Heel Pad Research Articles

Anthropo-fidelic behavior of elastic-plastic lattice structures

Vat photopolymerization is used to construct triply periodic minimal surfaces (TPMS) to match human heel pad stiffness. Five cell types are investigated at varying relative densities modeled to fulfill the roles of the two heel pad tissue constituents: the macrochamber and microchamber. Two photosensitive polymers (elastic 50A and flexible 80A) are tested in uniaxial compression to characterize the toughness and energy absorption apropos cell geometry and approximate density of a latticed volume using a Hookean approach and beam theory. This work substantiates the suitability of latticed models to reach the stiffness of the heel pad chambers. A microchamber (E = 60-450 kPa) and macrochamber (E=26-46 kPa) stiffness response is capable of being modeled with the use of elastic-plastic 50A (E=26.7-526.4 kPa) cellular solids of varying relative density. Models like the Schwarz80A at relative density (ρ*/ρs) ∼ 0.5 showed a comparable modulus of toughness (T=4.126 MPa) to the solid samples (T=7.5161 MPa). The Gyroid lattice consistently showed the capability of matching solid sample energy absorption rates in the 50A, and to outperform the solid samples in energy absorption for the 80A material. Comparing experimental and elastic-plastic theoretical results for the plateau stress and Young's modulus highlights the current model inadequacies for additively manufactured polymers. These findings can have practical applications in other areas such as light-weighting, structural design, ballistics, and soft robotics.

Different Measurement Methods of Heel Pad Thickness and their Clinical Implications: A Narrative Review

Different Measurement Methods of Heel Pad Thickness and their Clinical Implications: A Narrative Review

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.

The Effect of Customized Insole Pads on Plantar Pressure Distribution in a Diabetic Foot with Neuropathy: Material and Design Study Using Finite Element Analysis Approach

To reduce the trial and error in a real clinical scenario, the finite element analysis (FEA) can be effectively used to simulate various effective pad designs and a material selection to reduce and redistribute peak plantar pressure in a diabetic foot with neuropathy. The aim of this study was to investigate the effect of pad design and material stiffness on the reduction in plantar pressure in a diabetic foot with neuropathy using FEA. Three-dimensional foot models with a customized insole (CMI) were created to study the peak contact pressure. Ethylene vinyl acetate, Nora® Lunalastike, and thermoplastic polyurethane were assigned to the top, middle, and base layers of the CMI, respectively. Two types of pads were proposed: a heel pad and a heel–forefoot pad. Four different materials with different stiffnesses were assigned as pad materials including a void pad. The FEA revealed that pads with soft materials reduced peak plantar pressure more effectively than stiffer pads. The use of a softer heel–forefoot pad reduced the peak plantar pressure at the midfoot and forefoot compared with other pads. The findings suggest that the material and design selection for the fabrication of CMIs with pads are important factors in reducing plantar pressure and may be useful in the management of a neuropathic diabetic foot.

Diabetic patients with inadequate flow of the posterior tibial artery and in dialysis are not good candidates for Syme amputation

Objective: There is a renewed interest in Syme amputation (SA) as it is considered a “lower limb salvage” procedure. The aim of this study was to describe the characteristics and evolution of diabetic patients who underwent SA to search for factors that would affect the outcome by comparing a group of patients who had a successful amputation against those who required a major amputation. Methods: Seventeen diabetic patients submitted to non-traumatic SA between 2008 and 2016 were analyzed retrospectively. Results: Eight patients required a higher level of amputation. In this group, six patients continued with the posterior tibial artery (PTA) occluded despite the revascularization, and seven were on dialysis. When assessing the permeability of PTA and dialysis as predictors of failure, they multiplied the risk by 20 (cOR of 24 and 21, respectively). However, after adjusting for both factors, there was only clinical significance. Conclusion: SA in diabetic patients may be an alternative in those with a preserved heel pad tissue vascularization and permeable posterior tibial artery at the time of surgery. Patients on dialysis are likely to fail with this level of amputation. Level of Evidence IV; Therapeutic Studies; Retrospective Cohort Study.

