The plantar fat pad and the diabetic foot--a review

Adipose tissue allograft for the management of a pre-ulcerative plantar lesion in a diabetic neuropathic patient

This case describes a minimally invasive implantation of cryopreserved human adipose tissue allograft (CAT) in a diabetic neuropathic patient with a pre-ulcerative plantar lesion. No re-ulceration or adverse events have occurred out to 9 months. CAT provides healthcare providers with an option to manage patients at risk for plantar ulcers.

Sub-calcaneal plantar fat pad assessment using dual-energy computed tomography: First experience in the diabetic foot

BACKGROUND

This study assessed the use of dual-energy computed tomography (CT) to evaluate sub-calcaneal plantar fat pad changes in people with diabetic neuropathy.

METHODS

Dual-energy CT scans of people with diabetic neuropathy and non-diabetic controls were retrospectively included. Average CT values (in Hounsfield Units) and thickness (in centimeters) of the sub-calcaneal plantar fat pad were measured in mono-energetic images at two energy levels (40 keV and 70 keV). The CT values measured in patients with diabetic neuropathy were correlated to barefoot plantar pressure measurements performed during walking in a clinical setting.

FINDINGS

Forty-five dual-energy CT scans of people with diabetic neuropathy and eleven DECT scans of non-diabetic controls were included. Mean sub-calcaneal plantar fat pad thickness did not significantly differ between groups (diabetes group 1.20 ± 0.34 cm vs. control group 1.21 ± 0.28 cm, P = 0.585). CT values at both 40 keV (-34.7 ± 48.7 HU vs. -76.0 ± 42.8 HU, P = 0.013) and 70 keV (-11.2 ± 30.8 HU vs. -36.3 ± 27.2 HU, P = 0.017) were significantly higher in the diabetes group compared to controls, thus contained less fatty tissue. This elevation was most apparent in patients with Type 1 diabetes. CT values positively correlated with the mean peak plantar pressure.

INTERPRETATION

Dual-energy CT was able to detect changes in the plantar fat pad of people with diabetic neuropathy.

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.

Longitudinal physiological remoulding of lower limb skin as a cause of diabetic foot ulcer: a histopathological examination

OBJECTIVE

Diabetic foot ulcer (DFU) is recognised as a severe complication in patients with type 2 diabetes. With the increasing incidence of diabetes, it represents a major medical challenge. Several models have been proposed to explain its aetiology; however, they have never been assessed by longitudinal histopathological examination, which this study aims to address.

METHOD

Multiplex-immunofluorescence analysis was carried out with lengthwise serial skin specimens obtained from the medial thigh, lower leg, ankle, dorsum of foot and acrotarsium close to the DFU region of a patient with type 2 diabetes receiving above the knee amputation.

RESULTS

Proximal-to-distal gradual loss of peripheral nerve was demonstrated, accompanied by compromised capillaries in the superficial papillary plexus and distended CD31-positive capillaries in the dorsum of foot. Neural fibres and capillaries were also significantly compromised in the sweat gland acinus in the ankle and dorsum of foot. Injuries in the superficial papillary plexus, sweat gland acinus, and sweat gland-associated adipose tissues were accompanied by significant infiltration of macrophages. These results indicated that longitudinal impairment of local blood circulation could be the cause of peripheral neuropathy, which initiated ulcer formation. Resultant chronic inflammation, involving sweat gland-associated adipose tissue, gave rise to impairment of wound healing, and thus DFU formation.

CONCLUSION

Longitudinal histopathological examination demonstrated that impairment of local microvascular circulation (rather than the systemic complication caused by type 2 diabetes) was considered the primary cause of peripheral neuropathy, which initiated ulceration. Together with chronic inflammation in the superficial papillary plexus and sweat gland-associated adipose tissue, it resulted in the development of a DFU. Although this is a study of just one individual's limb, our study provided a unique observation, contributing mechanistic insights into developing novel intervening strategies to prevent and treat DFUs.

A quantitative comparison of plantar soft tissue strainability distribution and homogeneity between ulcerated and non-ulcerated patients using ultrasound strain elastography

The primary objective of this study was to develop a method that allows accurate quantification of plantar soft tissue stiffness distribution and homogeneity. The secondary aim of this study was to investigate if the differences in soft tissue stiffness distribution and homogeneity can be detected between ulcerated and non-ulcerated foot. Novel measures of individual pixel stiffness, named as quantitative strainability (QS) and relative strainability (RS) were developed. Strain Elastography data obtained from 39 (nine with active diabetic foot ulcers) patients with diabetic neuropathy. The patients with active diabetic foot ulcer had wound in parts of the foot other than the first metatarsal head and the heel where the elastography measures were conducted. RS was used to measure changes and gradients in the stiffness distribution of plantar soft tissues in participants with and without active diabetic foot ulcer. The plantar soft tissue homogeneity in superior-inferior direction in the left forefoot was found to be significantly (p < 0.05) higher in ulcerated group compared to non-ulcerated group. The assessment of homogeneity showed potentials to further explain the nature of the change in tissue that can increase internal stress. This can have implications in assessing the vulnerability to plantar soft tissue damage and ulceration in diabetes.

