title: The shear mechanical properties of diabetic and non-diabetic plantar soft tissue.
abstract: Changes in the plantar soft tissue shear properties may contribute to ulceration in diabetic patients, however, little is known about these shear parameters. This study examines the elastic and viscoelastic shear behavior of both diabetic and non-diabetic plantar tissue. Previously compression tested plantar tissue specimens (n=54) at six relevant plantar locations (hallux, first, third, and fifth metatarsal heads, lateral midfoot, and calcaneus) from four cadaveric diabetic feet and five non-diabetic feet were utilized. Per in vivo data (i.e., combined deformation patterns of compression followed by shear), an initial static compressive strain (36-38%) was applied to the tissue followed by target shear strains of 50% and 85% of initial thickness. Triangle waves were used to quantify elastic parameters at both strain levels and a stress relaxation test (0.25 s ramp and 300 s hold) was used to quantify the viscoelastic parameters at the upper strain level. Several differences were found between test groups including a 52-62% increase in peak shear stress, a 63% increase in toe shear modulus, a 47% increase in final shear modulus, and a 67% increase in middle slope magnitude (sharper drop in relaxation) in the diabetic tissue. Beyond a 54% greater peak compressive stress in the third metatarsal compared to the lateral midfoot, there were no differences in shear properties between plantar locations. Notably, this study demonstrates that plantar soft tissue with diabetes is stiffer than healthy tissue, thereby compromising its ability to dissipate shear stresses borne by the foot that may increase ulceration risk.
authors.affiliation: VA RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, Seattle, WA 98108, USA.
authors.forename: Shruti
authors.initials: S
authors.lastname: Pai
authors.forename: William R
authors.initials: WR
authors.lastname: Ledoux
mesh_terms: D000368:Aged; D000818:Animals; D019245:Compressive Strength; D017719:Diabetic Foot / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005545:Forefoot, Human / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D033081:Shear Strength; D013312:Stress, Physiological
references.citation: J Biomech. 2008 Aug 28;41(12):2689-95
references.pmid: 18672246
references.citation: Ann Biomed Eng. 2011 May;39(5):1517-27
references.pmid: 21327701
references.citation: Clin Biomech (Bristol, Avon). 2002 May;17(4):291-6
references.pmid: 12034122
references.citation: Clin Biomech (Bristol, Avon). 2007 Jan;22(1):67-73
references.pmid: 17011684
references.citation: Arch Phys Med Rehabil. 2002 Dec;83(12):1796-801
references.pmid: 12474190
references.citation: J Biomech. 2002 Dec;35(12):1523-31
references.pmid: 12445605
references.citation: J Biomech Eng. 1999 Aug;121(4):386-92
references.pmid: 10464692
references.citation: Diabetes Care. 1992 Jul;15(7):815-9
references.pmid: 1516497
references.citation: Clin Biomech (Bristol, Avon). 2001 Dec;16(10):921-5
references.pmid: 11733132
references.citation: J Biomech. 2010 Jun 18;43(9):1754-60
references.pmid: 20207359
references.citation: J Biomech. 2007;40(13):3045-9
references.pmid: 17449038
references.citation: J Comput Assist Tomogr. 2006 Mar-Apr;30(2):321-6
references.pmid: 16628057
references.citation: J Biomech Eng. 2002 Apr;124(2):244-52
references.pmid: 12002135
references.citation: Clin Biomech (Bristol, Avon). 2000 Jan;15(1):46-53
references.pmid: 10590344
references.citation: Biorheology. 1997 Nov-Dec;34(6):377-85
references.pmid: 9640354
references.citation: J Biomech. 2007;40(13):2975-81
references.pmid: 17433335
references.citation: Ultrasound Med Biol. 2000 Mar;26(3):451-6
references.pmid: 10773376
references.citation: J Biomech. 1997 Oct;30(10):1005-13
references.pmid: 9391867
references.citation: J Orthop Res. 1999 Sep;17(5):732-7
references.pmid: 10569484
references.citation: J Biomech. 2008;41(3):556-9
references.pmid: 18054025
references.citation: Diabet Med. 2000 Dec;17(12):854-9
references.pmid: 11168328
references.citation: J Biomech. 1998 Sep;31(9):801-7
references.pmid: 9802780
references.citation: J Biomech. 1978;11(8-9):407-19
references.pmid: 213441
references.citation: Diabetes Care. 2007 Oct;30(10):2643-5
references.pmid: 17620447
references.citation: Clin Biomech (Bristol, Avon). 2009 Oct;24(8):682-6
references.pmid: 19619918
references.citation: Med Eng Phys. 2001 Nov;23(9):633-45
references.pmid: 11755808
references.citation: Clin Biomech (Bristol, Avon). 2005 Mar;20(3):312-9
references.pmid: 15698705
references.citation: J Biomech. 2008;41(5):1119-23
references.pmid: 18242620
references.citation: J Diabetes Complications. 1999 May-Jun;13(3):129-34
references.pmid: 10509872
references.citation: J Biomech. 2007;40(4):883-90
references.pmid: 16677657
references.citation: Biorheology. 2002;39(6):735-42
references.pmid: 12454439
references.citation: Gait Posture. 2002 Feb;15(1):1-9
references.pmid: 11809575
references.citation: J Acoust Soc Am. 2008 Aug;124(2):1207-19
references.pmid: 18681608