Subject-specific axes of the ankle joint complex

Area of Science:

• Biomechanics
• Musculoskeletal modeling

Background:

• Accurate ankle joint modeling is crucial for understanding gait and foot biomechanics.
• Existing models often simplify the complex multi-axis nature of the talocrural and subtalar joints.

Purpose of the Study:

• To calculate and compare talocrural and subtalar hinge axes using a two-axis ankle model.
• To determine which set of axes (non-weight-bearing vs. weight-bearing) better fits walking data.
• To assess the overall appropriateness of the two-hinge ankle model for complex ankle motion analysis.

Main Methods:

• Utilized a two-axis ankle joint model and optimization process to derive hinge axes.
• Collected motion data for foot and shank in eight healthy adults during non-weight-bearing, weight-bearing, and walking activities.
• Fit the two-hinge ankle model to motion data and calculated joint ranges of motion.

Main Results:

• The two-hinge ankle model demonstrated a good fit to experimental data, with non-weight-bearing motion yielding the best fit.
• Calculated ankle axis orientations exhibited significant variability between motion types and subjects.
• No significant difference was found in the fit of non-weight-bearing versus weight-bearing models to walking data.
• The subtalar deviation angle was significantly closer for weight-bearing and walking compared to non-weight-bearing and walking.

Conclusions:

• Either non-weight-bearing or weight-bearing functional axes are adequate for modeling walking.
• Using weight-bearing functional motions may be marginally superior due to closer subtalar deviation alignment.
• The study raises questions about the two-hinge ankle model's suitability for applications requiring detailed analysis of individual ankle complex joint behaviors.