MECHANICAL STRENGTH
EVOLUTION OF A
RECONSTRUCTED FEMUR
DURING FOLLOW-UP
Taddei F.*, Martelli S.*, Montanari L.*, Greco
V.*, Leardini A.§, Viceconti M.*, Manfrini M.#
*Laboratorio
§Laboratorio
di Tecnologia Medica
di Analisi del Movimento
#Muscoloskeletal
Oncology Department
Clinical case
• 10 years old child
– Osteosarcoma at the distal left
femoral dyaphisis
– Operated in July 2001
– The tumor did not interest
sourrounding blood vessels and
nerves
• The patient was eligible for
limb salvage surgery
• Reconstruction of the distal
femur with a massive allograft
in conjunction with a
vascularised fibula autograft
LTM-IOR © 2006
Date of operation: 06/2001
Follow-up controls
Pre-op
LTM-IOR © 2006
1 month
7 months
13 months 29 months 36 months 44 months
FEM generation
•Segmentation
•Automatic mesh generation
•10-node tetrahedra
•Convergence test
•Material mapping
Taddei F, et al.. Med Eng Phys. 2004 Jan;26(1):61-9.AMIRA
LTM-IOR © 2006
v. 4.0 (Amiravis Inc, USA)
HyperMesh v. 7.0
BONEMAT_V2
(HyperWorks Inc., USA)
FEM in-vitro validation
Comparison with
experimentally measured
strains on 5 cadaveric
femurs
Taddei F, et al..J. Biomech. 2005 , e-pub ahead of print
Schileo E., et al, poster #67, EORS 2006
LTM-IOR © 2006
Boundary conditions
Model - motion registration
LTM-IOR © 2006
Boundary condition
• MS model:
– 9 bone segments
– 6 joints:
• hip (ball and socket)
• knee (hinge)
• ankle (hinge)
– 108 landmarks
– 84 muscles *
• Static optimisation
algorithm **
*Kepple T.M. et al., J Biomech. 1998, 31, 77-80.
**Friederich J.A. et al, J Biomech. 1990, 23(1), 91-5.
**Crowninshield R.D. et al.,J Biomech, 1981,14, 793-801.
LTM-IOR © 2006
Follow-up study
LTM-IOR © 2006
Results
Tumour lesion
Von Mises stress (Mpa)
LTM-IOR © 2006
Results
Risk of fracture definition
RF=e1/eyield *
eyield = 1.02% **
*Taylor D, Nat Mater 2003; 2(3):133-4.
*Bayraktar HH, et. al, J Biomech 2004; 37(1):27-35.
**Currey JD, J Biomech. 2004 Apr;37(4):549-56.
LTM-IOR © 2006
Results
Risk of fracture
LTM-IOR © 2006
Results
Risk of fracture
LTM-IOR © 2006
Results
Deformed shape
LTM-IOR © 2006
Results
Von Mises stress (MPa)
LTM-IOR © 2006
Results
Risk of fracture
LTM-IOR © 2006
Results
Mneral
density femoral
neck neck
Mineral
density
femoral
380
360
ro (mg/cm^3)
340
320
300
280
260
240
220
200
0
6
12
18
24
follow-up (months)
LTM-IOR © 2006
30
36
42
48
Results
Risk of fracture
LTM-IOR © 2006
Results
Von Mises stress (MPa)
LTM-IOR © 2006
Thank you!