| BackgroundCongenital clubfoot is a common foot deformity in children. Its estimated population incidence is 1 per thousand live births in most western countries, but it may vary from 0.39 per thousand in Chinese people. The incidence of boys is more than girls. Congenital clubfoot is a deformity including forefoot adduction and cavus, hindfoot equines and varus and secondary distal tibia internal rotation. It is the important cause of the disabled children. At present, Ponseti method have been recognized an conservative and most effective method for treat the congenital clubfoot in early age all over the world. The success rate of the Ponseti method has been in excess of 90%, The aim of congenital clubfoot treatment is to achieve a functional, painless, plantigrade, flexible foot. Ponseti method consists of three phases:manipulation followed by weekly serial casting as the first phase, percutaneous Achilles tenotomy and post-tenotomy casting as the second phase, and a bracing protocol as the third phase. Percutaneous Achilles tenotomy is an important step of Ponseti technique, which may be required in more than 90% of patients to correct the unyielding hindfoot equines to protect the normal development of foot arch. An Achilles tenotomy is a simple and safe technique with tow invasiveness. In addition, there is no stiffness of the foot after tenotomy when compared with other traditional extensive soft-tissue releases. Ponseti have described that a Ponseti-type Achilles tenotomy creates a gap that heals, eventually leaving the tendon in continuity. It does not appear to the risk of rupture. Under 4 years of age can repeat the percutaneous heel-cord tenotomy. All of this shows that the importance of percutaneous Achilles tenotomy in Ponseti method.Although, percutaneous Achilles tenotomy is a simple, safe, minimally invasive technique, many orthopaedic surgeons are still worried about the healing and function of the ruptured Achilles tendon after percutaneous Achilles tenotomy. It will cause children with great pain, so they are reluctant to use percutaneous Achilles tenotomy to correct the residual equines deformity. Especially the older children with CCF. Orthopaedic surgeons often preferred to using open Achilles lengthening, suturing the stumps, and think this procedure may reduce the risk of rupture, improve the mechanical strength of the healing Achilles tendon after surgery。 However, due to the particularity of anatomical structure of the Achilles tendon, the open surgery destroyed the blood supply of the Achilles tendon and stripped the surrounding soft tissue in excess, increasing the risk of infection and necrosis of it. In addition, the Ponseti did not report the limit age of children of the operation technology, this blocked the application and popularization of Ponseti method in developing countries.In order to define the mechanical properties of the healed Achilles tendon and limit of age of patient who was performed percutaneous Achilles tenotomy. The result can provide the important clinical evidence and theory basis for treatment of rupture Achilles tendon and choice surgery scheme.ObjectiveTo reseach the biomechanical and histological properties of healing of rupture Achilles tendon of rabbit in different age after percutaneous tenotomy, observing the healing and function of the ruptured Achilles tendon. Then to explore the best age for healing after percutaneous Achilles tenotomy and provide experimental basis for clinical practice.Methods1. Rabbits groupThe forty-eight SPF level New Zealand rabbits in different ages were divided into four groups according to the same age (provided by the animal experimental center of south hospital), the male and female unlimited, group 2, group 4, group 8, group 12, respectively. Each group had 12 rabbits with same weight. Then each group was randomly divided into two groups again and each group had 6 rabbits. According to the same age divided into group 2A and group2B, group4A and group4B, group8A and group8B, groupl2A and groupl2B.2. Rabbits modelSelect the rabbits of each group A and fixed the limbs in the prone position. Remove the surgical site’shairs, chloorhexidine and alcohol disinfect the skin, The rabbits were anesthetized with lidocaine. Under aspetic conditions, the bilateral Achilles tendons of the rabbits were cut transversely 1.0cm proximal to its calcaneal insection. After the Achilles tendon was totally rupture, The wound was washed with physiological saline after the surgical procedure without suturing and binded up with Sterile gauze. Apply a long-leg cast with the ankle at neutral, and all of the rabbits were not needed to injected with penicillin to prevent infection postoperatively. The rabbits were feeded in animal experiment center in the south hospital in single cage, to control the room temperature at 25℃,60%humidity, ultraviolet disinfection and exhaust on a regular basis.3. InterventionThe rabbits were feeded in animal experiment center in the south hospital in single cage, to control the room temperature at 25 ℃,60% humidity, ultraviolet disinfection and exhaust on a regular basis. Remove of the cast after 4 weeks.4. Outcome observationWe observe dally activities, live, wound infection, tower limbs activities of the rabbits and the Achilles tendon in general situation after remove of the cast at four weeks. The Achilles tendon tissue samples were obtained after operation for HE staining. We also observed the new blood vessels, fibroblasts and inflammatory cells under a microscope.5. Outcome measureAfter 16 weeks, The Achilles tendon tissue samples