PSAT196 Monostotic Paget's disease of the bone involving the calcaneus

Abstract Introduction Paget's disease of bone (PDB) is a chronic bone disorder that is fairly common in older age. It is characterized by an initial increase in osteoclastic activity followed by excessive osteoblastic activity with disorganized bone architecture. PDB may involve any bone and may be monostotic or polyostotic. Herein, we report the rare occurrence of monostotic Paget's involving the calcaneus. Case Description A 71-year-old white male with PMH of prostate cancer status post radical prostatectomy presented with acute onset severe left heel and ankle pain. Pain was localized to the retrocalcaneal area and heel pad limiting his physical activity. He denied recent trauma. Physical exam was significant for swelling and tenderness of the left heel. Left foot X-rays showed a slightly enlarged calcaneus with very coarse trabeculae consistent with PDB. A total body bone scan done previously because of the prostate cancer showed intense uptake in the left calcaneus but no significant uptake elsewhere. Laboratory workup showed an elevated total serum alkaline phosphatase of 164 U/L (40-129 U/L) and bone specific alkaline phosphatase 65 ug/L (0.0-20 ug/L). He was treated with a single infusion of Zoledronic acid with good clinical response evidenced by improvement in pain and swelling as well as a significant decrease in bone specific alkaline phosphatase to 10 ug/L six months post-infusion. Discussion Monostotic PDB only represents about 20% of PDB cases. The pelvis is the most common location followed by the femur as described by Bachiller-Corral et al (Bone, 2013). In our review of the English literature, we found only nine cases of monostotic PDB involving the calcaneus. The mean age of presentation was 60 years old and most of the cases presented as chronic heel pain not responding to conservative pain alleviating measures. Conventional radiography showed the characteristic features of PDB but the changes observed were difficult to differentiate from that of a malignant process. That led to further imaging in most cases by either CT, MRI scan or SPECT scan. Three out of nine patients were reported to receive bisphosphonate therapy with successful remission with a long duration of disease suppression. Good response to therapy highlights the importance of proper diagnosis. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.

Repair of avulsion flap injury of heel by multiple point anchorage using Kirschner wires-a case series

<p>The heel pad is a dense band of fibrous tissue with complex anatomy. Injuries to heel pad are uncommon but very challenging due to its precarious blood supply. In this study we tried fixing acute heel pad avulsion injuries using multiple Kirschner wires and results were evaluated according to the American orthopedic foot and ankle society hind foot score. Results were excellent for 3 -out of 9 patients and good for 6 patients according to the AOFAHS scoring system. Anchorage of acute heel pad avulsion injuries using multiple Kirschner wires is an effective and reliable treatment modality.</p>

MR-based quantitative measurement of human soft tissue internal strains for pressure ulcer prevention.

Pressure ulcers are a severe disease affecting patients that are bedridden or in a wheelchair bound for long periods of time. These wounds can develop in the deep layers of the skin of specific parts of the body, mostly on heels or sacrum, making them hard to detect in their early stages. Strain levels have been identified as a direct danger indicator for triggering pressure ulcers. Prevention could be possible with the implementation of subject-specific Finite Element (FE) models. However, generation and validation of such FE models is a complex task, and the current implemented techniques offer only a partial solution of the entire problem considering only external displacements and pressures, or cadaveric samples. In this paper, we propose an in vivo solution based on the 3D non-rigid registration between two Magnetic Resonance (MR) images, one in an unloaded configuration and the other deformed by means of a plate or an indenter. From the results of the image registration, the displacement field and subsequent strain maps for the soft tissues were computed. An extensive study, considering different cases (on heel pad and sacrum regions) was performed to evaluate the reproducibility and accuracy of the results obtained with this methodology. The implemented technique can give insight for several applications. It adds a useful tool for better understanding the propagation of deformations in the heel soft tissues that could generate pressure ulcers. This methodology can be used to obtain data on the material properties of the soft tissues to define constitutive laws for FE simulations and finally it offers a promising technique for validating FE models.

Comparison of material properties of heel pad between adults with and without type 2 diabetes history: An in-vivo investigation during gait.

