Biomedical Engineering Reference
In-Depth Information
200.00%
Above screw
Beneath screw
150.00%
100.00%
50.00%
0.00%
Titanium
Cortical
bone
Cancellous
bone
1/2
cancellous
bone
No screw
-50.00%
-100.00%
Screw modulus
FIgure 6.4
Influence of the screw modulus on bone SED alteration above and beneath the screw.
SED (MPa)
>1.000e-05
+1.000e-05
+9.167e-06
+8.333e-06
+7.500e-06
+6.667e-06
+5.833e-06
+5.000e-06
+4.167e-06
+3.333e-06
+2.500e-06
+1.667e-06
+8.333e-07
+0.000e+00
Anterolateral
FIgure 6.5
SED distribution in the interference screw.
can offer initial graft fixation and gradually be replaced by the host tissue. However, the interaction
between the biodegradation process and bone remodeling remains unclear. Consequently, complica-
tions caused by undesirable biodegradation have been frequently reported (Konan and Haddad 2009).
The present study indicated that the in vivo SED distribution in the screw was nonuniform (Figure 6.5).
However, the material used in most biodegradable screws is homogeneous. Since mechanical envi-
ronments can influence the biodegradation process, the mechanical strength and morphology of the
screw may change nonuniformly and undesirably in the long term, which may serve as a predisposing
factor for surgical failure. In this light, the present study could provide preliminary knowledge for the
screw-bone interaction, and contribute to the optimal design of a biodegradable screw.
In conclusion, this chapter developed an FE model of the human knee joint with an ACL recon-
struction. The numerical results confirmed that the bone SED distribution and stress orientation were
altered after surgery. These changes occurred around the bone tunnel, and could activate abnormal
bone remodeling. The consequential bone resorption and micro-damage may serve as a predisposing
factor for tunnel enlargement and osteoarthritis. The material properties of the screw could also influ-
ence the postoperative SED distribution in the tibia. On the premise of sufficient fixation strength,
using a screw with a modulus similar to that of bone could decrease the risk of stress shielding, and thus
could offer a more favorable surgical outcome. These findings together with histology factors could
help us to understand the pathomechanism of the sequelae, and help to improve surgical techniques.
aCknowledgmentS
This work was supported by the National Natural Science Foundation of China (Nos. 10925208,
11120101001), the National Science and Technology Pillar Program (Nos. 2012BAI18B05,
2012BAI18B07), and the 111 Project (No. B13003).
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