Heel Fat Pad Research Articles

A Step in the Right Direction: A Prospective Randomized, Controlled Crossover Trial of Autologous Fat Grafting for Rejuvenation of the Heel.

The shock-absorbing soft tissues of the heel are composed of dermis and specialized fat pads. Heel fat pad atrophy is common and can be painful and debilitating. In our previous work, autologous fat grafting was effective for treating pain from forefoot fat pad atrophy. The authors hypothesized that autologous fat grafting to the heel would relieve pain and improve function in patients with heel fat pad atrophy. Patients with heel fat pad atrophy and associated pain were recruited and randomized into 2 groups. Group 1 received autologous fat grafting on enrollment and was followed for 2 years. Group 2 received offloading and activity modification for 1 year, then crossed over, underwent autologous fat grafting, and was followed for 1 year afterward. Outcome measures included ultrasound-measured fat pad and dermal thickness; pedobarograph-measured foot pressures and forces; and patient-reported outcomes as measured by the Manchester Foot Pain and Disability Index. Thirteen patients met the inclusion criteria and completed the study. Seven (12 affected feet) were randomized into Group 1; and 6 (9 affected feet) were randomized into Group 2. The average age was 55 years and BMI was 30.5 kg/m2. Demographics did not significantly differ between groups. Heel fat pad thickness increased after autologous fat grafting but returned to baseline at 6 months. However, autologous fat grafting increased dermal thickness significantly and also increased fat pad thickness under a compressive load compared with controls at 6 and 12 months. Foot pain, function, and appearance were also significantly improved compared with controls at 6 and 12 months. Autologous fat grafting improved patient-reported foot pain, function, and appearance and may rejuvenate local soft tissues in patients with heel fat pad atrophy.

Lesions of the heel fat pad.

The heel fat pad (HFP) is a specialized soft tissue structure formed of adipose tissue that overlies the inferior and posterior aspect of the calcaneus and provides the cushioning effect of the heel. Lesions of the HFP are rare and can be a cause of debilitating heel pain that may often pose a challenge to clinicians. This study provides a series of lesions identified within the HFP. A retrospective review of heel pad lesions over a 12 year period was conducted at our tertiary orthopaedic oncology centre. All lesions of the heel fat pad were included in the study. Plantar fasciitis was excluded. There were 17 heel pad lesions identified, of which the majority (n = 15) were benign. We highlight a wide spectrum of pathologies that can occur in the HFP. Although rare, clinicians should be aware of these lesions, to initiate appropriate management.

Rearfoot disorders and conservative treatment: a narrative review.

Rearfoot disorders are frequently encountered in clinical practice. We reviewed common rearfoot disorders and present conservative treatments, focusing on shoe modification and the application of insoles or orthoses. Achilles tendinopathy is caused by excessive mechanical loads on the gastrocnemius and soleus muscles. Heel lifts, rocker shoes, and the AirHeel Brace can be used to reduce symptoms. Haglund's deformity is an osseous prominence of the posterosuperior part of the calcaneus bone, the pain from which can be alleviated by reducing pressure on the affected area by appropriately modifying the back of the shoe to prevent contact with the lesion. The pain from retrocalcaneal bursitis can be controlled by lifting the heel and loosening the shoe counter. Plantar fasciitis causes plantar heel pain, and its orthotic treatments include the application of a heel cup, heel pad, heel wedge, Thomas heel, and night splint. Calcaneal stress fractures are generally caused by repetitive loads and occur mainly in sporting activities. Patellar tendon-bearing (PTB) orthoses are helpful in reducing the load on the calcaneal bone. Heel fat pad atrophy refers to the loss of the fat pad that absorbs shock in the heel. To reduce pain caused by heel fat pad atrophy, rocker soles, heel pads, and solid ankle cushion heels (SACHs) may be used. Tarsal tunnel syndrome is caused by compression of the tibial nerve within the tarsal tunnel and its symptoms can be managed by rocker soles, supporting medial arches, Thomas heels, and SACHs. Shoe modification or application of orthoses can be helpful for managing rearfoot pain. However, for the active and wide application of these conservative treatment methods, more clinical studies should be conducted.

