Analysis of a Chronic Lateral Ankle Instability Model in the Rat: Conclusions and Suggestions for Future Research.

The purpose of this study was to evaluate potential osteoarthritic alterations within the ankle using a surgically-induced chronic lateral ankle instability (CLAI) model. Twelve rats were assigned randomly to either the control ( n = 4) or CLAI group ( n = 8). Surgery was performed on the right ankle. Osteoarthritis was assessed through in-vivo micro-CT at 8 weeks and a clinical analysis. Macroscopic analysis, high-resolution ex-vivo micro-CT and histological examination were conducted after euthanasia at 12 weeks. Three subgroups (SG) were analyzed. SG1 comprised the operated ankles of the CLAI group ( n = 8). SG2 consisted of the non-operated ankles of the CLAI group ( n = 8). SG3 included both sides of the control group ( n = 8). In-vivo micro-CT revealed no significant differences among the three subgroups when analyzed together ( p = 0.42), and when comparing SG1 with SG2 ( p = 0.23) and SG3 ( p = 0.43) individually. No noticeable clinical differences were observed. After euthanasia, macroscopic analysis employing OARSI score, did not demonstrate significant differences, except between the medial tibia of SG1 and SG3 ( p = 0.03), and in the total score comparison between these two subgroups ( p = 0.015). Ex-vivo micro-CT did not reveal any differences between the three subgroups regarding bony irregularities and BV/TV measurements (SG1 vs. SG2 vs. SG3: p = 0.72; SG1 vs. SG2: p = 0.80; SG1 vs. SG3: p = 0.72). Finally, there was no difference between the three subgroups regarding OARSI histologic score ( p = 0.27). These findings indicate that the current model failed to induce significant osteoarthritis. However, they lay the groundwork for improving the model's effectiveness and expanding its use in CLAI research, aiming to enhance understanding of this pathology and reduce unnecessary animal sacrifice.