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Egypt. The tensile machine Lloyd instruments LR10K (Lloyd
Instruments Ltd, West Sussex, UK) was used to measure bio-
mechanical properties of the tendons. A load deformation
curve and other biomechanical parameters were obtained,
including: load at break in Newton (N) (amount of load ap-
plied beyond which the tendon will fail), stiffness in Newton/
millimeter (N/mm) (resistance to deformation), ultimate tensile
strength in Newton (N) (maximum stress that tendon can with-
stand while being pulled before necking), elastic modulus in
Newton/millimeter2 (N/mm2) (the slope of the stress strain
curve in the elastic deformation region) and work done in milli 8 was significantly higher than those of weeks 3 and 5
Joule (mJ) (the amount of energy transferred by a force acting
through a distance) [22].
Each tendon was clamped at each end of serrated grips;
jaws secured the calcaneus at one end and the musculotendi-
nous junction at the other. The musculotendinous junction
end of the Achilles tendon was fixed between two pieces of
sandpaper and was mounted and secured with quick-setting
superglue (Aron Alpha, Toagosei Co Ltd, Tokyo, Japan).
The system was loaded to 250 N load cells. Each tendon was
loaded to failure (till tendon rupture) at a constant crosshead
speed of 50 mm/min. The specimen was kept moist throughout
testing using normal saline to avoid tensile strength changes
associated with drying.
Histopathological study
Specimens were fixed in 10% neutral buffered formalin for one
week, dehydrated in alcohol, cleaned in Xylol and embedded
in paraffin. The blocks were cut at 6 lm thickness and the sec-
tions were stained with (Hematoxyline and Eosin H&E) for
histological examination [23].
Statistical analysis
Statistical analysis was performed using ‘‘SPSS’’ for windows
evaluation version 15.0. According to the experimental design,
the study included five dependent variables which were the
measured biomechanical parameters and two independent
variables which were time and MES. The biomechanical
results were presented in the form of mean, standard deviation
(SD) and the percentages of these measures in relation to that
of the normal intact Achilles tendons. Factorial ANOVA was
used to determine the effect of time and MES and a Post –hoc
test (LSD) was then used to determine differences between
weeks 3, 5, 8 and the differences between control, cathodal
and anodal groups. Significance level was set at (0.05).
Results
Biomechanical results
The results of all biomechanical parameters of the tenotomized
and repaired tendons in the three experimental groups were
Table 1 Biomechanical values of normal group.
Load at break (N) Stiffness (N/mm)
Mean 215.66 124.95
SD 9.72 5.78
SD = standard deviation, N: Newton, UTS: ultimate tensile strength, N/mm: Newton/millimeter, mJ: milli Joule
A.F. Ahmed et al.
found to be lower compared to those of the normal intact ten-
dons with the highest percent of improvement recorded from
the three studied groups at week 8 for all the biomechanical
measures (Tables 1 and 2).
Load at break
Effect of time: Load at break differ significantly throughout
the study periods (3, 5, 8 weeks) within each groups
(P = 0.000). In the three studied groups, load at break at week
(P = 0.000), and at week 5 load at break was also significantly
higher than week 3 (P = 0.000) (Table 3).
Effect of MES: As shown in Table 4, load at break values of
the cathodal and anodal groups at weeks 3, 5, 8 was signifi-
cantly higher than the control group (P = 0.000) and that of
the cathodal group was significantly higher than that of the an-
odal group at weeks 3 (P = 0.04) and anodal group was signif-
icantly higher than cathodal group at weeks 5 and 8 (P = 0.01,
and 0.001 respectively).
Stiffness
Effect of time: Regarding changes across study period, Stiff-
ness at week 8 was significantly higher than those of weeks 3
and 5 (P = 0.000), and at week 5 also was significantly higher
than week 3 (P = 0.000) (Table 3).
Effect of MES: As shown in Table 4, stiffness values of the
cathodal and anodal groups at weeks 3, 5, 8 were significantly
higher than the control group (P = 0.000) and that of the
cathodal group was significantly higher than that of the anodal
group at weeks 3 (P = 0.04) while at weeks 5 and 8 that of the
anodal group were significantly higher than cathodal group
(P = 0.000).
Ultimate tensile strength (UTS)
Effect of time: Regarding changes across study period, UTS at
week 8 was significantly higher than those of weeks 3 and 5
(P = 0.000), and at week 5 also was significantly higher than
week 3 (P = 0.001, 0.003, and 0.004 for control, cathodal
and anodal groups respectively) (Table 3).
Effect of MES: As shown in Table 4, UTS of the cathodal
and anodal groups at weeks 3, 5, 8 were significantly higher
than the control group (P = 0.000) and that of the cathodal
group was significantly higher than that of the anodal group
at weeks 3 (P = 0.02) while at weeks 5 and 8 that of the anodal
group were significantly higher than cathodal group
(P = 0.006 and 0.000 respectively).
Elastic modulus
Effect of time: Elastic modulus of the three groups at week 8
was significantly higher than those of weeks 3 and 5
UTS (N) Elastic modulus (N/mm2) Work done (mJ)
301.21 54.84 2093.00
15.68 4.64 74.65