ObjectiveThis study was aimed to compare the material properties of heel pad between diabetes patients and healthy adults, and investigate the impact of compressive loading history and length of diabetes course on the material properties of heel pad.MethodsThe dual fluoroscopic imaging system (DFIS) and dynamic foot-ground contact pressure-test plate were used for measuring the material properties, including primary thickness, peak strain, peak stress, stiffness, viscous modulus and energy dissipation ratio (EDR), both at time zero and following continuous loading. Material properties between healthy adults and DM patients were compared both at time zero and following continuous weight bearing. After then, comparison between time-zero material properties and properties following continuous loading was performed to identify the loading history-dependent biomechanical behaviour of heel pad. Subgroup-based sensitivity analysis was then conducted to investigate the diabetes course (<10 years vs. ≥10 years) on the material properties of heel pad.ResultsTen type II DM subjects (20 legs), aged from 59 to 73 (average: 67.8 ± 4.9), and 10 age-matched healthy adults (20 legs), aged from 59 to 72 (average: 64.4 ± 3.4), were enrolled. Diabetes history was demonstrated to be associated with significantly lower primary thickness (t=3.18, p=0.003**), higher peak strain (t=2.41, p=0.021*), lower stiffness (w=283, p=0.024*) and lower viscous modulus (w=331, p<0.001***) at time zero, and significantly lower primary thickness (t=3.30, p=0.002**), higher peak strain (w=120, p=0.031*) and lower viscous modulus (t=3.42, p=0.002**) following continuous loading. The continuous loading was found to be associated with significantly lower primary thickness (paired-w=204, p<0.001***) and viscous modulus (paired-t=5.45, p<0.001***) in healthy adults, and significantly lower primary thickness (paired-w=206, p<0.001***) and viscous modulus (paired-t=7.47, p<0.001***) in diabetes group. No any significant difference was found when conducting the subgroup analysis based on length of diabetes course (<10 years vs. ≥10 years), but the regression analysis showed that the length of diabetes history was positively associated with the peak strain, at time zero (r=0.506, p<0.050) and following continuous loading (r=0.584, p<0.010).ConclusionsDiabetes patients were found to be associated with decreased primary thickness and viscous modulus, and increased peak strain, which may contribute to the vulnerability of heel pad to injury and ulceration. Pre-compression history-dependent behaviour is observable in soft tissue of heel pad, with lowered primary thickness and viscous modulus.

Effectiveness of High Intensity Hilthera 4.0 Laser Treatment on Patients with Plantar Fasciitis

Plantar fasciitis is one of the most common causes of heel pain. Conservative lines of treatment include non-steroidal anti-inflammatory drugs, corticosteroid injections, Physiotherapy, stretching exercises and using heel pads or orthotics. The purpose of the study is to investigate the effects of high intensity Hilthera 4.0 laser treatment on pain and functional capacity in patients with acute plantar fasciitis. Total 30 participants were randomly recruited and were evaluated before the first treatment session and after 8 sessions of treatment with Hilthera 4.0 Laser. Treatment Parameters are frequency (Hz) 25, one shot emission (MJ) 500, and a total energy 3000W for 15 minutes each session. Outcome measures are VAS score for measuring Pain and Foot Function Index score for measuring Foot Function. IBM SPSS version 16.0 software was used for statistical analysis. Paired sample t-tests are used to measure the pre and post test results. Results shows that there is a significant difference in VAS Score and Foot Function Score pre and post treatment with ‘p’ value &lt; 0.05 when Hilthera 4.0 laser is used for pain and Foot function in patients with Plantar Fasciitis. In conclusion Hilthera 4.0 Laser Therapy is effective in treating pain and Functional limitation in patients with Plantar Fasciitis. KEY WORDS: Plantar Fasciitis, Hilthera 4.0 Laser Therapy, VAS Score, Foot Function Index Score

Decreased Mechanical Work Demand in the Chopart Joint After Total Ankle Replacement.

