Risk factors for the development and evolution of deep tissue injuries: A systematic review.

AIMS: The aim of this systematic review is to identify the current epidemiological evidence indicating the unique risk factors for deep tissue injury (DTI) compared to grade I-IV pressure injury (PI), the proportion of DTI which evolve rather than resolve and the anatomical distribution of DTI. METHODS: A systematic literature search was undertaken using the MEDLINE and CINAHL Plus databases using the search terms 'Deep tissue injury OR DTI [Title/abstract]'. A google scholar search was also conducted in addition to hand searches of relevant journals, websites and books which were identified from reference lists in retrieved articles. Only peer-reviewed English language articles published 2009-2021 were included, with full text available online. RESULTS: The final qualitative analysis included nine articles. These included n = 4 retrospective studies, n = 4 prospective studies and n = 1 animal study. CONCLUSION: The literature indicates that the majority of DTI occur at the heel and sacrum although in paediatric patients they are mainly associated with medical devices. Most DTI are reported to resolve, with between 9.3 and 27% deteriorating to full thickness tissue loss. Risk factors unique to DTI appear to include anaemia, vasopressor use, haemodialysis and nicotine use although it is unclear if these factors are unique to DTI or are shared with grade I-IV PI. Factors associated with deterioration include cooler skin measured using infrared thermography and negative capillary refill. With 100% of DTI showing positive capillary refill in one study resolving without tissue loss (p = 0.02) suggesting this may be an effective prognostic indicator. More prospective studies are required focusing on establishing causal links between risk factors identified in earlier retrospective studies. Ideally these should use statistically powered samples and sufficient follow up periods allowing DTI outcomes to be reached. Further work is also needed to establish reliable diagnostic criteria for DTI in addition to more studies in the paediatric population.

The biomechanical efficacy of a dressing with a soft cellulose fluff core in protecting prone surgical patients from chest injuries on the operating table.

Pressure ulcers are soft-tissue damage associated with tissue exposure to sustained deformations and stress concentrations. In patients who are proned for ventilation or surgery, such damage may occur in the superficial chest tissues that are compressed between the rib cage and the support surface. Prophylactic dressings have been previously proven as generally effective for pressure ulcer prevention. In this study, our goal was to develop a novel computational modelling framework to investigate the biomechanical efficacy of a dressing with a soft cellulose fluff core in protecting proned surgical patients from chest pressure ulcers occurring on the operating table, due to body fixation by the Relton-Hall frame. We compared the levels of mechanical compressive stresses developing in the soft chest tissues, above the sternum and ribs, due to the trunk weight, whilst the body is supported by the Relton-Hall frame pads, with versus without the prophylactically applied bilateral dressings. The protective efficacy index for the extremely high stresses, above the 95th-percentile, were 40.5%, 25.6% and 24.2% for skin, adipose and muscle, respectively, indicating that the dressings dispersed elevated soft-tissue stresses. The current results provide additional support for using soft cellulose fluff core dressings for pressure ulcer prophylaxis, including during surgery.

Deep tissue injury: a narrative review on the aetiology of a controversial wound.

Deep tissue injuries (DTIs) were added to pressure ulcer grading systems in 2009. Since then, they have been associated with the same aetiological processes as other forms of pressure injury (PI). This is despite notable clinical differences in their presentation along with variations in natural history that suggest they are the consequence of processes distinct from those that cause other PIs. Understanding the aetiology of DTIs is essential to guide prevention and treatment in addition to ensuring healthcare governance processes deeply tied to pressure injury are effective and efficient. Current understanding of the aetiology of DTI has significant gaps, with several key challenges impeding progress in this area of PI research, including inconsistent reporting by healthcare services and the limitations of animal and computer models in addition to the ethical barriers to conducting studies on human subjects. Synthesis of early studies with studies undertaken before 2009 is also limited by the variety in definitions of DTI used before that published by the European Pressure Ulcer Advisory Panel, the National Pressure Injury Advisory Panel and the Pan Pacific Pressure Injury Alliance in 2009. To date, few prospective clinical studies have been conducted. This article presents a narrative review on the clinical and animal study evidence indicating contemporary understanding of DTI.

How patient migration in bed affects the sacral soft tissue loading and thereby the risk for a hospital-acquired pressure injury.

