Biomedical Engineering Reference
In-Depth Information
28.3.1
Bioartificial Ligament and Tendon
A new tissue engineering strategy has recently been attempted
in ligament and tendon reconstruction.
30
The ideal ligament and
tendon replacement scaffold should be biodegradable, porous and
biocompatible, show adequate mechanical strength, and promote
the formation of ligament or tendon tissue and blood vessels. Sev-
eral groups have reported the potential construction of ligament
and tendon scaffolds using a carbon copolymer, collagen, silk, and
biodegradable polymers, such asPGA and PLA.
31
−
37
The use of composite anterior cruciate ligament (ACL) prosthe-
ses,whicharecomposedofacollageninductorandasyntheticfiber
(Dacron
R
),wasinvestigatedasapossiblemeansofACLreconstruc-
tion. Composite ACL prostheses were implanted in 10 sheep mod-
els for six months. The tibial portion showed an osseous ingrowth
around the braid, and numerous vessels were observed. In that
study, a synthetic fiber functioned as a support for mechanical
strength, and the use of a collagen scaffold resulted in the migra-
tionofcellsandvessels.
31
However,becausetheDacrontubeusedin
that study was a nonbiodegradable polymer, it induced long-lasting
inflammation at the site of implantation. The mechanical properties
and biocompatibility of the carbon-PLA-polycapralactone (carbon-
copolymer) composite ligament prosthesis make it suitable for use
asascaffoldmaterialfortherepairandreconstructionofhumanlig-
aments and tendons.
32
However, long-term studies indicate that the
carbon fiber slowly breaks up at the site of implantation and subse-
quently appears in the regional lymph nodes.
33
Therefore, a natural polymer, collagen, was used as a scaffold
material in an attempt to reduce the inflammatory reaction. How-
ever, rapid degradation is often a problem with collagen.
34
,
36
As a
result,reinforcedcompositescaffoldswerefabricatedbyembedding
parallel collagen fibers within a PLA polymer, but the ligament rup-
tured in 20% of the implants.
36
The results of the studies conducted to date indicate that a new
biocompatible biomaterial with strong mechanical properties and
slowdegradationisneeded.Anumberofstudieshaverecentlybeen
conducted to evaluate the possibility of ligament reconstruction
using silk or PGA.
37
The results of recent studies conducted using
silk materials were satisfactory in terms of both biocompatibility
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