Wheelchair cushions for persons with spinal cord injury: an update

Stiffening of the gluteal muscle increased the intramuscular stress: An in-silico implication of deep tissue injury

Objectives

Deep tissue injury is a common form of pressure ulcers in muscle tissues under bony prominences caused by sustained pressure or shear, which has a great impact on patients with restricted mobility such as spinal cord injury. Frequent spasms in spinal cord injury patients featured by muscle stiffening may be one of the factors leading to deep tissue injury. The purpose of this study was to investigate the relationship between the gluteal muscle shear modulus and intramuscular compressive/shear stress/strain.

Methods

A semi-3D finite element model of the human buttock was established using COMSOL software and the acquired biomechanical data were analyzed through Pearson correlation and Spearman correlation.

Results

Results showed that the compressive stress, strain energy density, and average von Mises stress increased with the increase of the gluteal muscle shear modulus.

Conclusion

These results may indicate muscle stiffening caused by muscle spasms could lead to higher deep tissue injury development risk as well as shed light on effective treatments for relieving muscular sclerosis mechanically.

Evaluation of pelvis postural systems in spinal cord injury patients: Outcome research

OBJECTIVES

Compare three commercially available postural systems to determine the best for treatment of patients suffering from spinal cord injury lesion below the cervical spine.

DESIGN

Outcome Research.

SETTING

Ambulatory.

PARTICIPANTS

Thirteen patients were recruited for this study between March 2016 and July 2016 from the Occupational Therapy clinic of "Policlinico Umberto I" hospital in Rome and Occupational Therapy of "CPO" hospital in Ostia. The patient samples consisted of eleven men (84.6%) and two women (15.4%). All the patient are suffering by SCI with a lesion below the cervical spine.

INTERVENTION

We evaluate postural systems customized by three different companies. Patients tried each pelvis device for a duration of one week, after which they have been asked to fill in questionnaire concerning static stability, temperature, movement adaptability, transfers and dynamical stability during the activities of every-day life. The impact on the health status has been evaluated by means of a further questionnaire (Health Status Scale SF-12) submitted to the patients.

OUTCOME MEASURES

Quality of life and daily life activities.

RESULTS

The analysis of the data from the questionnaire, along with those of objective nature associated with the mapping of the pressure due to weight distribution, has allowed the selection of the most appropriate clinical solution.

CONCLUSION

This study has allowed two significant conclusions: the central role of the interplay between the patient and occupational therapist in the decision role and the clear evidence that patients with spinal cord injury felt definite differences between cushion stability and were able to indicate a specific typology providing the best satisfaction.

The Prepared Mind

Every day, in clinics and hospitals around the world, occupational therapists care for patients with serious problems requiring viable solutions. Each patient is unique, and his or her problem does not necessarily correspond to existing practice models. Practitioners must adapt standard approaches to provide effective outcomes, yet problems exist for which few or no beneficial approaches have been identified. Such clinical issues require solutions to be generated de novo from the practitioner's body of knowledge and past experience. Yet, no single new intervention can be used without prior validation of its efficacy. Only a therapist with a prepared mind can accept such challenges, recognize what is known and not yet known, design studies to acquire that needed knowledge, and translate it into successful clinical treatment strategies. The occupational therapist with a prepared mind is one willing to seize unexpected opportunities and construct new paradigms of practice. Innovation through scientific inquiry requires a prepared mind.

Comparing Wheelchair Cushions for Effectiveness of Pressure Relief: A Pilot Study

The purpose of this study was to determine if there were differences in pressure relieving abilities among six commonly prescribed wheelchair cushions and whether differences were related to the participant's body mass. In addition, the participant's perception of cushion comfort was investigated. A convenience sample of 40 adult wheelchair users were recruited from a rehabilitation hospital. Participants sat on the following six cushions for 5 minute periods: Flexseat, Jay 2, Pindot, ROHO High, ROHO Low, and Stimulite. Pressure measurements were recorded with the Xsensor Pressure Mapping System, a new instrument available to therapists. It was discovered that ROHO High and ROHO Low cushions were more effective in relieving pressure than the other cushions. Cushion pressure relieving abilities were largely dependent on the individual's body mass. ROHO cushions were also perceived to be more comfortable than all other cushions tested regardless of body mass and pressure relief.

