Heel Pad Stiffness in Plantar Heel Pain by Shear Wave Elastography

Changes in functional characteristics of heel fat pad with age

BACKGROUND

This study aimed to investigate age-related changes in the heel fat pad's microchamber and macrochamber layers, particularly focusing on load-induced alterations. Understanding these changes is crucial for elucidating age-related differences in foot mechanics and their potential implications for mobility and comfort.

METHODS

Fifty-five healthy individuals were divided into three age groups: young adults (≤29 years), middle-aged adults (30-44 years), and elderly individuals (≥45 years). Ultrasonic imaging was utilized to measure the thickness of the heel fat pad's microchamber and macrochamber layers under varying load conditions. Thickness, percentage changes, and ratios of load-induced thickness changes were calculated to assess age-related differences.

FINDINGS

Under no-load conditions, both microchamber and macrochamber layers of the heel fat pad were significantly thicker in middle-aged and elderly individuals than in young adults. When load was applied middle-aged and elderly participants exhibited smaller changes in the macrochamber layer and larger changes in the microchamber layer compared to young adults.

INTERPRETATION

Our findings suggest that age influences the structural characteristics and response of the heel fat pad to mechanical loading. Thicker heel fat pad layers in middle-aged and elderly individuals under no-load conditions may reflect age-related changes in fat distribution or composition. Moreover, differences in load-induced thickness changes indicate altered mechanical properties with age, potentially affecting shock absorption and overall foot function. Understanding these age-related variations can help develop interventions aimed at preserving foot health and mobility across the lifespan.

A narrative review of the measurement methods for biomechanical properties of plantar soft tissue in patients with diabetic foot

This article provides an overview of the development history and advantages and disadvantages of measurement methods for soft tissue properties of the plantar foot. The measurement of soft tissue properties is essential for understanding the biomechanical characteristics and function of the foot, as well as for designing and evaluating orthotic devices and footwear. Various methods have been developed to measure the properties of plantar soft tissues, including ultrasound imaging, indentation testing, magnetic resonance elastography, and shear wave elastography. Each method has its own strengths and limitations, and choosing the most appropriate method depends on the specific research or clinical objectives. This review aims to assist researchers and clinicians in selecting the most suitable measurement method for their specific needs.

Reliability and Validity of Shore Hardness in Plantar Soft Tissue Biomechanics

Shore hardness (SH) is a cost-effective and easy-to-use method to assess soft tissue biomechanics. Its use for the plantar soft tissue could enhance the clinical management of conditions such as diabetic foot complications, but its validity and reliability remain unclear. Twenty healthy adults were recruited for this study. Validity and reliability were assessed across six different plantar sites. The validity was assessed against shear wave (SW) elastography (the gold standard). SH was measured by two examiners to assess inter-rater reliability. Testing was repeated following a test/retest study design to assess intra-rater reliability. SH was significantly correlated with SW speed measured in the skin or in the microchamber layer of the first metatarsal head (MetHead), third MetHead and rearfoot. Intraclass correlation coefficients and Bland-Altman plots of limits of agreement indicated satisfactory levels of reliability for these sites. No significant correlation between SH and SW elastography was found for the hallux, 5th MetHead or midfoot. Reliability for these sites was also compromised. SH is a valid and reliable measurement for plantar soft tissue biomechanics in the first MetHead, the third MetHead and the rearfoot. Our results do not support the use of SH for the hallux, 5th MetHead or midfoot.

Ultrasonic Evaluation of the Heel Fat Pad Under Loading Conditions Using a Polymethylpentene Resin Plate: Part 2. Reliability and Agreement Study

Previously, we developed an instrument to evaluate the heel fat pad (HFP) two-layer structure, under varying loading conditions, with ultrasonography from the plantar surface through a polymethylpentene resin plate; the measured values were equivalent to those obtained without this plate. The study described here aimed to determine the intra- and inter-examiner reliabilities of the HFP thickness measurements and the agreement between long- and short-axis measured values using this instrument. Two examiners successively recorded the HFPs of 40 healthy adults twice under the no loading and loading conditions on the long- and short-axis scans. The HFPs were classified into two layers, and their thicknesses were measured. Short-term intra- and inter-examiner reliabilities were determined using the intraclass correlation coefficients. Measurements were repeated 1 mo later to determine the long-term intra-examiner reliability. The agreement between the measured long- and short-axis values was investigated by calculating the minimal detectable changes. The determined short- and long-term intra-examiner reliabilities ranged from 0.750 to 0.999 and from 0.765 to 0.952, respectively. Inter-examiner reliability ranged from 0.765 to 0.997. Differences may occur between the values measured at different axes. The measurements using this evaluation instrument were reliable, and it is best to unify the measurement axis for quantitative research.

