In vitro assessment of a motion-based optimization method for locating the talocrural and subtalar joint axes

Area of Science:

• Biomechanics
• Musculoskeletal Modeling
• Human Motion Analysis

Background:

• Accurate ankle complex joint axis location is critical for precise musculoskeletal modeling.
• Existing noninvasive methods lack demonstrated accuracy for determining these axes.
• Joint axis location influences calculations of muscle and ground reaction forces.

Purpose of the Study:

• To assess the accuracy of a computational optimization method for locating ankle complex joint axes.
• To compare estimated talocrural and subtalar axis locations with mean helical axes.
• To evaluate the method's performance using simulated data, a mechanical linkage, and cadaver specimens.

Main Methods:

• A computational optimization method fitting a two-revolute model to measured motion was employed.
• Motions were applied to cadaver specimens under axial load.
• A video-based motion analysis system tracked bone-mounted markers on the tibia, talus, and calcaneus.

Main Results:

• The optimization method demonstrated high accuracy (1-5 degrees difference) with computer-generated data and a mechanical linkage.
• Significant inaccuracies (exceeding 20 degrees difference) were observed when applied to cadaver specimens.
• The method's performance degraded in biological specimens compared to controlled environments.

Conclusions:

• Computational optimization methods using two-revolute models may be limited for determining anatomical ankle joint axes from measured motion.
• Non-revolute behavior in biological joints presents challenges for these modeling approaches.
• Further research is needed to improve noninvasive methods for accurate ankle axis localization in biomechanical studies.