were obtained in all the groups. Then remove the tendon tissues, preservation at 0 degrees physiological saline. Then test the maximum tensile strength of Achilles tendon under the constant temperature. To analysis the biomechanical characteristics of Achilles tendon through the statistical analysis software.6. StatisticsThe statistical analysis software IBM SPSS 20.0 was used for the data analysis. The measurement data was presented with mean (+SD). The comparison in all groups was analyzed with 2*2 factorial design ANOVA, the LSD multiple comparison was used when variance analysis is significant; Within groups compared with single factor analysis of variance method; Comparing the two groups by using two independent T test sample.Results1. All the animals survived till the end of the experiment with good activities. At 4 weeks, remove of the cast, and no wound infection. All the rabbits’skin wound and rupture Achilles tendon heal in a good condition in group 2,4,8,12. In group A it can palpable a continuous structure at the gap, which significantly smaller than the group B, and the dorsiflexion of the foot of the group A is significantly larger than group B. At 16 week, all the rupture Achilles tendon of group A healed, At the gap it can palpable a continuous and stronge structure like tendinous tissue, which is a bit smaller than the group B. The length of Achilles tendon of group A is 1 cm longer than the group B. The diameter is smaller than group B, there was slightly adhesion between the Achilles tendon and tendon membrane.2.2.1 In group 2A HE staining showed that the Achilles tendon tissue is continuous, complete. The fibers form closely liking a funicular, the arrangement of the fibers is slight irregularly and creases in longitudinal growth. The fibrob lasts grow into bulk distribution, like oval shape and arranged irregularly. There are a large number of mature fibroblasts, the nucleus are like fusiform, there is a little inflammatory cell infiltration and angiogenesis forming, but more fibroblasts forming. The tendinous membrane is continuous, slightly rough surface. HE staining showed that the Achilles tendon tissueis continuous and complete in Group 2B. The fibers arrange closely and regularly, the fibroblast is like oval cells, the nucleus is like fusiform. The tendinous membrane is continuous and smooth.2.2 In group 4A, HE staining showed that the Achilles tendon tissue is continuous and complete. The fibers form closely liking a funicular, the arrangement of the fibers is slight irregularly and creases in longitudinal growth. The fibroblasts grow into bulk distribution, like oval shape and arranged irregularly. There are a large number of mature fibroblasts, the nucleus are like fusiform, there is a little inflammatory cell infiltration and angiogenesis forming, but more fibroblasts forming. The tendinous membrane is continuous, slightly rough surface. HE staining showed mat the Achilles tendon tissue is continuous and complete in Group 4B. The fibers arrange closely and regularly, the fibroblasts are like oval cells, the nucleus is like fusiform. The tendinous membrane is continuous and smooth.2.3 In group 8A HE staining showed that the Achilles tendon tissue is continuous, complete. There are spaces between the fibers, the arrangement of the fibers is significantly irregularly and creases in longitudinal growth. There are a little number of mature fibroblasts, the nucleus are like elongated shape, there are inflammatory cell infiltration and angiogenesis forming, and less fibroblasts forming. The tendinous membrane is continuous, but significantly rough surface. HE staining showed that the Achilles tendon tissueis continuous and complete in Group 8B. The fibers arrange closely and regularly, the fibroblasts are like oval cells, the nucleus is like fusiform. The tendinous membrane is continuous and smooth.2.4 In group 12A, HE staining showed that the Achilles tendon tissue is continuous and complete. There are significantly spaces between the fibers, the arrangement of the fibers is significantly irregularly and creases in longitudinal growth. There are a little number of mature fibroblasts, the nucleus are like etongated shape, there are inflammatory cell infiltration and angiogenesis forming, and less fibroblasts forming. The tendinous membrane is continuous, but significantly rough surface. HE staining showed that the Achilles tendon tissue is continuous and complete in Group 2B. The fibers arrange closely and regularly, the fibroblasts are like oval cells, the nucleus is like fusiform. The tendinous membrane is continuous and smooth.3. Biomechanical testPostoperative 16 weeks, There were significant differences between different age groups (F= 97.842, p= 97.842);There were significant differences between group A and group B (F= 2105.073, p= 2105.073);There have the interaction effects between age and group (F= 472.916, p= 472.916), and comparing two groups with age as a result, it had statistical significance (p< 0.05); In the group A and group B, the comparison between the group with age were statistically significant. For group 2, group 4, group 8, group 12 the group A and the group B was statistically significant difference.Conclusion1. In the process of rabbit percutaneous Achilles tenotomy model, the rupture Achilles tendon can restore its continuity at 4 week after operation.2. The younger of rabbits, the faster the Achilles tendon healing and the better of mechanical properties and the structure arrangement of healed Achilles tendon after 16 weeks. |
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