| Backgrounds:Limb lengthening according to Illizarov theory and frame is a technical revolution of 1900'. It can be used for atrophic nonunion, focal osteomyelitis, bone defect and extremities inequality. However, nerve, vessel, muscle and so on are bound to be influenced due to limb length increase. The study of the direction have deepening day by day, especially on muscle. Objectives:To study histopathology effect of tibial lengthening on the muscular fiber of gastrocnemius with different rate and proportion by limb-lengthening animal model of experiment rabbits. Methods:Nine rabbits of five-month age with body weigh ambit 2.55-2.80kg were selected and divide 3 groups for A-C randomly. These rabbits were feeded 1 week before experiment. Hind legs of each rabbit were get and experimental leg were selected randomly. To measure length of every leg and make limb-lengthening animal model. Opposite side legs were used for control group without any treatment. The tibia planed to lengthen 10% by 1mm/d for A group, to lengthen 10% by 2mm/d for B group and to lengthen 20% by 2mm/d for C group. To lengthen one time a day for all 3 groups. Limb lengthening started 5 days after operation for all 3 groups lengthening side legs. X-rays were obtained at lengthening complete to observe distraction callus. These rabbits were esecute after feeding 4 weeks again. To measure bilateral tibial length. To cut bilateral gastrocnemius and measure the length of belly and achilles. To get medial gastrocnemius for speciments and paraffin sections of transvers plane were prepared, then stained with HE, PAS, Masson trichrome. A semi-quantitative analysis scoring system raised by Lee et al was applied. The statistical test of histopathologic scores, based on the ordinal scale, among the lengthening groups was done by the Kruskal-Wallis test, followed by the Wilcoxon rank-sum test for individual comparisons among the lengthening groups and within each lengthening group between the lengthened side and the control side. Results:The X-ray at lengthening complete revealed distraction callus can be found for A group, but can not be found for B and C groups. Gastrocnemius length of all 3 groups lengthening side increased following tibia, but lengthened amplitude were not equal to bone, Its belly accounted main part in it and achilles accounded secondary part. Statistical result of histopathologic scores displayed limb lengthening can influence histopathologic appearance of surrounding muscles. Muscle fiber size variation and internalization of nucleus were influenced by limb lengthening obviously after increased lengthening rate and propotion. Following lengthening rate and propotion increased, severity of histopathologic appearance tend to increase. Conclusions:Limb lengthening can promote muscle grow. Gastrocnemius length can increase following tibia, especially belly, but lengthened amplitude were not equal to bone. Statistical comparison of results proved limb lengthening can influence histopathologic appearance of surrounding muscles. After increased lengthening rate and propotion, severity of histopathologic appearance tend to increase. Tendon has ability to lengthen in limb lengthening. In this experiment, the achillis of rabbit's lengthening side appeared a little increasing, but the amplitude were small. The weight didn't occur obvious change according to lengthening rate and propotion. If the rate is too rapid, as 2mm/day, the distraction callus will be in question. There are very many reasons to influence limb lengthening, and lengthening rate and proportion are capital factors in them. They can creat significant influence to the growth and maturation of distraction callus, adaptability of surrounding soft tissue will be taken effection as well. |
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