Optimization Design of the Inner Structure for a Bioinspired Heel Pad with Distinct Cushioning Property

In the existing research on prosthetic footplates, rehabilitation insoles, and robot feet, the cushioning parts are basically based on simple mechanisms and elastic pads. Most of them are unable to provide adequate impact resistance especially during contact with the ground. This paper developed a bioinspired heel pad by optimizing the inner structures inspired from human heel pad which has great cushioning performance. The distinct structures of the human heel pad were determined through magnetic resonance imaging (MRI) technology and related literatures. Five-layer pads with and without inner structures by using two materials (soft rubber and resin) were obtained, resulting in four bionic heel pads. Three finite element simulations (static, impact, and walking) were conducted to compare the cushioning effects in terms of deformations, ground reactions, and principal stress. The optimal pad with bionic structures and soft rubber material reduced 28.0% peak vertical ground reaction force (GRF) during walking compared with the unstructured resin pad. Human walking tests by a healthy subject wearing the 3D printed bionic pads also showed similar findings, with an almost 20% decrease in peak vertical GRF at normal speed. The soft rubber heel pad with bionic structures has the best cushioning performance, while the unstructured resin pad depicts the poorest. This study proves that with proper design of the inner structures and materials, the bionic pads will demonstrate distinct cushioning properties, which could be applied to the engineering fields, including lower limb prosthesis, robotics, and rehabilitations.

Elasticity evaluation of the plantar fascia: A shear wave elastography study involving 33 early-stage plantar fasciopathy subjects

Background: Plantar fasciopathy, the most common foot condition seen in elderly and athletic populations, can be diagnosed and differentially diagnosed with imaging modalities such as ultrasound shear wave elastography (SWE). However, standard guidelines for ultrasound elastography of the plantar fascia are lacking. The purpose of this study was to determine the impact of the region of interest (ROI) on the evaluation of the plantar fascia elasticity and confirm the screening accuracy of SWE in the early-stage of plantar fasciopathy. Methods: This was an observational case‒control study involving 50 feet of 33 early-stage plantar fasciopathy subjects (the plantar fasciopathy group) and 96 asymptomatic feet of 48 healthy volunteers (the non-pain group). Clinical information, including age, gender, height, weight, visual analogue scale (VAS) score, American Orthopaedic Foot and Ankle Scale score (AOFAS), and the symptom duration, were recorded. All participants underwent both conventional ultrasound and SWE evaluation. The plantar fascia elastic parameters included SWE_single-point, calculated with a single-point ROI set at the greatest thickness of the plantar fascia, and SWE_multi-point, calculated by multipoint ROIs set continuously from the origin at the calcaneus to about 2 cm from the calcaneal origin. Results: The plantar fasciopathy group presented a higher VAS score (median [IQR), 4.00 (3.00) vs. 0.00 (0.00), p < 0.001] and lower AOFAS score [median (IQR), 79.50 (3.00) vs. 100.00 (10.00), p < 0.001] than the non-pain group. The median plantar fascia thickness of the plantar fasciopathy group was significantly greater than that of the non-pain group [median (IQR), 3.95 (1.37) mm vs 2.40 (0.60) mm, p < 0.001]. Abnormal ultrasound features, including echogenicity, border irregularities, and blood flow signals, were more prominent in the plantar fasciopathy group than in the non-pain group (29% vs. 0%, p < 0.001; 26% vs. 1%, p < 0.001; 12% vs. 0%, p < 0.001, respectively). Quantitative analysis of the plantar fascia elasticity revealed that the difference between the value of SWE_single-point and SWE_multipoint was significant [median (IQR), 65.76 (58.58) vs. 57.42 (35.52) kPa, p = 0.02). There was a moderate and significant correlation between the value of SWE_single-point and heel pain. However, there was no correlation between the value of SWE_multipoint and heel pain. Finally, we utilized the results of SWE_single-point as the best elastic parameter reflecting clinical heel pain and found that SWE_single-point could provide additional value in screening early-stage plantar fasciopathy, with an increase in sensitivity from 76% to 92% over conventional ultrasound alone. Additionally, compared with conventional ultrasound and SWE, the use of both improved the accuracy of screening for plantar fasciopathy. Although there were no significant differences in the negative predictive value of conventional ultrasound, SWE, and their combination, the positive predictive value when using both (90.20%) was significantly greater than that when using conventional ultrasound (74.50%) or SWE alone (76.50%). Conclusion: The plantar fascia elastic parameter calculated with single-point ROIs set at the greatest thickness of the plantar fascia is positively correlated with fascia feel pain. Single-point analysis is sufficient for the screening of the early-stage plantar fasciopathy using SWE. SWE_single-point may provide additional valuable information for assessing the severity of plantar fasciopathy.

