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Off-loading or the Orthotic approach to wheelchair seating has been used successfully to provide seating that optimizes tissue protection at the ischial tuberosities (ITs), sacrum and greater trochanters. Recent publications indicate the significance of preventing tissue compression to reduce ulcer formation. Comparative Magnetic Resonance Imaging (MRI) of individuals seated on two cushion types provides direct evidence of tissue unloading resulting in the reduction in tissue compression. Measurement of tissue compression in MRI images provides the cumulative impact of compression and shear resulting in ultimate tissue thickness documented here. In this study's application of MRI to off-loading cushions (OLC), an alternate form of tissue protection was observed. Instead of incorporating immersion and envelopment, loads were transferred from high-risk areas, such as bony prominences, to lower risk soft tissues. This method shows both shearing and compression of load bearing tissues in seated individuals with the OLC in place. Tissue thickness measurements determined by MRI analysis indicate that the OLC provides greater reduction in tissue deformation than the air cell cushion (ACC). Deformation of tissues loaded by the OLC is not significantly different from the deformations seen with the ACC. This research represents the first reported use of MRI to document the comparative off-loading capabilities of two cushions and the resultant tissue compression and ulceration risk. While MRI analysis may not be incorporated in daily cushion prescription, this paper proposes a methodology in which MRI analysis of tissue deformation on comparative cushions allows the determination of best-case cushion selection for reduction of ischial pressure ulcer (PU) risk.

We examined the effects of 4 different wheelchair seatings on physiological and perceptual measures in 21 healthy, pre-pubertal children (9 ± 2 years). Participants were able-bodied and did not regularly use a wheelchair. Participants sat for 2 h in Neutral (∼22.5 °C, ∼40%RH) and Hot (∼35 °C, ∼37%RH) conditions. Four seating technologies were: standard incontinent cover and cushion (SEAT1); standard incontinent cover with new cushion (SEAT2) were tested in Neutral and Hot; new non-incontinent cover with new cushion (SEAT3); new incontinent cover and new cushion (SEAT4) were tested in Neutral only. Measurements included skin blood flow (SkBF), sweating rate (SR) and leg skin temperature (TlegB) on the bottom of the leg (i.e. skin-seat interface), heart rate (HR), mean skin temperature, tympanic temperature, thermal comfort, and thermal sensation. During Neutral, SkBF and TlegB were lower (∼50% and ∼1 °C, respectively) and SR higher (∼0.5 mg cm−2·min−1) (p 0.05). During Hot, HR and temperatures were higher than in Neutral but there were no differences (p > 0.05) between SEATs. New cover and cushion improved thermoregulatory responses during Neutral but not Hot. An impermeable incontinent cover negated improvements from cushion design. Seat cover appears more important than seat cushion during typical room conditions.

Aim To establish a research approach for describing how different wheelchair cushion designs impact buttocks tissue deformation during sitting. Materials and methods The buttocks of 4 individuals with spinal cord injury and significant atrophy were scanned sitting in a FONAR Upright MRI. Scans were collected with the individuals' buttocks fully suspended without pelvic support, and seated on 3 different commercially available wheelchair cushions. Multi-planar scans were analyzed to provide 3D renderings and measurements of tissue thickness and shape. Results Bulk tissue thicknesses at the ischium, which rarely included muscle, were reduced by more than 60% on enveloping cushion designs studied (i.e., Roho HP and Matrx Vi), and more variably (23–60%) on an orthotic off-loading design (i.e., Java). Adipose was typically displaced posterior and superior from the unloaded condition, with more lateral displacement on the Roho HP and Matrx Vi and more medial displacement present on the Java. Large changes in angle at the sacro-coccygeal joint indicated significant loading on the region. Deformation at the greater trochanter was more consistent across surfaces. Greater interface pressures tended to be associated with greater deformation, but the relationship varied by individuals and was highly non-linear. Conclusions The buttocks in this study all deformed significantly, but at different locations and in different manners across all 3 surfaces. Attention needs to be paid to the regions of greatest deformation. A future metric of shape compliance should consider cushion performance at all high risk regions, and changes to the amount and shape of tissue in the regions of interest.

