Study Of MRI And Histopathology On Animal Models Of Knee-joint Subchondral Bone Bruises

Objective To observe the manifestation of MRI and histopathology of animal model of knee-joint subchondral bone bruises created by a weight by means of free fall from different altitude, provide some references and evidences for clinical diagnosis and treatment of bone bruises.Methods Total 30 New Zealand White rabbits were divided into 3 groups by random number table;(High、Moderate and Low energy group) 10 in each group.The Medial tibia platform of rabbits of each group were struck by a 0.5kg weight by means of free fall from different heights( 0.6m、0.5m and 0.4m) through a transparent hollow pipe with scale. All animals were detected by MRI after 4 hours、after 1 week and after 3 week.Knees of 3 rabbits in each group were dissected when being sacrificed after MRI scanning,and specimens of knee-joint were scanned by Micro CT. The histological changes of the subchondral bone of tibial plateau were observed through microscope.Analyze the SNR and Bone morphology parameters of bone bruises.Results The manifestation of T2 WI and fat suppressed sequence T2 WI of animal models after4 hours appeared as areas of high signal intensity.The SNR of each sequence in 3 groups were statistically significant(p<0.05) by the completely random design analysis of variance and the SNR of High、Moderate and Low energy group were gradually decrease(p<0.05)in further analysis. After 1 and 3 week the representation of T2 WI and fat suppressed sequence T2 WI also represented as areas of high signal intensity,but it was weaken after 3 week and the SNR of each sequence in 3 groups were statistically significant(p < 0.05). Repeated measurement data analysis of variance: Time effect and interaction between time and processing effect were statistically significant(p<0.05);SNR in 3 weeks with time linearly reduced(p < 0.05), the SNR of High,Moderate and Low energy group were gradually decrease(p < 0.05). The consequences of Micro CT: After 4 hours, the differences of Tb. Sp in each group were statistically significant(p<0.05); After 1 week and 3 weeks,Tb. N and Tb. Sp in High and Moderate energy group had no statistical difference(p<0.05), but compared with low energy group the differences were statistically significant(p<0.05).Hemorrhages and edemas were prominent in histological examination of the subchondral bone areas of bone bruises and 1trabecula bone micfracture was observed in High energy group.After 3 weeks, hemorrhages and edemas still existed in the subchondral bone areas of bone bruises.Conclusion Animal models of knee-joint bone bruises can be manufactured by free fall facility;The expressions of T2 WI and fat suppressed sequence T2 WI of each animal model are areas of high signal intensity, different levels of bone bruises of subchondral bone caused by different impact forces and the SNR gradually decrease over time;Upon histological examination,hemorrhages and edemas are prominent at the subchondral bone areas of bone bruises, and trabecula bone micfracture can exist part of animal models.