Anterior Tibiotalar Fat Pad Involvement in Ankle Osteoarthritis: MRI Features in Patients 1 Year After a Lateral Ankle Sprain

Objective To investigate the characteristics of the anterior tibiotalar fat pad (ATFP) in the ankle joint in a population of patients 1 year after an ankle sprain and its correlation with systemic factors and local articular pathology. Design The study is a secondary analysis of an observational case-control study. We included 206 patients who were followed 6-12 months after ankle sprain. T1 MRI scans were assessed for signal intensity and area of ATFP by mapping the fat pad using dedicated imaging software (Mimics 18.0). Quantitative values of intensity and area were generated. Linear regression analysis was used to examine the association between both local and systemic factors and the ATFP. Variables with a P value <0.2 were entered in 5 stepwise multivariate models: (1) age-sex-body mass index (BMI); (2) anamnesis; (3) physical examination; (4) radiographic findings; and (5) MRI findings. Predictors in these separate models were entered in the final model. Results The final multivariate model showed a significant positive association between age (P = 0.04; 95% confidence interval [CI] = 1.13 +/- 1.06), BMI (P = 0.05; 95% CI = 3.61 +/- 3.53), and sex (P < 0.01; 95% CI = -49.26 +/- 30.04) with T1 intensity. The final model also showed a significant negative association between age (P < 0.01; 95% CI = -0.57 +/- 0.34), diffuse cartilage loss in the lateral talus (P = 0.03; 95% CI = -0.71 +/- 0.63), and Kellgren and Lawrence score in the tibiotalar joint (P < 0.01; 95%CI = -21.61 +/- 7.24) and ATFP area. A positive association was found between BMI (P < 0.01; 95% CI = 2.25 +/- 1.15) and ATFP area. Conclusion This study demonstrates a correlation between ATFP and both systemic factors and local pathology in the ankle joint.