Pressure ulcers are hazardous to people with diminished sensory and motor functions who remain in the same position for a long time. An important reason for the occurrence of pressure ulcers is the inability of wheelchair users to make postural changes by themselves with no appropriate method of pressure release. In this study, we researched the effects of applying an air cell inflate-deflate alternating sequence cushion prototype to relieve pressure from tissue loaded areas. Moreover, the hypothesis that the alternating sequence could stimulate blood reperfusion in loaded tissues and redistribute interface pressure on support area was also tested. Ten healthy volunteers were recruited to try the prototype cushion for 65 min of continuous loading; 5 min on static mode and 60 min on alternating mode. This study was conducted on healthy people because their sensitivity allowed them to state clearly and in detail, in a feedback questionnaire, any discomfort experienced with the use of our cushion. In order to address our hypothesis, interface pressure, and bilateral ischial oxygenated and deoxygenated hemoglobin were measured. After applying the alternating cushion, the interface pressure was redistributed over a larger contact area. Besides, blood perfusion was improved according to increments in oxygenated hemoglobin and decrements in deoxygenated hemoglobin of ischial regions during loaded condition. Feedback questionnaire showed that the participants did not feel pain or discomfort using the alternating cushion. The overall results showed positive effects on healthy tissue which has encouraged us to design a study involving subjects who use wheelchairs for mobility.

AIM OF THE STUDY Tissue deformation is recognized as an important risk factor for pressure injuries. This study investigated the effects of anatomy and wheelchair cushion type on tissue deformation. MATERIALS AND METHODS Direct 3-dimensional tissue deformation response was measured for six participants sitting on six different wheelchair cushions using MR imaging. Two participants had a traumatic spinal cord injury (SCI) within one year of the assessment, two sustained traumatic SCI at least 13 years prior, and two were without SCI. Tissue deformation was quantified using the difference in volume of tissue beneath the ischial tuberosity (IT) between unloaded and loaded (sitting) conditions. RESULTS The participants with SCI tended to have less muscle tissue volume beneath their ITs while sitting compared to participants without SCI. Reductions in muscle and fat volumes in the loaded conditions varied depending on both cushion and participant. Higher interface pressures tended to be associated with lower unloaded tissue thicknesses. CONCLUSION The study showed no single cushion type tested produced the lowest amount of tissue deformation across all participants. Individual anatomy and cushion type affect deformation response of tissue and related pressure injury risk.

Aim of the study The aim of this study was to describe an individual's 3-dimensional buttocks response to sitting. Within that exploration, we specifically considered tissue (i.e., fat and muscle) deformations, including tissue displacements that have not been identified by research published to date. Materials and methods The buttocks anatomy of an able-bodied female during sitting was collected in a FONAR Upright MRI. T1-weighted Fast Spin Echo scans were collected with the individual seated on a custom wheelchair cushion with a cutout beneath the pelvis ("unloaded"), and seated on a 3″ foam cushion ("loaded"). 2D slices of the MRI were analyzed, and bone and muscle were segmented to permit 3D rendering and analyses. Results MRIs indicated a marked decrease in muscle thickness under the ischial tuberosity during loaded sitting. This change in thickness resulted from a combination of muscle displacement and distortion. The gluteus and hamstrings overlapped beneath the pelvis in an unloaded condition, enveloping the ischial tuberosity. But the overlap was removed under load. The hamstrings moved anteriorly, while the gluteus moved posterior-laterally. Under load, neither muscle was directly beneath the apex of the ischial tuberosity. Furthermore, there was a change in muscle shape, particularly posterior to the peak of the ischial tuberosity. Conclusion The complex deformation of buttocks tissue seen in this case study may help explain the inconsistent results reported in finite element models. 3D imaging of the seated buttocks provides a unique opportunity to study the actual buttocks response to sitting.

