Assessment of mechanical conditions in sub-dermal tissues during sitting: A combined experimental-MRI and finite element approach

Linder-Ganz, Eran; Shabshin, Nogah; Itzchak, Y; Gefen, Amit

doi:10.1016/j.jbiomech.2006.06.020

Cited by 278 publications

(262 citation statements)

References 47 publications

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“…Using a rat model, Linder-Ganz and Gefen [13] reported the compressive strain between 3 and 9% within the muscles beneath the ischial tuberosity, which was supported by our data of 6.9% (for the Normal sitting posture) within the muscle in the same area. However, in a later human subject study of Linder-Ganz et al [14], a substantially higher compressive strain (70-84%) was reported for the gluteus muscle, which deviated from our findings and their previous data on rats. It is thought that this difference may be due to the discrepancies between the material characteristics used in the models and the structural and geometrical features of the joints, bones and soft-tissues simulated.…”

Section: Discussioncontrasting

confidence: 99%

Evaluation of a new sitting concept designed for prevention of pressure ulcer on the buttock using finite element analysis

et al. 2007

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Excessive compressive load induces pressure related soft tissue damage, i.e. pressure ulcer (PU), in buttock area in wheelchair users. In solving this problem, our previous study has introduced a concept of Off-Loading sitting, which partially removes the ischial support to reduce pressure under buttocks. However, the effect of this sitting concept has only been evaluated using the interface pressure and tissue perfusion measurements. The objective of this investigation was to evaluate the Off-Loading posture for its ability to reduce internal pressure and stress in deep buttock tissues. This evaluation was performed on a 3D finite element (FE) model which was established and validated in a sitting posture and has realistic material properties and boundary conditions. FE analysis in this study confirmed that the pressure relief provided by Off-Loading posture created profound effect in reducing the mechanical stress within deep tissues. It was concluded that Off-Loading posture may prove beneficial in preventing sitting related PU.

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Section: Discussioncontrasting

confidence: 99%

Evaluation of a new sitting concept designed for prevention of pressure ulcer on the buttock using finite element analysis

et al. 2007

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“…As a last step of validation, we compared the peak internal muscle stress data obtained from each participating subject using the present method with their peak stress data obtained using our previously reported MRI-FE method [39]. Briefly, the MRI-FE is not a conventional FE theoretical analysis but rather a stress evaluation that approaches a direct measurement of the stress distributions in tissues in a noninvasive manner [39].…”

Section: Model Validation Studiesmentioning

confidence: 99%

“…A positive feedback mechanism was observed, in which the damaged area continues to expand under prolonged compression [14,38]. It is hypothesized that damage first occurs under the IT, where compression stress concentrations can be as high as 32 ± 9 kPa (mean ± standard deviation [SD]) according to a recent integrated magnetic resonance imaging (MRI) and FE study of sitting (nondisabled) subjects [39]. The wound then spreads with a snowball effect, as tissue undergoes structural and mechanical changes, and draws more stress to the injured area.…”

Section: Introductionmentioning

confidence: 99%

“…Other studies have adopted a much more accurate approach, estimating stresses in the muscles under the IT using FE and complex calculations, at the cost of immediacy and portability [4,36,39]. In particular, a new method for evaluating the individual's internal stress state in muscle and fat tissues of the buttocks that employs MRI measurements of internal tissue deformation coupled with FE analyses of resulting tissue stresses was recently introduced by our group [39]. Never before have the two approaches been fused together to monitor patient-specific internal muscle stresses in real-time while allowing patient mobility.…”

Section: Introductionmentioning

confidence: 99%

“…The goals of this study were therefore (1) to develop a patient-specific system for real-time evaluation of internal mechanical stresses in the gluteus muscle under the IT of wheelchair users, (2) to employ the system and determine differences between gluteal muscle stresses in individuals with paraplegia versus control subjects during sitting as well as explore whether these differences provide additional information to that provided by the commonly accepted interface pressure measurements, and (3) to compare stress data from this new system with conservative (non-real-time) subject-specific MRI-FE analyses for the same subject group [39] in order to validate the muscle stress evaluations.…”

Section: Introductionmentioning

confidence: 99%

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Toward real-time detection of deep tissue injury risk in wheelchair users using Hertz contact theory

Agam

Gefen²

2008

JRRD

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Abstract-This study assessed the suitability of a new portable system that is based on Hertz's contact theory for evaluating internal gluteal muscle stresses under the ischial tuberosities of wheelchair users in real-time as a risk indicator for a deep tissue injury. Sitting in a wheelchair was monitored and processed with the portable system for six control subjects and five individuals with paraplegia. We compared the resultant internal peak and average muscle stresses and stress integrals over time (stress doses) of the control subjects with those of the subjects with paraplegia and validated the results against previously published subject-specific finite element (FE) stress data for the same subjects. Individuals with paraplegia were characterized by peak muscle compression stresses (mean +/-standard deviation = 109 +/-41 kPa) that were 2.4-fold higher than in control subjects (p < 0.03). A Bland-Altman comparison indicated that stresses recorded by the present system were in satisfactory agreement with previous subject-specific magnetic resonance imaging-FE analyses. We conclude that the present stress monitoring system has the potential to be a practical means for evaluating internal muscle stresses during everyday life of individuals with paraplegia.

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Use of MRI images to measure tissue thickness over the ischial tuberosity at different hip flexion

et al. 2011

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The goal of this experiment was to investigate changes in the thickness of the soft tissue overlying the ischial tuberosity (IT) due to changes in hip flexion angle and the addition of a sitting load. Eleven healthy subjects were tested. An apparatus constructed from foam blocks and an air bladder was used to position the subjects in different postures within an MRI tube. MRI images of the buttocks and thigh were obtained for four postures: Supine, 45° Hip Flexion, Non-Weight-Bearing 90° Hip-Flexion, and Weight-Bearing 90° Hip-Flexion. The thickness of muscle, adipose tissue, and skin was measured between the IT tip and skin surface, perpendicular to the cushion placed beneath the thighs. The tissue overlying the IT was found to be significantly (P < 0.001) thinner in 90° Hip-Flexion (73.8 ± 9.0 mm) than in the supine position (135.9 ± 8.1 mm). Muscle thickness decreased significantly from Supine to Non-Weight-Bearing 90° Hip-Flexion (59.1 ± 8.5%, P < 0.001), and further decreased from Non-Weight-Bearing to Weight-Bearing 90° Hip-Flexion (46.2 ± 7.9%, P < 0.001). Under Weight-Bearing 90° Hip-Flexion, the muscle tissue deformed significantly (P < 0.001) more than the adipose tissue and skin. We concluded that the tissue thickness covering the IT significantly decreased with hip flexion, and further decreased by nearly half during loading caused by sitting. In addition, the muscle tissue experienced the largest deformation during sitting. The results of this study may improve our understanding of risk factors for pressure ulcer development due to changes in tissue padding over the IT in different postures.

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Assessment of mechanical conditions in sub-dermal tissues during sitting: A combined experimental-MRI and finite element approach

Cited by 278 publications

References 47 publications

Evaluation of a new sitting concept designed for prevention of pressure ulcer on the buttock using finite element analysis

Evaluation of a new sitting concept designed for prevention of pressure ulcer on the buttock using finite element analysis

Toward real-time detection of deep tissue injury risk in wheelchair users using Hertz contact theory

Use of MRI images to measure tissue thickness over the ischial tuberosity at different hip flexion

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