OBJECTIVETo study the effects of pressure changes on the experimental articular cartilage by utilizing Ilizarov distraction technique.

METHODSThe Ilizarov external fixators were fixed at the left ankle joints of 18 experimental dogs, and the fixators were stretched with a speed of 1 mm/d to create a varus deformity. After three weeks, the ankle varus was 15 degree; when the degree was confirmed by X-ray film, the same traction was retained for 3 weeks. Then the traction decreased at the same speed of 1 mm/d to correct the deformity for 3 weeks. At the 3rd, 7th and 9th weeks, articular cartilages were separated from medial foot of the experimental and normal side to do morphology observation after HE stain, which were group A, group B, group C and group D respectively separately. The gray scale values were obtained using Image-Pro Plus 6.0 software and compared among the 4 groups using SPSS 13.0. The microstructure of cartilage was observed through transmission electron microscopy.

RESULTS(1) The Mankin scores: there was significant difference between group A and group B (P=0.043<0.05); and significant difference between group B and group C (P=0.038<0.05). (2) The values of gray scale: there was significant difference between group A and group B (P=0.047<0.05); significant difference between group B and group C (P=0.045<0.05); significant difference between group A and group D (P=0.039<0.05); no significant difference between group C and group D (P=1.23>0.05).

CONCLUSIONUsing Ilizarov technique, when the pressure between the cartilage surface of the ankle joint increases, the necrosis of articular cartilage occurred; and when the stress between the articular cartilage surface decreases, the damaged articular cartilage can be restored.