The relationship of heel fat pad thickness with age and physiques in Japanese

BackgroundIn understanding the onset factors associated with Plantar heel pain and the structure of heel fat pad, measuring its thickness is the most basic frequently reported evaluation. This study aimed to determine changes to heel fat pad thickness associated with age and gender and the relationship between heel fat pad thickness, age, and physique in Japanese. MethodsThis study was carried out in 1126 healthy individuals between the ages of 1 and 96 years. Participants were categorized according to age. Heel fat pad thickness was measured with an ultrasonography device using a linear ultrasonography probe. FindingsHeel fat pad tends to become thicker from ages 1–5 to 30–44 years and thinner from ages 30–44 to 80–96 years. Heel fat pad thickness in males and females was similar within each group, and males had higher heel fat pad thickness than females of corresponding ages. Heel fat pad thickness of males had a good correlation with height and body mass. Moreover, male heel fat pad thickness had a fair correlation with age. Heel fat pad thickness of females had a moderate correlation with height and body mass and a fair correlation with age. InterpretationHeel fat pad thickness became thicker from ages 1–5 to 30–44 years and thinner from ages 30–44 to 80–96 years. Females had a lower heel fat pad thickness than males of corresponding ages. This result suggests that higher heel fat pad thickness in males is related to body mass and height.

A Cadaveric Study of the Plantar Fascia for the In-Step Plantar Fasciotomy

The in-step plantar fasciotomy has remained a viable option for treatment of plantar fasciitis. The level of the in-step procedure has previously been described as 1.5 cm distal to the anterior heel fat pad. The authors are unaware of any study defining mean width and thickness of the plantar fascia at specific distances from its insertion. The authors performed a standardized cadaveric dissection of 25 fresh frozen cadaveric specimens from a local region in Pennsylvania. Each fascial band width and thickness of the plantar fascia was measured at the fascial insertion, 2 cm distal from insertion, and 3 cm distal from insertion. The mean (± standard deviation) width of the medial, central, and lateral band of the plantar fascia 3 cm from its insertion was 25.3 ± 5.3, 25 ± 3.41, and 23.3 ± 4.49 mm, respectively. At the same anatomic distance, the band thicknesses were 1.5 ± 0.82, 3.3 ± 0.85, and 1.9 ± 0.33 mm, respectively. The literature describes 2 techniques. The first is transecting between one-third to two-thirds of the plantar fascia during a fasciotomy from medial to lateral. The second is identifying, isolating, and releasing the central band. Our study allows to further quantify this, equating to 24.5 to 49 mm in total medial to lateral transection at 3 cm distal from insertion and an isolated central band equating to 25 ± 3.41 mm. With quantitative measurements of transection length, the surgeon will avoid having to estimate and potentially overtransect. This may help in preventing postoperative sequela related to overcorrection.