Head-of-bed (HOB) elevation is a common clinical practice in hospitals causing the patient's body to slide down in bed because of gravity. This migration effect likely results in tissue shearing between the sacrum and the support surface, which increases the risk for pressure injuries. StayInPlace (HillRom Inc.) is a commercial migration-reduction technology (MRT) incorporated in intensive care bedframes. Yet, the effects of migration-reduction on tissue shear stresses during HOB elevation are unknown. We analysed relationships between migration and resulting sacral soft tissue stresses by combining motion analysis and three-dimensional finite element modelling of the buttocks. Migration data were collected for 10 subjects, lying supine on two bedframe types with and without MRT, and at HOB elevations of 45°/65°. Migration data were used as displacement boundary conditions for the modelling to calculate tissue stress exposures. Migration values for the conventional bed were 1.75- and 1.6-times greater than those for the migration-reduction bed, for elevations of 45° and 65°, respectively (P < .001). The modelling showed that the farther the migration, the greater the tissue stress exposures. Internal stresses were 1.8-fold greater than respective skin stresses. Our results, based on the novel integrated experimental-computational method, point to clear biomechanical benefits in minimising migration using MRT.

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. In this paper we quantified the spatial-temporal changes in mechanical properties upon damage development and recovery in a rat model of deep tissue injury. Deep tissue injury was induced in nine rats by two hours of sustained deformation of the tibialis anterior muscle. Magnetic resonance elastography (MRE), T2 -weighted, and T2 -mapping measurements were performed before, directly after indentation, and at several timepoints during a 14-day follow-up. The results revealed a local hotspot of elevated shear modulus (from 3.30 ± 0.14 kPa before to 4.22 ± 0.90 kPa after) near the center of deformation at Day 0, whereas the T2 was elevated in a larger area. During recovery there was a clear difference in the time course of the shear modulus and T2 . Whereas T2 showed a gradual normalization towards baseline, the shear modulus dropped below baseline from Day 3 up to Day 10 (from 3.29 ± 0.07 kPa before to 2.68 ± 0.23 kPa at Day 10, P < 0.001), followed by a normalization at Day 14. In conclusion, we found an initial increase in shear modulus directly after two hours of damage-inducing deformation, which was followed by decreased shear modulus from Day 3 up to Day 10, and subsequent normalization. The lower shear modulus originates from the moderate to severe degeneration of the muscle. MRE stiffness values were affected in a smaller area as compared with T2 . Since T2 elevation is related to edema, distributing along the muscle fibers proximally and distally from the injury, we suggest that MRE is more specific than T2 for localization of the actual damaged area.

Changes of tissue images visualised by ultrasonography in the process of pressure ulcer occurrence.

OBJECTIVE: Ultrasonography is suitable for assessing pressure ulcers, and several features of ultrasonographic images that indicate abnormalities have been reported. However, no study has compared ultrasonographic images between normal and pressure-loaded skin and subcutaneous tissue from the same patients. This study aimed to assess lateral thoracic tissue using ultrasonography for both pre- and postoperative conditions and investigate changes in the tissue caused by loading. Surgeries were performed with patients in the park-bench position. METHOD: A nursing researcher obtained ultrasonographic images of the skin and subcutaneous tissue of the lower thoracic region in areas in contact with the surgical table one or two days before and after surgery. This study focused on three groups of two patients who had a category I pressure ulcer (PU), blanchable erythema, or normal skin on their lateral thoracic region. RESULTS: A total of six patients participated. Postoperatively, muscle layers became thinner and less clear compared with pre-operative conditions in patients with the Category I pressure ulcers. These patients complained of significant pain in the areas of their pressure ulcers. CONCLUSION: Thickness of muscle layers could be an early sign of deep tissue injury.

Ultrasound imaging of tissue overlying the ischial tuberosity: Does patient position matter?

