Biomedical Engineering Reference
In-Depth Information
capable of enhancing the rate of bone-healing because of its nanostruc-
tural and compositional similarity to natural bone in main composition
and hierarchical microstructure. Such kinds of composites can be readily
incorporated into the bone metabolism, rather than remaining as a perma-
nent implant [105].
Composites that are nHAC-based have now been successfully used
for thousands of cases in clinical applications, including all the various
types of hard tissue repair. Yu et al. have reported 64 cases of posterolateral
fusion in patients from 46 to 79 years old. In all cases the wound healed
and no abnormity was found in local and systematic examinations during
long-term follow-up [106]. The safety of nHAC/PLA composites used in
lumbar posterolateral fusion has already been proven. The study shows
that using this composite combined with autologous bone leads to results
similar to those found for autologous bone. The composites can thus be
used as a supplement to autologous bone. Carefully controlled random-
ized clinical trials must nevertheless be carried out to verify the use of this
biomimetic nHAC composite substitute for each spine application where
it will be used. We can look forward to soon entering an exciting new era
in the availability of biomimetic bone graft materials for the enhancement
of lumbar spine fusion and for other orthopaedic surgery.
2.5 ConcludingRemarks
Bone is a type of complex calcifi ed tissue with hierarchical levels of orga-
nization. Although the hierarchical structures of many kinds of bone
tissues, including human compact bone, long bone and woven bone,
have been well described, there are still many open questions regarding
the formation of the hierarchical nanostructure. For example, how do the
related genes, biomacromolecules, matrix, and bone cells function syner-
gically to direct the hierarchical assembly of collagen and inorganic ions
forming such unique structures at the molecular level? What are the key
regulators for the size, shape, and crystallography of Ca-P minerals? A
deep-going understanding of the natural bone mineralization processes
will provide sophisticated strategies for biomimetic fabrication of novel
bone repair materials and other advanced technology engineering mate-
rials. The self-assembly of mineralized collagen fi brils in bone and its
biomimetic synthesis have been reviewed in this article. The biomimetric
mineralized collagen fi brils are organic/inorganic hybrid materials
resembling the self-assembly of in vivo nanocomposites from nanoscale
to micrometer scale, which have been successfully applied for the fabrica-
tion of biomimetic bone grafting materials. However, the clinical effects
of the biomimetic bone grafting materials are close but not as good as
the autologous bone grafts. It is believed that the main gap on repairing
Search WWH ::




Custom Search