Effects of conventional and alternating cushion weight-shifting in persons with spinal cord injury

A repeated-measures study of 13 adult full-time wheelchair users with spinal cord injury (SCI) was carried out to determine whether alternating-pressure air cushion (APAC) use compared with independent pressure relief (IPR) provides reliable, effective pressure relief for individuals with SCI. Bilateral mean ischial interface pressure (IP), transcutaneous oxygen tension (TcPO2), and unilateral laser Doppler blood flow were evaluated. Blood flow component contributions were determined using short-time Fourier transform (STFT)-based spectral analysis. IPR assessment was carried out at recruitment. Study participants then used an APAC for 2 wk every 3 mo for 18 mo. IPR weight-shifting decreased mean ischial IP (p < 0.05) and increased mean TcPO2 (p < 0.05). All variables rapidly returned to preintervention levels following weight-shifting except for the cardiac component of blood flow. APAC-induced weight-shifting decreased mean ischial IP (p < 0.05). Mean TcPO2 increased and was higher than for IPR. STFT analysis indicated that quiet sitting following APAC-induced weight-shifting produced a higher neurogenic component of blood flow than following IPR (p = 0.02). Thus, IPR positively affects multiple aspects of tissue health but produces transient improvements and must be repeated regularly. APAC activation dynamically and continuously alters IP distribution with more sustained positive tissue health effects.

Utilization and user satisfaction with alternating pressure air cushions: a pilot study of at-risk individuals with spinal cord injury

PURPOSE

An appropriate wheelchair cushion is integral to pressure ulcer (PU) prevention for the wheelchair user with SCI. For users who find it difficult to remember or perform weight shifts, an alternating pressure air cushion (APAC) may off-load pressure to minimize PU risk. APACs are considered mobility assistive technology (AT). Effective AT delivery includes consideration of the AT consumer as a unique individual. The Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST) is a structured and standardized method to measure user satisfaction with AT.

METHOD

Twelve full time wheelchair users with SCI were provided with an APAC six times for 2 weeks daily home use every 3 months. At the completion of the 18-month study period, the 8-variable QUEST 2.0b questionnaire was applied to evaluate satisfaction with APAC use.

RESULTS

Users were generally quite satisfied with APAC weight (p < 0.01 relative to neutral). Durability was more likely to be an area of concern. Overall, 92% of participants considered themselves quite satisfied or very satisfied with APAC use (p < 0.001).

CONCLUSIONS

Users with SCI were satisfied with the overall performance of the APAC tested after repeated periods of use. The majority of user's were very satisfied with APAC comfort overall. Implications for Rehabilitation Abandonment of AT may be reduced if user satisfaction is evaluated. The QUEST 2.0b is a useful and valid measure of user satisfaction with alternating pressure air cushions. In the current study cohort, users with SCI were satisfied with the performance and comfort of the APAC tested after repeated periods of use.

mobilityRERC state of the science: How science influences public policy in seating and mobility

In the United States (US), wheeled mobility and seating equipment is classified as Durable Medical Equipment (DME). DME includes a wide array of devices including canes, walkers, home oxygen equipment, hospital beds, and wheelchairs. Seating and mobility devices reflect a wide range of DME, from relatively simple standard manual wheelchairs and cushions to highly complex manual and power wheelchairs and custom seating systems. This wide range of complexity results in a wide range of policies that govern the provision of seating and mobility equipment. This article results from a presentation during the Wheeled Mobility Rehabilitation Engineering Research Center's (RERC's) State of the Science Conference in 2012. The presentation was designed to proffer key concepts related to coverage policies and policy decision-making. Topics covered include an introduction to key policy issues impacting seating and mobility equipment, a description of the barriers that prevent or hinder research being used to inform coverage policy decisions, discussion of the challenges surrounding evidence-based policy decisions regarding seating and mobility, and suggestions of strategies for including policy makers and other stakeholders in setting research priorities and in reporting research findings.

IMPLICATIONS FOR REHABILITATION

In the United States, wheeled mobility and seating equipment are classified as Durable Medical Equipments which are governed by a wide range of policies. Researchers should be encouraged to supplement research articles with articles that explicitly address clinical and policy implications of the work. Policy-makers should be encouraged to engage researchers to insure the breadth of knowledge and evidence is represented and understood.