BACKGROUND: Deep Tissue Pressure Injury (DTI) occurs in the tissues underlying the skin that may not have visible signs of skin breakdown and may be detected by ultrasound. The optimal position for ischial region ultrasound image acquisition to facilitate assessment of the tissue proximal to the ischias not been determined. OBJECTIVE: To evaluate the mean difference in geometric and grey scale measures of tissues overlying the ischial tuberosity (IT) acquired from ultrasound images in supine and lateral recumbent simulated sitting positions from adults with spinal cord impairment (SCI). METHODS: Nine individuals (3 acute and 6 chronic) with SCI or disease with neurological level of injury C4-T12 and AIS A-D and who used a wheelchair for mobility were recruited and underwent ultrasound acquisition in the supine and lateral recumbent positions. One participant was imaged twice on a separate day. Three images from the left (n = 8) and right (n = 2) IT were scanned using a 6 - 18 MHz linear ultrasound probe (Acuson S2000) with participants' hips and knees flexed to 90° in both the supine and lateral recumbent positions using a single rater protocol. MATLAB Image Processing Toolbox with a customized script was used to obtain mean and maximal thickness, echogenicity and contrast of skin, subcutaneous tissue and muscle. Wilcoxon Signed Rank Test and Bland Altman analysis was used to determine if there were differences between the two image acquisition positions and to construct limits of agreement. RESULTS: Thickness and contrast measures were similar in the supine and lateral recumbent positions (p > 0.05). Muscle echogenicity was lower in the supine position (p = 0.04). CONCLUSION: There is agreement in geometric and grey scale measures of tissues over the IT between the supine and lateral recumbent positions with the exception of muscle echogenicity, which was lower in the supine position. Since DTI is thought to originate in the muscle and echogenicity plays in a role in abnormal tissue imaging diagnosis, further studies are recommended to determine the impact of body position on muscle echogenicity prior to being used in prospective studies.

Modelling an adult human head on a donut-shaped gel head support for pressure ulcer prevention.

Patients who are stationary endure prolonged pressures and shear loads at contact areas between their body and the support surface, which over time may cause pressure ulcers (PUs). Donut-shaped gel head supports are commonly used to protect the occiput, which is among the most common anatomical sites for PUs; however, the biomechanical efficacy of these devices is unclear. To investigate their effects on scalp tissues, we have used our three-dimensional anatomically realistic finite element model of an adult head, to which we have added a donut-shaped gel head support. We then compared the occipital scalp tissue loads' occurrence while the donut-shaped gel head support is in use with those associated with a fluidised head positioner and a standard medical foam. The donut-shaped gel head support inflicted the greatest exposure to tissue mechanical stresses, particularly to the high (and therefore dangerous) stress domain, when compared to the other positioners. We concluded that while the donut-shaped gel head support is designed to avert tissue loads away from the occiput and disperse them to the surroundings, in practice, it fails to do so. In fact, the donut-shaped gel head support imposes the head-weight forces to transfer through a relatively narrow ring of scalp tissues, hence increasing the risk of developing occipital PUs. KEY MESSAGES: a donut-shaped gel head support is meant to reduce the occurrence of pressure ulcers in scalp tissues to investigate the effects of donut-shaped gel head support on scalp tissues, we have used our anatomically realistic computational model of an adult head the donut-shaped gel head support imposes the head-weight forces to transfer through a relatively narrow ring of scalp tissues the highly distorted and deformed tissues at that ring are at a high risk for injury.

Sodium pyruvate pre-treatment prevents cell death due to localised, damaging mechanical strains in the context of pressure ulcers.

We demonstrate sodium pyruvate (NaPy) pre-treatment as a successful approach for pressure ulcer (PU) prevention by averting their aetiological origin-cell-level damage and death by large, sustained mechanical loads. We evaluated the NaPy pre-treatment effect on permeability changes in the cell's plasma membrane (PM) following application of in vitro damaging-level strains. Fibroblasts or myoblasts, respectively, models for superficial or deep-tissue damage were grown in 0 or 1 mM NaPy, emulating typical physiological or cell culture conditions. Cells were pre-treated for 4 hours with 0 to 5 mM NaPy prior to 3-hour sustained, damaging-level loads (12% strain). PM permeability was quantified by the cell uptake of small (4 kDa), fluorescent dextran compared with unstrained control using fluorescence-activated cell sorting (FACS). Pre-treatment with 1 mM, and especially 5 mM, NaPy significantly reduces damage to PM integrity. Long-term NaPy pre-exposure can improve protective treatment, affecting fibroblasts and myoblasts differently. Pre-treating with NaPy, a natural cell metabolite, allows cells under damaging-level mechanical loads to maintain their PM integrity, that is, to avoid loss of homeostasis and inevitable, eventual cell death, by preventing initial, microscale stages of PU formation. This pre-treatment may be applied prior to planned periods of immobility, for example, planned surgery or transport, to prolong safe time in a position by preventing initial cell damage that can cascade and lead to PU formation.

