Journal of Rehabilitation Research & Development (JRRD)

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Volume 47 Number 1, 2010
   Pages 31 — 42

Abstract — Use of weight-bearing MRI for evaluating wheelchair cushions based on internal soft-tissue deformations under ischial tuberosities

Nogah Shabshin, MD;1 Gil Zoizner, BSc;2 Amir Herman, MD;3-4 Vlad Ougortsin, MD;3 Amit Gefen, PhD5*

1Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer, Israel; 2Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; 3Department of Orthopaedic Surgery, Sheba Medical Center, Tel Aviv, Israel; 4Department of Statistics, University of Haifa, Mount Carmel, Haifa, Israel; 5Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel

Abstract — Deep tissue injury (DTI) is a severe type of pressure ulcer, in which damage initiates under intact skin, in soft tissues that are mechanically deformed by load-bearing bony prominences. Sitting-acquired DTI typically occurs in the gluteus muscles that could sustain deformations by the weight-bearing ischial tuberosities (ITs). No clinical method currently exists for measuring internal tissue deformations; so design and selection of wheelchair cushions are based mostly on meas-uring sitting pressures. Our objective was to evaluate the influence of different commercial cushions on internal soft-tissue deformations under the ITs, using weight-bearing magnetic resonance imaging (MRI). We specifically compared muscle, superficial fat, and effective (muscle and fat together) tissue deformations while subjects (n = 10) sat on four cushions (two viscoelastic and two foam) and directly on a rigid support. Deformations were maximal in muscle tissue (mean ~70%), twice more the amount than in fat (~30%). Effective soft-tissue deformations were ~50% to ~60%. Although cushions mildly reduced muscle deformations in the order of 10%, theoretically, our interpretation suggests that this deformation level adds safe sitting time. This study demonstrated that weight-bearing MRI is applicable for evaluating wheelchair cushions and, in the future, may be a tool to systematically support cushion design and selection.

Keywords: bedsores, decubitus, deep tissue injury, foam, open MRI, pressure sores, pressure ulcer, rehabilitation, sitting pressures, viscoelastic.

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