BIOMECHANICAL CHANGES AND BALANCING ABILITY OF ADJACENT JOINTS IN A MOUSE MODEL OF LATERAL ANKLE INSTABILITY

Changtao Wan, Xianxun Wang, Siyuan Shao, Ge Zeng^*

Department of Orthopedics, the Third People's Hospital of Hubei Province, Wuhan 430033, Hubei Province, China

Objective: To analyse the changes of biomechanics and balancing ability of adjacent joints in a mouse model of lateral ankle instability. 

Methods: Sixty clean grade healthy male C57BL/6J mice were randomly selected and divided into a sham operation group (Group S), a calcaneal fibular ligament group (Group C) and a calcaneal fibular ligament and anterior talofibular ligament group (Group A), with 20 mice in each group. The mouse model of lateral ankle instability was established. The balance beam test was carried out before the operation, 3 days after the operation, 1 week after the operation, 3 weeks after the operation and 6 weeks after the operation. The pathological changes of the joints were observed with safranin o-solid green staining, and the International Society for Osteoarthritis Research (OARSI) scores of the ankle joint, the talonavicular joint and the subtalar joint were compared. The surface changes of the subchondral bone of the calcaneus, talus and proximal scaphoid were observed with a scanning electron microscope. An atomic force microscope was used to observe the changes of the elastic modulus of the superior and inferior articular surfaces of the talus, the inferior articular surface of the talus, the distal articular surface of the talus and tibia, and the proximal articular surface of the scaphoid. 

Results: Six weeks after the operation, the passage time of Group C was significantly shorter than that of Group S and Group A (P<0.05). The number of mice in Group A was significantly higher than in Group C (P<0.05). The thickness of the cartilage layer in Group S was uniform, the structure was complete, and the surface was flat; the cartilage layer in Group C was thinner compared to Group S, and the surface showed occasional small defects; the cartilage layer in Group A was thinner, the surface was incomplete, and joint degeneration appeared. Compared with Group S, the OARSI scores of the distal navicular joint, ankle joint and the lower articular joint of Group C were significantly increased (P<0.05); compared with Group C, the OARSI scores of the same joints of Group A were significantly higher (P<0.05). The structure of the bone under the articular surfaces of Group S was complete, and the continuity was good; in Group C, there were many fractures and obvious osteosclerosis on the surface of the lower articular cartilage area; and in Group A, there were large areas of bone fracture, which lost integrity, and rough surfaces. Compared with Group S, the elastic moduli of the upper and lower articular surfaces of the talus and the upper, distal and proximal articular surfaces of the proximal scaphoid in Group C were significantly lower (P<0.05). Compared with Group C, the elastic modulus of the upper and lower articular surfaces of the talus and the upper, distal and proximal articular surfaces of the proximal articular surface of the scaphoid were significantly reduced in Group A (P<0.05). 

Conclusion: Instability of the lateral ankle joint can lead to the degeneration of adjacent joints and reduce the balancing ability of mice.