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David Pickles
09-06-1994, 01:34 AM
Here is a summary of the messages I received in response to the following
query which I posted recently. Many thanks to all those who replied...

My question:

"Can anybody give me any advice or pointers to relevant literature on the
effects on the biomechanical properties of human tissue of different
methods of sterilization? It is a requirement that all human tissue used
for research here is either sterilized or HIV-screened, and the latter is
not always possible.

I am concerned primarily with bone rather than soft tissue, and really
thinking in terms of irradiation, but any info on effects of other
treatments (eg formalin) would be appreciated."

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From: Azza Mahmoud

These 2 articles came to my hand while reviewing some articles related
to bone biomechanical measurements, and they addressed among the effects
of sterilization on Bone specimens. I hope you find them helpful.

1. Influence of Environmental Factors on Experimental Strain Measurements
on Bone. Marco Viceconti, Aldo Toni and Armando Giunti. Proceedings of
XIVth Congress of the international Society of Biomechanics. paris,
France, July 4-8,1993.

2. Basic Biomechanical Measurements of Bone: A tutorial. C.H. Turner, D.
B. Burr Bone, 14, 595-608, 1993.

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From: "Marco Viceconti"

we made some test of the effects of preservation on the stiffness of bone
materials. As starting reference, you can use data from Gaynor Evans
books. Then, our data can be find in:

Viceconti, M., Toni, A. and Giunti, A. Strain gauge measurements of hard
tissues: factors influencing measurements. In: Experimental Mechanics.
Technology Transfer between High Tech Engineering and Biomechanics,
edited by Little, E.G. London: Elsevier Science Publishers, 1992, p.
177-184.

As summary: Frozen wrapped in cloth (-20=B0C) -2.9% in stiffness
Frozen wrapped in polyethilene (-20=B0C) -7.9% in stiffness
in 4% formalin solution +5.2% in stiffness
Embalmed and rehydrated +14.8% in stiffness

More recently we made some tests on bovine ribs sterilized in autoclave
(steam at high temperature); of course the changes are huge, but this
needed when you use the bone for grafts in vivo.

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From: isingerk@info.curtin.edu.au (Kevin Singer)

David: we have been examining the issue of formalin fixation effects on
vertebral bone - published recently in Clinical Biomechanics 9: 175-179
[May issue]. We would like to explore this further by varying the % and
time frames of fixation - using the sheep lumbar spine model. Our interest
relates to using fixed bone for our human vertebral column research. You
might also examine the paper by Cavanaugh JM & King AI in: Journal of
Orthopaedic Research 1990, 8: 159-166. 2.5 My colleague at Royal Perth
Hospital [Rob Day, project bioengineer][robday@uniwa.uwa.edu.au] can
describe further some recent work on irradiation using human bone samples.
These new data are to be presented at the Orthopaedic Society meeting
later this year.

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From: mehta@zermatt-ra.SWMED.EDU (Shreefal Mehta)

We currently use both animal and human cadaveric bone. After storing them
by freezing (wrapped in paper wet with NaCl solution) we usually clean off
the fat and then "sterilize" the tissue by storing in 50% EtOH/water
solution before use....

Formalin does change the mechanical properties of bone but i seem to
recall reading that the difference is usually not noticeable. Of course,
"noticable" depends on the scale and sensitivity of your tests..

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From: wch@bihobl2.bih.harvard.edu (Wilson C. Hayes)

We have two papers that may be of interest to you. The first deals with
the effects of heat and freezing on the mechanical properties of bonvine
bone. The second is on the effects of formalin fixation on the structural
properties of rat bone. If you send us a surface mail address, we will
forward the two papers. It may take about a week to get them out,
however, since we have several people on vacation.

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From: neil@isgtec.com (Neil Glossop)

This is not really an answer, but rather a redirection. I suggest that you
check with the bone bank in your local hospital, since this is very
common. Bone from (for example) total hips (the femoral head) is
routinely banked in Toronto anyway. I believe they use a gamma ray
technique to sterilise it prior to freezing.

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...and one other appropriate reference, for the sake of completeness:


Finlay JB et al. (1992) Embalming effects upon the mechanical properties
of bone: preliminary experiments. In: Experimental Mechanics. Technology
Transfer between High Tech Engineering and Biomechanics, ed. Little EG.
London: Elsevier, 177-184.


No information on the effects of irradiation came up: if anybody knows
of some, I would be most grateful to hear of it.

David Pickles

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