Evaluation and optimisation of a footwear assessment tool for use within a clinical environment

Footwear has been documented as a significant factor in the aetiology of foot pain in the general population. Assessing footwear in a clinical setting continues to be practitioner specific and there is limited guidance to direct advice. Health professionals must have access to clinically appropriate and reliable footwear assessment tools to educate patients on healthier footwear choices. The primary aim of this study was to critique what elements should be in a footwear assessment tool with a secondary aim of testing the agreed tool for validity.

A combined Nominal Group Technique and then a Delphi technique from purposively sampled experts of foot health professions were employed to critique elements of footwear assessment. The agreed tool was then tested by practising podiatrists on 5 different shoes to assess the validity and reliability of the measures.

Twelve test evaluation criteria were identified receiving significant ratings to form the final footwear assessment tool consisting of five footwear themes. Application of the tool in a clinical setting validated the themes of footwear characteristics, footwear structure, motion control and wear patterns. However, the assessment of footwear fit was not reliable.

The footwear tool was refined based on the collective consensus achieved from the rounds creating a more clinically appropriate tool. The validity of this tool was assessed as high in some of the themes but for those that were lower, a training need was identified.

Reliability of ultrasound in evaluating the plantar skin and fat pad of the foot in the setting of diabetes

Ultrasound can be used to assess injury and structural changes to the soft-tissue structure of the foot. It may be useful to assess the feet of people with diabetes who are at increased risk of plantar soft-tissue pathological changes. The aim of this study was to determine if ultrasound measurements of plantar soft-tissue thickness and assessments of tissue acoustic characteristics are reliable in people with and without diabetes mellitus. A repeated measures design was used to determine intra-observer reliability for ultrasound measurements of plantar skin and fat pad thickness and intra- and inter-observer reliability of plantar skin and fat pad tissue characterisation assessments made at foot sites which are at risk of tissue injury in people with diabetes. Thickness measurements and tissue characterisation assessments were obtained at the heel and forefoot in both the unloaded and compressed states and included discrete layers of the plantar tissues: skin, microchamber, horizontal fibrous band, macrochamber and total soft-tissue depth. At each site, relative intra-observer reliability was achieved for the measurement of at least one plantar tissue layer. The total soft-tissue thickness measured in the unloaded state (ICC 0.925-0.976) demonstrated intra-observer reliability and is the most sensitive for detecting small change on repeated measures. Intra-observer agreement was demonstrated for tissue characteristic assessments of the skin at the heel (k = 0.70), fat pad at the lateral sesamoid region (k = 0.70) and both skin and fat pad at the second (k = 0.80, k = 0.70 respectively) and third metatarsal heads (k = 0.90, k = 0.79 respectively). However, acceptable inter-observer agreement was not demonstrated for any tissue characteristic assessment, therefore the use of multiple observers should be avoided when making these assessments.

Pedobarographic Statistical Parametric Mapping may identify specific plantar pressure patterns in patients with diabetes mellitus among different degrees of peripheral neuropathy: A pilot study

AIMS

Peripheral neuropathy (PN) in patients with diabetes can lead to changes in the distribution of plantar pressure during walking, which can be recorded with pedobarography. Compared to traditional spatial data reduction analysis, the pedobarographic Statistical Parametric Mapping (pSPM) allows comparison of the footprints with the advantage that sub-regions do not need to be defined a priori. Aim of the study was to test the potential of pSPM in identifying specific distribution of spatial pressure in different stages of PN.

METHODS

PN was defined according to usual tools (i.e., tendon reflexes and sensory tests). Four groups were compared: patients with diabetes without PN (n = 24; 239 steps); with signs of mild PN (n = 12; 117 steps); with signs of severe PN (n = 6; 52 steps) and a control group without diabetes (n = 12; 124 steps). Traditional spatial data reduction and pSPM were performed to compare plantar pressures in the different groups.

RESULTS

In patients with PN, traditional spatial data reduction analysis showed lower plantar pressures with PN severity. pSPM analysis is able to better define the initial changes: mild PN patients presents higher pressures on the anterior side of the metatarsal heads compared to patients without neuropathy. Patients with severe PN are characterised by higher pressures under the medial foot arch compared to other groups.

CONCLUSIONS

pSPM may identify specific features of plantar pressure distribution during walking in patients with mild PN and may become a useful screening tool for a timely identification of this complication.

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.

