measured by shear wave elastography. However, there has been no study investigating the association of rate of force development with shear elastic modulus in older adults. Methods: The muscle strength and shear elastic modulus of the medial gastrocnemius muscle in both legs were measured in 17 elderly men and 10 elderly women (mean ± SD; 70.7 ± 4.1 years; 160.6 ± 8.0 cm; 58.7 ± 9.5 kg). We investigated the rate of force development of plantar flexors and shear elastic modulus of medial gastrocnemius muscle using by shear wave elastography. Results: Our results showed that there were no significant associations between normalized rate of force development and shear elastic modulus of medial gastrocnemius muscle. Conclusion: This suggests that the capacity of rapid force production could be related not to muscle stiffness of the medial gastrocnemius muscle, but to neuromuscular function in older individuals.

Biomechanical Efficacy of Shear-Reducing Diabetic Insoles: Elaborations on Future Design Criteria

ABSTRACT Introduction Increasing evidence suggests that plantar shear forces and related stresses play a major role in diabetic foot ulcerations. Several orthotic devices are commercially available to reduce plantar shear forces within the shoe. The biomechanical efficacy of these devices was not tested in vivo. To measure spatiotemporal characteristics of gait to assess the efficacy of such shear-reducing insoles (SRIs), control insoles were also tested for comparison purposes. Material and Methods Eighteen healthy volunteers walked along a 30.5-m line while wearing three types of insoles in randomized order. Spatiotemporal parameters of gait were quantified. Statistical comparisons between the control and SRIs were conducted using repeated measures analysis of variance. Intraclass correlation coefficients (ICCs) were also calculated to reveal the repeatability of the trials. Step length, gait speed, and cadence of the subjects remained similar regardless of the insole type. Results No significant difference was observed in any variable. The ICC values revealed excellent repeatability. Conclusions The lack of changes in gait parameters in these results suggest that shear-reducing diabetic inserts did not decrease plantar shear forces as intended. This might be caused by unrealistic in vitro testing conditions during the prototype development. Future designs should also consider friction at the lateral walls of the inserts, an increase in step repetition that accompanies a decrease in gait speed and/or step length, and a possible temperature increase within the shoe. We conclude that the future SRIs need to be redesigned based on comprehensive biomechanical guidelines.

Factors Associated With Callus in Patients with Diabetes, Focused on Plantar Shear Stress During Gait.

The aim of this study is to identify whether plantar shear stress in neuropathic patients with diabetes with callus is increased compared with those without callus. The differences in foot deformity, limited joint mobility, repetitive stress of walking, and ill-fitting shoes between patients with callus and those without callus were also determined. Subjects were recruited from the Diabetic Foot Outpatient Clinic. A newly developed in-shoe measurement system, which has flexible and thin insoles, enabled measurement of both plantar pressure and shear stress simultaneously when subjects walked as usual on a 10 m walkway. It was found that plantar shear stress adjusted for weight during the push-off phase was increased by 1.32 times in patients with callus compared with those without callus (mean ± SD: 0.0500 ± 0.0160 vs 0.0380 ± 0.0144, P = .031). Moreover, hallux valgus deformity, reduction in dorsiflexion of the ankle joint and increase in plantar flexion were showed in feet with callus. Increased plantar shear stress may be caused by gait change that patients having callus push off with the metatarsal head instead of the toe as a result of foot deformity and limited joint mobility. It was found that plantar shear stress adjusted for weight during the push-off phase was increased in patients with callus compared with those without callus by using the newly developed measurement system. These results suggest that reduction of plantar shear stress during the push-off phase can prevent callus formation in neuropathic patients with diabetes.

3P2-J05 歩行中に靴内でフットウェアが足底に与える圧力およびせん断力の評価(看護とメカトロニクス)

3P2-J05 歩行中に靴内でフットウェアが足底に与える圧力およびせん断力の評価(看護とメカトロニクス)

American Society of Biomechanics Clinical Biomechanics Award 2012: Plantar shear stress distributions in diabetic patients with and without neuropathy

BackgroundThe exact pathology of diabetic foot ulcers remains to be resolved. Evidence suggests that plantar shear forces play a major role in diabetic ulceration. Unfortunately, only a few manuscripts exist on the clinical implications of plantar shear. The purpose of this study was to compare global and regional peak plantar stress values in three groups; diabetic patients with neuropathy, diabetic patients without neuropathy and healthy control subjects. MethodsFourteen diabetic neuropathic patients, 14 non-neuropathic diabetic control and 11 non-diabetic control subjects were recruited. Subjects walked on a custom-built stress plate that quantified plantar pressures and shear. Four stress variables were analyzed; peak pressure, peak shear, peak pressure-time and shear-time integral. FindingsGlobal peak values of peak shear (p=0.039), shear-time integral (p=0.002) and pressure-time integral (p=0.003) were significantly higher in the diabetic neuropathic group. The local peak shear stress and shear-time integral were also significantly higher in diabetic neuropathic patients compared to both control groups, in particular, at the hallux and central forefoot. The local peak pressure and pressure-time integral were significantly different between the three groups at the medial and lateral forefoot. InterpretationPlantar shear and shear-time integral magnitudes were elevated in diabetic patients with peripheral neuropathy, which indicates the potential clinical significance of these factors in ulceration. It is thought that further investigation of plantar shear would lead to a better understanding of ulceration pathomechanics, which in turn will assist researchers in developing more effective preventive devices and strategies.

