Human movement analysis using stereophotogrammetry. Part 3. Soft tissue artifact assessment and compensation

Area of Science:

• Biomechanics
• Human Movement Analysis
• Optoelectronic Stereophotogrammetry

Background:

• Skin deformation and displacement create soft tissue artifact (STA), a major error source in human movement analysis.
• STA exceeds instrumental error, mimics bone movement frequencies, and varies by task and subject, particularly affecting thigh motion.
• Reliable in vivo kinematic data is limited to flexion/extension axes at the hip, knee, and ankle due to STA.

Purpose of the Study:

• To provide a comprehensive review of current methods for assessing, minimizing, and compensating for soft tissue artifact (STA).
• To highlight the limitations STA imposes on accurate 3D skeletal kinematics estimation in human movement analysis.
• To suggest future directions for effective STA compensation.

Main Methods:

• Review of existing literature on soft tissue artifact (STA) assessment, minimization, and compensation techniques.
• Categorization of techniques into skin surface modeling and joint motion constraint approaches.
• Analysis of STA characteristics including magnitude, frequency content, task dependency, and inter-subject variability.

Main Results:

• Soft tissue artifact (STA) is a critical error source in stereophotogrammetry, often exceeding instrumental error.
• STA magnitude is greatest in the thigh and affects motion about non-flexion/extension axes more significantly.
• Current compensation techniques have not yet fully resolved the challenge of reliable 3D skeletal kinematics estimation.

Conclusions:

• Effective STA compensation requires either subject-specific assessment through ad hoc exercises or characterization from large population datasets.
• Integrating joint motion constraints into STA minimization approaches offers a promising alternative.
• Addressing STA is crucial for advancing clinical practice and biomechanical research in human movement analysis.