A review of foot finite element modelling for pressure ulcer prevention in bedrest: Current perspectives and future recommendations.

Pressure ulcers (PUs) are a major public health challenge, having a significant impact on healthcare service and patient quality of life. Computational biomechanical modelling has enhanced PU research by facilitating the investigation of pressure responses in subcutaneous tissue and skeletal muscle. Extensive work has been undertaken on PUs on patients in the seated posture, but research into heel ulcers has been relatively neglected.

A combined experimental and computational approach to evaluate microclimate control at the support surface interface.

Temperature and humidity conditions at the interface between a support surface and the skin, termed microclimate, has been implicated in the development of pressure ulcers. Support surface technologies have been developed to control microclimate conditions, although only a few standard test methods exist to evaluate their performance. This study describes a combined experimental-computational approach to analyzing microclimate control systems.

Risk factors for developing heel ulcers for bedridden patients: A finite element study.

Background: The heel is one of the most common sites of pressure ulcers and the anatomical location with the highest prevalence of deep tissue injury. Several finite element modeling studies investigate heel ulcers for bedridden patients. In the current study we have added the implementation of the calf structure to the current heel models.

An evaluation of dermal microcirculatory occlusion under repeated mechanical loads: Implication of lymphatic impairment in pressure ulcers.

Objective: Pressure ulcers are caused by prolonged mechanical loads deforming the underlying soft tissues. However, the mechanical loads for microcirculatory occlusion are unknown. The present study was designed to characterize the simultaneous response of microvascular and lymphatic structures under repeated mechanical loading.

The expression of anaerobic metabolites in sweat and sebum from human skin subjected to intermittent and continuous mechanical loading.

Pressure ulcers (PUs) represent a substantial burden to both patients and healthcare providers. Accordingly, effective prevention strategies should follow early detection of PUs. Anaerobic metabolites, such as lactate and pyruvate, are promising noninvasive biomarkers indicative of tissue ischaemia, one of the major mechanisms leading to PU development.

There is an individual tolerance to mechanical loading in compression induced deep tissue injury.

Background: Deep tissue injury is a type of pressure ulcer which originates subcutaneously due to sustained mechanical loading. The relationship between mechanical compression and damage development has been extensively studied in 2D. However, recent studies have suggested that damage develops beyond the site of indentation.

Magnetic resonance elastography of skeletal muscle deep tissue injury.

The current state-of-the-art diagnosis method for deep tissue injury in muscle, a subcategory of pressure ulcers, is palpation. It is recognized that deep tissue injury is frequently preceded by altered biomechanical properties. A quantitative understanding of the changes in biomechanical properties preceding and during deep tissue injury development is therefore highly desired.

Myoglobin and troponin concentrations are increased in early stage deep tissue injury.

Pressure-induced deep tissue injury is a form of pressure ulcer which is difficult to detect and diagnose at an early stage, before the wound has severely progressed and becomes visible at the skin surface. At the present time, no such detection technique is available. To test the hypothesis that muscle damage biomarkers can be indicative of the development of deep tissue injury after sustained mechanical loading, an indentation test was performed for 2 h on the tibialis anterior muscle of rats.

Investigating the influence of intermittent and continuous mechanical loading on skin through non-invasive sampling of IL-1α.

Pressure ulcers (PUs) are a major burden to both patients, carers and the healthcare system. It is therefore important to identify patients at risk and detect pressure ulcers at an early stage of their development. The pro-inflammatory cytokine IL-1α is a promising indicator of tissue damage.

Ultrasonography Detects Deep Tissue Injuries in the Subcutaneous Layers of the Buttocks Following Spinal Cord Injury.

Ultrasonography may have potential as an effective diagnostic tool for deep tissue injury (DTI) in tissues overlying bony prominences that are vulnerable when under sustained loading in sitting. Three cases of DTI in the fat and muscle layers overlying the ischial tuberosity of the pelvis in 3 persons with spinal cord injury (SCI) with different medical histories and abnormal tissue signs are described. There is a need for prospective studies using a reliable standardized ultrasonography protocol to diagnose DTI and to follow its natural history to determine its association with the development of pressure injuries.

MRI based 3D finite element modelling to investigate deep tissue injury.

Pressure ulcers occur due to sustained mechanical loading. Deep tissue injury is a severe type of pressure ulcer, which is believed to originate in subcutaneous tissues adjacent to bony prominences. In previous experimental-numerical studies the relationship between internal tissue state and damage development was investigated using a 2D analysis.

A model of human skin under large amplitude oscillatory shear.

Skin mechanics is of importance in various fields of research when accurate predictions of the mechanical response of skin is essential. This study aims to develop a new constitutive model for human skin that is capable of describing the heterogeneous, nonlinear viscoelastic mechanical response of human skin under shear deformation. This complex mechanical response was determined by performing large amplitude oscillatory shear (LAOS) experiments on ex vivo human skin samples.

An advanced magnetic resonance imaging perspective on the etiology of deep tissue injury.