Biomechanical Effects of Plastic Heel Cup on Plantar Fasciitis Patients Evaluated by Ultrasound Shear Wave Elastography

The plastic heel cup has been adopted to treat plantar heel problems for years. However, its mechanisms and biomechanical effects are yet to be fully understood. The purpose of this study was to investigate the effects of the plastic heel cup on the microchamber and macrochamber layers of the heel pad by comparing the stiffness (in terms of the shear wave speed) and thickness of these two layers with and without a plastic heel cup during static standing. Fifteen patients with unilateral plantar fasciitis were recruited. The shear wave speed and thickness of the microchamber and microchamber layers of each symptomatic heel pad during standing measured by ultrasound shear wave elastography were compared between conditions with and without a plastic heel cup. It was found that a plastic heel cup reduced the shear wave speed of the microchamber layer to 55.5% and increased its thickness to 137.5% compared with the condition without a plastic heel cup. For the microchamber layer, the shear wave speed was reduced to 89.7%, and thickness was increased to 113.6% compared with the condition without a plastic heel cup. The findings demonstrate that a plastic heel cup can help to reduce the stiffness and increase the thickness for both layers of the heel pad during standing, suggesting that the mechanism of a plastic heel cup, and its resulting biomechanical effect, is to reduce the internal stress of the heel pad by increasing its thickness through confinement.

An in vivo model for overloading-induced soft tissue injury

This proof-of-concept study demonstrates that repetitive loading to the pain threshold can safely recreate overloading-induced soft tissue damage and that localised tissue stiffening can be a potential marker for injury. This concept was demonstrated here for the soft tissue of the sole of the foot where it was found that repeated loading to the pain threshold led to long-lasting statistically significant stiffening in the overloaded areas. Loading at lower magnitudes did not have the same effect. This method can shed new light on the aetiology of overloading injury in the foot to improve the management of conditions such as diabetic foot ulceration and heel pain syndrome. Moreover, the link between overloading and tissue stiffening, which was demonstrated here for the first time for the plantar soft tissue, opens the way for an assessment of overloading thresholds that is not based on the subjective measurement of pain thresholds.

Ultrasonic Evaluation of the Heel Fat Pad under Weight-Bearing Conditions Using a Polymethylpentene Resin Plate: Part 1

To evaluate the two-layer structure of the heel fat pad (HFP) from non-weight-bearing to full-weight-bearing conditions, we developed an instrument that assesses these changes from the sole through a polymethylpentene resin plate (PMP) with ultrasonography. For actual use, we investigated the influence on measured values and ultrasonogram appearance by interposing the PMP. Additionally, as the PMP may be bent under weight-bearing conditions, its influence on the measured values was investigated. First, two examiners measured the distances inside the phantom with and without a PMP. Second, ultrasonograms were obtained from 40 healthy adults with and without a PMP, and the thicknesses of the whole layer and the two layers of the HFP were measured using the same ultrasonogram. For each experiment, reproducibility was investigated. Third, the distances inside the phantom were measured and compared through the bent PMP, which models the weight-bearing condition, and the flat PMP. The reproducibility of the measurements was equivalent with and without the PMP interposed. Potential bias in measured values arising from deformation of PMP under weight-bearing conditions was not detected. Overall, the PMP's interposition and the bending of the PMP might not influence the measured values and reproducibility of the measurements.