Distribution of internal pressure around bony prominences: implications to deep tissue injury and effectiveness of intermittent electrical stimulation

The overall goal of this project is to develop interventions for the prevention of deep tissue injury (DTI), a form of pressure ulcers that originates in deep tissue around bony prominences. The present study focused on: (1) obtaining detailed measures of the distribution of pressure experienced by tissue around the ischial tuberosities, and (2) investigating the effectiveness of intermittent electrical stimulation (IES), a novel strategy for the prevention of DTI, in alleviating pressure in regions at risk of breakdown due to sustained loading. The experiments were conducted in adult pigs. Five animals had intact spinal cords and healthy muscles and one had a spinal cord injury that led to substantial muscle atrophy at the time of the experiment. A force-controlled servomotor was used to load the region of the buttocks to levels corresponding to 25%, 50% or 75% of each animal's body weight. A pressure transducer embedded in a catheter was advanced into the tissue to measure pressure along a three dimensional grid around the ischial tuberosity of one hind leg. For all levels of external loading in intact animals, average peak internal pressure was 2.01 ± 0.08 times larger than the maximal interfacial pressure measured at the level of the skin. In the animal with spinal cord injury, similar absolute values of internal pressure as that in intact animals were recorded, but the substantial muscle atrophy produced larger maximal interfacial pressures. Average peak internal pressure in this animal was 1.43 ± 0.055 times larger than the maximal interfacial pressure. Peak internal pressure was localized within a ±2 cm region medio-laterally and dorso-ventrally from the bone in intact animals and ±1 cm in the animal with spinal cord injury. IES significantly redistributed internal pressure, shifting the peak values away from the bone in spinally intact and injured animals. These findings provide critical information regarding the relationship between internal and interfacial pressure around the ischial tuberosities during loading levels equivalent to those experienced while sitting. The information could guide future computer models investigating the etiology of DTI, as well as inform the design and prescription of seating cushions for people with reduced mobility. The findings also suggest that IES may be an effective strategy for the prevention of DTI.

Comparison of the pressure redistribution qualities of two air-filled wheelchair cushions for people with spinal cord injuries

BACKGROUND/AIM

People with spinal cord injuries are at high risk of developing pressure ulcers. Wheelchair cushions that redistribute pressure are one prevention strategy to reduce the risk of pressure ulcers in this population. Currently, therapists have only limited evidence concerning the pressure redistribution qualities of wheelchair cushions to guide their cushion selection in clinical practice. The aim of this study was to compare the pressure redistribution qualities of two air-filled cushions currently recommended for people with spinal cord injuries.

METHODS

A series of single case studies, based on the methodology used in a previous study, was undertaken on three inpatients with complete spinal cord injury. Interface pressure readings were compared between a Roho® and Vicair® cushion using the Xsensor® Pressure Mapping System. The Roho® cushion is comprised of a series of soft, flexible, inter-connected air cells, and the Vicair® cushion contains separate, sealed cells of air.

RESULTS

The Roho® cushion recorded significantly fewer cells with pressures ≥100 mmHg than the Vicair® cushion for the three participants.

CONCLUSION

This study has provided evidence that the Roho® cushion has superior pressure redistribution qualities than the Vicair® cushion for a small sample of patients with complete spinal cord injury.

Intermittent electrical stimulation redistributes pressure and promotes tissue oxygenation in loaded muscles of individuals with spinal cord injury

Deep tissue injury (DTI) is a severe form of pressure ulcer that originates at the bone-muscle interface. It results from mechanical damage and ischemic injury due to unrelieved pressure. Currently, there are no established clinical methods to detect the formation of DTI. Moreover, despite the many recommended methods for preventing pressure ulcers, none so far has significantly reduced the incidence of DTI. The goal of this study was to assess the effectiveness of a new electrical stimulation-based intervention, termed intermittent electrical stimulation (IES), in ameliorating the factors leading to DTI in individuals with compromised mobility and sensation. Specifically, we sought to determine whether IES-induced contractions in the gluteal muscles can 1) reduce pressure in tissue surrounding bony prominences susceptible to the development of DTI and 2) increase oxygenation in deep tissue. Experiments were conducted in individuals with spinal cord injury, and two paradigms of IES were utilized to induce contractions in the gluteus maximus muscles of the seated participants. Changes in surface pressure around the ischial tuberosities were assessed using a pressure-sensing mattress, and changes in deep tissue oxygenation were indirectly assessed using T₂*-weighted magnetic resonance imaging (MRI) techniques. Both IES paradigms significantly reduced pressure around the bony prominences in the buttocks by an average of 10-26% (P < 0.05). Furthermore, both IES paradigms induced significant increases in T₂* signal intensity (SI), indicating significant increases in tissue oxygenation, which were sustained for the duration of each 10-min trial (P < 0.05). Maximal increases in SI ranged from 2-3.3% (arbitrary units). Direct measurements of oxygenation in adult rats revealed that IES produces up to a 100% increase in tissue oxygenation. The results suggest that IES directly targets factors contributing to the development of DTI in people with reduced mobility and sensation and may therefore be an effective method for the prevention of deep pressure ulcers.

