A Mouse Model Of Osteoarthritis Caused By Lateral Ankle Instability

[Objective] Ankle sprain is one of the most common sports injuries in daily life.If it is not been well treated,it will develop chronic ankle instability,even ankle osteoarthritis.Most of the current research on ankle biomechanics is based on clinical in vivo experiments,cadaveric models or finite element analysis(FEA)models,the level of evidence is low.In this study,in order to study the biomechanical mechanism of ankle instability from a higher level of evidence,we will establish a mouse model that utilizes behavioral and histological methods to study macroscopic and microscopic changes in ankle joint injury.[Methods]Twenty-four 8-week old male C57BL/6J mice were randomly divided into three groups.The lateral collateral ankle ligaments were cut off by microscopic surgery to simulate ankle sprain.For CFL group,mice were cut off calcaneofibular ligament(CFL)to simulate moderate ankle sprain;For CFL+ATFL group,mice were cut off both anterior talofibular ligament(ATFL)and CFL;For SHAM group,mice were cut only the skin without ligaments ruptured.At 1 week to 8 weeks postoperatively,all mice were trained 30 minutes a day using a wheel running fatigue tester to accelerate the production of osteoarthritis.The mice were tested by beam walking test and footprint gait analysis to assess their balance before surgery and 3 days,1 week,2 weeks,3 weeks,4 weeks,6 weeks and 8 weeks postoperatively.The number of times the hind foot slipped off the beam(times)and the duration to cross the beam(seconds)were recorded as statistical data.Stride length asymmetry,paw overlap asymmetry,fore/hind foot base width and stance hind/fore foot were all recorded as statistical data.After 8 weeks,the mice were sacrificed and the ankle joint specimens were removed.The safranin O-fast green was performed to evaluate the production of ankle osteoarthritis.[Results]In beam walking test,for slippery times,ATFL+CFL group shows significant difference(p < 0.05)from SHAM group on D3,W1,and W2 postoperatively.CFL group shows significant difference(p=0.0005<0.05)from SHAM group on W2 postoperatively.At 6 weeks postoperatively,CFL group and CFL + ATFL group had shorter time compared with SHAM group,the difference was statistically significant(p = 0.0312,0.0110 <0.05).At 3 days and 1 week after operation,the duration to cross the beam of SHAM group was significantly decreased(p = 0.015 <0.05).In the footprint gait analysis of mice,the hind foot base width of CFL + ATFL group at 3 weeks,5 weeks and 7 weeks postoperatively was significantly different from that of preoperative,the difference was statistically significant(p=0.011,p=0.018,p=0.017<0.05).There was a significant difference(P <0.05)between the CFL group and the CFL + ATFL group in the stance hind foot at the 2nd week,the 3rd week,the 4th week,the 5th week and the 7th week.At 8 weeks,the mice were sacrificed and their ankle specimens were taken for safranin O-fast green staining,the degree of ankle joint degeneration in CFL + ATFL group was greater than that in CFL group and SHAM group.The degree of ankle joint degeneration in CFL group was greater than that in SHAM group.[Conclusion]The mouse model can provide a new idea and method for the clinical study of osteoarthritis caused by lateral ankle instability.Through the behavioral and histological analysis of the mouse model,we found that ankle ligaments injury will affect the formation of chronic ankle instability and post traumatic osteoarthritis.