Dynamic 3D scanning as a markerless method to calculate multi-segment foot kinematics during stance phase:...

Area of Science:

• Biomechanics
• Gait Analysis
• Medical Imaging

Background:

• Traditional multi-segmental foot kinematic analysis relies on optical marker-sets or inertial sensors.
• These methods require precise placement of markers on anatomical landmarks.
• A markerless approach using dynamic 3D scanning (D3DScanning) has not been previously explored for foot kinematics.

Purpose of the Study:

• To introduce and evaluate a novel markerless dynamic 3D scanning (D3DScanning) method for analyzing multi-segmental foot kinematics.
• To develop a 4-segment foot model (shank, calcaneus, metatarsus, hallux) based on surface anatomy.
• To assess the repeatability and validity of the D3DScanning method compared to marker-based approaches.

Main Methods:

• A 4-segment foot model was created by manually selecting segments on a static 3D scan.
• Segments were tracked in dynamic scans using the iterative closest point (ICP) algorithm to match static scan segments.
• Joint rotations (Sha-Cal, Cal-Met, Met-Hal) were calculated, excluding the first and last 10% of the stance phase due to scan quality.
• The method was applied to 5 healthy subjects (6 trials each).

Main Results:

• The D3DScanning method demonstrated good repeatability (1°-2.5° intra-subject standard deviation) for the shank-calcaneus (Sha-Cal) and calcaneus-metatarsus (Cal-Met) joints.
• Repeatability for the metatarsus-hallux (Met-Hal) joint was lower (>3°).
• Repeatability appeared to be subject-dependent.
• Qualitative comparison with a marker-based model showed consistent rotational patterns.

Conclusions:

• Markerless D3DScanning provides a viable and repeatable method for analyzing multi-segmental foot kinematics.
• The technique simplifies subject preparation and offers intuitive visual output, enhancing clinical usability.
• Further refinement may be needed for higher-accuracy Met-Hal joint analysis.