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Ernie Wu
07-14-1994, 04:47 AM
Many thanks to all those out there who sent in helpful suggestions.
Sharon is gearing up to try a number of them. I'll post a brief
message to let the list know what finally worked.

Ernie

Following are the suggestions from the generous folks who responded.
I hope those authors will forgive my light editing to save bandwidth.

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From: "Donal McNally"

We use dental stone to hold our specimens in place. You have to
embed the ends of the bone a little, but since your bones are so
long compared to their width, this should not be a problem. The
stone (not plaster) is strong in compression and resist the
specimen 'turning out' quite well.

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From: "Traci Wenzel"

I don't know what kind of tests she is doing, but we have found
that Krazy Glue (or cyanoacrylate of any kind) holds bone pretty
well when glued to acrylic or aluminum...
(splice)
..I've used it for gluing cubes of cancellous bone (~8mm
square) to plastic for slicing on an Isomet and for gluing cylinders
of cancellous bone (again ~8mm) to Aluminum disks to prevent the
ends from slipping during compression tests. Application is simple
--put a blob of glue on the plastic or aluminum, blot the end of
bone that you want to glue, and stick it on. It hardens in a few
seconds and holds very well. I would guess that she might have a
chance with cortical bone if she could cut off the condyles, giving
her a smooth regular surface to glue to.

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From: "Richard Hillam"

We perform alot of mechanical tests on bones that vary from human spines
to small bones 2mm in diameter.

The difficulty with finding an adhesive is that most don't like water but
in order to mechanically test a bone, it must remain hydrated. I've tried
epoxy but without much success. Depending on the bone shape and test to be
performed, we use either cyano-acrylate (eg. M=M M-bond 200), commonly
called Super glue! or green dental cement (Kerr Suprastone). The former
is very strong but requires thorough surface preparation ie all blood +
debris removed, scrape away the periosteum then defat using 50/50 ether
chloroform mixture. You can then go ahead and bond. The latter is not
an adhesive but is excellent at moulding to the contours of the bone to
firmly hold it in place whilst compressing, for example. It is very hard,
non-compressive and once cured it will maintain its strengh in water. We
use it for compressive tests on spines and vertebrae. It is very
exothermic during curing!

What ever you do, try and avoid trimming or cutting the bone to make it
more convenient, as this obviously affects the mechanical properties. You
may need to construct a custom jig.

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From: yhc3@cornell.edu (Young Hui Chang)

.. have you tried plain
old cyanoacrylate (on a very clean dry surface; i.e., prepping with
acetone). Another idea might be to try some dental adhesives. I can't think
of it at the moment, but I did some work in dental materials a few years
ago and we were using a few different dental bonding agents.

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From: "Howard J. Dananberg, DPM"
Jay Phillips, DPM

Try Histacryl. This is a bone cement used in surgery for small bones. It
is
also applicable in nerve repair in Europe. Good Luck.

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From: msanders@sirius.uvic.ca (Michael Sanders)

I HAVE HAD SIMILAR PROLBEMS IN
TESTING THE COMPRESSIVE PROPERTIES
OF VERTEBRAL BODIES. I FINALLY FOUND
A SUITABLE MATERIAL WITH FAST SETTING
EXPANSION CONCRETE. ROCKITE FROM HARTLINE
PRODUCTS CORP. WAS THE BRAND FOUND TO WORK
OKAY. NO MATERIAL HAD ALL THE STIFFNESS AND
FAST SETTING PROPERTIES THAT WAS REQUIRED,
BUT THIS WAS THE BEST.

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

One study of microtensile
testing that was performed by J Rho and R Ashman
here in Dallas, is published in J Biomech., 26(2):111-119 (1993).

As also explained in Rho's dissertation, the specimens were inserted
into 1 mm diameter holes drilled into the ends of rods, and after drying,
the bone samples were glued in place with a cyanoacrylate glue. The samples
were then tested in the dry state (no puns intended ;-) ).

