| Objective:(1)An animal model of impacting injury of medial femoral condyle was established to observe the pathological change and biomechanical characteristics of medial femoral condyle cartilage after different impacting injury.(2)To investigate the preventive effect of the Sodium Hyaluronate to post-traumatic osteoarthritis by injecting in articular cavity.Materials and methods: (1)The different cartilage injury models of the medial femoral condyle of rabbit in vivo was made by impacting of low(0.9J) and high-energy(6.3J).(2)56 New Zealand adult rabbits were divided randomly into low-energy and high-energy two groups, each group was 28. One side was experimental group,the opposite side as control group.Four rabbits were killed at each of the following intervals:4 days,l week,2 weeks,4 weeks, 8 weeks, 16 weeks and 32 weeks after impacting injury.The specimens were observed as pathology histological sections and strained by HE, TUNEL to measured the rate of chondrocyte apoptosis.The sections were strained by HE,Safranin O .The values of gray scale were obtained by imaging analysis.The sections were strained by type II collagen monoclonal antibodyimmunohistochemically and in situ hybridization of mRNA of type II collagen .The values of gray scale and positive chondrocytes were obtained by imaging analysis.The ultrastructures of the chondrocytes and cartilage were observed by scaning electron microscope(SEM) and transmission electron microscope(TEM).The biomechanical properties such as instantaneous shear modulus,equiliburium shear modulus and maximal elastic rate were measured by pulse compression way. All of the data were analyzed by t test.Results:(1)In high-energy group(6.3J),the cracks were observed in cartilage but not in the calcified cartilage zone and subchondral bone through HE sections,the distortion and rupture of the collagen fiber framework were observed in the middle and deep zone through SEM.In low-energy group(0.9J),the cracks were not observed in the cartilage ,calcified cartilage zone and subchondral bone,the distortion and rupture of the collagen fiber framework were not observed in cartilage through SEM.(2)In early stage of post-injury,the rate of chondrocyte apoptosis in low and high-energy was significantly higher than control group.After 4 weeks.the rate of chondrocyte apoptosis decreased to the level of control group in low-energy.In high-energy group,the rate of chondrocyte apoptosis was constantly upgraded-phase,higer significantly than the level of control group.(3)In low-energy group,the Mankin'score was not significantly different from the control group.In high-energy group, was constantly upgraded-phase,higher significantly than the level of control group.(4)In low-energy group,the value of gray scale of type II collagen was significantly different from the control group.In high-energy group, the value of gray scale of type II collagen wasnot significantly different from the control group in 4 days,1 week,2 weeks,After 4 weeks the value of gray scale of type II collagen was significantly different from the control group.(5)In low-energy group, the rate of positive chondrocytes of mRNA of type II collagen was not significantly defferent from the control group. In high-energy group, the rate of positive chondrocytes of mRNA of type II collagen was not significantly different from the control group in 4 days,1 week. After 2 weeks the rate of positive chondrocytes of mRNA of type II collagen was significantly different from the control group.(6)In low-energy group, the instantaneous shear modulus and equiliburium shear modulus were degraded in 4 days,1 week and 2 weeks,but were not significantly different from the control group.From 4 weeks, the instantaneous shear modulus and equiliburium shear modulus restored to the level of control group.In the high-energy group, the instantaneous shear modulus and equiliburium shear modulus were degraded in 4 days,1 week and 2 weeks,but were significantly different from the control group.From 4 weeks the instantaneous shear modulus quickly degraded and from 8 weeks the equiliburium shear modulus also quickly degraded. (7)In low-energy group,the maximal elastic rate was degraded in 4 days,1 week and 2 weeks,but was not significantly different from the control group.From 4 weeks, the maximal elastic rate restored to the level of control group.In high-energy group, the maximal elastic rate was degraded in 4 days,1 week and 2 weeks,but was not significantly different from the control group.From 4 weeks, the maximal elastic rate constantly degraded.(8)After the articular cartilage was injuried by impacting through injecting Sodium Hyaluronate in articular cavity, the rate of chondrocyte apoptosis wasdecreased significantly, the rate of positive chondrocytes of mRNA of type II collagen and the value of gray scale of type II collagen were increased significantly.Conclusion:(1)The rabbits with impacting medial femoral condyle showed as a good animal model to study traumatic osteoarthritis.(2)It was appear the upgrade of the rate of chondrocyte apoptosis and the degrade of the content of proteoglycan during the early stage through the impacting of the low-energy.They restored to the normal level after 2 weeks,because of the integrity of collagen fiber framework.The content of type II collagen,the rate of positive chondrocytes of mRNA of type II collagen and biomechanical properties were not significantly different from the control group.(3)In high-energy group,because of the crack of cartilage,the distortion and rupture of the collagen fiber framework,the rate of chondrocyte apoptosis gradually upgraded,the content of proteoglycan and type II collagen, the rate of positive chondrocytes of mRNA of type II collagen constantly degraded, instantaneous shear modulus,equiliburium shear modulus and maximal elastic rate constantly decreased.(4)The degeneration of articular cartilage that the impacting resulted in the cracks of articular cartilage and the distortion and rupture of the collagen fiber framework were observed in by impacting could be preventive through injecting Sodium Hyaluronate in articular cavity.
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