End-stage ankle arthritis alters dynamic stability during gait as measured by margin of stability between limbs and compared to healthy controls.

Objective: This study aimed to assess dynamic stability in individuals with end-stage ankle arthritis compared to healthy controls by evaluating the margin of stability (MoS) during gait.

Design: A cohort of 50 participants with end-stage ankle arthritis (AA) and 50 matched healthy controls (HC) were analyzed from an IRB approved database. Kinematic data were collected using an eight-camera motion analysis system, and MoS was calculated based on the extrapolated center of mass (XCoM) and the base of support (BoS). Statistical analysis was performed using a linear mixed effects model with gait speed as a covariate.

Results: The analysis revealed a significant interaction between the group (AA vs. HC) and limb (arthritic vs. non-arthritic) at heel-strike and midstance. The non-arthritic limb demonstrated a significantly smaller AP MoS during heel-strike compared to the arthritic limb and either of the limbs of the HC group (p < 0.001). The arthritic limb demonstrated a significantly greater ML MoS during midstance compared to the non-arthritic limb and either of the limbs of the HC group (p < 0.001). AA group had significant slower gait speed (p < 0.001), smaller step length (p = 0.015) and smaller locomotor rehabilitation index (p < 0.001) than HC.

Conclusion: Individuals with end-stage ankle arthritis exhibit altered dynamic stability during gait, with a significantly smaller AP MoS on the non-arthritic limb at heel-strike and greater ML MoS on the arthritic limb at midstance compared to healthy controls. Our results suggest that individuals with ankle arthritis are less stable when navigating single limb support of the arthritic limb. Further research should further examine the associations with fall risk in patients with ankle arthritis and evaluate the effectiveness of therapeutic interventions targeting these factors.