| Background:Distraction osteogenesis of external fixator poroma is mainly used to cure the unequal length and deformity caused by trauma, tumor, osteopathy and congenital dysplasia, etc. With the limb lengthening broadly carried out clinically, The key factors to restrict the scale of lengthening is not knitting or neurovascular any more, but the hypofunction and soft tissue contractura of adjacent joint changes. How to effectively solve the problems that Lengthening may lead to, such as hypofunction of joint, regression articular cartilage and ankylosis of joint have been the focus in this area.Objective: To investigate the form of organization and ultramicro structural change of knee cartilage of the rabbit caused by slow distraction during limb lengthening of the tibia osteotomy. And still to investigate the adaptation of the knee cartilage with the tress stimulus during slow distraction when lengthening. To provide theoretical foundation to safely carrying out the lime lengthening clinically.Method:50healthy rabbits were randomized into two groups. There are5rabbits in control group, and45in experimental group which was randomized into limb lengthening group (group A),4weeks delay observation (group B),8were weeks delay observation (group C)。Each group was subdivided into three sub-groups according to distraction degree, which were1cm(10%) group (A1, B1, C1),2cm (20%)group(A2, B2, C2),3cm(30%) group (A3, B3, C3).There were9groups in all and5rabbits in each one. Double hind limbs were without any treatment. Right hind in experimental group was lengthened, after the upper tibia osteotomy and conducted by unilateral external distractor (distract0.5mm for each time, twice per day) at a speed of1mm/d. Determine the extent of the lengthening and the iconography changing of knee joint by X-rays. Draw material from knee cartilage and observe observe the tibial plateau articular cartilage morphosis changing by means of scanning electron microscope transmission electron microscope.Result:1.Establish the animal models successively. There was no obvious iconography change of knee at every time phase in each group.2.Pale of cartilage on tibial flat were just noted in3cm group (A3,B3,C3), without obvious ulcer and osteophyma.3. After30%lengthening, morphosis of knee cartilage is damaging changed, including the thinning of the surface layer, the disorder of the cell array, disappears of cell nucleus, decrease of the cell body, the increase of acidophily. Ultrastructure register as disordered arranged of cartilage cell, regression of some part of the cell, there is crack in cartilage matrix, the decrease of cellular organ such as rough endoplasmic reticulum, the thickening and crack of the joint surface in the structure of reticular fibre. When coming to the consolidation period, the organism can repair by itself, but till eight weeks after lengthening, it can’t recover perfectly.Conclusion:1. Rabbit is an optimal option of limb lengthening animal model. The rabbit limb lengthening model were established successfully. This model can be applied to the following experiments entirely and can acquired the precise data.2. The articular cartilage showed certain adaption to stimulation of distraction during low degree distractions and the injure is small. To greater distraction degrees some abnormality in metabolism of arthrodial cartilage may occure, and with the increase of lengthening, the injure is more severe..3. During the process of limb lengthening, pathologic change of related articular cartilage is temporary; When the lengthening is stopped, the stimulation of distraction decrease or disappear, so cartilage can repair itself by self functional compensation. The more increasing, the later of the repair itself. |
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