Technical note: A new method for measuring long bone curvature using 3D landmarks and semi-landmarks

Area of Science:

• Paleoanthropology
• Biomechanics
• Forensic Anthropology

Background:

• Quantifying long bone curvature is crucial for understanding biomechanics and evolutionary adaptations.
• Traditional methods for measuring femur curvature, such as coordinate calipers and graph paper, exhibit varying degrees of reliability and measurement error.
• A need exists for more precise and consistent methods to analyze skeletal morphology.

Purpose of the Study:

• To introduce and evaluate a novel method for quantifying human femur curvature using geometric morphometrics and semi-landmark analysis.
• To compare the accuracy and reliability of the new method against traditional measurement techniques.
• To assess the impact of semi-landmark number on measurement error and curvature analysis.

Main Methods:

• Geometric morphometric analysis and semi-landmark data collection applied to the human femur.
• Comparison with traditional methods: coordinate calipers and graph paper projection.
• Utilizing equidistant semi-landmarks to preserve curvature signals and Principal Components Analysis (PCA) for shape description.

Main Results:

• The graph paper method is more reliable than coordinate calipers for traditional measurements.
• Measuring the point of maximum curvature yields lower measurement error than measuring subtense.
• The new 3D landmark-based method offers more reliable subtense estimation than traditional techniques.
• Measurement error increases with the number of semi-landmarks used in curvature analysis.

Conclusions:

• The novel geometric morphometric method provides a reliable and low-error approach for quantifying long bone curvature.
• Equidistant semi-landmarks and PCA effectively capture curvature shape and reduce measurement error.
• This technique holds significant promise for functional and forensic analyses of human populations and fossil remains.