Biomedical Engineering Reference
In-Depth Information
Table 6.1
(continued)
Experimental vari-
able
X
L
c
in pres-
ence of
X
,
mm
L
c
in absence of
X
, mm
Shift length,
L, mm
a
References
Early-forming vs. late-
forming fibrin matrix
15.5
12.5
3.0
Williams et al. 1987
Axially vs. randomly
oriented fibrin
11.4
≤ 6.7
≥ 4.7
Williams 1987
Rapidly degrading CG
matrix (NRT
i
) vs. no
CG matrix
8.5
Yannas et al. 1988b;
Chang et al. 1990;
Chang and Yannas
1992
≥ 13.4
≥ 4.9
Axial vs. radial orien-
tation of pore channels
in NRT
i
10.0
Chang et al. 1990;
Chang and Yannas
1992
≥ 13.4
≥ 3.4
Laminin-coated col-
lagen sponge vs. no
laminin coating
11.7
Ohbayashi et al.
1996
≤ 6.0
> 5.7
Polyamide filament-
s
h
vs. no filaments
18.4
Lundborg et al. 1997
≤ 11.0
≥ 7.4
NRT
g
in collagen tube
vs. silicone tube
i
> 25
7.7
> 17.3
Spilker 2000
a
Regenerative activity increases with the shift length,
DL
, the difference between the
Lc
value
for the test configuration and the internal control (or the unfilled silicone tube standard). Stan-
dard: silicone tube,
L
c
= 9.7. Detailed rat and mouse data in Appendix 6.4
b
Parentheses indicate use of the value for the silicone standard (used in the absence of internal
control data)
c
EVA
ethylene-vinyl acetate copolymer (Aebischer et al. 1989b)
d
PLA
poly(lactic acid) (Seckel et al. 1984)
e
LA/ε-CPL
copolymer, copolymer of lactic acid and ε-caprolactone (Dunnen et al. 1993a, b)
f
Cyt C
, cytochrome C
g
NRT
, nerve regeneration template, a graft copolymer of type I collagen and chondroitin
6-sulfate, similar in structure to dermis regeneration template (
DRT
). It was originally studied
as a filling for silicone tubes (e.g., Yannas et al. 1985, 1987a, c, 1988, 1991; Chang and Yannas
1990; Chang and Yannas 1992). After about 2000, tubes fabricated from a version of
NRT
that
omitted chondroitin 6-sulfate were generally used (Chamberlain et al. 2000a; Soller et al. 2013)
h
Eight polyamide filaments, each 250 μm in diameter, placed inside the silicone tube
i
Obtained by implanting the experimental tube in the cross-anastomosis (
CA
) surgical proce-
dure (Lundborg et al. 1982a) in which both contralateral sciatic nerves of the rat are transected;
the right sciatic nerve is transected proximally at the sciatic notch allowing the right distal
segment to be placed near the left proximal stump inside the opposite ends of the experimental
tube. The
CA
procedure allows study of gap lengths over 20 mm
6.1.5
Long-Term Assays (
>
20 weeks): Fidelity of Regeneration
Having described above an assay for the self-consistent evaluation of tubulated
configurations using short-term data (typically < 20 weeks), we now proceed to a
selection of suitable long-term assays. These assays report the extent to which the
regenerate has achieved physiological function, as shown by a comparison of func-
tional data for the regenerate with normal values.