The thickness of heel fat-pad in patients with plantar fasciitis

ObjectiveThe aim of this study was to investigate the thickness of heel fat pad (THP) and to detect the relationship between the plantar fasciitis (PF) and age, occupation, BMI, longitudinal arch, the thickness of heel fat-pad in the patients with PF. MethodsA total of 50 patients (29 women and 21 men; mean age: 46.5 years (range: 22–70)) that were diagnosed with PF were included to this study. Patients' affected side were compared with the healthy opposite side with the angle of medial arch (AMA) and first metatarsophalangeal angle (FMTPA) on the foot radiograms, and THP and thickness of first metatarsal fat pad (TFMFP) using ultrasonography (USG) of both feet. ResultsThe mean AMAs of feet with pain and without pain were 122.56° and 120.60°, respectively. The mean FMTPAs of feet with pain and without pain were 14.72° and 14.40°, respectively. The mean THPs of feet with pain at the point of the medial calcaneal tubercle and the mean TFMFPs of the feet with pain at the point of the first metatarsal head were 19.45 mm and 6.75 mm, respectively. The mean THPs of feet without pain at the point of the medial calcaneal tubercle and the mean TFMFPs of the feet without pain at the point of the first metatarsal head were 19.94 mm and 6.75 mm, respectively. It was observed that the mean AMA in the heels with pain was significantly higher than that of the heel without pain (p < 0.05) and the mean THP in the heels with pain was significantly thinner than that of the heel without pain (p < 0.05). ConclusionThe results indicate that USG is an accurate and reliable imaging technique for the measurement of THP in the diagnosis of plantar fasciitis and the heel pad was thinner in the painful heels of patients with plantar fasciitis. Level of evidenceLevel III, Diagnostic Study.

Changes in calcaneal pitch and heel fat pad thickness in static weight bearing radiographs while wearing shoes with arch support and heel cup orthotics

BackgroundFoot orthoses have been shown to reduce the collapse of the longitudinal arch and to constrain soft tissue displacement under the heel. However, there has not been a study that has shown the effectiveness of both the arch and heel features in the same orthosis. This study quantitatively analyzed if the calcaneal pitch and the heel pad thickness will be affected by the use of an arch support and heel cup insole in a static weightbearing stance while wearing sports shoes. MethodsTwenty-four (24) feet from 12 elite-level female soccer players with a mean age of 25 ± 3.99 years (20–33 years old) were studied. Lateral weightbearing radiographs with and without orthotics were obtained in order to measure the calcaneal pitch angle and heel fat pad thickness for each foot. A subjective outcome measure was used and the scores were classified as bad (0–2), fair (3–5), good (6–8), or excellent (9-10). ResultsThe calcaneal pitch angle increased in all but three cases by an average of 1.05° (range, −1.14 to 3.19) after wearing orthotics (p < 0.01). The heel fat pad thickness increased in all cases with an average of 1.25 mm (range, 1.05 to 1.47; p < 0.01)). 9 of 12 subjects (75%) reported excellent (n = 2) or good (n = 7) overall subjective scores with insole wear. ConclusionUnder static weightbearing conditions, the arch support and heel cup features of a foot orthosis help improve the height of the calcaneal pitch and the thickness of the heel fat pad, respectively.

Compressed Fixation Combined with Vacuum-Assisted Closure for Treating Acute Injury of the Heel Fat Pad.

BackgroundTreating acute injury of the heel fat pad is different from treating common soft tissue damage. Due to the paucity of literature on the topic, we described our initial experience treating acute injury of the heel fat pad to determine the ideal treatment method.Material/MethodsA total of 53 patients with acute injury of the heel fat pad admitted to our hospital were selected for the study and were randomly divided into 2 groups: the compressed fixation combined with vacuum-assisted closure group and the only reimplanted and sewn group. Twenty-seven of the heel fat pads were compressed and fixed using a flat, hard piece of plastic and hollow screws; then, they were covered with a vacuum-assisted closure device. The other 27 were only sewn without tension. The clinical results were evaluated according to the American Orthopedic Foot and Ankle Society hindfoot score and the British Medical Research Council function evaluation criteriaResultsIn the compressed fixation combined with vacuum-assisted closure group, flaps of 12 feet with retrograde avulsion injury survived successfully. Partial flap necrosis occurred in 8 feet. Seven feet underwent repair using the neurocutaneous vascular resupinated island flap. Results were excellent or good for 74% of patients according to the AOFS. However, in the only reimplanted and sewn group, results were excellent or good for 44% of patients according to the AOFS.ConclusionsCompressed fixation with vacuum-assisted closure is effective for treating acute injury of the heel fat pad, with high success rates and good utility.

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

IntroductionPersonal 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 methodsThis 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). ResultsAP_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). ConclusionIt 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.