Medical imaging for plantar heel pain: a systematic review and meta-analysis

Background

Medical imaging can be used to assist with the diagnosis of plantar heel pain. The aim of this study was to synthesise medical imaging features associated with plantar heel pain.

Methods

This systematic review and meta-analysis conducted searches in MEDLINE, CINAHL, SPORTDiscus, Embase and the Cochrane Library from inception to 12th February 2021. Peer-reviewed articles of cross-sectional observational studies written in English that compared medical imaging findings in adult participants with plantar heel pain to control participants without plantar heel pain were included. Study quality and risk of bias was assessed using the National Institutes of Health quality assessment tool for observational cohort and cross-sectional studies. Sensitivity analyses were conducted where appropriate to account for studies that used unblinded assessors.

Results

Forty-two studies (2928 participants) were identified and included in analyses. Only 21% of studies were rated ‘good’ on quality assessment. Imaging features associated with plantar heel pain included a thickened plantar fascia (on ultrasound and MRI), abnormalities of the plantar fascia (on ultrasound and MRI), abnormalities of adjacent tissue such as a thickened loaded plantar heel fat pad (on ultrasound), and a plantar calcaneal spur (on x-ray). In addition, there is some evidence from more than one study that there is increased hyperaemia within the fascia (on power Doppler ultrasound) and abnormalities of bone in the calcaneus (increased uptake on technetium-99 m bone scan and bone marrow oedema on MRI).

Conclusions

People with plantar heel pain are more likely to have a thickened plantar fascia, abnormal plantar fascia tissue, a thicker loaded plantar heel fat pad, and a plantar calcaneal spur. In addition, there is some evidence of hyperaemia within the plantar fascia and abnormalities of the calcaneus. Whilst these medical imaging features may aid with diagnosis, additional high-quality studies investigating medical imaging findings for some of these imaging features would be worthwhile to improve the precision of these findings and determine their clinical relevance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13047-021-00507-2.

Plantar Soft Tissue Characterization Using Reverberant Shear Wave Elastography: A Proof-of-Concept Study

Plantar soft tissue stiffness provides relevant information on biomechanical characteristics of the foot. Therefore, appropriate monitoring of foot elasticity could be useful for diagnosis, treatment or health care of people with complex pathologies such as a diabetic foot. In this work, the reliability of reverberant shear wave elastography (RSWE) applied to plantar soft tissue was investigated. Shear wave speed (SWS) measurements were estimated at the plantar soft tissue at the first metatarsal head, the third metatarsal head and the heel from both feet in five healthy volunteers. Experiments were repeated for a test-retest analysis with and without the use of gel pad using a mechanical excitation frequency range between 400 and 600 Hz. Statistical analysis was performed to evaluate the reliability of the SWS estimations. In addition, the results were compared against those obtained with a commercially available shear wave-based elastography technique, supersonic imaging (SSI). The results indicate a low coefficient of variation for test-retest experiments with gel pad (median: 5.59%) and without gel pad (median: 5.83%). Additionally, the values of the SWS measurements increase at higher frequencies (median values: 2.11 m/s at 400 Hz, 2.16 m/s at 450 Hz, 2.24 m/s at 500 Hz, 2.21 m/s at 550 Hz and 2.31 m/s at 600 Hz), consistent with previous reports at lower frequencies. The SWSs at the plantar soft tissue at the first metatarsal head, third metatarsal head and heel were found be significantly (p<0.05) different, with median values of 2.42, 2.16 and 2.03 m/s, respectively which indicates the ability of the method to differentiate between shear wave speeds at different anatomical locations. The results indicated better elastographic signal-to-noise ratios with RSWE compared to SSI because of the artifacts presented in the SWS generation. These preliminary results indicate that the RSWE approach can be used to estimate the plantar soft tissue elasticity, which may have great potential to better evaluate changes in biomechanical characteristics of the foot.

