Document Type : Full Research Paper


1 Associate Professor, Physical Therapy Department, Medical Sciences School, Tarbiat Modares University

2 Assistant Professor, Biomedical Engineering School, Amirkabir University

3 Instructor, Anatomy Department, Medical School, Baghiyatallah University of Medical Sciences

4 MSc Graduated, Physical Therapy Department, Medical Sciences School, Tarbiat Modares University

5 Assistant Professor, Physical Therapy Department, Rehabilitation School, Tabriz University of Medical Sciences



In this study 22 male Guinea Pigs, 4-6 months old, weighting 400-450 g were used. A computer controlled indentor system was used to apply a controlled pressure. The applied pressure was 291 mmHg for 3 hours over the trochanter region of animal hind limb. The animals were divided in three groups; in group 1, pressure was applied 3 hours continuously, in group 2, pressure was applied 90 minutes at two days and in group 3, Pressure was applied in two cycles of 90 minutes with 15 minutes rest between them. To study the biomechanical and histological changes, tissue was removed 7 days after pressure application. Uniaxial tensile test was performed at a deformation rate of 20 mm/min. In this test, the contralateral site on the experimental animal served as intra-animal control. Tissue biopsy was taken and stained with H&E and Trichorome for histological examination. Continuous pressure induced muscle necrosis. Also ultimate stress, stiffness, ultimate strain and area under the load-deformation curve decreased significantly. These results suggest that application of continuous pressure is the major cause of ischemia and necrosis of soft tissue.


Main Subjects

[1]     Kloth L.C., Mcculloch J.M., Feedar J.A.; Wound healing. : Alternatives in management; Davis Company; Philadelphia; 1990: 161-167.
[2]     Maklebust J., Mondoux L., Sieggreen M., Pressure relief characteristics of various support surface used in the prevention and treatment of pressure ulcers; J Enterostom Ther 1988; 13: 85-89.
[3]     Krouskop T.A., Noble P.C., Garber S.L., Spancer W.A., The effectiveness of preventive management in reducing the occurrence of pressure sores; J Rehabil Res Dev 1983; 20(1):74-83.
[4]     Brand P,W., Pressure sores-The problem. In bed sore biomechanics; Baltimore; MD: University Park Press; 1975; p.19-23.
[5]     Cook T.H., Mechanical properties of human skin with aging; in: Balin AK, Kligman AM, editors; Aging and the skin; New York: Raven Press; 1989; p. 205-225.
[6]     Pereira J.M., Mansour J.M., Davis B.R., Technical note: dynamic measurement of the viscoelastic properties of skin; J Biomech; 1991; 24: 157-162.
[7]     Vogel H.G., Measurement of some viscoelastic properties of rat skin following repeated load; Connect Tissue Res 1976; 4: 163-168.
[8]     Fung Y.C.B., Biomechanics mechanical properties of living tissue; New York: Springer Verlag; 1981. p. 203-212.
[9]     Gibson T., Kennedi R.M., Craik J.E., The mobile micro architecture of dermal collagen; Br J Surg 1965; 52: 764-770.
[10] Ridge M.D., Wright V., The directional effects of the skin; J Invest Dermatol 1966b; 46: 341-346.
[11] Stark H.L., Directional variations in the extensibility of human skin; Br J Plas Surg 1977; 30: 105-114.
[12] Schneider D.C., Davidson T.M., Nahum A.M., In vitro biaxial stress-strain response of human skin; Arch otolaryngol 1984; 110: 329-333.
[13] Sُُkalak R., Chain S., Handbook of Bioengineering; McGraw Hill, New York; 1986; p. 11-3-11-25.
[14] Daniel R.K., Priest D.L., Wheatley D.C., Etiologic factors in pressure sores: An experimental model; Arch Phys Med Rehabil 1981; 62: 492-497.
[15] Edsberg L.E., Mates R.E., Baier R.E., Lauren M., Mechanical characteristics of human skin subjected to static versus cyclic normal pressure; Arch Phys Med Rehabil 1999; 36(2): 133-141.
[16] Doillon C.J., Dunn M.G., Bender E., Silver F.H., Collagen fiber formation in repair tissue: development of strength and toughness; Collagen Rel Res 1985; 5: 481- 492.
[17] Edsberg L.E., Cutway R., Anain S., Natiella J.R., Microstructural and mechanical characterization of human tissue at and adjacent to pressure ulcers; J Rehabil Res Dev 2000; 37(4): 463-471.
[18] Maibach HI, Lowe NJ; Models in dermatology; Basel; Karger 1989; Vol 44; p. 71-78.
[19] ترکمان گیتی، فلاح علی، شرفی علی اکبر، کاتوزیان حمیدرضا، فقیه زاده سقراط، مفید محمود؛ طراحی و ساخت دستگاه تولید کننده نیروهای مکانیکی به منظور ایجاد زخم فشاری کنترل شده در حیوانات آزمایشگاهی؛ دانشور 1378، 24: 59-64.
[20] ترکمان گیتی، فلاح علی، شرفی علی اکبر، کاتوزیان حمیدرضا، مفید محمود؛ پاسخ پوست به نیروهای فشاری اعمال شده در مدل خوکچه هندی، فصلنامه مهندسی پزشکی زیستی، 1383، (1)، 93-100.
[21] Kosiak M., Etiology of decubitus ulcers; Arch Phys Med Rehabil 1961; 42: 19-29.
[22] Husain T., An experimental study of some pressure effects on tissues, with reference to the bed-sore problem; J Phatol bacteriol 1953; 66: 347-358.
[23] Dinsdale S.M., Mechanical factors in pathogenesis of ischemic skin ulcers in swine; Ph.D Thesis; University of Minnesota; 1970.
[24] Herrman E.C., Knapp C.F., Donofrio J.C., Salcido R., Skin perfusion responses to surface pressure-induced ischemia: Implication for the developing pressure ulcers; J Rehabil Res Dev 1999; 36(2): 109-120.
[25] Krouskop T.A., Reddy N.P., Spencer W.A., Secor J.W.; Mechanisms of decubitus ulcer formation; Med Hypotheses 1987; 4: 37-39.
[26] Reddy NP; Interstitial fluid flow as a factor in decubitus ulcer formation; Biomechanics 1981; 14(12): 879-881.
[27] Goldestein B., sanders J., Skin response to repetitive mechanical stress: A new experimental model in pig; Arch Med Rehabil 1998; 79:265-272.
[28] Nola G.T., Vistnes L.M., Differential response of skin and muscle in the experimental production of pressure sores; Plast Reconst Surg 1980; 66(5): 728-733.
[29] Salcido R., Fisher S.B., Donofrio J.C., Bieschke M., Knapp C., Liang R., LeGrand E.K., Carney J.M., An animal model and computer controlled surface pressure delivery system for the production of pressure ulcers; J rehabil Res Dev 1995; 32(2): 149 161.
[30] Edsberg L.E., Natiella J.R., Baier R.E., Earle J., Microstructural characteristics of human skin subjected to static versus cyclic pressure; J Rehabil Res Dev 2001; 38(5): 477-486.