Long-Term Prognosis of Plantar Fasciitis: A 5- to 15-Year Follow-up Study of 174 Patients With Ultrasound Examination.

Background:Plantar fasciitis (PF) affects 7% to 10% of the population. The long-term prognosis is unknown.Purpose:Our study had 4 aims: (1) to assess the long-term prognosis of PF, (2) to evaluate whether baseline characteristics (sex, body mass index, age, smoking status, physical work, exercise-induced symptoms, bilateral heel pain, fascia thickness, and presence of a heel spur) could predict long-term outcomes, (3) to assess the long-term ultrasound (US) development in the fascia, and (4) to assess whether US-guided corticosteroid injections induce atrophy of the heel fat pad.Study Design:Cohort study; Level of evidence, 3.Methods:From 2001 to 2011 (baseline), 269 patients were diagnosed with PF based on symptoms and US. At follow-up (2016), all patients were invited to an interview regarding their medical history and for clinical and US re-examinations. Kaplan-Meier survival estimates were used to estimate the long-term prognosis, and a multiple Cox regression analysis was used for the prediction model.Results:In all, 174 patients (91 women, 83 men) participated in the study. All were interviewed, and 137 underwent a US examination. The mean follow-up was 9.7 years from the onset of symptoms and 8.9 years from baseline. At follow-up, 54% of patients were asymptomatic (mean duration of symptoms, 725 days), and 46% still had symptoms. The risk of having PF was 80.5% after 1 year, 50.0% after 5 years, 45.6% after 10 years, and 44.0% after 15 years from the onset of symptoms. The risk was significantly greater for women (P < .01) and patients with bilateral pain (P < .01). Fascia thickness decreased significantly in both the asymptomatic and symptomatic groups (P < .01) from 6.9 mm and 6.7 mm, respectively, to 4.3 mm in both groups. Fascia thickness (P = .49) and presence of a heel spur (P = .88) at baseline had no impact on prognosis. At follow-up, fascia thickness and echogenicity had normalized in only 24% of the asymptomatic group. The mean fat pad thickness was 9.0 mm in patients who had received a US-guided corticosteroid injection and 9.4 mm in those who had not been given an injection (P = .66).Conclusion:The risk of having PF in this study was 45.6% at a mean 10 years after the onset of symptoms. The asymptomatic patients had PF for a mean 725 days. The prognosis was significantly worse for women and patients with bilateral pain. Fascia thickness decreased over time regardless of symptoms and had no impact on prognosis, and neither did the presence of a heel spur. Only 24% of asymptomatic patients had a normal fascia on US at long-term follow-up. A US-guided corticosteroid injection did not cause atrophy of the heel fat pad. Our observational study did not allow us to determine the efficacy of different treatment strategies.

Chemical Pancreatitis Associated With Primary Systemic Amyloidosis Infiltrating the Pancreas