Early diagnosis of deep tissue injury remains problematic due to the complicated and multifactorial nature of damage induction and the many processes involved in damage development and recovery. In this paper, we present a comprehensive assessment of deep tissue injury development and remodeling in a rat model by multiparametric magnetic resonance imaging (MRI) and histopathology. The tibialis anterior muscle of rats was subjected to mechanical deformation for 2 h.

Adaptation of a MR imaging protocol into a real-time clinical biometric ultrasound protocol for persons with spinal cord injury at risk for deep tissue injury: A reliability study.

Background: High strain in soft tissues that overly bony prominences are considered a risk factor for pressure ulcers (PUs) following spinal cord impairment (SCI) and have been computed using Finite Element methods (FEM). The aim of this study was to translate a MRI protocol into ultrasound (US) and determine between-operator reliability of expert sonographers measuring diameter of the inferior curvature of the ischial tuberosity (IT) and the thickness of the overlying soft tissue layers on able-bodied (AB) and SCI using real-time ultrasound.

Material And Methods: Part 1: Fourteen AB participants with a mean age of 36.

3D Fiber Orientation in Atherosclerotic Carotid Plaques.

Atherosclerotic plaque rupture is the primary trigger of fatal cardiovascular events. Fibrillar collagen in atherosclerotic plaques and their directionality are anticipated to play a crucial role in plaque rupture. This study aimed assessing 3D fiber orientations and architecture in atherosclerotic plaques for the first time.

Diphtheria toxoid and N-trimethyl chitosan layer-by-layer coated pH-sensitive microneedles induce potent immune responses upon dermal vaccination in mice.

Dermal immunization using antigen-coated microneedle arrays is a promising vaccination strategy. However, reduction of microneedle sharpness and the available surface area for antigen coating is a limiting factor. To overcome these obstacles, a layer-by-layer coating approach can be applied onto pH-sensitive microneedles.

Nondestructive mechanical characterization of developing biological tissues using inflation testing.

One of the hallmarks of biological soft tissues is their capacity to grow and remodel in response to changes in their environment. Although it is well-accepted that these processes occur at least partly to maintain a mechanical homeostasis, it remains unclear which mechanical constituent(s) determine(s) mechanical homeostasis. In the current study a nondestructive mechanical test and a two-step inverse analysis method were developed and validated to nondestructively estimate the mechanical properties of biological tissue during tissue culture.

Cytokine IL1α and lactate as markers for tissue damage in spineboard immobilisation. A prospective, randomised open-label crossover trial.

Background: Spinal immobilisation using a rigid long spineboard is a well-established procedure in trauma care. During immobilisation, the body is exposed to high tissue-interface pressures. This may lead to a localised inflammatory response of the skin, which may be used to monitor the body's response to different types of immobilisation device.

Lmna knockout mouse embryonic fibroblasts are less contractile than their wild-type counterparts.

In order to maintain tissue homeostasis and functionality, adherent cells need to sense and respond to environmental mechanical stimuli. An important ability that adherent cells need in order to properly sense and respond to mechanical stimuli is the ability to exert contractile stress onto the environment via actin stress fibers. The actin stress fibers form a structural chain between the cells' environment via focal adhesions and the nucleus via the nuclear lamina.

Computationally Designed 3D Printed Self-Expandable Polymer Stents with Biodegradation Capacity for Minimally Invasive Heart Valve Implantation: A Proof-of-Concept Study.

The evolution of minimally invasive implantation procedures and the remodeling potential of decellularized tissue-engineered heart valves require stents with growth capacity to make these techniques available for pediatric patients. By means of computational tools and 3D printing technology, this proof-of-concept study demonstrates the design and manufacture of a polymer stent with a mechanical performance comparable to that of conventional nitinol stents used for heart valve implantation in animal trials. A commercially available 3D printing polymer was selected, and crush and crimping tests were conducted to validate the results predicted by the computational model.

Understanding the requirements of self-expandable stents for heart valve replacement: Radial force, hoop force and equilibrium.

A proper interpretation of the forces developed during stent crimping and deployment is of paramount importance for a better understanding of the requirements for successful heart valve replacement. The present study combines experimental and computational methods to assess the performance of a nitinol stent for tissue-engineered heart valve implantation. To validate the stent model, the mechanical response to parallel plate compression and radial crimping was evaluated experimentally.

A MRI-Compatible Combined Mechanical Loading and MR Elastography Setup to Study Deformation-Induced Skeletal Muscle Damage in Rats.

Deformation of skeletal muscle in the proximity of bony structures may lead to deep tissue injury category of pressure ulcers. Changes in mechanical properties have been proposed as a risk factor in the development of deep tissue injury and may be useful as a diagnostic tool for early detection. MRE allows for the estimation of mechanical properties of soft tissue through analysis of shear wave data.

On the importance of 3D, geometrically accurate, and subject-specific finite element analysis for evaluation of in-vivo soft tissue loads.

Pressure ulcers are a type of local soft tissue injury due to sustained mechanical loading and remain a common issue in patient care. People with spinal cord injury (SCI) are especially at risk of pressure ulcers due to impaired mobility and sensory perception. The development of load improving support structures relies on realistic tissue load evaluation e.