Post-sprain versus post-fracture post-traumatic ankle osteoarthritis: Impact on foot and ankle kinematics and kinetics

Background Common etiologies for post-traumatic ankle osteoarthritis are ankle fractures and chronic ankle instability. As the nature of trauma is different for these two etiologies, it might be expected that the two subtypes of post-traumatic ankle osteoarthritis would display different foot mechanics during gait. Research question The objective of this exploratory cross-sectional study was to compare the foot kinematics and kinetics of patients suffering from post-fracture ankle osteoarthritis with those of patients suffering from post-sprain ankle osteoarthritis. Methods Twenty-nine subjects with end-stage post-traumatic ankle osteoarthritis and fifteen asymptomatic control subjects participated in this study. All patients suffered from post-traumatic ankle osteoarthritis secondary to ankle-related fracture (Group 1; n = 15) or to chronic ankle instability (Group 2; n = 14). A four-segment kinematic and kinetic foot model was used to calculate intrinsic foot joint kinematics and kinetics during gait. Vector field statistical analysis MANOVA was used to assess differences between groups for the entire three-component intrinsic foot joint angles and moments. Results MANOVA showed significant differences between the groups. Post-hoc analyses suggested that the differences between post-fracture ankle osteoarthritis group and controls were caused by a combination of less adducted Shank-Calcaneus position and less plantarflexion at this joint. Post-hoc analyses also suggested that both pathological groups exhibited a decreased plantarflexion moment for Shank-Calcaneus, Chopart, Lisfranc joints compared to controls. Analyses of both pathological groups versus controls for power suggested lower Shank-Calcaneus and Lisfranc power generation during pre-swing phase. Significance No significant differences were found between the two pathological groups in this exploratory study. Alterations in foot kinematics and kinetics were mainly found about the dorsi-/plantarflexion axis during the pre-swing phase of the stance phase for both pathological groups compared to controls. Observed differences were not limited to the painful ankle joint, but seem also to have affected the kinetics of the neighbouring foot joints.