Optimization of Nonlinear Hyperelastic Coefficients for Foot Tissues Using a Magnetic Resonance Imaging Deformation Experiment

Accurate prediction of plantar shear stress and internal stress in the soft tissue layers of the foot using finite element models would provide valuable insight into the mechanical etiology of neuropathic foot ulcers. Accurate prediction of the internal stress distribution using finite element models requires that realistic descriptions of the material properties of the soft tissues are incorporated into the model. Our investigation focused on the creation of a novel three-dimensional (3D) finite element model of the forefoot with multiple soft tissue layers (skin, fat pad, and muscle) and the development of an inverse finite element procedure that would allow for the optimization of the nonlinear elastic coefficients used to define the material properties of the skin muscle and fat pad tissue layers of the forefoot based on a Ogden hyperelastic constitutive model. Optimization was achieved by comparing deformations predicted by finite element models to those measured during an experiment in which magnetic resonance imaging (MRI) images were acquired while the plantar surface forefoot was compressed. The optimization procedure was performed for both a model incorporating all three soft tissue layers and one in which all soft tissue layers were modeled as a single layer. The results indicated that the inclusion of multiple tissue layers affected the deformation and stresses predicted by the model. Sensitivity analysis performed on the optimized coefficients indicated that small changes in the coefficient values (±10%) can have rather large impacts on the predicted nominal strain (differences up to 14%) in a given tissue layer.

Insole-Type Simultaneous Measurement System of Plantar Pressure and Shear Force During Gait for Diabetic Patients

Plantar foot ulceration is one diabetic complication shown to be associated with both pressure and shear force. There are plantar pressure measurement systems, but it is still difficult to measure plantar shear force while walking. The aim of this study is to establish a simultaneous in-shoe measurement system of plantar pressure and shear force during a gait. The design of the measurement system is based on F-scan pressure-distribution-sensor sheets and shear-sensor sheets. An insole with a shear-sensor sheet was arranged to be applicable for measurement of diabetic having neuropathy patients without damaging their skin. It was found that the system gets proper different shear force data in response to gait patterns, such as shuffle walking and flat-floored walking. We confirmed, moreover, the repeatability of the system for 5 healthy individuals. Experimental results show that weight-adjusted plantar shear stress during the pushoff phase of a gait increases in diabetic patients with calluses more than in patients without calluses. After a clinical study of diabetic patients, the system can be applied not only for the prevention of diabetic foot but also for the broad evaluation of gait posture.

Shear sensing based on a microstrip patch antenna

A microstrip patch antenna sensor was studied for shear sensing with a targeted application of measuring plantar shear distribution on a diabetic foot. The antenna shear sensor consists of three components, namely an antenna patch, a soft foam substrate and a slotted ground plane. The resonant frequency of the antenna sensor is sensitive to the overlapping length between the slot in the ground plane and the antenna patch. A shear force applied along the direction of the slot deforms the foam substrate and causes a change in the overlapping length, which can be detected from the antenna frequency shift. The antenna shear sensor was designed based on simulated antenna frequency response and validated by experiments. Experimental results indicated that the antenna sensor exhibits high sensitivity to shear deformation and responds to the applied shear loads with excellent linearity and repeatability.

The effect of prior compression tests on the plantar soft tissue compressive and shear elastic properties

Background Changes in the shear plantar soft tissue properties with diabetes likely play a role in plantar ulceration, yet little is known about these characteristics. We recently conducted in vitro shear tests on specimens previously tested in compression to characterize the tissue under both these loading modes. However, previously tested specimens might not provide representative mechanical properties as prior testing may have altered the tissue. The purpose of this study was to test the effect of prior compression testing on the plantar soft tissue shear and compressive properties using paired specimens in a twopart study.

1A2-O08 糖尿病患者における胼胝保有要因解明のための足底圧力・剪断力同時測定システム(看護とメカトロニクス)

1A2-O08 糖尿病患者における胼胝保有要因解明のための足底圧力・剪断力同時測定システム(看護とメカトロニクス)

Design and Development on Piezoelectric Ceramic Type Insole 3D Force Measurement System Based on LabVIEW

According to the requirements of measurement of plantar pressure and shear stress in the meantime, this thesis puts forward a plan to construct a new insole plantar pressure and shear stress system based on multifunction data acquisition modular and Lab VIEW. Then the hardware part and software part are designed and developed respectively. There are 3 sensors are arrayed at each measurement point, that means 3 sensors are assembled in 3 different directions of X,Y and Z . The piezoelectric ceramic type sensors are designed, manufactured and calibrated according to scientific methods. Meanwhile, the DAQ card is selected carefully. Of course, the software part is developed based on Lab VIEW. A series of tests are performed in order to validate the function of the measurement system. The results satisfy the anticipated design requirements. At last, the problems and application trend of the measurement system are predicted.