Study aim Pressure ulcers (PU) are a common comorbidity among wheelchair users. An appropriate wheelchair cushion is essential to relieve pressure and reduce PU development during sitting. The microenvironment, specifically excessive heat and moisture, impacts risk for PU development. An effective wheelchair cushion should maintain a healthy microenvironment at the seating interface. Measurement of heat and moisture can characterize microenvironmental conditions at the wheelchair cushion interface under load. We describe the development of a Sitting MicroEnvironment Simulator (SMES) for the reliable assessment of wheelchair cushion microenvironments. Materials The prototype SMES was developed for use mounted on a Materials Testing Systems (MTS) 810 ® uniaxial servo-hydraulic loading rig and used to assess microenvironmental conditions for Jay Medical Jay 2 ® , Roho High Profile Dry Floatation ® and Low Profile Dry Floatation ® cushions and a novel modular gel cushion. Methods Each cushion was assessed for two hours in triplicate. The SMES was used to load the cushions to 300N ± 10N, with an interface surface temperature of 37 °C±1 °C and fluid delivery of 13 mL/h±1 mL/h of water. Interface temperature and humidity were measured at the left ischial tuberosity (IT) region every five minutes. Results Heat and moisture responses were similar for the three commercial cushions. The modular gel cushion stayed cooler for at least 15 min longer than any commercial cushion. Conclusions The SMES maintained performance to technical specifications for over one hundred hours of total testing and is a reliable tool for characterizing the microenvironmental conditions of wheelchair cushions.

The paper describes a clinical controlled trial of an armchair with integral pressure-reducing cushion, which took place on two elderly acute medical wards in a district general hospital. The aim of the study was to evaluate whether the armchair would have an impact on reducing the occurrence of pressure sores. All patients were provided with a mattress or overlay in accordance with the hospital policy on mattress provision following a Waterlow risk assessment. Patients on ward A were provided with an armchair with integral pressure-reducing cushion, whilst patients on ward B continued to use their existing bedside armchair. Nominal data were collected on all pressure sores in patients who were not bedridden. Ward A had a significantly lower incidence of hospital-acquired pressure sores compared to ward B, and non-hospital-acquired pressure sores on this ward showed more improvement than those on ward B.

A sitting-acquired pressure ulcer (PU) is a common injury in wheelchair-bound patients. Preventative measures for the post spinal cord injury (SCI) population include prescription of a supportive thick cushion on the wheelchair, in order to better distribute loads between the buttocks and support surface (which are quantifiable using interface pressure measurements), and potentially, to minimize internal soft tissue loads (which are typically unknown). Information about the biomechanical efficacy of commercially-available structured cushion designs such as air-cell-based (ACB) cushions, gel, and honeycomb-like cushions is sparse. Considering the importance of such evaluations to patient safety and quality of life, we studied the biomechanical performances of an ACB cushion in comparison to standard, flat foam cushions with different stiffness properties. Using a set of finite element (FE) model variants, we determined the mechanical stresses in muscle, fat, and skin tissues under the ischial tuberosities during sitting. Tissue stress analyses were conducted in a reference SCI anatomy, incorporating pathoanatomical and pathophysiological changes associated with chronic SCI, including bone shape adaptation, muscle atrophy, and spasms. We found up to 57% greater immersion and 4 orders-of-magnitude lower muscle, fat, and skin tissue stresses for the ACB cushion. We also found the ACB cushion provides better protection against the aforementioned bone shape adaptation, muscle atrophy, and spasms. Hence, theoretically, the use of a suitable ACB cushion should provide longer safe sitting times for SCI patients with respect to standard foam cushions.

Introduction There are many static pressure-reducing cushions commercially available consisting of foams, gels, air or a combination of these. There is, however, little evidence available on their effectiveness to guide prescription. In practice, comfort tends to be a major factor in determining whether a pressure-reducing cushion will continue to be used, although it is unclear as to what determines comfort. The aim of this study was to assess if perceptions of comfort could be associated with the measurable parameters of interface pressure and temperature. This pilot study was undertaken in the community with individuals who were totally reliant upon a wheelchair for their mobility who each used a series of four different cushions for up to 7 days. Method The temperature and humidity characteristics of four commercially available pressure-reducing cushions of differing mediums were measured using data loggers for a continuous period of up to 7 days. Snap-shot interface pressure measurements were taken and perceptions of comfort were obtained via specifically designed questionnaires. Results The cushions that wheelchair users found to be the most comfortable for them were not necessarily those, which provided them with the lowest interface pressures. If a cushion was discontinued by the wheelchair user, it was invariably a "softer" medium. Wheelchair users tended to acknowledge discomfort only after 2 days continuous use. Conclusion There are potential implications for clinical practice with respect to how cushions are issued to wheelchair-reliant individuals. Findings support the undertaking of a larger study.

