| Objective: Tendon injury occurs from time to time in daily life,and the proportion of cases with Achilles tendon injury increases year by year.Achilles tendon is the thickest tendon among all tendons in the human body.It often has too much strength in strenuous exercise,resulting in partial or complete tear of Achilles tendon fibers.Due to relatively few tendon blood vessels,the repair and regeneration ability of tendon injury is poor.Achilles tendon rupture often needs surgical treatment,which not only causes huge economic losses to patients,but also brings physical and mental pain to patients after postoperative rehabilitation.The traditional fixation of Achilles tendon rupture in the extended position to reduce the tendon tension is considered to be conducive to prevent the possibility of tendon rupture,but it is easy to form Achilles tendon contracture and other related complications.Research shows that there are many longitudinal collagen fibers around tendon cells,which can make the tendon adapt to a certain strength of stretching,so that the tendon has a certain degree of stretching.In early clinical trials,our team tested some mechanical indexes under functional external fixation and compared them with extended external fixation.The results showed that functional external fixation performed better than traditional extended external fixation.However,under the external fixation of functional position,the change trend of tensile stress at the broken end of Achilles tendon after Achilles tendon rupture is still unknown.The expression characteristics of related proteins and genes under different fixation methods and continuous tensile stress are also unclear,and there is no relevant literature on it in recent years.In this experiment,biomechanical sensors were used to detect the biomechanical changes of rabbit Achilles tendon rupture in vivo.By observing the changes of Achilles tendon tension,we can provide a reliable basis for the safety of functional external fixation after Achilles tendon rupture.And detect the expression of related genes and proteins in the healing process of ruptured Achilles tendon under functional position external fixation and extension position external fixation,and compare different fixation methods to further explore whether functional position external fixation is feasible.Methods:Experiment 1: 20 male Japanese white rabbits weighing 2-2.5 kg were selected.After fasting and drinking,they were anesthetized by intramuscular injection.The right lower limb of the rabbit was selected as the measurement side and divided into three groups(A.intact group,B.disconnected group,C.in vivo measurement group)to measure the mechanical changes of the broken end of the Achilles tendon in the living rabbit Achilles tendon rupture model under different fixed body positions.The mechanical sensor was sutured to the hind limb of the rabbit to measure the change trend of the tensile stress of the broken end fixed in the functional position and extension position.Maintain the body position when measuring the functional position,and observe the changes of mechanical values for 5,10,15 and 20 minutes.Experiment 2: 20 adult healthy Japanese white male rabbits,weighing 2-2.5 kg,were selected again.The rabbit’s lower limbs were planned to be repaired by "acute rupture of Achilles tendon".The left and right legs of the same rabbit were fixed in functional position and extension position respectively.They were divided into group A(functional position external fixation group)and group B(extension position external fixation group).Group A was composed of 20 rabbits’ left lower limbs and group B was composed of 20 rabbits’ right lower limbs;On the 1st,3rd,7th,14 th and 30 th days after repair of Achilles tendon rupture,four rabbits were randomly selected for lower limb specimens.The expressions of collagen type Ⅰ,type Ⅲ protein and tendon protein C under different fixation methods were detected by qPCR and WB.Results: 1.At 5min,10 min,15min and 20 mih after operation,the tension at the broken end of Achilles tendon with external fixation in functional position decreased gradually with time.When the ankle was fixed at 90 °,the tension at the broken end reached the peak immediately.Then,the tension of Achilles tendon under external fixation in functional position decreased sharply at 0-5min,and then decreased gradually with time at 5-15 min.After 15 min,it finally became stable,but not 0,There was continuous tensile stress at the broken end of the functional position external fixation Achilles tendon,and finally maintained a small tension(3-5% of the peak tension).The tensile stress of the extension position external fixation was 0.There was significant difference in the tensile stress changes between the functional position external fixation and the extension position external fixation rabbit Achilles tendon in the non disconnection group,the disconnection group and the in vivo measurement group(P < 0.05)There was no obvious abnormality in the change of external fixation force of functional position between the disconnection group and the in vivo measurement group,and the difference was not significant in the statistical comparison of the three groups(P > 0.05).2.On the 7th and 14 th day after repair of Achilles tendon rupture,the levels of type Ⅰ and Ⅲ collagen and tendon protein C in qPCR and protein expression were gradually increased in each group(P < 0.05);On the same day(7 days,14 days and 30 days),the expression levels of type I collagen,type Ⅲ collagen,tendon protein C protein and gene in functional position fixation were significantly higher than those in extension position fixation(P < 0.05);The expression of functional position external fixation was earlier than that of straight position external fixation at the protein and gene levels(P < 0.05).Conclusion:1.After the repair of acute rupture of Achilles tendon in rabbits,the external fixation of Achilles tendon in functional position has creep effect,and the tension at the broken end decreases greatly,which can prevent the secondary rupture of Achilles tendon under the continuous tension.2.Under functional external fixation,there is a continuous tensile stress of 3-5% of the peak tension at the broken end of Achilles tendon,which may be the appropriate tension to promote Achilles tendon healing.3.The expression content and timing of tenascin C may be an index to effectively judge the start and end time of Achilles tendon repair.4.Under external fixation in functional position,the tensile stress at the broken end of Achilles tendon promotes the secretion of collagen type Ⅰ and type Ⅲ proteins of Achilles tendon,which is more effective in promoting Achilles tendon healing than traditional external fixation in straight position. |
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