The only reason for your failure with diff glues that i can deduce,
is that you are trying to keep your specimens wet.
In that case, it is not really possible to glue them using cyanoacrylate
or methylmethacrylate glues. However, if you wish
to pursue the wet specimen approach, then i suggest an underwater
epoxy that is available at the local hardware store.. It hardens,
(bnut here is another problem) with an exothermic reaction, even
under water. It is used to seal boat leaks etc etc etc.

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From: "Amy C. Courtney"

..I have successfully tested
machined specimens as small as 2 mm in diameter and 3 cm long.
Others in my laboratory have successfully tested whole rat bones
of similar size using different techniques.

(and later)

..For machined specimens of similar
dimensions, I have used both custom and off-the-shelf three-jaw chucks
mounted in an instron machine to hold the ends of the specimens. There
are some careful techniques required for mounting the specimens, but I
found it worked well.

Those in my lab who test rat bones test them in compression, and
mount the specimens in methylmethacrylate in small vial caps. Two caps
are used to 'encapsulate' the ends of a vertebrae, one cap is used to
support the distal end of a femur. The compressive load is applied
either to the top cap or to the head of the rat femur.

The methacrylate that I have had success with is 'room
temperature curing' dental methacrylate, which is probably the same thing
she has tried already. However, Perhaps the bones are coming out for the
following reason: When the methacrylate cures, the heat causes fat to
melt and ooze, creating a very slippery interface rather than a bond with
the bone. I have found that working carefully to remove soft tissue from
the ends of the bones, and even drying just the very ends with alcohol
before embedding helps. This is assuming that the bones are slipping
out, not actually fracturing at the ends near the embedding site.

Other colleagues in my lab have tested small samples of
trabecular bone in tension. They also found the need to clean out the
very ends of the bone that were actually embedded prior to using
cyanoacrylate (super glue) to bond the bone ends to endcaps.

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From: "Thomas G. Loebig"

Have you tried using auto body filler, aka "bondo"? Nonetheless, it
works well and is used by other researchers. There are various brands
such as Snowite(sp?), Bondo, etc. Be careful to get the kind without
fiberglass. I believe that it is a type of epoxy but I never checked
that out since it is a good "off the shelf" filler available at auto
parts stores. Like with methacrylates, make sure the surface of the
bone is dry.

(And later...)

Since the bones pull-out before failure, it sounds like these specimens
are very straight, at least at the ends, with no bumps to grab on to.
If the bones are not damaged during the test, you might try applying a
drop or two of SuperGlue (cyanoacrylate) to the tips and reinserting
them into your blocks. As long as the mating surfaces are clean
(electronic contact cleaner or rubbing alcohol), the fit is tight, and
you hold pressure on the joint for about 30 seconds, you will get a
very strong bond that with the right amount of surface area, will
provide enough force to hold the specimen until the bone breaks.
If you can do this, and it works on a new or previously used specimen,
I would suggest first coating the bonding surface of the bone with a
release agent such as vaseline or any teflon containing lubricant
(I don't know if WD-40 would work but you can try it, we use TRI-FLOW
with Teflon and petroleum lubes). Once the PMMA, Bondo, epoxy, etc.
sets up, it should be easy (relatively) to remove the bones. You
should then have a near perfect mold for your bones. Then you can
clean them and glue them and get on with the test!
I am assuming that you are doing some type of tensile test and that
can be a pain. Fixation problems like this are common and a source of
frustration to us all.
Reasons for pull-out are most likely that the materials you used
before don'treally form a chemical bond with the bone and the pores
in the bone (assuming cortical) are too small for the polymers to
grab well. The materials are also not much more than fillers and
therefore not adhesives. Although some of the epoxies have adhesive
qualities, they must be specially formulated for the application.
SuperGlue, however, is an adhesive that is used extensively in the
medical profession for microsurgery when sutures are too large to
connect tissue. I've been told that it was invented precisely as a
tissue adhesive but have never found independent confirmation of that.
I can tell you from personal experience that formulations of the
methyl- and ethyl- cyanoacrylates are used almost exclusively for
bonding electrical resistance strain gauges to bone and that they
work extremely well. Let me know if this works for you, good luck.

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From: "Ed Wachtel"

We do testing of small trabecular and cortical bone specimens and
have had excelent success with Lopctite prism 401 cyanoacrylate adhesive.
Good luck