The broad long-term objectives of this grab application are two-fold: First, new stump/socket interface materials for persons with artificial limbs will be developed. The materials will reduce the occurrence of skin breakdown and enhance skin adaption into a load-tolerant and durable tissue. Second, rehabilitative and therapeutic treatment methods to enhance skin integrity will be created.
The specific aims are directed at interface mechanics, materials, and tissue response. Interface normal and shear stresses will be measured on below-knee amputee subjects during ambulation. Those data will be used to enhance an analytical model to predict interface stresses. A quantitative relationship between the magnitude and direction of interface stress and the time-to-breakdown in skin will be determined. Using both the analytical model and the quantitative relationship between interface stresses and tissue breakdown, tissue response for different prosthetic liner materials will be compared. Liners with variable material properties will be evaluated to determine if they induce a lower risk of breakdown than homogenous liners. To allow the analytical model to be extended to develop prosthetic designs and treatment strategies that induce a favorable response, i.e. cause the skin to adapt to become durable and load tolerant, basic studies on tissue adaptation to mechanical stress will be conducted. The health relatedness of the project is to improve the health and function of persons with amputations. The development of prosthetic liner and ultimately the prevention of skin breakdown will prevent secondary disability and morbidity in the amputee population. We propose to address these objectives using a combination of experimental and analytical techniques. Two types of experiments will be conducted. First, using human amputee subjects, interface stresses in clinical data collection sessions will be measured using custom- designed triaxial force transducers. Second, using an animal model, tissue response will be measured for different interface stress magnitudes and directions. Time-to-breakdown will be measured under different combinations of normal and shear stress. To evaluate adapted skin, morphological and biochemical techniques will be used to assess changes in collagen fibril diameter and crosslinking compared with control. For the analytical techniques, the finite elements modeling method will be used to predict skin stresses in amputee subjects, then extended to predict time-to-breakdown for different prosthetic liner designs.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
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Special Emphasis Panel (SRC (12))
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University of Washington
Biomedical Engineering
Schools of Medicine
United States
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Zachariah, Santosh G; Sorenson, Elizabeth; Sanders, Joan E (2005) A method for aligning trans-tibial residual limb shapes so as to identify regions of shape change. IEEE Trans Neural Syst Rehabil Eng 13:551-7
Sanders, J E; Zachariah, S G; Jacobsen, A K et al. (2005) Changes in interface pressures and shear stresses over time on trans-tibial amputee subjects ambulating with prosthetic limbs: comparison of diurnal and six-month differences. J Biomech 38:1566-73
Zachariah, Santosh G; Saxena, Rakesh; Fergason, John R et al. (2004) Shape and volume change in the transtibial residuum over the short term: preliminary investigation of six subjects. J Rehabil Res Dev 41:683-94
Sanders, Joan E; Nicholson, Brian S; Zachariah, Santosh G et al. (2004) Testing of elastomeric liners used in limb prosthetics: classification of 15 products by mechanical performance. J Rehabil Res Dev 41:175-86
Wang, Y-N; Sanders, J E (2003) How does skin adapt to repetitive mechanical stress to become load tolerant? Med Hypotheses 61:29-35
Sanders, Joan E; Mitchell, Stuart B; Zachariah, Santosh G et al. (2003) A digitizer with exceptional accuracy for use in prosthetics research: a technical note. J Rehabil Res Dev 40:191-5
Hafner, Brian J; Sanders, Joan E; Czerniecki, Joseph et al. (2002) Energy storage and return prostheses: does patient perception correlate with biomechanical analysis? Clin Biomech (Bristol, Avon) 17:325-44
Sanders, J E; Fergason, J R; Zachariah, S G et al. (2002) Interface pressure and shear stress changes with amputee weight loss: case studies from two trans-tibial amputee subjects. Prosthet Orthot Int 26:243-50
Saxena, Rakesh; Zachariah, Santosh G; Sanders, Joan E (2002) Processing computer tomography bone data for prosthetic finite element modeling: a technical note. J Rehabil Res Dev 39:609-14
Sanders, Joan E; Mitchell, Stuart B; Wang, Yak-Nam et al. (2002) An explant model for the investigation of skin adaptation to mechanical stress. IEEE Trans Biomed Eng 49:1626-31

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