Primary systemic AL amyloidosis is characterized by widespread extracellular deposition of fibrilforming monoclonal immunoglobulin light chains commonly associated with plasma cell dyscrasias. GI involvement is largely hepatic and luminal but clinical manifestations are highly variable. Pancreatic involvement is particularly rare. We present a case of systemic AL amyloidosis infiltrating the pancreas in the setting of newly diagnosed multiple myeloma. A 56 year-old man presented with worsening abdominal pain, nausea and vomiting after recent admission for epigastric pain and a lipase of 3000. He tolerated oral intake but noted 30 pounds of unintentional weight loss over three months, early satiety, and orthostatic syncope. He denied use of alcohol or medications. He had epigastric tenderness, tender hepatomegaly, and diffuse muscle wasting. Lipase was 3271 (73-393 U/L), alkaline phosphatase 160 (45-117 U/L), and hemoglobin 8 g/dL. A protein gap and nephrotic-range proteinuria were also observed. The remaining hepatic indices, triglycerides, calcium and IgG4 level were unremarkable. CT abdomen and EGD/EUS revealed a normal appearing pancreas, common bile duct without stones, no focal masses or calcifications and diffuse liver enlargement. Fine needle biopsy of the liver yielded nonrepresentative pancreatic acinar tissue with peri-acinar eosinophilic material staining positive for Congo red largely within the small vessels consistent with amyloidosis. Amyloid was also seen in biopsies of the heel fat pad, stomach, and liver. A monoclonal IgA kappa spike and a 20% population of bone marrow kappa restricted plasma cells confirmed the diagnosis of AL amyloidosis secondary to multiple myeloma (MM). He began treatment for MM however had subsequent exacerbations of his presenting symptoms with a persistently elevated lipase (>2000) on repeat admissions. Reports of systemic amyloidosis involving the pancreas range across asymptomatic infiltration to invariably fatal pancreatitis as a result of inflammatory AA amyloidosis. In these cases amyloid deposition was predominately perivascular resulting in small vessel obstruction. This case is unique in that it histopathologically resembles previous cases of pancreatic amyloidosis but manifested as a clinically milder chemical, subacute pancreatitis with a persistently elevated lipase. Although rare, pancreatic amyloidosis emphasizes the diverse GI manifestations of systemic amyloidosis.

Fat grafting for chronic heel pain following surgery for adult flatfoot deformity: Pilot study

IntroductionAutologous fat grafting is now a highly popular technique in plastic and reconstructive surgery, with broad applicability for various surgical procedures. Fat grafting can impart contours and augmentation, nourish tissue, modulate scar tissue, and produce regeneration at the recipient site. In this pilot study, the authors suggest that fat grafting may be useful therapeutic adjunct for cases of chronic heel pain following surgery for adult flatfoot deformity. Materials and methodsEight patients with chronic heel pain following surgery for adult flatfoot deformity underwent autologous subcutaneous heel fat grafting and recorded their levels of pain relief for 6 months postoperatively. ResultsThe authors recorded a statistically significant difference (p<0.001) between pain scale values recorded before (t0) and six months postoperatively (t6). From t0 to t6, mean pain scale values changed from 8.125 to 2.413. ConclusionsVolumetric enhancement of the subcutaneous heel fat pad significantly ameliorated weight-bearing pain in these patients.

Material properties of the heel fat pad across strain rates

The complex structural and material behaviour of the human heel fat pad determines the transmission of plantar loading to the lower limb across a wide range of loading scenarios; from locomotion to injurious incidents. The aim of this study was to quantify the hyper-viscoelastic material properties of the human heel fat pad across strains and strain rates. An inverse finite element (FE) optimisation algorithm was developed and used, in conjunction with quasi-static and dynamic tests performed to five cadaveric heel specimens, to derive specimen-specific and mean hyper-viscoelastic material models able to predict accurately the response of the tissue at compressive loading of strain rates up to 150s−1. The mean behaviour was expressed by the quasi-linear viscoelastic (QLV) material formulation, combining the Yeoh material model (C10=0.1MPa, C30=7MPa, K=2GPa) and Prony׳s terms (A1=0.06, A2=0.77, A3=0.02 for τ1=1ms, τ2=10ms, τ3=10s). These new data help to understand better the functional anatomy and pathophysiology of the foot and ankle, develop biomimetic materials for tissue reconstruction, design of shoe, insole, and foot and ankle orthoses, and improve the predictive ability of computational models of the foot and ankle used to simulate daily activities or predict injuries at high rate injurious incidents such as road traffic accidents and underbody blast.

Sonographic measurements of the achilles tendon, plantar fascia, and heel fat pad are reliable: A test-retest intra- and intertester study.

