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View Full Version : Responses on soft tissue viscoelasticity and preconditioningin-vivo vs. in-vitro



Hagai Eshel
02-21-1999, 04:08 PM
>
> Dear Biomch-l, below please find my original posting and the 5 responses
>
> > Dear Biomech-L
> > I am a graduate student studying the viscoelasticity and preconditioning
> > of rat skin in-vitro using uni axial cyclic stretch protocol.
> > As a part of my research I would like to relate the results in-vitro to
> > actual in-vivo properties, and therefore would like to know if you have
> > any references to correlate in-vivo to in-vitro viscoelasticity and
> > preconditioning, in any soft tissue?
> > A summary of replies will be posted
> > Thanks in advance
> > Hagai Eshel
>
> Dear Hagai Eshel,
> One source of information about this topic can be obtained from papers
> published by A.H. Hoffman and P. Grigg (i.e., do a medline search on their
> names). Grigg has published one study [Grigg P (1996) Stretch sensitivity
> of mechanoreceptor neurons in rat hairy skin. J Neurophysiol 76(5):2886-95]
> in which he reports the 2D stiffness moduli for rat hairy skin. In other
> studies co-authored by Grigg and myself, we found that to achieve a
> "pseudo-elastic" state, we had to pre-condition rat skin by stretching it
> about 10 times at physiological levels of load.
>
> Partap S. Khalsa, D.C., Ph.D.
> Asst. Prof. of Biomedical Eng. & Orthopaedics
> S.U.N.Y. at Stony Brook
>
> Hi Hagai:
>
> Well, the issue you've raised is an old one and there is no definitive
> answer on the utility or futility of preconditioning as it bears on
> in vivo behaviour. Basically, one uses preconditioning for one of two
> reasons:
>
> (i) It somehow puts the tissue in a structural/mechanical state similar
> to that it would experience in vivo. This argument is usually
> marshalled for tissues which undergo cyclic loading in vivo: say,
> cardiovascular tissues, periodontal ligament, cartilage etc. It
> really wouldn't apply to rat skin--even with frisky rats.
>
> (ii) It puts the tissue in some reproducible state which another
> investigator could duplicate. Coupled with the reduced standard
> deviations you get from preconditioning before data collection,
> this argument has a lot of attraction. It's really a pragmatic
> choice.
>
> In either case, you should be wary of supposing that any uniaxial test
> in vitro will give you mechanical properties which truly reflect those
> in vivo. First of all, rat skin is surely subject to biaxial loading.
> Second, when any tissue is cut into samples and removed from the body,
> the continuous collagen fibre network is cut and new constraints on
> fibre movement are imposed by the gripping system. This will be
> equally true in uniaxial or biaxial testing.
>
> Steve Waldman in my lab has some very provocative data on the role that
> gripping with sutures or clamps plays in determining the mechanical
> properties one see in biaxial testing of soft tissues--preconditioned
> or not.
>
> Good luck with the work.
>
> Mike
>
> ================================================== ===========
> J. Michael Lee, Ph.D.
> Interim Director, Biomedical Engineering Programme
>
> Associate Professor of Biomaterials (902) 494-6734 (Voice)
> Chair, Dept. of Applied Oral Sciences (902) 494-2527 (FAX)
> Dalhousie University
> 5981 University Avenue jmlee@is.dal.ca
> Halifax, Nova Scotia (902) 494-2162 Tissue Mechanics Lab
> Canada B3H 3J5 (902) 494-6784 Tissue Structure Lab
> ================================================== ===========
> That which is not good for the bee-hive
> cannot be good for the bee.
>
> --Meditations of Marcus Aurelius
> ================================================== ===========
>
> Dear Hagai,
>
> I don't mean to deter you, but your proposal is extremely difficult
> for many reasons that you should at least be aware of. The main
> problem is "preconditioning" itself is poorly understood. The
> problems with in vivo skin testing mostly have to do with nonuniform
> strain fields. Since I can't really do this discussion justice, I'll
> refer you to Lanir's review article:
> - Lanir Y. Skin Mechanics. In: Chien RSaS, ed. Handbook of
> Bioengineering. New York: McGraw-Hill, 1986; 11.1-11.25.
>
> and the seminal artiles on quantifying the mechanical properties of
> skin...
> - Lanir Y, Fung YC. Two-dimensional mechanical properties of rabbit
> skin-I. Experimental system. Journal of Biomechanics 1974; 7:29-34.
> - Lanir Y, Fung YC. Two-dimensional mechanical properties of rabbit
> skin-II. Experimental results. Journal of Biomechanics 1974;
> 7:171-182.
