Biomedical Engineering Reference
In-Depth Information
ress in documenting functional recovery [104]. Indeed, the use of biomechanical parameters
has given valuable insight into the effects of the sciatic denervation/reinnervation, and thus
represents an integration of the neural control acting on the ankle and foot muscles, which is
very useful and accurate to evaluate different therapeutic approaches [103-105].
3.2.1. Functional Assessment
After injury and treatment of animals, follow-up results are very important for analysis of
functional recovery. Animals are tested preoperatively (week 0), and every week during 12
and 20 weeks, for axonotmesis and neurotmesis of the rat sciatic nerve, respectively. Motor
performance and nociceptive function are evaluated by measuring extensor postural thrust
(EPT) and withdrawal reflex latency (WRL), respectively [55, 58, 94]. For EPT test, the affect‐
ed and normal limbs are tested 3 times, with an interval of 2 minutes between consecutive
tests, and the 3 values are averaged to obtain a final result. The normal (unaffected limb)
EPT (NEPT) and experimental EPT (EEPT) values are incorporated into an equation (Equa‐
tion (1)) to derive the percentage of functional deficit, as described in the literature [106]:
(
)
% Motor deficit
=
é
NEPT - EEPT / NEPT
ù
´
100
(1)
ë
û
The nociceptive withdrawal reflex (WRL) was adapted from the hotplate test developed by
Masters et al. [107]. Normal rats withdraw their paws from the hotplate within 4s or less.
The cutoff time for heat stimulation is set at 12 seconds to avoid skin damage to the foot.
For Sciatic Functional Index (SFI), animals are tested in a confined walkway that they cross,
measuring 42 cm long and 8.2 cm wide, with a dark shelter at the end. Several measure‐
ments are taken from the footprints:
i.
distance from the heel to the third toe, the print length (PL);
ii.
distance from the first to the fifth toe, the toe spread (TS); and
iii.
distance from the second to the fourth toe, the intermediary toe spread (ITS).
In the static evaluation (SSI) only the parameters TS and ITS, are measured. For SFI and SSI,
all measurements are taken from the experimental (E) and normal (N) sides. Prints for meas‐
urements are chosen at the time of walking based on precise, clear and completeness of foot‐
prints. The mean distances of three measurements are used to calculate the following factors
(dynamic and static):
(
)
(
)
Toe spread factor TSF
=
ETS - NTS / NTS
(2)
(
)
(
)
Intermediate toe spread factor
ITSF
=
EITS - NITS / NITS
(3)
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