Subluxing fractured plantar fat pad: a case series and description of novel sonographic findings

Plantar fat pad syndrome has received little attention in the literature. A variety of structural changes of the plantar fat pad have been described in the literature, including atrophy, contusion, and fractured fat pad. This case series presents 4 patients (5 heels) with subluxation of a fractured plantar fat pad on dynamic ultrasound. Patients with subluxing fractured fat pad typically present with heel pain and a "snapping" or "popping" sensation when weight-bearing. Other causes of heel pain were excluded, and all patients in this series had an MRI that initially did not report any findings in the fat pad. Retrospective review of the MRI showed evidence of diffuse low T1 and T2 infiltration. To the authors' knowledge, subluxation of the plantar fat pad and the respective correlation to MRI findings have not been described in the literature. Here we describe the sonographic findings of this novel condition.

Effects of Loading and Boundary Conditions on the Performance of Ultrasound Compressional Viscoelastography: A Computational Simulation Study to Guide Experimental Design

Most biomaterials and tissues are viscoelastic; thus, evaluating viscoelastic properties is important for numerous biomedical applications. Compressional viscoelastography is an ultrasound imaging technique used for measuring the viscoelastic properties of biomaterials and tissues. It analyzes the creep behavior of a material under an external mechanical compression. The aim of this study is to use finite element analysis to investigate how loading conditions (the distribution of the applied compressional pressure on the surface of the sample) and boundary conditions (the fixation method used to stabilize the sample) can affect the measurement accuracy of compressional viscoelastography. The results show that loading and boundary conditions in computational simulations of compressional viscoelastography can severely affect the measurement accuracy of the viscoelastic properties of materials. The measurement can only be accurate if the compressional pressure is exerted on the entire top surface of the sample, as well as if the bottom of the sample is fixed only along the vertical direction. These findings imply that, in an experimental validation study, the phantom design should take into account that the surface area of the pressure plate must be equal to or larger than that of the top surface of the sample, and the sample should be placed directly on the testing platform without any fixation (such as a sample container). The findings indicate that when applying compressional viscoelastography to real tissues in vivo, consideration should be given to the representative loading and boundary conditions. The findings of the present simulation study will provide a reference for experimental phantom designs regarding loading and boundary conditions, as well as guidance towards validating the experimental results of compressional viscoelastography.

Foot fat pad: Characterization by mesenchymal stromal cells in rats

Foot fat pad (FFP) is a highly functionalized fat depot of great significance for weight bearing in the foot. Mesenchymal stromal cells (MSCs) in subcutaneous adipose tissues are widely studied for regenerative potentials. MSCs in FFP, which may contribute to the physiological and pathological conditions of the foot, have not been characterized. In this study, MSCs were isolated from FFP (designated as MSCs-ffp) and subcutaneous adipose tissue (designated as MSCs-sub) from rats. The cell surface markers, proliferation, and efficiency of colony formation were compared between MSCs-ffp and MSCs-sub. In addition, MSCs-ffp were induced for osteogenic, chondrogenic, and adipogenic differentiation. The tri-lineage differentiation potentials were compared between MSCs-ffp and MSCs-sub by the expression of Runx2, Sox9, and proliferator-activated receptor gamma (PPAR-γ), respectively, using quantitative polymerized chain reaction. The expression of elastin and associated genes by MSCs-ffp were also evaluated. MSCs-ffp, like MSCs-sub, expressed CD44, CD73, and CD90. MSCs-ffp and MSCs-sub proliferated at similar rates but MSCs-ffp formed more colonies than MSCs-sub. MSCs-ffp were capable of differentiating into osteogenic, chondrogenic, and adipogenic lineages. Under the conditions of osteogenic and adipogenic differentiation, MSCs-sub expressed more Runx2 and PPAR-γ, respectively, than MSCs-ffp. The undifferentiated MSCs-ffp upregulated the expression of fibulin-5. In conclusion, MSCs-ffp shared common biology with MSCs-sub but were more efficient in colony formation, less adipogenic and osteogenic, and participated in elastogenesis. The unique features of MSCs-ffp may relate to their roles in the physiological functions of FFP.