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 36.7 ± 12.09 years with 7 males and 7 females had their 3 soft tissue layers in loaded and unloaded sitting measured independently by 2 sonographers: tendon/muscle, skin/fat and total soft tissue and the diameter of the IT in its short and long axis. Part 2: Nineteen participants with SCI were screened, three were excluded due to abnormal skin signs, and eight participants (42%) were excluded for abnormal US signs with normal skin. Eight SCI participants with a mean age of 31.6 ± 13.6 years and all male with 4 paraplegics and 4 tetraplegics were measured by the same sonographers for skin, fat, tendon, muscle and total. Skin/fat and tendon/muscle were computed. RESULTS: AB between-operator reliability was good (ICC = 0.81-0.90) for 3 soft tissues layers in unloaded and loaded sitting and poor for both IT short and long axis (ICC = -0.028 and -0.01). SCI between-operator reliability was good in unloaded and loaded for total, muscle, fat, skin/fat, tendon/muscle (ICC = 0.75-0.97) and poor for tendon (ICC = 0.26 unloaded and ICC = -0.71 loaded) and skin (ICC = 0.37 unloaded and ICC = 0.10). CONCLUSION: A MRI protocol was successfully adapted for a reliable 3 soft tissue layer model and could be used in a 2-D FEM model designed to estimate soft tissue strain as a novel risk factor for the development of a PU.

What makes a good head positioner for preventing occipital pressure ulcers.

Patients who are stationary endure prolonged soft tissue distortions and deformations at contact areas between their body and the support surface, which may lead to the onset of pressure ulcers (PUs) over time. A novel technology for patient positioning employs innovation in materials science, specifically viscoelastic materials with shape memory properties that compose the Z-Flo™ head positioner (Mölnlycke Health Care, Gothenburg, Sweden). Head positioners are generally known to reduce the occurrence of PUs in scalp tissues and the ears, but quantitative assessments of their biomechanical efficacy are missing in the literature. To determine potential differences in mechanical loads formed in the soft tissues of the back of the head while in contact with 2 head positioner types, Z-Flo vs flat medical foam, we developed 2 comparable finite element model configurations, both including the same 3-dimensional adult head. For both model variants, stresses in skin and fat peaked at the occiput. The skin at the back of the resting head is subjected to greater stress values with respect to fat; however, the Z-Flo positioner reduced the exposure of both skin and fat tissues to elevated stresses considerably (by a factor of 3) compared to the medical foam support. We found the Z-Flo device effective in reducing tissue loads at the surface of the head as well as internally in scalp tissues, with a particular strength in reducing internal tissue shear. The Z-Flo device achieves this protective quality through highly effective immersion and envelopment of the back of the head, generated in the process of manual moulding of the device in preparation for use. Additional protection is achieved through the viscoelastic response of the filling material of this positioner, which relaxes promptly and considerably under the weight of the head (by more than 2-fold within approximately 1 s) as opposed to the elastic recoil of the foam that pushes back on scalp tissues.

Subepidermal moisture detection of heel pressure injury: The pressure ulcer detection study outcomes.

We examined subepidermal moisture (SEM) and visual skin assessment of heel pressure injury (PrI) among 417 nursing home residents in 19 facilities over 16 weeks. Participants were older (mean age 77 years), 58% were female, over half were ethnic minorities (29% African American, 12% Asian American, 21% Hispanic), and at risk for PrI (mean Braden Scale Risk score = 15.6). Blinded concurrent visual assessments and SEM measurements were obtained at heels weekly. Visual skin damage was categorised as normal, erythema, stage 1 PrI, deep tissue injury (DTI) or stage 2 or greater PrI. PrI incidence was 76%. Off-loading occurred with pillows (76% of residents) rather than heel boots (21%) and often for those with DTI (91%). Subepidermal moisture was measured with a device where higher readings indicate greater moisture (range: 0-70 tissue dielectric constant), with normal skin values significantly different from values in the presence of skin damage. Subepidermal moisture was associated with concurrent damage and damage 1 week later in generalised multinomial logistic models adjusting for age, diabetes and function. Subepidermal moisture detected DTI and differentiated those that resolved, remained and deteriorated over 16 weeks. Subepidermal moisture may be an objective method for detecting PrI.

Pressure Combined with Ischemia/Reperfusion Injury Induces Deep Tissue Injury via Endoplasmic Reticulum Stress in a Rat Pressure Ulcer Model.

