In the traditional
curriculum anatomy is thought and learned in the preclinical years. According
to local circumstances more or less work is devoted to dissection or prosected
specimen. Whereas this may be a method to acquire knowledge in systematic
anatomy and topography it does not help very much in understanding applied
aspects, f.i. x-ray anatomy.
With the rise
of modem imaging methods the demand for correlated sections increased.
Such specimen should be available in later phases of the curriculum when
students deal with patient -oriented material. Plastination is a technique
to preserve such specimen without any preserving fluids.
easily be stored and handled by students according to their needs. Currently
a set of plastinated sections is collected at our learning resource center
for correlation with x-ray anatomy.
has been developed for teaching as well as for research. It had been invented
about 20 years ago at Heidelberg by Dr. von Hagens and proved to be the
superior method for preservation of gross specimen. Vienna was the first
place to introduce this new method in the late 70ies. Nowadays the method
is applied in more than 200 institutes for Human Anatomy, Clinical Pathology,
Biology and Zoology worldwide. The ,,International Society for Plastination"
was founded in 1986, the first issue of Journal of the International Society
of Plastination appeared in 1987.
allows for preservation of specimen with completely visible surface and
high durability. Plastinated specimen are odorless, not toxic and mechanically
resistant to a high degree. Plastination is a procedure, during which water
and fat of gross specimen are replaced by a polymerisable resin. First,
specimen are dehydrated in an intermedium (f.e. acetone) with a boiling
point below that of the resin. Than the intermedium is continuously evaporated
under vacuum conditions. In this phase the resin replaces the intermedium.
Finally, the resin is polymerised. Optical properties - opaque or transparent
- and mechanical properties - smooth and flexible or hard - can be chosen
by appropriate composition of plastination resins.
The three most
important resins and hence plastination techniques are Silicone (S-10),
Epoxy (E-12) and Polyesther (P-40).
Principle of the Plastination Procedure
specimens start from fixed material and every established fixation method
is applicable. We use formaIin in
between 5 and 20%. To enhance color preservation, the Kaiserling solution
is suitable. Perfusion-fixed animals and
injected human cadavers yield well fixed organs in their correct anatomical
positions. Organs removed at autopsy are fixed by
and infiltration, taking care to restore their natural shape. Hollow organs
have to be dilated during fixation, a step essential
plastination. All embalming fluids containing long chain alcohol (e.g.,
glycerol) have to be removed before dehydration, as they
spoil the final specimens. Fixation can be omitted when epoxy resins are
used (epoxy resins have fixing properties), resulting in
color preservation. However, care should be taken with respect to possible
and defatting are mandatory since water and lipids can not be exchanged
directly against polymers. As known from
a proper dehydration procedure must avoid shrinkage. The degree of defatting
is essential in plastination The two methods
are stepwise dehy-dration in graded ethanol and freeze substitution with
dehydration is used when a histological exami-nation of the plastinated
specimen is intended, The disadvantage of ethanol is
for replacement by a low boiling intermediary solvent (acetone or methylene
chloride). In addition, stepwise ethanol
causes con-siderable shrinkage (roughly 50%) and is time consuming. Ethanol
dehydration is advantageous for embalmed
because it easily removes (especially after addition of H202) the long
chain alcohol contained in the embalming fluid.
dehydration procedure for plastination is freeze substitution in acetone
at -25°C. This method saves time, requires less
compared with ethanol dehydration, and causes only minor tissue shrinkage.
It is the only way to dehydrate brain tissue with a
(less than 10%) shrinkage. During freeze substitution, specimens (precooled
to + 5°C) freeze immediately on immersion into
cold acetone (technical grade), thereby stabilizing the specimens shape
instantly. Within the next 3-5 weeks (including 2-3
of the acetone), the specimens become completely dehydrated. The only disadvantage
of freeze substitution is theformation of ice crystals in specimens
which will also be used for histology. This can be overcome by processing
specimens containing 20-100%
which acts as a freeze protecting agent.
dehydration, the defatting is accomplished simultaneously with the dehydration
procedure. In freeze substitution, defatting
an additional acetone bath at room temperature. For lipid-rich specimens
(containing bones, subcutaneous or subserous
tissue), defatting may be achieved in a final bath of methylene chloride.
For plastination purposes, acetone is ideal because it
as dehydration agent, defatting agent and intermediary solvent all at the
same time and readily mixes with all the different resins
and most important step in plastination is re-placement of the intermediary
solvent (which occupies the spaces originally
with water and lipids) by curable polymers. This is achieved by means of
a vacuum during forced impregnation. The specimen,
within a vola-tile intermediary solvent (acetone or methylene chloride),
is placed into the polymer solution. The intermediary
has a high vapor pressure and a low boiling point (acetone: + 56°C,
methylene chloride: + 40°C), while the polymer solution has
vapor pressure and a high boiling point. Therefore, when a vacuum is applied,
only the intermediary solvent is continuously
out of the specimen and through the surrounding polymer solution in the
form of gaseous bubbles. The surrounding resin is
eventually cleared completely of the intermediary solvent, and therefore
only one impregnation bath is needed. Thus, the quantity
consumed is very small and approximates, for silicone, at most to the volume
of the specimens.
of impregnation depends both, on the specimen and on the class of polymer
used. Generally, polymers with a higher viscosity
a longer impregnation time than polymers of lower viscosity. The larger
and denser the specimen, the slower an impregnation
be preferably with a low viscosity resin. To accomplish impregnation,
any small oil driven vacuum vane pump is sufficient, speed
be adjusted by varying the vacuum by means of an air bypass valve. Gas
bubble formation, easily observed through a window, is a
indicator of the speed of impregnation. A too rapid extraction of the intermediary
solvent causes a collapse of the structural
of the specimens (i.e., shrinkage) and must be prevented. Very delicate
specimens are preferably processed via methylene
Its high specific gravity (1.3) ensures that the specimens will sink to
the bottom of the impregnation bath (specific gravity
1) and therefore they must not be weighted down.
impregnation is carried out either at room tem-perature when using epoxy
and polyester resin or at - 25°C in a deep freezer
working with silicone rubber. In the cold, the gas bubbles will rise slowly
to the surface, without splashing. A final vacuum in the
between 2 and 15 mm Hg is necessary. At room temperature forced impregnation
generally goes faster and with strong bubbling,
the polymers are less viscous and have a shorter processing time.
of the specimens is carried out after removal from the impregnation bath;
the residual polymer of the bath should stay fluid
Three specific techniques are applied, which differ markedly from the usual
curing of polymers cast in molds.
curing procedure, specially developed for plastination is used for silicone
specimens. In this technique, the decisive crosslinking
agent is not a constituent of the impregnation bath, but is applied later
to the specimens in a gaseous form. In a closed chamber, the impregnated
specimens are exposed to an atmosphere which is continuously saturated
with the gaseous hardener evaporating from a stock solution inside the
chamber. Continuous evaporation and circulation of the gas is achieved
by a small membrane pump speeding up the curing process.
of specimens impregnated with epoxy resin (E 12) or polymerizing emulsion
(PEM) takes advantage of the tissue amines
within the specimens. Amines are effective accelerators. Together with
anhydrides, used as hardeners for epoxy resins or
mixtures, they are sufficient to fully cure the specimens at+50°C.
of polyester-copolymers can be initiated by UVA-light followed by a heat
treatment (+50°C). The inherent advantages are a long
time in the dark, and a lower temperature peak during their markedly exothermic