Biomedical Engineering Reference
In-Depth Information
It can be concluded that the most appropriate design for load-bearing artifi cial joints would be
an advanced material, which will be soft as well as strong enough. In comparison with homoge-
neous materials, composites offer a variety of advantages, which can be useful during the design of
the advanced material. These include the possibility for engineers to exercise considerable control
over material properties. By varying the type and distribution of the reinforcing phase in the com-
posite, it is possible to obtain a wide range of elastic properties to enable better mechanical compat-
ibility with bone and the other tissue while maintaining high strength and durability.
21.6 SUMMARY
The human body is generally adoptive to the articular joints; however, these joints must satisfy a long
list of requirements that can be met with the application of several materials formed into composite
structures. By gradually changing the material combinations, volume fractions and anisotropy at
different locations, very effective and effi cient structures can be produced. Articular cartilage can be
modeled as a fi ber-reinforced, porous, permeable composite material. Fluid-fi lled, porous engineer-
ing materials can be used to reconstruct the subchondral bone properties. Presently, it is not possible
to replace these structures with the same effectiveness by engineering materials and designs. When
the AC and subchondral bone layers are resected in human joint arthroplasty, the biomaterials (i.e.,
metal and polyethylene) used to replace and mimic them do not fulfi ll properties and functions of
natural composite structures. Existing differences between natural and artifi cial materials can be the
reason for unsatisfactory results of TJRs. Complications occur over several years, as a result of the
introduction of interfaces, decreased lubrication properties, and changed load distribution. Structure
and properties of the cartilage and subchondral bone should be restored in prosthesis design.
Currently, most of the repair strategies meet the aim to regenerate defected AC, although, many
fail to prevent future degeneration of the repaired surrounding host tissues. The repair tissue is often
of a fi brocartilaginous nature without the zonal organization of AC. Where hyaline cartilage is pro-
duced, it is often of an immature nature and does not have a true articular surface.
Future research may need to focus on the combination of biodegradable scaffolds and autolo-
gous cells to produce a mechanically functional hyaline repair tissue. The advanced materials (i.e.,
fi ber-reinforced composites or other hybrid materials) fabricated using modern, rapid manufactur-
ing techniques and nanotechnologies may offer new opportunities. These materials should better
mimic the functional, physical, and mechanical behavior of tissues in anatomical joints.
ACKNOWLEDGMENTS
We would like to thank Prof D. Hutmacher for his inspiration and sharing his knowledge in tissue
engineering with us.
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