Pressure ulcer is a complex and significant health problem in long-term bedridden patients, and there is currently no effective treatment or efficient prevention method. Furthermore, the molecular mechanisms and pathogenesis contributing to the deep injury of pressure ulcers are unclear. The aim of the study was to explore the role of endoplasmic reticulum (ER) stress and Akt/GSK3ß signaling in pressure ulcers. A model of pressure-induced deep tissue injury in adult Sprague-Dawley rats was established. Rats were treated with 2-h compression and subsequent 0.5-h release for various cycles. After recovery, the tissue in the compressed regions was collected for further analysis. The compressed muscle tissues showed clear cellular degenerative features. First, the expression levels of ER stress proteins GRP78, CHOP, and caspase-12 were generally increased compared to those in the control. Phosphorylated Akt and phosphorylated GSK3ß were upregulated in the beginning of muscle compression, and immediately significantly decreased at the initiation of ischemia-reperfusion injury in compressed muscles tissue. These data show that ER stress may be involved in the underlying mechanisms of cell degeneration after pressure ulcers and that the Akt/GSK3ß signal pathway may play an important role in deep tissue injury induced by pressure and ischemia/reperfusion.

Differential diagnosis of suspected deep tissue injury.

Deep tissue injury (DTI) can be difficult to diagnose because many other skin and wound problems can appear as purple skin or rapidly appearing eschar. The diagnosis of DTI begins with a thorough history to account for times of exposure to pressure, such as 'time down' at the scene or time during which the patient was flat and could not respond. Patients with light skin tones present with classic skin discolouration of purple or maroon tissue, a defined border around the area of injury, and often surrounding erythema is evident. Persistent erythema and hyperpigmentation, rather than blanching, should be used to determine pressure injury in dark skin tone patients. Differential diagnosis includes stage 2 pressure ulcers, incontinence-associated dermatitis, skin tears, bruising, haematoma, venous engorgement, arterial insufficiency, necrotising fasciitis and terminal skin ulcers. Many skin problems can also have a purple hue or rapidly developing eschar, and a working knowledge of dermatology is needed.

The aetiology of deep tissue injury: a literature review.

Deep tissue injury affects patients of all ages in a variety of healthcare settings. It is therefore essential that nurses are aware of the underlying pathogenesis, in order to accurately assess the pressure ulcer risk of vulnerable patients, and to subsequently reduce patient harm. The majority of pressure ulcers are avoidable, however, a variety of intrinsic and extrinsic factors can contribute towards the development of deep tissue injury. Understanding the body's internal responses to external pressure will enable nurses to recognise that a visual assessment alone may not necessarily identify patients at risk of deep tissue damage. This article reviews the evidence for the internal causative mechanisms of deep tissue injury, while linking to clinical practice and pressure ulcer prevention.

Bodily pain intensity in nursing home residents with pressure ulcers: analysis of national minimum data set 3.0.

Clinical reports suggest that superficial pressure ulcers produce pain, but that pain decreases as the wound advances in stage. This study of the relationship between pressure ulcer stage and bodily pain intensity in nursing home residents was a secondary analysis of the national Minimum Data Set 3.0 assessment data in long-term care facilities, collected from nursing home residents at least 65 years of age. Data were examined from residents with pressure ulcers who completed a bodily pain intensity interview between January and March 2012 (N = 41,680) as part of the MDS comprehensive assessment. After adjusting for other variables (e.g., cognition, functional impairment, presence of comorbidities, use of scheduled pain medication, and sociodemographic variables), bodily pain intensity for those with more severe pressure ulcers in comparison to those with Stage I ulcers was higher by 11% (Stage II), 14% (Stage III), 24% (Stage IV), and 22% (suspected deep tissue injury). Because multivariate analysis showed that greater bodily pain intensity was associated with an advanced stage of pressure ulcer, health care providers should assess bodily pain intensity and order appropriate pain management for nursing home residents with pressure ulcers, particularly for those with advanced pressure ulcers who are vulnerable to greater bodily pain intensity.

The biomechanical efficacy of dressings in preventing heel ulcers.

The heels are the most common site for facility-acquired pressure ulcers (PUs), and are also the most susceptible location for deep tissue injuries. The use of multilayer prophylactic dressings to prevent heel PUs is a relatively new prevention concept, generally aimed at minimizing the risk for heel ulcers (HUs) through mechanical cushioning and reduction of friction at the dressing-support interface. We used 9 finite element model variants of the posterior heel in order to evaluate the biomechanical performance of a multilayer dressing in prevention of HUs during supine lying. We compared volumetric exposures of the loaded soft tissues to effective and maximal shear strains, as well as peak stresses in the Achilles tendon, without any dressing and with a single-layer or a multilayer dressing (Mepilex(®) Border Heel-type), on supports with different stiffnesses. The use of the multilayer dressing consistently and considerably reduced soft tissue exposures to elevated strains at the posterior heel, on all of the tested support surfaces and when loaded with either pure compression or combined compression and shear. The aforementioned multilayer design showed (i) clear benefit over a single-layer dressing in terms of dissipating tissue strains, by promoting internal shear in the dressing which diverts loads from tissues; (ii) a protective effect that was consistent on supports with different stiffnesses. Recent randomized controlled trials confirmed the efficacy of the simulated multilayer dressing, and so, taken together with this modeling work, the use of a prophylactic multilayer dressing indicates a great promise in taking this route for prevention.