To determine intra- and interobserver reliability and precision of sonographic (US) scanning in measuring thickness of the Achilles tendon, plantar fascia, and heel fat pad in patients with heel pain. Seventeen consecutive patients referred with heel pain were included. Two evaluators blinded to the diagnosis performed independently US scanning of both feet without any dialogue with the patient. The examiner left the room, and the next examiner entered. All patients had two US scans performed by each examiner. Two months later, the US images were randomly presented to the evaluators for measurements. Reliability and agreement were assessed by calculation of intraclass correlation coefficient (ICC), 95% limits of agreement (LOA), and typical error (TE). LOA was calculated as a percentage of the mean thickness of each structure to obtain a unitless parameter. We found excellent intratester reliability (ICC 0.78-0.98) and good intertester reliability using one measurement (ICC 0.72-0.91) and excellent (ICC 0.85-0.95) when using average of two measurements. The intratester agreements were good with LOA: 9.5-23.4% and TE: 3.4-8.4%. The intertester agreements were acceptable using one measurement with LOA: 16.1-36.4%, and better using two measurements with LOA: 14.4-33.2%. US is a reliable technique of measurement in the daily clinic, and one single measurement is sufficient. In research, we recommend that the same observer performs the US measurements, if one single scanning is preferred; if more researchers are involved, the average measurement of two US scans is recommended. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:480-486, 2016.

Characterization of the nonlinear elastic properties of soft tissues using the supersonic shear imaging (SSI) technique: inverse method, ex vivo and in vivo experiments.

Dynamic elastography has become a new clinical tool in recent years to characterize the elastic properties of soft tissues in vivo, which are important for the disease diagnosis, e.g., the detection of breast and thyroid cancer and liver fibrosis. This paper investigates the supersonic shear imaging (SSI) method commercialized in recent years with the purpose to determine the nonlinear elastic properties based on this promising technique. Particularly, we explore the propagation of the shear wave induced by the acoustic radiation force in a stressed hyperelastic soft tissue described via the Demiray-Fung model. Based on the elastodynamics theory, an analytical solution correlating the wave speed with the hyperelastic parameters of soft tissues is first derived. Then an inverse approach is established to determine the hyperelastic parameters of biological soft tissues based on the measured wave speeds at different stretch ratios. The property of the inverse method, e.g., the existence, uniqueness and stability of the solution, has been investigated. Numerical experiments based on finite element simulations and the experiments conducted on the phantom and pig livers have been employed to validate the new method. Experiments performed on the human breast tissue and human heel fat pads have demonstrated the capability of the proposed method for measuring the in vivo nonlinear elastic properties of soft tissues. Generalization of the inverse analysis to other material models and the implication of the results reported here for clinical diagnosis have been discussed.

The Treatment of Pain with Heel Fat Pad Syndrome by Hyaluronic Acid Injection: A casereport

The Treatment of Pain with Heel Fat Pad Syndrome by Hyaluronic Acid Injection: A casereport

What Is on the Horizon? Adding a New Item to Our List: Mechanical Connective Soft Tissue

In the mid 1990s, the specialty of physical medicine and rehabilitation (PMR muscles, nerves, and blood vessels are not considered connective soft tissues [2]. In the history of medicine, the connective soft tissues have not been considered as important as the nonconnective soft tissues (particularly muscle) or bone. This viewpoint is clearly reflected in the definition of physiatrists as provided by the AAPM&R [1], “PM&R physicians are nerve, muscle, bone, and brain experts who treat injury or illness nonsurgically to decrease pain and restore function,” no connective soft tissues are mentioned. However, it should be noted that most of the connective soft tissues, except for skin, function “mechanically” and certain of these mechanical connective soft tissues (MCST), such as intervertebral disks, knee meniscus, rotator cuff tendons, collateral ligaments, plantar fascia, and heel fat pad, play key roles in common musculoskeletal pain conditions and disability. We need to revisit these MCSTs.