The purpose of this study is to quantify hammock effects over artificial bony prominence using a newly developed buttocks model similar to human buttocks, and examine differences between various cushions and covers. A repeated measures design was used where immersions were measured with diverse weights on each type of cushion with or without covers. Polyurethane foam and air-cell cushions were used. Elastic original covers (cover 1) were evaluated for each cushion, and another less elastic cover (cover 2) was also used for the foam cushion. "Immersion" was defined as the difference in gauge readings between no load and each loading phase. Hammock effect was estimated by calculating the difference in load with and without a cover at any immersion from the approximate regression equation on immersion. All intraclass correlations were more than 0.99. The absolute hammock effect for each cover for each cushion increased as the immersion deepened. For the air-cell cushion, the relative hammock effect also increased and was higher than that for foam cushion at deeper immersion. For the foam cushion, the relative hammock effect on the cushion with cover 2 (160.5–188.6%) was higher than that with cover 1 (107.3–123.7%) at any immersion. The hammock effect could be quantified by the validated and reliable model. The mechanical property of the covers, the pressure redistributing property of the cushions and the length of bony prominence all influenced the intensity of the hammock effect.

mattresses and cushions then used to assist the healing of established sores. Few varieties of pressure-redistributing surfaces for use in bed were encountered, with the most common support surface being the large cell ripple mattress (49% of all mattress and bed use). Whereas patients with established sores were seated on 30 different special cushions, many (n=24) of which were rarely encountered, being used with fewer than 9 patients. Clark and Crow 2 also noted the wide range of cushions available for use in hospital, again many were rare, with often only one of any particular type of cushion available. Why are such a variety of special cushions used? - particularly when one considers that special mattress and bed use has become more focused upon a narrow range of products 3 • One potential reason for the diversity of cushions used within the NHS is the current lack of clear evidence that these products are effective. Even when indirect evidence of effectiveness, such as interface pressure measurements are considered, the available data does not greatly assist care providers to make considered judgments of the relative merits of different products. Souther et al 4 having measured interface pressures beneath the right ischial tuberosity of subjects sitting upon a variety of cushions concluded that 'No cushion evaluated reduced mean pressure below mean capillary pressure' and that 'this goal may not be attainable'. Hibbs 5 made recommendations for the widespread use of an air-filled cushion, the ROHO (Raymar, Hodgkinson & Corby Ltd). Even this product applies relatively high pressures to the ischial tuberosities; for example among tetraplegic subjects, an average interface pressure beneath the ischial tuberosities of71.5 mmHg has been recorded 6 • Given the uncertain effectiveness of cushions that are currently available, Bliss 7

While the wound is healing, the mosteffective way of preventing infections and pain is to avoid sitting. However, this is a virtual impossibility fora new mother to achieve for the five or six days when discomfort is at its greatest. Therefore the relief of perineal pain following childbirth is a long established problem in midwifery practice, with the most usual solution being the provision of pressure relieving cushions4. The majority of these have been based on the 'ring' concept in which the hole is placed under the perineum.

METHODS AND MATERIALS B.A.S.E. The methods and materials for this trial were exactly the same Average Maximum Minimum as those adopted in the comparison of the Nimbus and Pegasus Sacrum 32.4 51.1 17.9 11.1 20.8 13.1 Airwave mattresses published in April 1992 edition of this Trochanter 58.7 79.4 36.4 J oumal. Those requiring further details of the method employed 19.5 27.7 8.1 should refer to that article. The only differences are that this Ischium 49.5 trial was funded by Talley Ltd., whereas the previous trial was 64.7 37.6 10.3 14.7 11 funded by Huntleigh Technology and the trial published in the QUA TIRO July edition was funded by Pegasus. This serves to emphasise that the authors of this article are independent and are only Average Maximum Minimum concerned with the performance of the products, not with Sacrum 27.1 47.7 9 9.2 8.7 10 promoting the products of any individual companies. Trochanter 50.7 81.2 25.5* 14.8 33.7 14.5 RESULTS The data was analysed in two ways Ischium 42.5** 56.4* 28.3** 14 17.6 13.6