Lateral Ankle Sprain in a Mouse Model: Lifelong Sensorimotor Dysfunction

Abstract

Context:  Ankle sprains are the most common orthopaedic injury that occurs during sport and physical activity. Many individuals who sprain their ankles develop chronic ankle instability (CAI), a condition characterized by recurrent injury, decreased physical activity, and decreased quality of life. These residual impairments are believed to persist for the remainder of the patient's life, in part due to the link between CAI and posttraumatic ankle osteoarthritis. However, this belief remains speculative due to the lack of long-term prospective investigations. Objective:  To use a mouse model of mild (MILD) and severe (SEVERE) ankle sprains to quantify balance and locomotor adaptations across the lifespan. Design:  Cohort study. Setting:  University research laboratory. Patients or Other Participants:  Fifty male mice (CBA/J) were randomly placed into a control (SHAM), MILD, or SEVERE group and housed individually. Intervention(s):  The MILD group underwent surgical transection of a single right hind-limb lateral ankle ligament, and the SEVERE group had 2 of the lateral ligaments transected. The SHAM group underwent a sham surgery during which no lateral ligaments were transected. Main Outcome Measure(s):  After surgically inducing the ankle sprain, we measured balance and gait using a balance beam and footprint test before and every 6 weeks for 78 weeks. Results:  Age-related declines in balance but not stride length were exacerbated by an ankle sprain (P < .001). Balance and stride lengths changed with age (P < .001). Foot slips were worse in the SEVERE (4.32 ± 0.98) and MILD (3.53 ± 0.98) groups than in the SHAM group (2.16 ± 0.99; P < .001). Right-limb stride length was shorter in the SEVERE group (6.45 cm ± 0.41 cm) than in the SHAM group (6.87 cm ± 0.40 cm; P = .04). Conclusions:  Transecting the lateral ligaments of a mouse hind foot resulted in lifelong sensorimotor dysfunction. Declines starting at 42 weeks postinjury may have represented the onset of posttraumatic osteoarthritis.