Effect Of Different Intensity Treadmill Exercise On Healing Of Achilles Tendon Rupture In Rats

BackgroundAchilles tendon rupture is a common disease in the orthopedic clinical, which often trauma in2-6cm above Achilles tendon attachment point. Because of difficult healing caused by poor blood supply, Achilles tendon rupture is a kind of serious injury and have consumed a lot of human and material resources on its diagnosis and treatment over the years. There are two ways, surgical treatment and conservative treatment, for the treatment of Achilles tendon rupture, but they both have conspicuous beneficial and disadvantages in rehabilitation of this trauma. In recent years, in order to assess the efficacy of conservative treatment and surgical treatment, a large number of scholars have conducted studies on randomized controlled experimental and systematic reviews, and they proved that there was no significant difference in functional recovery of both treatments. Surgery treatment can reduce the re-rupture of the Achilles tendon, but there is a higher risk of complications. Therefore, there are still a lot of controversy in determining which is the best treatment strategy for Achilles tendon rupture.Fortunately, recent studies have shown that functional exercises in early conservative treatment can significantly reduce the occurrence of re-fracture and reduce the risk of surgery. In addition, Achilles tendon healing requires not only the differentiation and proliferation of Achilles tendon cells, also requires a certain amount of mechanical environment in order to rehabilitate its biological characteristics. Andersson et al documented that early mechanical stimulation can promote the biological characteristics of the Achilles tendon, at the same time, they proved that there were no statistically significant in Rats’Achilles tendon healing biomechanical after they had run at a constant speed (9m/min) for15min,30min,60min. Ilizarovls et al Proposed that Achilles tendon cells which were cultured in Vitro produced different stimulus signal through the induction of different tensile stress. Thus, we could speculate that early mechanical stimulation can promote Achilles tendon healing and improve the biomechanical properties in Achilles tendon rupture healing. Moreover, Exercise intensity may play more important role on the Achilles tendon cell signal compared with exercise time. Based on the above assumptions, we hope that this study could figure out the impact of early exercise on the repair of Achilles tendon rupture from the point of biomechanics and tissue biology. And that could provide a theoretical basis for the early rehabilitation after Achilles tendon rupture surgery in clinical.ObjectiveEarly active mechanical stimulation can promote the healing of the tendon, to observe the effect of different intensity treadmill exercise on the healing of rat’s Achilles tendon rupture so as to provide the experimental basis for clinical practice.Methods1. rats groupThe thirty-two rats were randomly devided into four groups with random digital tables. It was the immobilization group, treadmill exercise with five meters per minute group、with ten meters per minute group and with fifteen meters per minute respectively. And each group had eight rats.2. rats modelSelect the Sprague-Dawley rats (provided by the animal experimental center of south hospital), a total of thirty-two rat, regardless of their gender, weighting190-240g. The rats wer feeded in animal experiment center in the south hospital, to control the room temperature at25℃,60%humidity, ultraviolet disinfection and exhaust on a regular basis. The rats were anesthetized with pentobarbital. Under aspetic conditions, chlorhexidine and alcohol disinfect the skin, and Remove the surgical site’s hairs.the bilateral Achilles tendons of the rats were cut transversely7mm proximal to its calcaneal insection and a2mm long segment was removed to enlarge the defect. The wound was washed with physiological saline after the surgical procedure. Then stitching the wounds with5-0suture line. And all of the rats were injected with penicillin for three days to prevent infection postoperatively.3. IntervationAfter the surgical procedure, the immobilization group immobilize with tail suspension. Treadmill exercise group began to run after3days, treadmill exercise with the five meters per minute spped、ten meters and fifteen meters speed were running30minute one day. the treadmill set time still take the rat tail suspension.4. outcome observationWe observe the rat wound infection, daily activities, live, and the Achilles tendon in general situation at two and four week. The tendon tissue samples were harvest after operation for immunolistochemical staining. We also observed the new blood vessels, fibroblasts and inflammatory cells under a microscope.5. outcome measureThe Achilles tendon specimens were embedd and sectioned. Then the I type collagen fibers adn TGF beta was immunohistochemical staining with SP method. And the yellow part is the positive expressionThe positive density values of type I collagen fibers and TGF beta were calculated by an image analysis software. The biomechnical test which was consisted of the most gliding excursion, and the ultimate tensile strength was implemented at four weeks in four groups.6.StatisticsThe statistical analysis software SPSS13.0was used for the data analysis. The measurement data was presented with mean(±SD). The comparison between groups was analyzed with ANOVA, the LSD multiple comparison was used when variance analysis is significant, if not, Dunnett method was used. And the significant difference was P value(<0.05).Results1. All the animals survived till the end of the experiment, and no wound infection, all the skin wound heal in a good condition, the Achilles tendon and tendon tissue can observe the hyperemia and edema. All the anastomotic space grow with fusiform shape. The tendon have a poor mobility and a soft character at two week. At Postoperative4weeks group, tendon edema and hyperemia gradually decreased. TheAchilles tendon almost healed, the anastomotic space was mainly tendinous tissue, and the sliding character was better in the treadmill exercise group.2. HE staining showed that a lot of inflammatory cell infiltration and angiogenesis formation can be observed in all the group,but less fibroblasts forming, the fibroblasts grow into bulk distribution, like oval shape and arranged irregularly. And in immobilization group, there are more inflammatory cell infiltration,but less fibroblasts forming. At Postoperative4weeks group, inflammatory cell infiltration and angiogenesis gradually decreased. And the5meteres group decreased notable. There are lots of fibroblasts in the treadmill exercise group, with longitudinal growth and closely packed. In the immobilization group, also visible fibroblast growth. But the fibroblasts grow poor and arrange more clutter.3. Immunohistochemical staining:Positive staining of type I collagen fibers was observed at2、4weeks postoperatively. The positive staining of collagen fibers in treadmill exercise groups was significantly higher than that in immobilization group((F=4.697;P=0.015;F=3.924;P=0.028)). There are no obvious diference in the treadmill exercise groups. And the Positive staining of TGF beta in treadmill exercise groups was significantly higher than that in immobilization group at2week. But at4week, the TGF beta in treadmill exercise groups was significantly lower than that in immobilization group.(F=3.990, P=0.027; F=6.304, P=0.000)4.The biomechanical tests showed:there was no significant statistical differences in the most gliding excursion between4groups at4weeks postoperatively (F=0.224;P=0.89,). The ultimate tensile strength of treadmill exercise groups were significantly higher than immobilization group and (F=5.835, P=0.005), but there are no obvious diference in the treadmill exercise groups.ConclusionsEarly active mechanical stimulation can reduce the inflammation, and can promote the proliferation of type I collagen fiber in Achilles tendon, which may be associated with its altering the expression of TGF-β1, also can increase the strength of the Achilles tendon.on the healing process of Achilles tendon rupture in rats. Early active mechanical stimulation can promote the healing of the tendon; the Low-level mechanical stimulation is sufficient to improve tendon healing in rats; intense exercise can improve the healing of the Achilles tendon, but increase the risk of inflammation.