Sex differences in heel pad stiffness during in vivo loading and unloading

Due to conflicting data from previous studies a new methodological approach to evaluate heel pad stiffness and soft tissue deformation has been developed. The purpose of this study was to compare heel pad (HP) stiffness in both limbs between males and females during a dynamic unloading and loading activity. Ten males and 10 females volunteered to perform three dynamic trials to unload and load the HP. The dynamic protocol consisted of three continuous phases: foot flat (baseline phase), bilateral heel raise (unloading phase) and foot flat (loading phase) with each phase lasting two seconds. Six retroreflective markers (3 mm) were attached to the skin of the left and right heels using a customised marker set. Three‐dimensional motion analysis cameras synchronised with force plates collected the kinematic and kinetic data throughout the trials. Three‐way repeated measures ANOVA together with a Bonferroni post hoc test were applied to the stiffness and marker displacement datasets. On average, HP stiffness was higher in males than females during the loading and unloading phases. ANOVA results revealed no significant differences for the stiffness and displacement outputs with respect to sex, sidedness or phase interactions (p > .05) in the X, Y and Z directions. Irrespective of direction, there were significant differences in stiffness between the baseline and unloading conditions (p < .001) but no significant differences between the baseline and loaded conditions (p = 1.000). Post hoc analyses for the marker displacement showed significant differences between phases for the X and Z directions (p < .032) but no significant differences in the Y direction (p > .116). Finally, females portrayed lower levels of mean HP stiffness whereas males had stiffer heels particularly in the vertical direction (Z) when the HP was both unloaded and loaded. High HP stiffness values and very small marker displacements could be valuable indicators for the risk of pathological foot conditions.

Morphological and mechanical properties of plantar fascia and intrinsic foot muscles in individuals with and without flat foot

PURPOSE

Many musculoskeletal disorders are associated with over-pronated foot and decreased medial longitudinal arch (MLA) height. Foot intrinsic muscles and plantar fascia (PF) are the primary structures that support MLA. An important reason for the over-pronated foot and the reduction in the MLA height may be the morphological characteristics of the foot intrinsic muscles and PF as well as changes in their mechanical properties. The aim of the present study is to investigate the morphologic structure and mechanical properties of PF, flexor hallucis brevis (FHB), flexor digitorum brevis (FDB), and abductor hallucis (AbH) muscles in individuals with flat foot and to compare the results with those of healthy individuals.

METHODS

The study included 80 participants, 40 with flat foot and 40 with normal foot posture. The foot posture of the participants was assessed using the Foot Posture Index. PF, FHB, FDB, and AbH thickness and stiffness were measured with an ultrasonography device using a linear ultrasonography probe.

RESULTS

Individuals with flat foot had higher AbH thickness compared to individuals with normal foot posture ( p < 0.001), whereas both groups were similar in terms of PF ( p = 0.188), FHB ( p = 0.627), and FDB ( p = 0.212) thickness. Stiffness values of the assessed tissues were similar in both groups ( p > 0.05).

CONCLUSION

AbH thickness was higher in individuals with flat foot; however, PF, FHB, and FDB thickness were similar in both groups. In addition, our results suggest that foot posture is not related to the stiffness of the assessed tissues.

In Vivo Measurement of Plantar Tissue Characteristics and Its Indication for Foot Modeling

Plantar heel pain is one of the most common musculoskeletal disorders and generally causing long term discomfort of the patients. The objective of the present study is to combine in vivo experimental measurements and finite element modelling of the foot to investigate the influences of stiffness and thickness variation of individual plantar tissues especially the heel pad on deformation behaviours of the human foot. The stiffness and thickness variance of individuals were measured through supersonic shear wave elastography considering detailed heel pad layers refered to in literature as: dermis, stiffer micro-chamber layer, softer macro-chamber layer. A corresponding foot model with separated heel pad layers was established and used to a sensitivity analysis related to the variance of above-mentioned tissue characteristics. The experimental results show that the average stiffness of the micro-chamber layer ranged from 24.7 (SD 2.4) kPa to 18.8 (SD 3.5) kPa with the age group increasing from 20-29 years old to 60-69 years old, while the average macro-chamber stiffness is 10.6 (SD 1.5) kPa that appears to slightly decrease with the increasing age. Both plantar soft tissue stiffness and thickness of male were generally larger than that of female. The numerical simulation results show that the variance of heel pad strain level can reach 27.5% due to the effects of stiffness and thickness change of the plantar tissues. Their influences on the calcaneus stress and plantar pressure were also significant. This indicates that the most appreciate way to establish a personalized foot model needs to consider the difference of both individual foot anatomic geometry and plantar soft tissue material properties.