The success of total ankle replacement (TAR) must be based on restoring reasonable mechanical balance with anatomical structures that can produce mechanical joint work through elastic (eg, tendons, fascia) or viscoelastic (eg, heel pad) mechanisms, or by active muscle contractions. Yet, quantifying the work distribution across the affected joint and the neighboring foot joints after TAR is lacking. Therefore, the objective of this study was to investigate if there is a change in the joint work distribution across the Ankle, Chopart, Lisfranc and Metatarsophalangeal joints during level walking before and after patients undergo TAR. Fifteen patients with end-stage ankle osteoarthritis scheduled for primary TAR for pain relief were recruited and peer-matched with a sample of 15 control subjects. All patients underwent a 3D gait analysis before and after surgery, during which a kinetic multisegment foot model was used to quantify intersegmental joint work. The contribution of the Ankle joint (P = .007) to the total foot and ankle positive work increased significantly after TAR. In contrast, a significant decrease in the contribution to the total foot and ankle joint positive work (P < .001) were found at the Chopart joint after TAR. The foot joints combined produced a significant increase in a net mechanical work from +0.01 J/kg before surgery to +0.05 J/kg after TAR (P = .006). The findings of this study corroborate the theoretical rationale that TAR reduces significantly the compensatory strategy in the Chopart joint in patients with end-stage ankle osteoarthritis after TAR. However, the findings also showed that the contribution of the ankle joint of patients after TAR to the total foot and ankle joint positive work remained impaired compared to the control group.

The Effectiveness of Two Types of Night Splints on the Range of Motion of the Ankle Joint, Pain Intensity, and Quality of Life (QoL) in Patients With Plantar Fasciitis: A Pilot Study With Parallel Groups

Objective Plantar fasciitis is the most common cause of heel pain. The night splints are used to prevent nocturnal contractures happening in the calf muscles and plantar fascia. The objective of this study was to investigate the effects of using a tension night splint for calf and plantar fascia on the range of motion of foot and ankle complex, pain severity, and quality of life. Materials &amp; Methods 30 people (27 female) with plantar fasciitis volunteered in a parallel-group clinical study. Participants were allocated to three study groups: a tension calf splint, a tension plantar fascia splint, and a control group (heel pad). The study outcomes were the range of motion of foot and ankle complex, pain severity, and quality of life measured with a goniometer, visual analog scale, and 36-Item Short Form Survey (SF-36) questionnaire, respectively. The post-session was four weeks after participants received their interventions. The analysis of covariance statistical test was used to analyze the within and between-group differences. Results The analysis of covariance test showed statistically significant differences for pain (F=9.35, P=0.001, η2=0.44) and extension of the first metatarsophalangeal (F=4.76, P=0.017, η2=0.27). There was no statistically significant difference in the quality of life and the ankle dorsiflexion range between groups (P&gt;0.05). The Bonferroni post-hoc showed a significant reduction of the reported pain post-session in all study groups (P&lt;0.05). The calf tension splint caused a greater extension of the first metatarsophalangeal post-session (P=0.02). Conclusion All three orthoses used in this study significantly reduced pain in people with plantar fasciitis. The results also suggest that a tension calf splint has greater effectiveness in improving pain severity and soft tissue flexibility than a tension fascia splint.

Outcome of Local Corticosteroid Injection by Ultrasound- versus Palpation-Guided Technique in Plantar Fasciitis

Background: Plantar fasciitis is a common cause of heel pain. Conservative treatment is often effective, but in many cases, invasive procedures may be required. Local corticosteroid injection is the most frequently used invasive technique and can be given under ultrasound (USG) or palpation guidance. We sought to compare the outcome of local corticosteroid injection by USG and palpation guidance in plantar fasciitis. Methods: This was a prospective randomized study of patients who presented with heel pain between July 2015 and November 2016 and were screened for plantar fasciitis by USG. Patients with confirmed plantar fasciitis were managed conservatively for 4 weeks. The 60 consecutive patients not responding to the conservative treatment were randomized into two groups. Group A (n = 30) received a corticosteroid injection under USG guidance. Group B (n = 30) received a corticosteroid injection under palpation guidance. Patients were followed up at 3 and 6 weeks. We compared the visual analog scale score, plantar fascia thickness, and heel pad thickness in both groups. Results: There was significant pain relief in both groups after 3 and 6 weeks of local corticosteroid injection, with greater relief noted in the USG-guided group. There was a significant decrement in plantar fascia thickness in both groups after 3 and 6 weeks; however, a greater decrement was observed in the USG-guided group. Neither group showed a significant difference in heel pad thickness after 3 and 6 weeks. Conclusions: Ultrasound-guided injection provided better pain relief and a greater reduction in plantar fascia thickness than palpation-guided injection.

