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Marco Viceconti
09-18-1995, 11:14 PM
To: BIOMCH-L

Dear Colleagues,
here enclosed is an announcement of the "Standardized Femur
Program" proposed by the Laboratory for Biomaterials Technology of the
Rizzoli Institute in the frame of the Prometeo project.

It is available on the market a bone analogue, hereinafter referred as
"composite femur", made of glass fibre reinforced epoxy and polyurethane
foam. Differently from many similar products for surgical simulation, this
bone replica was designed to mimic as close as possible the mechanical
behaviour of a human femoral bone (Beals, 1987; Szivek, 1990; Szivek, 1991;
Cristofolini, 1995).

The advantages of using a standardized artificial analogue for in vitro
studies are obvious; in fact an increasing number of published experimental
works report the use of the composite femur in place of cadaver bones
(Bianco, 1989;McKellop, 1991; Otani, 1993a; Otani, 1993b; Cristofolini,
1994; Harman, 1995).

It is here proposed to use the three dimensional geometry of this composite
femur as a standardized reference for finite element models of the human
femur. These models are used in orthopaedic Biomechanics to investigate
the mechanical behaviour of the bone under load. This would allow every
researcher to use all the published experimental measurements made on the
composite femur as calibration data. Furthermore, a common reference
geometry would allow the inter-laboratories replication of numerical
studies. This cross-calibration approach has already been used in our lab
with good results (McNamara, 1994; McNamara, 1995).

We used this particular commercial bone replica as reference geometry
because in our knowledge it is the only available on the market which was
designed to replicate the mechanical behaviour of a human bone (Inquiry on
BIOMCH-L, 15/5/1995). Nevertheless, this program will not endorse in any
way the company which produce the composite femur; on the contrary the
diffusion of this reference geometry could create market opportunities for
other commercial subjects.

To further support this proposal, we have made available at no cost through
Internet the solid model of the composite femur, converted in formats which
should be readable by most commercial CAD/CAE programs. Although already
useful the available models could be improved; if our initiative will be
approved by the community, more and better models will be made available.

REFERENCES
- Beals, N. (1987) Evaluation of a composite Sawbones femur model. Research
Report ML-87-25. Richards Medical Company, Memphis, Tennessee.
- Bianco, P.T., Bechtold, J.E., Kyle, R.F., Gustilo, R.B. (1989) Synthetic
composite femurs for use in evaluation of torsional stability of cementless
femoral prosthesis. Proc. Biomechanics Symposium (Edited by Torzilli, P.A.,
Friedman, M.H.), pp.297-300 ASME AMD.
- Cristofolini L., Cappello A., Toni A. (1994) "Experimental errors in the
application of photoelastic coatings on human femurs with uncemented hip
stems", Strain 30(3): 95-103.
- Cristofolini L., Viceconti M., Cappello A., Toni A. (1995) "Structural
validation of commercially available composite femur models", J.
Biomechanics, In press.
- Harman, M.K., Toni, A., Cristofolini, L., Viceconti, M. (1995) Initial
stability of uncemented hip stems: an in-vitro protocol to measure
torsional interface motion. Medical Engineering and Physics 17(3):
163-171.
- McKellop, H., Ebramzdeh, E., Niederer, P.G., Sarmiento, A. (1991)
Comparison of the stability of press-fit hip prosthesis femoral stems using
a synthetic model femur. J. Orthop. Res. 9, 297-305.
- Mcnamara B.P., Cristofolini L., Toni A., Taylor D. (1994) "Effect of
bone-prosthesis interface bonding on stress shielding in cementless THA.",
Advances in Bioengineering 1994, Askew M.J. Ed., ASME-BED, New York publ.:
vol. 28 201-202
- Mcnamara B.P., Cristofolini L., Toni A., Taylor D. (1995) "Evaluation of
experimental and finite element models of synthetic and cadaveric femora
for pre-clinical design-analysis", J. Clinical Materials, In press.
- Otani, T., Whiteside, L.A., White, S.E., McCarthy, D.S. (1993b). Effect
of femoral component material properties on cementless fixation in total
hip arthroplasty. J. Arthrop. 8, 67-74.
- Otani, T., Whiteside, L.A., White, S.E.. (1993a) Strain distribution in
the proximal femur with flexible composite and metallic femoral components
under axial and torsional loads. J. Biomed. Materials Res. 27, 575-585.
- Szivek, J.A., Gealer, R.L. (1991) Comparison of the deformation response
of synthetic and cadaveric femora during simulated one-legged stance. J.
Appl. Biomaterials 2, 277-280.
- Szivek, J.A., Weng, M., Karpman, R. (1990) Variability in the torsional
and bending response of a commercially available composite femur. J. Appl.
Biomaterials 1, 183-186.


Marco Viceconti 1
Massimiliano Casali 1
Luca Cristofolini 1 4
Aldo Toni 1 2
Barbara Massari 3
Sanzio Bassini 3

1 Laboratory for Biomaterials Technology, Rizzoli Institute
2 Orthopaedic Clinic, University of Bologna
3 C.I.N.E.C.A.
4 Engineering Faculty, University of Bologna


**************** THE STANDARDIZED FEMUR PROPOSAL ***************

- What is the "Standardized Femur"?
The standardized femur is the 3D computer model of a femoral bone analogue
produced by Pacific Research Labs (Vashon Island, Washington, USA) which
is becoming a de facto standard in experimental orthopaedic Biomechanics.

- Why to use the "Standardized Femur"?
More and more experimental data based on this bone analogue are becoming
available in the literature; we propose to adopt this geometry as a
reference for finite element studies in orthopaedic Biomechanics . This
will produce two advantages:
1) because of the common geometry, it will be easier to compare results
from different FEM studies.
2) Every researcher building FE models will be able to use data from
experimental tests available in literature to calibrate his model.

- Where is the "Standardized Femur"?
Information on the femoral bone analogue and all of the geometry files are
available through a link available in the Biomechanics WWW pages or
directly at the following URL:
(http://www.cineca.it/prometeo/stand_fem.htm)
Actually only data referring to the smaller size adult femur are available.
Together with the CT scan images we used to generate the model (all
converted in TIFF format), you will find also files containing the inner
and outer contours of every slice. Lastly, an IGES model of the inner and
outer surface is available.

- How to obtain the "Standardized Femur"?
If you try to download a file, a dialog box will request your
username-password. The "Standardized Femur" files containing the model are
publicly available for research purposes to anyone who makes an explicit
request. However, we would like you to acknowledge the source of the
geometrical model every time you use it (we are looking for fame!). Thus,
we devised this mechanism: you download the "Transfer Agreement Form"
available on-line, fill it out, sign it, and send it to us by regular mail.
When we receive it, we shall send you the password which allows you to
download the files. Files download will be possible only after September
15th, 1995.

************ END OF THE STANDARDIZED FEMUR PROPOSAL ************


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MARCO VICECONTI
(lk1boq74@icineca.cineca.it)
Laboratorio di Tecnologia dei Materiali tel. 39-51-6366865
Istituti Ortopedici Rizzoli fax.
39-51-6366863
via di barbiano 1/10, 40136 - Bologna, Italy

Tiger! Tiger! Burning bright in the forest of the night,
what immortal hand or eye could frame thy fearful symmetry?
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