Effect of Gender on Mechanical Properties of the Plantar Fascia and Heel Fat Pad

BACKGROUND

The purpose of the study was to investigate the plantar fascia and heel fat pad stiffness and thickness parameters in females and compare these values with those of males.

METHODS

This study was carried out in 60 healthy sedentary participants (30 female, 30 male) between the ages of 19 and 50 years. Shear wave velocity (SWV) and thickness of the plantar fascia and heel fat pad were measured with an ultrasonography device.

RESULTS

Males had a higher plantar fascia ( P = .037) and heel fat pad ( P = .001) thickness compared with females, but SWV of the plantar fascia ( P = .673), heel fat pad microchamber layer ( P = .240), and heel fat pad macrochamber layer ( P = .636) were similar in both groups. Body mass had a strong correlation with the plantar fascia ( r = 0.64, P < .001) and heel fat pad thickness ( r = 0.68, P < .001). Height had a moderate correlation with the plantar fascia ( r = 0.44, P < .001) and heel fat pad thickness ( r = 0.42, P = .001).

CONCLUSION

Plantar fascia and heel fat pad stiffness were similar in both genders; however, females had a lower plantar fascia and heel fat pad thickness compared with males. Correlation analysis results suggest that higher plantar fascia and heel fat pad thickness in males may be related to higher body mass and height.

LEVELS OF EVIDENCE

Level III: Retrospective comparative study.

Effects of morphological and mechanical properties of plantar fascia and heel pad on balance performance in asymptomatic females

INTRODUCTION

Personal differences in morphological and mechanical properties of plantar fascia and heel fat pad may be an important parameter regarding an individual's balance performance. The purpose of this study was to investigate the effect of thickness and stiffness of heel fat pad and plantar fascia on balance performance in asymptomatic sedentary females.

MATERIALS AND METHODS

This study was carried out on 37 asymptomatic sedentary females between the ages of 19 and 35 years. Balance assessments during single-leg standing were carried out using Biodex Balance Systems (Biodex Medical Systems, Shirley, NY, USA). In this study, the individuals' balance performance was assessed using the center of balance (COB) parameters, which were the standard deviation of the COB amplitude in the anterior-posterior (AP_SD) and medial-lateral (ML_SD) directions. Stiffness and thickness measurements of heel fat pad and plantar fascia were performed using an ACUSON S3000 Ultrasound System and a 9L4 probe (4-9MHz) (Siemens Medical Solution, Mountain View, CA, USA).

RESULTS

AP_SD during single-leg standing tests had a moderate correlation with heel pad thickness (r=0.46, p=0.004) and heel pad stiffness (r=0.41, p=0.011), and a fair correlation with plantar fascia thickness (r=0.34, p=0.038) and plantar fascia stiffness (r=0.38, p=0.021). ML_SD during single-leg standing tests had a moderate correlation with heel pad thickness (r=0.41, p=0.013) and heel pad stiffness (r=0.53, p=0.001), and a fair correlation with plantar fascia thickness (r=0.40, p=0.015).

CONCLUSION

It was found that higher plantar fascia and heel fat pad stiffness and thickness are related to higher postural sway in anterior-posterior and medial-lateral directions based on the single-leg balance tests. These results suggest that the morphological and mechanical properties of plantar fascia and heel fat pad play an important role in balance performance.

Three-Dimensional Shear Wave Elastography of Skeletal Muscle: Preliminary Study

OBJECTIVES

Two-dimensional (2D) shear wave elastography (SWE) can measure the elasticity of skeletal muscle, tendons, and ligaments. Three-dimensional (3D) SWE has been used to detect breast cancer but has not been applied to the musculoskeletal system. This study aimed to investigate whether 3D SWE could be used in skeletal muscles in vivo.

METHODS

The study enrolled 20 healthy volunteers at Beijing Chaoyang Hospital from August to October 2016. Two-dimensional and 3D SWE scans were used to measure the Young modulus of the flexor carpi radialis in the relaxed state. Longitudinal and transverse scanning was performed. Data were analyzed by a 1-way analysis of variance/least significant difference post hoc test, a paired t test, and Bland-Altman plots.

