United States Department of Veterans Affairs

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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Researchers Dupret-Bories et al recently tested a titanium tracheal prosthesis in sheep to determine the best surgical implantation method. In time, the prosthesis may serve as a substitute for laryngeal cartilage. To learn more about this novel prosthesis, see the slide show, read the article, and listen to the podcast describing the research and other published research in Volume 48, Issue 7.