An open source lower limb model: Hip joint validation.

Area of Science:

• Biomechanics
• Musculoskeletal modeling
• Medical device analysis

Background:

• Musculoskeletal lower limb models can predict hip contact forces (HCFs) comparable to in vivo measurements.
• However, predicted muscle recruitment often mismatches measured electromyographic (EMG) signals.

Purpose of the Study:

• To assess if HCFs can be accurately estimated from muscle force patterns consistent with EMG measurements.
• To validate a lower limb model implemented in OpenSim against patient data.

Main Methods:

• Implemented a lower limb model in OpenSim using published anatomical data.
• Validated the model against HCFs from gait and stair climbing trials of arthroplasty patients.
• Estimated hip joint muscle tensions by minimizing a polynomial function of muscle forces, comparing results to literature EMG profiles.

Main Results:

• Calculated HCFs increased with the objective function's polynomial power.
• The best HCF estimation, consistent with experimental EMG, occurred when minimizing a quadratic objective function.
• Average HCF overestimation at peak force was 10.1% for walking and 7.8% for stair climbing.

Conclusions:

• The validated lower limb model accurately estimates HCFs using EMG-consistent muscle forces.
• The model can generate balanced muscle and joint contact forces for biomechanical applications.
• The developed model is publicly available for research use.