>
> And here are some article on interesting methods for measuring
> "biophysical" properties of skin in vivo (not the intrinsic mechanical
> properties)...
> - Enomoto DN, Mekkes JR, Bossuyt PM, Hoekzema R, Bos JD.
> Quantification of cutaneous sclerosis with a skin elasticity meter in
> patients with generalized scleroderma. J Am Acad Dermatol 1996; 35(3
> Pt 1):381-7.
> - Gniadecka M, Gniadecki R, Serup J, Sondergaard J. Skin mechanical
> properties present adaptation to man's upright position. In vivo
> studies of young and aged individuals. Acta Derm Venereol 1994;
> 74(3):188-90.
> - Henry F, Goffin V, Pierard-Franchimont C, Pierard GE. Mechanical
> properties of skin in Ehlers-Danlos syndrome, types I, II, and III.
> Pediatr Dermatol 1996; 13(6):464-7.
> - Nikkels-Tassoudji N, Henry F, Pierard-Franchimont C, Pierard GE.
> Computerized evaluation of skin stiffening in scleroderma. Eur J Clin
> Invest 1996; 26(6):457-60.
> - Pierard GE, Nikkels-Tassoudji N, Pierard-Franchimont C. Influence of
> the test area on the mechanical properties of skin. Dermatology 1995;
> 191(1):9-15.
> - Viatour M, Henry F, Pierard GE. A computerized analysis of intrinsic
> forces in the skin. Clin Exp Dermatol 1995; 20(4):308-12.
> - Gniadecka M, Serup J. Suction Chamber Method for Measurement of Skin
> Mechanical Properties: The Dermaflex. In: Jemec JSaGBE, ed.
> Non-invasive Methods and the Skin. Boca Raton: CRC Press, 1995;
> 329-334.
> - Fong SS, Hung LK, Cheng JC. The cutometer and ultrasonography in the
> assessment of postburn hypertrophic scar--a preliminary study. Burns
> 1997; 23 Suppl 1:S12-8.
> - Murray BC, Wickett RR. Correlations between Dermal Torque Meter,
> Cutometer, and Dermal Phase Meter measurements of human skin. Skin
> Research and Technology 1997; 3:101-106
>
>
> If you're only interested in correlating simple in vivo and in vitro
> measures with substantial disease states your goal may be attainable.
> However, you have to be very careful not to obscure your results with
> edge effects (due to grips etc) and poor choice of specimen location
> and orientation (due to inhomogeneity and anisotropy).
>
> Good luck, I'd be very interested in your results,
>
> Kristen Billiar, Ph.D.
> Organogenesis Inc
> Canton, MA
> kbilliar@organo.com
>
> Dear Hagai Eshel,
>
> There is a paper from Vogel (1982) in Bioeng. Skin, 3, 198-209 entitled
> "Mechanical properties of rat skin as compared by in vivo and in in vitro
> measurement".
>
> Good Luck.
>
> Hugues Lafrance, Ph.D.
> Baxter Healthcare Corp
> CVG/CVS RnD
>
> E-mail : hugues_lafrance@baxter.com
>
> please provide me with your responses. I am also interested in this question
> Thanks
> *************************************************
> Tim Foutz,Ph.D.,PE
> Associate Professor
> Biomechanics
> Dept. of Biological and Agr. Engineering
> Driftmier Engineering Center
> The University of Georgia
> Athens, Ga 30602
>
> Everyone has a photographic memory
> Some don't have film
> .......RWMc
>
> **************************************************
>
> ---------------------------------------------------------------
>
> Subject: Re: Soft tissue viscoelasticity and preconditioning in-vivo vs.
> in-vitro
> Date: Thu, 4 Feb 1999 10:23:19 -0500
> From: "Partap S. Khalsa, D.C., Ph.D."
> Reply-To: partap.khalsa@sunysb.edu
> To: BIOMCH-L@NIC.SURFNET.NL
> Newsgroups: bit.listserv.biomch-l
>
> Dear Hagai Eshel,
> One source of information about this topic can be obtained from papers
> published by A.H. Hoffman and P. Grigg (i.e., do a medline search on their
> names). Grigg has published one study [Grigg P (1996) Stretch sensitivity
> of mechanoreceptor neurons in rat hairy skin. J Neurophysiol 76(5):2886-95]
> in which he reports the 2D stiffness moduli for rat hairy skin. In other
> studies co-authored by Grigg and myself, we found that to achieve a
> "pseudo-elastic" state, we had to pre-condition rat skin by stretching it
> about 10 times at physiological levels of load.
>
> Partap S. Khalsa, D.C., Ph.D.
> Asst. Prof. of Biomedical Eng. & Orthopaedics
> S.U.N.Y. at Stony Brook
>

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