Intervertebral Disk Replacement - Keivan Anbarani's Electronic ...

It is interesting to note that the there is a maximum stress concentration of 15 MPa
on the artificial disc, versus an almost zero stress on the intact disc. Additionally, Figure 11
illustrates that more displacement can be achieved with an artificial disc versus the intact
intervertebral disc. In comparison to the traditional spinal fusion methods where the spine
is fixed and limits movement, using TDR not only restores the normal movement of the
spine but actually increases it by 4 degrees.
Case Study II: Human Cadaver Analysis
The second case study chosen for this report was done by Sun-­‐Kon et al. where an
artificial intervertebral disc is implanted into a human cadaver. However, in this study, all
the discs from L1 to S1 were replaced and similarly a 400 N constant force was applied to
simulate normal loading on the spine. Extension, flexion, lateral bending and axial rotation
were then performed on the spine and similarly, results indicated that having an artificial
disc allows for more flexibility of the spine versus the limited spinal fusion method.
Figure 11. Comparison of Displacement angle for intact Discs and implanted Discs
Materials
Key features of artificial disc design are center of rotation, short-­‐ and long-­‐term stability,
and material interfaces. Material choice should also be determined by the needs of both the
articulating surface and the interface between prosthesis and vertebral body. Hallab et al,
identified several criteria important for optimizing materials selection in TDR-­‐
preservation of kinematics and biomechanics, preservation of intervertebral space,
biocompatibility, revisability, and life expectancy of the materials used (Table 4).
Significant knowledge gained from the development of hip and knee replacements have
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