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Both laser therapy and eccentric exercises are used in tendon injuries. However, the association of these physiotherapeutic modalities is yet little investigated. To evaluate the effect of low-level laser therapy associated to eccentric exercise downhill walking on Achilles tendinopathy of Wistar rats.
Eighteen Achilles tendon from 15 adult male Wistar rats were used. Tendons were distributed in six groups laser, eccentric exercise, laser and eccentric exercise, rest, contralateral tendon, and healthy tendon. Unilateral tendinopathy was surgically induced by transversal compression followed by scarification of tendon fibers. Clinical and biomechanical analyzes were conducted.
Achilles tendon was macroscopically evaluated and the transversal diameter measured. Euthanasia was performed 21 days after lesion induction. Swelling was observed within 72 hours postoperative. No fibrous adhesions were observed nor increase in transversal diameter of tendons. The concomitant use of low-level laser and the eccentric exercise of downhill walking, starting 24 hours after surgically induced tendinopathy, do not result in a tendon with the same biomechanical resistance or elasticity as a healthy tendon.
On the other hand, it also does not influence negatively the structure and function of the Achilles tendon. Fueron utilizados 18 tendones de Aquiles provenientes de 15 ratas Wistar machos adultos. Fue observado edema local en las primeras 72 horas del postoperatorio. The terminology tendinopathy is used to define several painful con-ditions that affect the tendons, which are accompanied by pain, swelling, loss of function, as well as changes in tissues adjacent to joints, where the tendinous structure runs its anatomical course.
Tendons play an important role in musculoskeletal system by transferring tensile loads from muscle stabilizing joints and, therefore, allowing appropriate mo-vement of the limbs 1. They also have the ability to undergo mechanical adaptation in response to forces by change their structure, composition and mechanical properties.
In contrast, an abnormal adaptation to these loads can lead to tendinopathy 2 , which can be associated with several both intrinsic and extrinsic factors to the tendon age, genetics, vascular supply 3. Once injured, depending on the severity, it may take months for complete tendon healing. Nevertheless, the biomechanical charac-teristics may not return to normality 4. Thus, the search for therapeutic procedures that promote faster healing and better quality of tendons has been the purpose of various studies.
In this context, low-level laser is a therapy used in tendon injuries, for promoting analgesia 5 , and for stimulating collagen 6 and growth factors synthesis, as well as angiogene-sis. According to some authors, the therapy allows faster tissue healing 7 , with appropriate structural organization of collagen fibers 8. Controlled physical activity is also considered an important alterna-tive not only for prevention, but also as a form of treating tendinopa-thies.
Among the used activities, those that use exercises with eccentric contraction stand out, where the force generated by the muscle is not sufficient to support the load imposed to it.
Thus, muscle fibers stretch out and elongate when contracting, which results in important physio-logical adaptations in strength and muscle mass. The downhill walking is a type of eccentric exercise that improves the tendon structure and increases the collagen production. These features promote a better quality of repair tissue, leaving the closest of its normal characteristics. The present study hypothesizes that the association of laser therapy with controlled eccentric exercise results in a more resistant and less stiff tendon.
Therefore, the purpose of this study was to evaluate by clinical and biomechanical analyzes the response to low-level laser therapy GaAs nm associated with eccentric exercise on tendinopathy of Achilles tendon of Wistar rats. Eighteen Achilles tendons, from 15 male adult Wistar rats Rattus norvegicus at age between 12 and 14 weeks, and body weight ranging between and g were used. Only animals with physical integrity of the locomotor system were included in the study after physical examination of sensitivity to pain and locomotion capacity table 1.
The observation of abnormalities in "spontaneous" behavior related to sensitivity to pain was evaluated by a subjective scale, classified from 0 to 5 9. The motor capacity was evaluated with scores that ranged from 0 to 10 , where the higher the score the closer the animal was to normality. For this evaluation, spontaneous activity of animals was observed, with respect to the movement of hindlimbs and deambu-lation.
Initially, the animals were individually placed in a 1. For this, six bars were used, each one with 1 m length, and widths of 7. All rats walked each bar twice, from the widest bar to the narrowest one.
All rats moved freely inside the cage, receiving industrial ration, and water ad libitum. Group "L" was composed by animals submitted to laser therapy, whereas group "E" to the eccentric exercise treadmill walking. Group "LE" tendons were submitted to both laser therapy and treadmill walking, whereas the group "R" rested during the whole healing process of tendons.
Group "H" animals had complete integrity of tendons, in other words, were healthy, and group "CL" was formed by contralateral limb to the injured tendon of groups R, E and LE randomly chosen. Animals of groups E and R were handled as if they were going to receive radiation; however the equipment was kept disconnected. The surgical induction of unilateral tendinopathy randomly cho-sen was based to the protocol described by Silva et al.
During the postoperative period, the wounds were daily cleaned with gauze soaked in running water. The treatment began 24 hours after injury induction, being applied daily for 20 days. During laser application, animals were manu-ally immobilized and positioned in ventral decubitus. The device was positioned perpendicular to the injury, and the radiation was always done at the same time, observing an interval of 24 hours between applications, as described by Silva et al.
Groups E and LE tendons were submitted to daily controlled eccen-tric exercise, from 24 hours after tendinopathy induction. With the purpose of prior adaptation to the exercise, the animals were exercised for seven consecutive days before surgical induction of injury.