Ultrasound in the Modern Management of the Diabetic Foot Syndrome: A Multipurpose Versatile Toolkit

Ultrasound (US) is a noninvasive and versatile technology that in recent years found acceptance in almost all the medical specialties, with diagnostic and interventional applications. In the diabetic foot syndrome (DFS), US found specific indications mainly in the screening, quantification, and follow-up of the vascular component of the pathology, but also in the study of the deformities and structural modifications induced by neuropathy and in the diagnosis and surgical management of infections, especially those that induce anatomical changes, like abscesses and fasciitis. This review will summarize all these application of US, giving special attention to the vascular aspects, and on the predominant role that US gained in recent times to guide the indication to revascularization, on the new standardized approach to the study of the arterial tree of the limb and the foot, the so-called duplex ultrasound arterial mapping, which significantly increased the utilization of US to plan the revascularizations in this complex pathology. Outside the vascular fields, the diagnosis of neuropathy and infection and the intraoperative use of US in the surgical management of abscesses and fasciitis will be discussed, leaving the last part to the new and interesting applications of US in the management of DFU, a field that is still in evolution, offering new possibilities to the health care professionals involved in the management of these chronic wounds. The variety of applications both in diagnostic and operative fields makes US a rather versatile technology-a toolkit-that should have a special place among those at reach of the specialists of DFS care.

The shape of the transverse arch in high heels while standing

Introduction

High heeled shoes have long been worn in society and they are known to cause biomechanical imbalances to not only the foot, but the whole musculoskeletal system. This study aims to show the detailed changes that happen to the shape of the transverse arch of the foot in high heels, using two different inclination degrees.

Methods

68 women participated in this study. Two custom-made high heels were made with inclinations of 15 degrees and 30 degrees (cm). A weight-bearing ultrasound was used to assess the coronal view of the transverse arch in standing. ANOVA and Tuckey tests were used to compare the results between 0 degrees, 15 degrees and 30 degrees inclinations.

Results

The transverse arch height was slightly increased as the heel height increased (0DI-15DI: p = 0.5852 / 15DI-30DI: p = 0.395 / 0DI-30DI: p = 0.0593). The transverse arch length (0DI-15DI: p = 0.0486 / 15DI-30DI: p = 0.0004 / 0DI-30DI: p = 0.1105) and the area under the metatarsal heads (0DI-15DI: p = 0.0422 / 15DI-30DI: p = 0.0180 / 0DI-30DI: p = 0.9463) significantly decreased as the heel height increased.

Discussion

The main changes were viewed in the 30 degrees inclinations compared to 0 degrees inclination. When the toes are dorsiflexed in high heels, it stimulates the Windlass mechanism which in turn stiffens the plantar fascia and adducts the metatarsal heads, while the soft tissues shrink in response to loads.

Conclusion

High heels affected the shape of the transverse arch even in short term standing, and these effects increased as the height of the heel increased.

Differences in the Sub-Metatarsal Fat Pad Atrophy Symptoms between Patients with Metatarsal Head Resection and Those without Metatarsal Head Resection: A Cross-Sectional Study

We aimed to evaluate the differences in the sub-metatarsal skin and fat pad atrophy between patients at a high risk of ulceration with and without previous metatarsal head resection. A cross-sectional study was performed in a diabetic foot unit involving 19 participants with a history of metatarsal head resection (experimental group) and 19 (control group) without a history of metatarsal head resection but with an ulcer in other locations in the metatarsal head. No participants had active ulcerations at study inclusion. Sub-metatarsal skin thickness and fat pad thickness in the first and second metatarsals were evaluated by an ultrasound transducer. The experimental group showed sub-metatarsal fat pad atrophy (3.74 ± 1.18 mm and 2.52 ± 1.04 mm for first and second metatarsal, respectively) compared with the control group (5.44 ± 1.12 mm and 4.73 ± 1.59 mm) (p < 0.001, confidence interval: (CI): 0.943-2.457 and p < 0.001, CI: 1.143-3.270 for first and second metatarsal, respectively); however, sub-metatarsal skin thickness was not different between groups (experimental 2.47 ± 0.47 mm vs. control 2.80 ± 0.58 mm (p = 0.063, CI: -0.019-0.672) and 2.24 ± 0.60 mm vs. 2.62 ± 0.50 mm (p = 0.066, CI: -0.027-0.786) for first and second metatarsal, respectively). Patients with previous metatarsal head resection showed sub-metatarsal fat pad atrophy, which could be associated with the risk of reulceration in the metatarsal head.

