Biomedical Engineering Reference
In-Depth Information
Max: 0.0232MPa
Max:
1.722MPa
Max:
1.154MPa
(a)
(b)
(c)
0
.05
.2
.5
1.5
.01
.1
.3
1
FIgure 22.2
(See color insert.)
The von Mises stresses in the left discs of the three models (the maximum
stresses were listed): (a) the bond model, (b) the contact model, and (c) the gap model.
table 22.1
maximum Stresses of discs in three models
bond
Contact
gap
Maximum tensile
stresses (MPa)
Anterior bands
0.716
0.430
0.013
Intermediate zone
0.759
0.542
0.056
Posterior band
2.580
0.318
0.586
Maximum pressures
(MPa)
Anterior bands
−0.539
−0.178
−0.009
Intermediate zone
−1.873
−0.651
−0.039
Posterior band
−2.098
−0.586
−0.231
2006). The maximum tensile stress (2.58 MPa) was much greater than the tensile strength (1.35
MPa [Kang et al. 1998]). In the gap model, stress concentration was observed in the posterior band,
while the stresses in the other bands were very low (Figure 22.2). The tensile stress was dominant in
the three bands (Table 22.1), inconsistent with the load-resistant properties of the discs (Kang et al.
2006). In the contact model, the maximum pressures of the discs occurred in the intermediate zones
(Table 22.1), in agreement with the physiological function of the discs and related biomechanical
research (Koolstra and van Eijden 2005; del Palomar and Doblare 2006c). Moreover, tensile stress
was dominant in the anterior band, accordant with the tension-bearing structure; compressive stress
was dominant in the posterior band, accordant with the pressure-bearing structure (Kang et al.
2006). Therefore, a more biologically appropriate stress distribution of the discs was obtained in
the contact model.
The stress distributions in the articular cartilages were also caused by the interaction between the
discs and the cartilages. In the condylar cartilages, the stresses in the anterior and central regions
were much greater than the posterior, medial, and lateral regions in all models. However, the mag-
nitudes of stresses were too small in the gap model due to the interaction between the discs and the
cartilages, similar to those in the discs. The maximum pressure was located at the central region in
the bond and gap models and at the anterior end in the contact model (Figure 22.3). The stress distri-
butions in the temporal cartilages were similar to the stress distributions in the condylar cartilages,
and the maximum pressures of the temporal cartilages fell over the anterior end in the three models
(Figure 22.3). Anatomical studies have found that injury to the condylar and temporal cartilages
usually occurs in the anterior segment (Oberg et al. 1971). Thus, the stress distributions of the con-
dylar and temporal cartilages were reasonable in the contact model.
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