After tendinopathy induction and during the realization of treat-ments, rats were submitted to physical evaluation of injury site and behavior tests described in Table 1. The first examination was performed 12 hours after surgery and the others every three days for 20 days.
Twenty-four observations were performed during the behavior tests, i. The local examination consisted of evaluation for presence of swelling. Initially it was observed if there was volume increase in the surgery site, and immediately after euthanasia, the transverse diameter of tendon was verified using a caliper rule, positioned in the middle point of the tendon between the myotendinous junction and its insertion in the calcaneal bone Tendon samples were obtained from animals in the different groups for biomechanical evaluation, by tensile testing of Achilles tendon du-ring the proliferative phase of the tendon healing process.
In addition, the transverse diameters of tendons were evaluated. Achilles tendons of the injured and contralateral limbs were dis-sected and subsequently removed, maintaining its insertion in the calcaneal bone. Next, the tendons together with the distal limb were involved in gauzes and placed in plastic containers containing 0.
For biomechanical analysis, limbs were defrosted under running water and dissected, so that the tendon was fixed in its origin to a small region where the gastrocnemius and soleus muscles are located and in its insertion with the whole region denominated "paw".
A tendon fragment of approximately 1 cm was tested to failure using a computer--controlled tissue testing devise Instron Brasil, Tocantins, Barueri, SP, Brazil , which provided a tendon strain diagram. The tendon was clamped and then load to failure was carried out at a strain rate of 0.
The variables maximum load N , stress at maximum load MPa and maximum extension mm were measured. The experiment was arranged in a completely randomized design with six treatments and three replicates tendons , evaluated at 21 days after injury induction.
The amount of tendons per group was the mi-nimum necessary to conduct the research, and allowed to conduct inferential analysis with an appropriate number of degrees of freedom for the residuals of the analysis of variance ANOVA. For physical and macroscopic evaluations, the contralateral and healthy groups were not considered. Data were initially submitted to descriptive analysis, and to Lilliefors and Cochran tests for normality and homogeneity of varian-ce, respectively.
ANOVA was used to check the effects of treatments on clinical and biomechanics analyzes. The analyses were carried out with the Statistica 12, software www. Throughout the experimental period, no limbs presented signs of infection. In the first evaluation, carried out 12 hours after tendinopathy induction, discrete intensity swelling in injured limbs was observed, which was maintained up to 72 hours.
During evaluation of sensitivity to pain, rats apparently presented no signs of discomfort, and maintained normal hindlimb posture. The-refore, all rats received score 0 absente for classification of sensitivity to pain adopted in the study.
Conversely, locomotor capacity evalu-ation revealed discrete lameness in all animals up to 72 hours after tendinopathy induction, observed during deambulation in open field.
The exercised tendons, but not treated with laser therapy, presented lower locomotor capacity than the others, since rats were unable to move on bars with 2. The mean values for group are shown in figure 1. Note that the group submitted to eccentric exercise performed during the expe-rimental period showed less walking ability, unlike the group submitted only to laser therapy. Two animal from the resting group during all evaluated times , one rat from the tendon treated with laser from the sixth evaluation and another one that received laser combined with eccentric exercise from the third evaluation were able to move on the bar 1.
All tendons submitted to biomechanical analysis ruptured in the myotendinous junction. Although the obtained values have demons-trated that tendons treated with laser and eccentric exercise needed higher load The local swelling observed for 72 hours was expected due to the surgical trauma.
The reduction of swelling in tendons submitted to eccentric exercise may be associated with the intensity of the treat-ment, since according to Lana et al. According to the authors, high-intensity exercise causes increased IL However, despite this cytokine trigger a pro-inflammatory effect, it is also related to an anti-inflammatory action, although not enough to reduce the volume of edema.
In tendons from the group treated only with laser therapy, the swelling reduction may be associated with laser action in improving local circulation, since according to Gur et al. Although the group that was maintained in rest received no treatment, the possibility of free movement inside the cage may also have been a positive factor to reduce swelling in these animals.
On the other hand, the absence of difference between groups in the tendon transverse diameter, at 21 days after injury induction, suggests that the Achilles tendon of rats, injured according to methodology adopted in the present study is macroscopically repaired in only three weeks. This fast tendinopathy recovery was confirmed by biomechanical analysis, which revealed no difference between groups.
The absence sensitivity to pain in the physical evaluation performed 12 hours after surgery may be associated with the analgesic admi-nistered, which may have masked the pain condition. However, rats remained with no pain in the following evaluations. In groups that received laser therapy, this absence can be justified by the analgesic effect of the low-level laser, which may result in increased levels of endorphins, and therefore increased pain threshold Despite the absence of sensitivity to pain, the possibility of discomfort of mechanical origin cannot be discarded, since the animals presented a discrete lameness during evaluation of the locomotor capacity.
Another hypothesis is the fact that the scale used for evaluation of sensitivity to pain may not have been adequate for the kind of induced injury. This scale adopted was based on the assessment of abnormal pain-related sensation in rats with sciatic nerve injury. Minville et al. According to the authors, the scale was effective in the iden-tification of pain, and the used drugs promoted dose-dependent anal-gesia. However, as the fracture was created with guillotine, it must have affected not only the bone tissue, but also the adjacent ones.
In addition, periosteal injuries originating from orthopedic procedures cause greater pain severity in the postoperative period, than those in soft tissues
Tendinopatía de Aquiles | Cirugía Ecoguiada.