Prevention of pressure-induced deep tissue injury using intermittent electrical stimulation

Pressure ulcers develop due to morphological and biochemical changes triggered by the combined effects of mechanical deformation, ischemia, and reperfusion that occur during extended periods of immobility. The goal of this study was to test the effectiveness of a novel electrical stimulation technique in the prevention of deep tissue injury (DTI). We propose that contractions elicited by intermittent electrical stimulation (IES) in muscles subjected to constant pressure would induce periodic relief in internal pressure; additionally, each contraction would also restore blood flow to the tissue. The application of constant pressure to the quadriceps muscles of rats generated a DTI that affected 60 ± 15% of the compressed muscle as assessed by magnetic resonance imaging. In contrast, in the groups of rats that received IES at 10- and 5-min intervals, DTI of the muscle was limited to 16 ± 16 and 25 ± 13%, respectively. Injury to the muscle was corroborated by histology. In an experiment with a human volunteer, compression of the buttocks reduced the oxygenation level of the muscles by ∼4%; after IES, oxygenation levels increased by ∼6% beyond baseline. Concurrently, the surface pressure profiles of the loaded muscles were redistributed and the high-pressure points were reduced during each IES-induced contraction. The results of this study indicate that IES significantly reduces the amount of DTI by increasing the oxygen available to the tissue and by modifying the pressure profiles of the loaded muscles. This presents a promising technique for the prevention of pressure ulcers in immobilized and/or insensate individuals.

User satisfaction, community participation and quality of life among Chinese wheelchair users with spinal cord injury: a preliminary study

The purpose of the present study was to investigate the relationships between spinal cord injury (SCI), wheelchair users' satisfaction, perceptions of their community participation and quality of life (QoL).Thirty-one community wheelchair users with SCI were administered the Chinese version of the Quebec User Evaluation of Satisfaction with assistive Technology (C-QUEST), the abbreviated Hong Kong version of the World Health Organization Quality of Life Questionnaire (WHO QoL-BREF (HK)) and selected items of 'Participation Restrictions' and 'Environmental Factors' of the International Classification of Functioning Disability and Health (ICF). Only a weak correlation was found between the C-QUEST services sub-scores and one ICF environmental factor, that is, health-related professionals (Spearman's r = 0.453; p < 0.05). The C-QUEST device sub-scores were also weakly correlated with four domain scores of the WHO QoL-BREF (HK) (Spearman's r = 0.412-0.567; p < 0.05). Social relationship, participation in leisure and driving activities had a moderate association with scores of the WHO QoL-BREF (HK) (-0.405 > Spearman's r > -0.583; p < 0.05). It is concluded that community participation (e.g. use of transportation) and human environment (e.g. friends and peers) were more related to QoL, than to users' satisfaction with a wheelchair. Further research with a larger sample is recommended to examine the variables related to SCI and QoL.

Utilizing research in wheelchair and seating selection and configuration for children with injury/dysfunction of the spinal cord

OBJECTIVE

To determine how research regarding wheelchair and seating selection and configuration could be applied to the pediatric population with spinal cord injury (SCI) and dysfunction.

METHODS

Extensive literature reviews were completed on (a) powered mobility options and age-appropriateness for training; (b) manual wheelchair configuration, pushrim biomechanics, and propulsion ergonomics; and (c) cushion selection and use of pressure-mapping devices. The findings in the literature review then were compared with clinical observations from Shriners Hospitals for Children, Philadelphia's Seating and Wheelchair Clinic.