Soft Tissue Reconstruction with Diabetic Foot Tissue Loss

Although substantial advances have been made in treatment of diabetic foot disease with respect to patient education, preventative measures, early intervention, and prophylactic procedures, most surgical interventions for this condition are reactionary. Patients still primarily present to emergency departments with acute infections and tissue necrosis. The surgical intervention for this results in soft tissue deficit, often with partial foot amputation, through excisional debridement of pathologic tissue. Minimizing this initial soft tissue loss, with subsequent reconstruction of the defect, forms the focus of this article with a detailed anatomic assessment of structures at risk in the forefoot, midfoot and rearfoot.

Distribution of the Highest Plantar Pressure Regions in Patients with Diabetes and Its Association with Peripheral Neuropathy, Gender, Age, and BMI: One Centre Study

The abnormal plantar pressure distribution and value play a key role in the formation of plantar calluses and diabetic foot ulcer. The prevalence of the highest pressure different distribution and its association with various factors among patients with diabetes is not well known. The study purpose was to evaluate the prevalence of different regions for the highest pressure on the sole and its association with selected factors among patients with diabetes. Medical records of nonulcer patients were retrospectively analysed. The relationship between pressure patterns on the sole obtained during a pedobarographic test as a semiquantitative assessment with colourful print analysis and neuropathy, gender, age, and BMI was searched. The most common location of the highest pressure was the central part of the forefoot. No association was found between the different highest pressure regions and age, sensory neuropathy, calluses, and foot deformities. The highest pressure on the lateral part of the foot and midfoot was observed more often in females and in patients with a BMI ≥ 35. The prevalence of the highest pressure on the forefoot was more common in patients with a BMI < 35. Conclusions. The most frequent regions of the highest pressure on the sole in patients with diabetes were the central part of the forefoot (2-3 metatarsal heads) with no simple relationship to the assessed variables other than BMI < 35. Female gender and higher BMI seem to be responsible for shifting the place of the highest pressure to other places of the foot.

Can ultrasound measures of intrinsic foot muscles and plantar soft tissues predict future diabetes-related foot disease? A systematic review

Introduction

Diabetes mellitus (DM) is associated with hyperglycaemia and advanced glycosylation end-products. In the foot, the consequences of chronic or uncontrolled diabetes are micro and macrovascular disease, neuropathy, reduced joint mobility and structural and soft tissue changes that increase the risk of ulcer development and amputation. Diabetes foot assessment currently includes a comprehensive history, neurological and vascular assessments and examination focussed on dermatological and musculoskeletal abnormalities. Whilst these assessments are helpful for predicting ulceration risk, direct identifiers that enable early therapeutic intervention are lacking. The intention of this review was to ascertain if B-mode ultrasound could be clinically applied to identify structural change in the diabetic foot and be utilised as an early predictor of ulceration risk.

Methods

Primary databases and grey literature sources were systematically searched. Selection criteria were that the study included a diabetic sample and used B-mode ultrasound to assess soft tissue structures of the foot (plantar skin, plantar fat pad or intrinsic muscles).

Results

Fifteen studies were identified for inclusion (combined diabetic sample of 773). Ultrasound demonstrated reductions in tissue thickness in diabetics compared to non-diabetics under first (p = 0.01) and second (p = 0.03) metatarsal heads, but not the third (p = 0.24). Statistical heterogeneity was high for ultrasound thickness measures under metatarsal heads four/five (I² 65%, 81%) and very high for plantar skin (I² 98%), heel pad (I² 76%) and intrinsic muscles (I² 91%, 81%). Extensor digitorum brevis (EDB) ultrasound measures were significantly thinner in diabetics for all dimension measures compared to healthy controls except one study, which reported no significant differences in EDB thickness.

Conclusions

No direct evidence was found to indicate B-mode ultrasound measures can predict soft tissue changes in the plantar foot in diabetes, although low level studies indicate ultrasound has the potential to identify structural change. Clinical, methodological and statistical heterogeneity limit result applicability. This review highlights the need for robust prospective longitudinal research to examine the predictive validity of this method.

Anatomical, Physiological, and Functional Diversity of Adipose Tissue

Adipose tissue depots can exist in close association with other organs, where they assume diverse, often non-traditional functions. In stem cell-rich skin, bone marrow, and mammary glands, adipocytes signal to and modulate organ regeneration and remodeling. Skin adipocytes and their progenitors signal to hair follicles, promoting epithelial stem cell quiescence and activation, respectively. Hair follicles signal back to adipocyte progenitors, inducing their expansion and regeneration, as in skin scars. In mammary glands and heart, adipocytes supply lipids to neighboring cells for nutritional and metabolic functions, respectively. Adipose depots adjacent to skeletal structures function to absorb mechanical shock. Adipose tissue near the surface of skin and intestine senses and responds to bacterial invasion, contributing to the body's innate immune barrier. As the recognition of diverse adipose depot functions increases, novel therapeutic approaches centered on tissue-specific adipocytes are likely to emerge for a range of cancers and regenerative, infectious, and autoimmune disorders.