3D printed auxetic heel pads for patients with diabetic mellitus

More than 422 million people worldwide suffered from diabetes mellitus (DM) in 2021. Diabetic foot is one the most critical complications resultant of DM. Foot ulceration and infection are frequently arisen, which are associated with changes in the mechanical properties of the plantar soft tissues, peripheral arterial disease, and sensory neuropathy. Diabetic insoles are currently the mainstay in reducing the risk of foot ulcers by reducing the magnitude of the pressure on the plantar Here, we propose a novel pressure relieving heel pad based on a circular auxetic re-entrant honeycomb structure by using three-dimensional (3D) printing technology to minimize the pressure on the heel, thus reducing the occurrence of foot ulcers. Finite element models (FEMs) are developed to evaluate the structural changes of the developed circular auxetic structure upon exertion of compressive forces. Moreover, the effects of the internal angle of the re-entrant structure on the peak contact force and the mean pressure acting on the heel as well as the contact area between the heel and the pads are investigated through a finite element analysis (FEA). Based on the result from the validated FEMs, the proposed heel pad with an auxetic structure demonstrates a distinct reduction in the peak contact force (∼10%) and the mean pressure (∼14%) in comparison to a conventional diabetic insole (PU foam). The characterized result of the designed circular auxetic structure not only provides new insights into diabetic foot protection, but also the design and development of various impact resistance products.

A Biomechanical and Evolutionary Perspective of the Menisci Indicate They Are Not Shock Absorbers

Human bipedalism entails high‐magnitude, short‐duration impact transient forces that occur every heel strike. These transient forces, or ‘shock’, are attenuated as they propagate up the body, and many structures have been proposed as ‘shock absorbers’ within the body. The medial and lateral menisci of the knee are a pair of fibrocartilaginous structures that have often been cited as shock absorbers. However, despite the frequency with which this claim is made in scientific literature, medical education and clinical practice, there is little primary data that supports the notion that the menisci function as shock absorbers.Here we compile evolutionary and biomechanical data to critique this oft‐cited notion. First, we show that the origin of this idea draws on a limited number of studies, each with caveats that make that evidence for a shock absorptive function dubious. We then review evolutionary and comparative evidence to show that human menisci are unremarkable in morphology compared with most other tetrapods. Humans possess two, crescentic‐shaped menisci that are similar in morphology to most mammals and many tetrapods. This suggests that the null hypothesis of meniscal function is one of similarity among tetrapods. Furthermore, we show that among tetrapods, shock during locomotion is uncommon; humans stand out as one of the only tetrapods that regularly experience high levels of shock during locomotion. Thus, a shock‐absorption function does not explain the origin of menisci, nor are human menisci specialized in any way that would explain this unique function during human gait. We further assess the mechanical material properties of menisci and show that the menisci overwhelmingly behave like springs and are poorly suited for energy absorption. We compiled data on phase angle and loss tangent, two properties used to assess energy absorption or release. Loss tangents of the menisci are typically between 0.1–0.2, close to an ideal spring (0.0) as opposed to an energy absorbing damper (&gt;1.0). Similarly, phase angles were generally &lt;10°, more similar to an idealized spring value of 0°, as opposed to a pure damper at 90°. Thus, when deformed menisci release most of this energy as opposed to shock absorbers, which dissipate energy.Finally, we integrated data on material properties of the meniscus and loading data from previous studies to estimate actual meniscal energy absorption in comparison to other known energy‐absorbing structures in the body. The heel pad, a well‐known contributor to absorbing energy from heel strike, absorbed 50–69% (0.70 +/‐ 0.11 J) of impact loading when using realistic loading conditions in vitro. All knee structures combined absorbed 0.12 +/‐ 0.01 J of impact energy, only 6–17% of the energy absorbed by the heel pad alone. Available loading data suggest that energy absorption of the menisci alone likely account for only ~4% of all energy absorption at the knee. Thus, our estimates of the total shock absorption capacity of the menisci is essentially negligible.These findings indicate that the menisci did not originally develop for shock‐absorption in tetrapods and did not develop a specialized shock absorbing function in humans.

