Biomedical Engineering Reference
In-Depth Information
The influence of the external fixator has also been studied. Lacroix and Prender-
gast [113] performed a three-dimensional simulation of fracture healing in which
a human tibia was attached to an external fixator. They analyzed two different load
patterns: healing was successful under the lower load and unsuccessful under the
higher load, similar to clinical observations. Gomez-Benito
et al
. [110] studied the
influence of the stiffness of the external fixator in the fracture healing pattern.
They simulated a simple transverse mid-diaphyseal fracture of an ovine metatar-
sus. Three different stiffnesses of the external fixator were simulated (2300, 1725
and 1150 N/mm). The model predicted that a lower stiffness of the fixator delays
fracture healing and causes a larger callus, similar to what has been observed exper-
imentally. This effect could be observed in the load transfer mechanism between
fractured bone and the different fixators through the healing process (Figure 4.7).
Simon
et al
. [90] also studied the effect of different stiffness fixators in the fracture
healing outcome.
Isaksson
et al
. [96] developed a poroelastic finite element model of an ovine tibia.
The influence of torsional and axial loads was studied in their simulations using
different mechanoregulatory algorithms. For both torsional and axial loads, they
predicted fracture union as was observed in vivo when using the mechanoregulatory
algorithm regulated by deviatoric strain and fluid velocity [60].
500
500
400
400
300
300
Bone
Fixator
Bone
Fixator
200
200
100
100
0
0
0
20 40
Days after fracture
60
80
0
20 40
Days after fracture
60
80
(a)
(b)
500
400
300
Bone
Fixator
200
100
0
0
20 40
Days after fracture
60
80
(c)
Figure 4.7
Reaction force evolution for different fix-
ator stiffnesses (a) 1150 N/mm
−
1
, (b) 1725 N/mm
−
1
,
(c) 2300 N/mm
−
1
[110].