The influence of corpulence on the mechanical properties of the human heel fat pad in elderly

Background The human heel fat pad (HFP) is an effective shock absorber [1]. A remodelling of body fat begins from the fifth decade of the human life. Diet may negatively influence this distribution and consequently lead to corpulence in elderly persons. Alcantara and colleges reported that fat content in the HFP increases with obesity [2]. Hence, the purpose of this investigation was to determine the effect of corpulence on the mechanical properties of the HFP in elderly. We hypothesized, that corpulence alters mechanical properties of the HFP compared to normal weighted elderly persons.

Three-dimensional morphology of heel fat pad: an in vivo computed tomography study

Heel fat pad cushioning efficiency is the result of its structure, shape and thickness. However, while a number of studies have investigated heel fat pad (HFP) anatomy, structural behavior and material properties, no previous study has described its three-dimensional morphology in situ. The assessment of the healthy, unloaded, three-dimensional morphology of heel pad may contribute to deepen the understanding of its role and behavior during locomotion. It is the basis for the assessment of possible HFP morphological modifications due to changes in the amount or distribution of the loads normally sustained by the foot. It may also help in guiding the surgical reconstruction of the pad and in improving footwear design, as well as in developing a correct heel pad geometry for finite element models of the foot. Therefore the purpose of this study was to obtain a complete analysis of HFP three-dimensional morphology in situ. The right foot of nine healthy volunteers was scanned with computed tomography. A methodological approach that maximizes reliability and repeatability of the data was developed by building a device to lock the foot in a neutral position with respect to the scan planes during image acquisition. Scan data were used to reconstruct virtual three-dimensional models for both the calcaneus and HFP. A set of virtual coronal and axial sections were extracted from the three-dimensional model of each HFP and processed to extract a set of one- and two-dimensional morphometrical measurements for a detailed description of heel pad morphology. The tissue exhibited a consistent and sophisticated morphology that may reflect the biomechanics of the foot support. HFP was found to be have a crest on its anterior dorsal surface, flanges on the sides and posteriorly, and a thick portion that reached and covered the posterior surface of the calcaneus and the achilles tendon insertion. Its anterior internal portion was thinner and a lump of fat was consistently present in this region. Finally, HFP was found to be thicker in males than in females.

The heel fat pad: mechanical properties and clinical applications

The human heel pad is a highly specialised fibroadipose tissue that is hierarchically structured to dissipate the stress associated with weight–bearing activities. While the properties of the heel pad, as a whole, are believed to reflect those of the collagen– and elastin–rich septa which envelope adipocytes and confine their movement, the scientific literature provides little consensus on the properties of healthy heel pads. Experiments conducted in vitro typically yield stiffness and loss properties that differ by an order of magnitude to those performed in vivo. Such differences may, in part, reflect the difficulty in measuring heel pad mechanics in vivo. This paper reports the findings of a novel series of experiments in which a digital fluoroscope, synchronised with a pressure platform, was used to obtain force–deformation data of the heel pad during gait. Transient loading profiles associated with walking were observed to induce rapidly changing deformation rates in the heel pad and resulted in irregular load–deformation curves. Initial stiffness (32 N.mm-1) of the heel pad was an order of magnitude lower than its final stiffness (212 N.mm-1), which, in turn, was similar to that reported for cadaveric heel pads (296 N.mm-1) when impacted at comparable energies of 1.45 J. While the energy dissipating ratio of the heel pad (0.66 ± 0.12) fell between those commonly cited for mechanical tests of cadaveric heels and impact loading in vivo, peak deformation of the fat pad (10.3 mm) approached that predicted for the limit of pain tolerance (10.7 mm), suggesting that the heel pad operates near its physiological maximum, even at the relatively modest speeds encountered during walking. In plantar heel pain, the elastic properties of the heel pad remained unaltered. However, energy loss within the tissue was reduced in symptomatic limbs and was also correlated with the sonographic thickness of the plantar fascial enthesis. These findings suggest that viscosity, rather than elasticity, of the heel fat pad may play an important role in the severity of heel pain and provides a previously unidentified link between the mechanical behaviour of the plantar fat pad and plantar heel pain.