Complete avulsion of the heel pad with talar and calcaneal fracture: salvage with multiple K-wire anchorage, internal fixation and free ALT flap

BackgroundDegloving of the sole of the foot is a rare and serious injury because the heel pad cannot be replaced by similar tissue. The management is challenging and only a few cases have been reported with different treatment regimens.MethodsHere, we report on a 46-year-old female patient with complex foot trauma consisting of complete avulsion of the heel pad at the hindfoot and a soft tissue defect at the posterior aspect of the heel accompanied by rupture of the anterior tibial tendon and fractures of the talus, calcaneus and midfoot. The sole of the foot was fixed to the calcaneus with multiple temporary Kirschner wires and moist wound dressings. The anterior tibial tendon was sutured. The soft tissue defect at the posterior heel was treated with a free anterolateral thigh flap. The fractures were fixed in staged procedures.ResultsAt 2-year follow-up, the patient had a durable soft tissue cover over the heel with full sensation over the sole and a pliable flap over the posterior aspect of the heel. The patient was able to fully bear weight and was pain free during her daily activities in comfortable, custom shoes. All fractures had healed, the talar neck fracture after one revision and bone grafting. The foot was plantigrade and stable with preserved painless but limited range of motion at the ankle, subtalar and mid-tarsal joints.ConclusionThe unique tissue at the sole of the foot can be salvaged even in cases of full degloving at the hindfoot with the simple method of anchorage with multiple temporary K-wires. Traumatic defects of the vulnerable skin at the posterior aspect of the heel requires durable coverage with free flap coverage. With staged treatment of all bone and soft tissue injuries, a favorable result can be obtained even in case of a complex foot trauma.

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.

Effect of loading history on material properties of human heel pad: an in-vivo pilot investigation during gait

BackgroundThis study was aimed to develop a novel dynamic measurement technique for testing the material properties and investigating the effect of continuous compression load on the structural and mechanical properties of human heel pad during actual gait.MethodsThe dual fluoroscopic imaging system (DFIS) and dynamic foot-ground contact pressure-test plate were used for measuring the material properties, including primary thickness, peak strain, peak stress, elastic modulus, viscous modulus and energy dissipation rate (EDR), both at time zero and following continuous loading. Ten healthy pilot subjects, aged from 23 to 72 (average: 46.5 ± 17.6), were enrolled. A “three-step gait cycle” is performed for all subjects, with the second step striking at a marked position on the force plate with the heel to maintain the location of the tested foot to be in the view of fluoroscopes. The subjects were measured at both relaxed (time-zero group) and fatigue (continuous-loading group) statuses, and the left and right heels were measured using the identical procedures.ResultsThe peak strain, peak stress, elastic modulus, and EDR are similar before and after continuous load, while the viscous modulus was significantly decreased (median: 43.9 vs. 20.37 kPa•s; p < 0.001) as well as primary thicknesses (median: 15.99 vs. 15.72 mm; p < 0.001). Age is demonstrated to be moderately correlated with the primary thicknesses both at time zero (R = -0.507) and following continuous load (R = -0.607). The peak stress was significantly correlated with the elastic modulus before (R = 0.741) and after continuous load (R = 0.802). The peak strain was correlated with the elastic modulus before (R = -0.765) and after continuous load (R = -0.801). The correlations between the viscous modulus and peak stress/ peak strain are similar to above(R = 0.643, 0.577, − 0.586 and − 0.717 respectively). The viscous modulus is positively correlated with the elastic modulus before (R = 0.821) and after continuous load (R = 0.784).ConclusionsBy using dynamic fluoroscopy combined with the plantar pressure plate, the in vivo viscoelastic properties and other data of the heel pad in the actual gait can be obtained. Age was negatively correlated with the primary thickness of heel pad and peak strain, and was positively correlated with viscous modulus. Repetitive loading could decrease the primary thickness of heel pad and viscous modulus.