RESULTS

The participants included 10 male and 10 female volunteers with a mean age ± SD of 25 ± 5 years. The Young modulus did not differ between 3D and 2D SWE for the sagittal plane (longitudinal scanning, 34.9 ± 5.7 versus 32.7 ± 5.2 kPa; P = .096) or transverse plane (transverse scanning, 9.1 ± 2.1 versus 9.2 ± 1.6 kPa; P = .877). The Young modulus did not differ between sagittal, transverse, and coronal planes for 3D SWE longitudinal scanning (34.9 ± 5.7, 34.3 ± 5.8, and 34.8 ± 5.9 kPa, respectively; P = .936) or 3D SWE transverse scanning (9.1 ± 2.0, 9.1 ± 2.1, and 8.8 ± 2.1 kPa; P = .838). However, the Young modulus for each individual plane (sagittal, transverse, or coronal) differed significantly between longitudinal and transverse scanning (P < .001).

CONCLUSIONS

Both 2D SWE and 3D SWE are suitable techniques for clinical use, depending on the examiner's experience/preference. However, 3D SWE provides a multiplanar/multislice view that better illustrates the spatial characteristics of muscle tissue. Three-dimensional SWE may be a new method for fully visualizing the musculoskeletal system.

Effects of Body Mass Index on Mechanical Properties of the Plantar Fascia and Heel Pad in Asymptomatic Participants

BACKGROUND

Musculoskeletal foot disorders have a high incidence among overweight and obese individuals. One of the important factors causing this high incidence may be plantar fascia and heel pad (HP)-related mechanical changes occurring in these individuals. The aim of the present study was to investigate the plantar fascia and HP stiffness and thickness parameters in overweight and obese individuals and compare these values with those of normal-weight individuals.

METHODS

This study was carried out in 87 (52 female, 35 male) healthy sedentary individuals between the ages of 19 and 58 years (34 ± 11 years). Participants were subsequently categorized according to body mass index (BMI) as normal weight (18.5 kg/m² < BMI < 25 kg/m²) or overweight and obese (BMI ≥25 kg/m²). Plantar fascia and HP thickness and stiffness were measured with an ultrasonography device using a linear ultrasonography probe.

RESULTS

Overweight and obese individuals had higher HP thickness ( P < .001), plantar fascia thickness ( P = .001), heel pad microchamber layer (MIC) stiffness ( P < .001), and heel pad macrochamber layer (MAC) stiffness ( P < .001), whereas they had lower plantar fascia stiffness ( P < .001) compared with the individuals with normal weight. BMI had a moderate correlation with HP thickness ( P < .001, r = 0.500), plantar fascia thickness ( P = .001, r = 0.536), MIC stiffness ( P < .001, r = 0.496), and MAC stiffness ( P < .001, r = 0.425). A negative and moderate correlation was found between BMI and plantar fascia stiffness ( P < .001, r = -0.439).

CONCLUSION

Increased BMI causes a decrease in the stiffness of plantar fascia and an increase in the thickness of the plantar fascia as well as the thickness and stiffness of HP. Increased body mass could cause changes in the mechanical properties of HP and plantar fascia.

LEVEL OF EVIDENCE

Level 3, comparative study.

Differences in the mechanical characteristics of plantar soft tissue between ulcerated and non-ulcerated foot

AIMS

The purpose of this study was to investigate the differences in mechanical properties of the plantar soft tissue between the ulcerated and non-ulcerated feet in patients with diabetic neuropathy.

METHODS

Thirty nine patients who met the inclusion criteria participated in this study. Ten out of 39 participants had an active ulcer at a site other than the plantar heel and the first metatarsal head. Real time ultrasound elastography was performed to measure the soft tissue thickness and stiffness of the heel pad and sub-metatarsal fat pad. To account for the qualitative nature of conventional real time elastography, relative tissue stiffness was assessed against that of a standardised ultrasound standoff material.

RESULTS

The results indicated that the ulcerated group had a significantly lower heel pad relative stiffness (t (37)=2.559, P=0.015, η2=0.150) in the left foot.

CONCLUSIONS

The observed difference in the stiffness of the heel pad between the ulcerated and non-ulcerated feet indicates a possible link between tissue mechanics and ulceration. Further analysis of the data proposed in this study provided a quantitative assessment of plantar fat pad deformability which can contribute to understanding the role of tissue biomechanics in ulceration.