Early Degeneration Of Adjacent Joints Secondary To Ankle Instability In A Mouse Model

Objective:This study aims to explore the biomechanical impact of ankle instability on anjacent joint degeneration,including subtalar joint(STJ)and talonavicular joint(TNJ)via a mouse model,in order to provide new thoughts and approaches for clinical diagnosing,preventing and treating related secondary joint diseases.Methods:Twenty four 8-week old male C57BL/6J mice were equally allocated to three groups.Both calcaneofibular ligament(CFL)and anterior talofibular ligament(ATFL)of left ankle were cut off in CFL+ATFL group to simulate severe ankle instability while only CFL was cut off in CFL group to simulate moderate ankle instability.The SHAM group only had skin incision but without any further operation.After the surgery,a running-wheel device was used to accelerate the effect of ankle instability for 8 weeks.Atomic force microscope(AFM)-based nanoindentation test was applied to reveal the degree of joint degeneration at the nanoscale by measuring the elastic modulus(EM)of articular cartilage(AC)for ankle joint,STJ and TNJ.Meanwhile,scanning electron microscope(SEM)inspection and histological analysis were also performed for evaluating the degenerative condition of each joint.Results:The Safranin-O/fast green staining showed an increasing trend of OARSI score and modified Mankin score among SHAM group,CFL group and CFL+ATFL group in all joints.For ankle joint,CFL+ATFL group was significantly higher SHAM group(P<0.01,P=0.027).For STJ,CFL+ATFL group was also higher SHAM group(P=0.033,P<0.01).For TNJ,CFL+ATFL group was also higher SHAM group(P=0.041,P=0.028).While compared with SHAM group,the CFL group was only significantly higher than SHAM group in ankle joint(P=0.018,P=0.029).Cracking and disintegration of trabecula within the subchondral bone(SCB)area were observed in all joints of CFL+ATFL group and CFL group under SEM,more remarkable in CFL+ATFL group.Such manifestation did not appear in SHAM group.The EM detected by AFM exhibited much lower values for CFL+ATFL group than SHAM group in all articular surfaces(P<0.01,P=0.018,P=0.035,P<0.01,P=0.017,P<0.01).While the EM of CFL group only showed significance in ankle joint compared with SHAM group(P=0.042,P=0.021).Conclusions:The findings of this study indicate that severe ankle instability can result in obvious degeneration of STJ and TNJ,while moderate ankle instability does not cause such changes.Meanwhile,it is possible that AFM being a new tool for detecting joint degeneration in clinical practice.