Biomechanical Properties of Heel Pad, Metatarsal Head Soft-Tissue and Foot Ulcers in Patients with Systemic Sclerosis: A Case Control Study.

Background:Systemic sclerosis is a chronic disease of connective tissue accompanied by fibrosis of the skin and inner organs and an increased risk of foot ulcers. Biomechanical indices such as soft-tissue thickness and compressibility may correlate with the risk of this phenomenon.Objective:The aim of this study was to assess heel pad and first metatarsal head (MTH) soft-tissue thickness and compressibility index (CI) in scleroderma patients compared to matched healthy individuals. Not all patients had foot ulcers.Methods:Heel pad thickness in standing (loaded) and lying (unloaded) positions were measured in 40 scleroderma patients by means of a lateral foot radiograph. CI was measured as the ratio of loaded to unloaded thickness. The Soft-tissue thickness of the first MTH was measured by ultrasound. Results were compared with 40 healthy controls of matched age and body mass index. All patients’ diagnoses were made based on the American College of Rheumatology classification criteria.Results:Forty scleroderma patients (36 females, 4 males) with the following demographics were studied; mean age (SD) 45(12), mean body mass index 25.5 (4), and mean disease duration=10(9.6) years; only 8 (20%) had digital ulcers. Patients’ heel pad thickness and CI in the dominant side and MTH soft-tissue thickness on both sides were significantly different compared to the control group. Comparison of results in patients with and without foot ulcers also showed a significant difference in soft-tissue thickness. Thickness was negatively associated with disease duration, but the CI did not change over time.Conclusion:Soft-tissue thickness of the foot decreases in scleroderma patients and is associated with foot ulcers and digital ulcers in the hands.

Sonographic Evaluation of the Heel Pad Thickness in Diabetics in Nigeria.

Diabetes mellitus is a chronic disease process affecting millions of people worldwide. Its prevalence is forecasted to reach a value of 7.7% by 2030. It carries severe morbidities and even mortality. Hyperglycemia and increased formation of advanced glycosylation end products causes the majority of soft tissue changes seen among diabetics. The effects are observed particularly in the heel pad and plantar fascia where thinning or thickening, fibre disorganization, calcification and hypoechoic foci are among the changes seen. This cross-sectional descriptive study was carried out at the Department of Radiology, OAUTHC, Ile Ife, Osun state, Southwest Nigeria. 40 years old and above subjects with Type 2 diabetes mellitus were recruited from the diabetic clinic of the institution and Ultrasound evaluation of the heel fat pad and plantar fascia were subsequently performed for those who met the criteria using ultrasound machine equipped with a 7.5- 12.0 MHz high frequency linear array transducer. The mean heel pad thickness on the right feet was greater than that of the left in the study subjects. There was statistical significant difference in the heel fat pad thickness of diabetic subjects and the control group, in both feet. (P=0.000). The heel pad thickness is higher in diabetic subject than in non-diabetic control subjects. However, there was no statistical significant difference in the right and left heel fat pad thickness of the participants of this study (P value 0.6062). Only HPT was a statistically significant predictor of foot ulcers among other variables after binary regression was computed. Using Spearman's rank correlation to test the relationship between the BMI of diabetic subjects and mean heel pad thickness, it revealed a moderate positive correlation, with good statistically significance (Spearman's rho = 0.4397, P=0.0000). The relationship between the BMI of diabetic subjects and mean plantar fascia thickness showed a weak positive correlation, with good statistical significance (Spearman's rho = 0.2635, P=0.0008). The duration of diabetes mellitus did not determine the heel pad thickness and plantar fascia thickness. The findings in the study suggested that history of foot ulcer in the diabetic predispose them to have reduce HPT and further foot ulcers. Sonographic measurement of heel pad thickness can therefore be an additional imaging modality to evaluate and be used in the management of the diabetic patients' feet.