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disarray (Fig. 5A). Regarding the cathodal group, tendons gested that microcurrent applications are believed to be effec-
showed better healing picture than control group with cellular tive by influencing and modifying cellular processes and
neotendon, newly formed small blood vessels and collagen fi- activity. Employing different levels of current, frequency and
bers that appeared in loose bundles. Obvious foreign body polarity have been shown to have diverse effects upon different
granulomatous reaction could be seen (Fig. 5B). The Anodal cell groups [9,25].
group, showed the best healing picture with spindle shaped
fibrocytes arranged parallel to the longitudinal axis of the col- Cathodal stimulation was suggested to promote and attract
lagen fibers which form compact bundles (Fig. 5C). macrophages [26]. During the first stage, macrophages play a
prominent role in healing. Not only do macrophages debride
Week 8: Light microscopy of untreated tenotomized right the injury site via phagocytosis, they facilitate angiogenesis,
Achilles tendon showed poorly aligned collagen bundles, migration of fibroblasts to the site of injury, and their prolifer-
inflammatory tissue reaction could be noticed (Fig. 6A). ation prior to collagen synthesis. Thus, although fibroblasts
Regarding the Cathodal group, the right Achilles tendon are dominant and produce the collagen of tendons, their met-
showed diminished granulation tissue with formation of prop- abolic process may be remarkably impaired in the absence of
erly aligned mature collagen bundles (Fig. 6B). While tendons macrophages that initiate the sequence of events that precede
in the anodal group, showed closely packed collagen bundles their migration [27]. The previous explanation may explain
with compressed fibrocytes. Both of them are well oriented the significant higher values of cathodal than anodal during
along the longitudinal axis of the tendon (Fig. 6C). the 3 week period.
Discussion and conclusion On the other hand, anodal stimulation was suggested to
facilitate migration and proliferation of epithelial cells so
The ultimate aim in treatment of tendon injury is to achieve improving wound closure [10,18]. Regarding tendon healing,
anatomical and functional healing [22]. Recently MES has MES with positive polarity was suggested to accelerate the
gained considerable attention for stimulating soft tissues repair process of tendon repair resulting in stronger tendons with re-
as wounds, bones, tendons and ligaments and promising re- duced contracture formation [13]. It was also reported that
sults have been reported [9,10,17–19]. tendons treated with anodal MES had higher breaking
strength than control which means that tendons became stron-
In this study, the results demonstrated that both cathodal ger and can withstand higher loads before breaking [14]. This
and anodal MES could improve the mechanical properties of might explain the significant improvement of both biomechan-
surgically repaired rabbits Achilles tendons at third, fifth and ical properties and healing picture of the healed tendons trea-
eighth weeks post-injury when compared with the controls. ted with anodal MES in the anodal group.
This was also proved by the presented histopathological find-
ings as tendons in the cathodal and anodal groups showed less Most of the studies conducted on the effect of MES on ten-
prominent inflammatory reactions with better aligned collagen don healing used single polarity Some reported that cathodal
fibers which were organized in parallel bundles. The biome- MES could enhance tendon healing [11,12], while others re-
chanical properties of tendons were reported to be directly re- ported positive results with anodal MES [13,14]. Up to our
lated to the amount and orderly orientation of collagen fibers knowledge, only one study was conducted by Owoeye et al.
which are responsible for transmitting the force generated by [14] were comparing the cathodal and nodal MES on tendon
the tendon to bone [24]. healing. The findings in our study regarding anodal MES agree
with them but contradict their result regarding cathodal MES.
The biomechanical testing of the regenerating tendons is In this study, authors found no significant effect for the cath-
considered as one of the criteria to judge the degree of tendon odal than control. However, the authors used implanted elec-
healing, greater tensile strength and load at break means in- trode with stainless which might have affected the outcome
creased ability to perform movement. While higher stiffness, also they used pulsed galvanic current in the form of twin spike
elastic modulus and work done means increase of the ability not in the form of rectangular which may be a factor to be con-
to withstand load for a longer period of time before sniping sidered. It was suggested that the waveform to be rectangular
[20,24]. that resemble body activity [8].
The improvement in both the biomechanical properties and According to the experimental design of the study, the plas-
healing process recorded in both MES groups could be ex- ter casts were removed at sixth day postoperative which al-
plained by the previously reported physiological effects of lowed early mobilization without any tendon rupture or
MES that related to enhancement of the intrinsic healing of recorded drawback of the results. MES mimic endogenous
the tendon include promoting ATP production, increasing electrical signal that guide cellular behavior which results in
amino acid uptake, enhancing active secretion of tenocytes stimulating intrinsic capacity of tendon to heal with minimal
and increasing collagen synthesis [4,8,9,11] complications [4,7]. So we can suggest that with MES applica-
tion to the surgically repaired tendons, safe early mobilization
Furthermore the results of the current study shed a light on could be allowed. Early cast removing and functional loading
the role of polarity of MES as a parameter during stimulation were reported to augment the healing strength of the experi-
of tendon healing throughout the different healing periods. mentally tenotomized Achilles tendons and to reduce the com-
According to the biomechanical and histopathological find- plications of prolonged immobilization [20,28]
ings, cathodal MES showed significant improvements than an-
odal MES in the 3-week, while anodal MES showed more The intensity and pulse frequency of MES used in the study
significant improvements in the 5 and 8 weeks. were chosen according to previous studies which suggested the
optimal range for the best biological effect of microcurrent
It was reported that the regenerating Achilles tendon therapy [8,13,14].
undergoes different stages of healing and each stage involves
a different set of cellular events [23]. Furthermore, it was sug- One limitation to this study was that, for standardization,
we induced complete surgical transection of the Achilles