RESULTS/DISCUSSION

A significant amount of research is published on propulsion ergonomics and pushrim biomechanics in adults with SCI. However, this literature review noted that there was limited research available on cushion selection and power mobility configuration. Many of the conclusions drawn from these publications are applied to pediatric patients and used during the decision-making process of wheelchair and cushion selection. However, it is critical to tailor the assessment to the pediatric population to meet their medical and functional needs.

CONCLUSION

Although some of the findings can be correlated to the pediatric population, there is a lack of research on wheelchair and seating selection and configuration as it specifically relates to the young person with SCI and dysfunction. Future studies need to be completed.

Effect of seat cushion on dynamic stability in sitting during a reaching task in wheelchair users with paraplegia

OBJECTIVES

To examine the effects of seat cushions on dynamic stability in sitting during a controlled reaching task by wheelchair users with paraplegia.

DESIGN

A randomized, controlled test.

SETTING

Rehabilitation center.

PARTICIPANTS

Nine wheelchair users with paraplegia.

INTERVENTIONS

Three types of cushions--an air flotation, a generic contoured, and a flat polyurethane foam--were tested during a controlled reaching task in ipsilateral and contralateral directions, at 45 degrees from the sagittal plane in the anterolateral direction. Center of pressure (COP) coordinates were monitored by using a pressure measurement system as well as a force platform under seat.

MAIN OUTCOME MEASURES

Trajectory of COP, maximal distance covered by COP, maximal velocity of COP; and the index of asymmetry between right and left maximal pressure under ischial tuberosities.

RESULTS

The generic contoured cushion allowed the COP to cover significantly (p <.02) a larger distance (81 +/- 28mm) when compared with the air flotation (63 +/- 25mm) or the flat foam (61 +/- 29mm) cushions. The COP velocity was significant (p <.05) for the generic contoured cushion (.14 +/-.05m/s) versus the air flotation (.10 +/-.04m/s) or the flat-foam (.10 +/-.03m/s) cushions. The index of asymmetry was higher for the generic contoured and the flat foam cushions. During reaching, maximal pressure under ipsilateral ischial tuberosity was significantly higher for the flat foam (275 +/- 70mmHg) and the generic contoured (235 +/- 81mmHg) cushions, when compared with the air flotation cushion (143 +/- 51mmHg).

CONCLUSION

Seat cushions can significantly affect sitting balance during reaching tasks. This study provided an objective method to assess the dynamic stability of wheelchair users when they perform activities of daily living requiring reaching. These findings have implications for wheelchair seating recommendations, especially seat cushion selection.

Do pressure relief cushions really relieve pressure?

In a laboratory setting, interface pressures of 29 cushions and a sheepskin were measured on 20 healthy volunteers. Each participant was seated in an upright posture with their back against the back of the chair, hands resting on the lap, knees bent at an angle of 90 degrees, and feet resting on the floor. Only 13 cushions had any pressure-reducing effect. Gel cushions and sheepskins appear to have no pressure-reducing effect. The category of foam includes both cushions that reduce interface pressure very well and cushions that increase interface pressure. The lowest interface pressures were measured on air cushions and on some foam cushions.

Sitting posture and prevention of pressure ulcers

The aim of this study was to gain insight about the influence of body posture on the pressure at the seat surface and to establish to what extent different seat cushions designed for incontinent patients reduce maximum pressures. Pressures were measured for 56 healthy volunteers in eight postures using four cushions. The posture in which the lowest maximum pressure was measured was the sitting-back posture with the lower legs on a rest. If the seat could not be tilted back, the maximum pressure in the upright sitting posture with the feet on the ground was significantly lower than sitting upright with the legs supported on a rest. Sliding down and slouching caused the highest maximum pressure. Regular checking of the posture and using positioning cushions should form part of any pressure-ulcer prevention protocol. The four selected cushions each have different pressure-reducing effects. A thick air cushion (Repose) has the lowest maximum pressure and is significantly better than the other cushions at reducing the high pressure when slouching or sliding down.