Establishment of a novel rat model for deep tissue injury deterioration.

Deep tissue injuries (DTIs) can become significant problems because of their rapid deterioration into deep pressure ulcers. Presently, no animal model of DTI deterioration has been developed. By concentrating pressure and shear stress in deep tissues while minimising pressure and shear stress in the overlying skin, we produced an effective rat model of DTI deterioration. Two-dimensional finite element method (FEM) simulated the distribution of pressure and shear stress under several pressure-loading conditions. FEM showed that concentrated shear stress in deep tissue with minimum shear stress in the overlying skin could be created by using a prominence and a cushion, respectively. On the basis of the results of FEM analysis, we selected suitable conditions for testing the rat DTI deterioration model. The compressed area was macroscopically observed until day 13, and histopathologic analysis via haematoxylin and eosin (H&E) staining was performed on days 3, 7 and 13. H&E staining showed that the distribution of tissue damage was similar to the predicted FEM results. Deep ulceration and tissue damage extending from deep tissues to the overlying skin and surrounding tissues were observed in the DTI deterioration model, which are similar to the clinical manifestations of DTI deterioration. In conclusion, a representative DTI deterioration model was established by concentrating high shear stress in deep tissues while minimising shear stress in the overlying skin. This model will allow a better understanding of the mechanisms behind DTI deterioration and the development of preventative strategies.

Combination of thermographic and ultrasonographic assessments for early detection of deep tissue injury.

Early detection and intervention of deep tissue injury are important to lead good outcome. Although the efficiency of ultrasonographic assessment of deep tissue injury has been reported previously, it requires a certain level of skill for accurate assessment. In this study, we present an investigation of the combination of thermographic and ultrasonographic assessments for early detection of deep tissue injury. We retrospectively reviewed 28 early-stage pressure ulcers (21 patients) presenting at the University of Tokyo Hospital between April 2009 and February 2010, surveying the associated thermographic and ultrasonographic findings. The wound temperature patterns were divided into low, even and high compared with the surrounding skin. Ultrasonographic findings were classified into unclear layer structure, hypoechoic lesion, discontinuous fascia and heterogeneous hypoechoic area. All 13 ulcers that were associated with low temperature showed good outcome; three ulcers had even temperatures and 12 ulcers showed high temperature on thermographic assessment. The two deep tissue injuries were rated high on thermographic assessment and showed heterogeneous hypoechoic area findings on ultrasonographic assessment. No non-deep tissue injury lesion was associated with these two findings simultaneously. The combination of thermographic and ultrasonographic assessments is expected to increase the accuracy of the early detection of deep tissue injuries.

In vivo strain measurements in the human buttock during sitting using MR-based digital volume correlation.

Advancements in systems for prevention and management of pressure ulcers require a more detailed understanding of the complex response of soft tissues to compressive loads. This study aimed at quantifying the progressive deformation of the buttock based on 3D measurements of soft tissue displacements from MR scans of 10 healthy subjects in a semi-recumbent position. Measurements were obtained using digital volume correlation (DVC) and released as a public dataset. A first parametric optimisation of the global registration step aimed at aligning skeletal elements showed acceptable values of Dice coefficient (around 80%). A second parametric optimisation on the deformable registration method showed errors of 0.99mm and 1.78mm against two simulated fields with magnitude 7.30±3.15mm and 19.37±9.58mm, respectively, generated with a finite element model of the buttock under sitting loads. Measurements allowed the quantification of the slide of the gluteus maximus away from the ischial tuberosity (IT, average 13.74 mm) that was only qualitatively identified in the literature, highlighting the importance of the ischial bursa in allowing sliding. Spatial evolution of the maximus shear strain on a path from the IT to the seating interface showed a peak of compression in the fat, close to the interface with the muscle. Obtained peak values were above the proposed damage threshold in the literature. Results in the study showed the complexity of the deformation of the soft tissues in the buttock and the need for further investigations aimed at isolating factors such as tissue geometry, duration and extent of load, sitting posture and tissue properties.