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Geometric mouse variation: implications to the axial ulnar loading protocol and animal specific calibration
David W Wagner1, Stephanie Chan, Alesha B Castillo
1VA Palo Alto Health Care System, Musculoskeletal Research Laboratory, Palo Alto, CA 94304-1290, USA. dwwagner@gmail.com
Journal of Biomechanics
|July 25, 2013
Summary
Animal-specific ulnar geometry significantly impacts load strain measurements. This study identifies key geometric measures and their relationship to strain, enabling more accurate animal-specific calibration without complex models.
Area of Science:
- Biomechanics
- Orthopedics
- Comparative Anatomy
Background:
- Axial ulnar load strain calibration shows significant variability, suggesting the need for animal-specific adjustments.
- Optimal geometric measures for animal-specific calibration are not well-defined, potentially due to experimental variations.
Purpose of the Study:
- To characterize variability in ulnar geometric measures influencing periosteal midshaft strain during axial loading.
- To quantify the relationship between geometric measure variance and periosteal strain under axial loading.
Main Methods:
- Microcomputed tomography (microCT) scans of 39 mouse forelimbs.
- Computation of seven geometric measures influencing periosteal strain.
- Estimation of animal-specific strains using a theoretical model based on the generalized flexure formula.
Main Results:
- Inter-animal geometric differences resulted in a simulated midshaft strain of -985 ± 148 με/N.
- Beam bending about the I(min) axis explained 89% of the variance in strain.
- Eccentricity in axial loading significantly contributed to strain variation, highlighting its importance for calibration.
Conclusions:
- Ulnar geometric measures exhibit inherent variability influencing periosteal strain.
- Eccentricity during axial loading is a critical factor for accurate animal-specific strain calibration.
- A simple method using microCT data allows for animal-specific strain computation, bypassing the need for physical calibration studies or finite element analysis.