A comparison of interface pressure readings to wheelchair cushions and positioning: a pilot study

Occupational therapists are often involved in assessing the seating needs of clients who have quadriplegia. One component of this process involves determining the appropriate use of wheelchair cushions and pressure relieving techniques in the prevention of pressure sores. The purpose of this study was to assess the effect of tilt and recline positioning and various wheelchair cushions on interface pressures at the ischial tuberosities and the sacrum of two subjects with C5 quadriplegia. In addition, interface pressures under bony prominences were assessed in the personal driving position (when the subject enters), neutral, 35 degree tilt, 45 degree tilt, and maximum recline (150 degrees). The results of this study indicate that for the two subjects evaluated, higher average interface pressures at the ischial tuberosities were obtained when using one of the three cushions under scrutiny. Furthermore, the general trend observed with both subjects is a reduction of pressure readings at the ischial tuberosities with tilt and recline positioning (especially with 45 degree tilt and 150 degree recline). The findings of this study are in keeping with previous studies which identified that individual and ongoing assessment is essential in providing the best cushion and pressure relief techniques for individuals.

Seating pressures with conventional and dynamic wheelchair cushions in tetraplegia

OBJECTIVE

To compare pressure relief from a dynamic wheelchair cushion to a tilt-in-space wheelchair with conventional cushions.

STUDY DESIGN

Repeated measures analysis.

SETTING AND SUBJECTS

Spinal cord injury unit; 16 tilt-in-space wheelchair users with motor-complete tetraplegia.

MAIN OUTCOME MEASURES

Interface pressure at ischial tuberosities.

RESULTS

Mean ischial pressure with subjects seated upright on the dynamic cushion during the low ischial pressure phase was lower than tilted pressure on the gel cushion, but it was not significantly different from tilted pressure on the dry-flotation cushion (dynamic/upright, 71 mm Hg; gel/tilted, 86 mm Hg; dry-flotation/tilted, 74 mm Hg; p<.05 dynamic vs. gel). Mean ischial pressure with subjects upright on the dynamic cushion during the high ischial pressure phase was significantly greater than the gel/upright and dry-flotation/upright conditions (dynamic/upright, 157 mm Hg; gel/upright, 128 mm Hg; dry-flotation/upright, 111 mm Hg; p<.001).

CONCLUSION

The dynamic cushion produces similar pressure relief over the ischial tuberosities during the low pressure phase to a tilt-in-space wheelchair and conventional cushions. The dynamic cushion may be an alternative to a tilt-in-space wheelchair for some individuals.

Seat interface pressures of individuals with paraplegia: influence of dynamic wheelchair locomotion compared with static seated measurements

OBJECTIVE

To provide a comparison of the seat interface pressures between static seating and dynamic seating during wheelchair locomotion of individuals with paraplegia.

DESIGN

Repeated measures multivariate analysis of variance (MANOVA) comparing two conditions: static seat and dynamic seat interface pressures.

SETTING

University campus and clinic.

PARTICIPANTS

Fifteen participants, each of whom propelled a manual wheelchair for at least 5 hours per week over the previous 6 months and functioned with a spinal cord injury/ disability level of T1 or below.

MAIN OUTCOME MEASURES

Peak pressure (PP) and pressure time integral (PTI) as measured by the Novel Pliance System, which consists of a flexible 32 x 32 capacitive sensor mat (each sensor 1.5 cm2) interfaced with a PC, was sampled at 10Hz. The participants were measured in their own wheelchair with a new Jay Active seat cushion.

RESULTS

The repeated measures MANOVA showed a difference in the PP and PTI between the static and dynamic measurements (Wilk's = .00, p < .05). Follow-up dependent t tests yielded a difference in PP (t = 5.40, p < 0.025) and no difference in the PTI between static and dynamic conditions (t = 1.45, p > 0.025). The PP during static seating (mean = 16.2 +/- 5.0 kPa [121 +/- 37.5 mmHg]) was less than during dynamic seat interface pressures during wheelchair locomotion (20.03 +/- 6.6 kPa [152.3 +/- 49.5 mmHg]). PP varied by up to 42% during the wheelchair locomotion cycle. The PTI was similar between static (30.1 +/- 9.3 kPa [225.75 +/- 69 mmHg]) and dynamic conditions (36.2 +/- 18.1 kPa [271 +/- 135.7 mmHg]).

CONCLUSIONS

The results from this study are consistent with some of the previous work on the nondisabled and a single case study, but with greater external validity because of the nature of the sample chosen and the methodology employed. PPs were greater during dynamic wheelchair locomotion compared with static seating interface pressures, with the peak varying up to 42% during the wheelchair locomotion cycle. The PTI indicates that the cumulative effect of the loading was comparable between conditions. The question that remains is whether this dynamic loading, resulting in a change in PP throughout the cycle, has a significant effect on tissue health.