Type of Document	Master's Thesis
Author	Reeves, Michael Wayne
URN	etd-0418102-220607
Title	An Evaluation of Storage, Hydration and Reporting Protocols for Biomechanical Testing of the Rat Femoral Neck
Degree	Master of Science (M.S.)
Department	Human Ecology
Advisory Committee	Advisor Name Title Maren Hegsted Committee Co-Chair Michael J. Keenan Committee Co-Chair Yan Chen Committee Member
Keywords	density rat frozen storage femoral neck protocol bone strength Young's modulus plastic strain biomechanical testing vacuum saline behavior hydration
Date of Defense	2001-12-17
Availability	unrestricted
Abstract The current study evaluated the effect of frozen storage and hydration under vacuum on density and breaking strength of the rat femoral neck. Femurs were frozen in saline for periods of 15, 34, 122, or 831 days. No significant effect on bone density was detected for freezing periods of 15, 34, and 122 days, indicating that frozen storage of specimens in saline is moisture-preserving for periods up to four months. Freezing periods of 34 and 122 days were used to examine the effect of frozen storage on bone biomechanical bahavior. Plastic strain increased for the 34-day storage period (p=0.0453) and decreased for the 122-day storage period (p<0.0001). Strain to failure (p<0.0001) and yield strain (p<0.0001) decreased and Young’s modulus (p=0.0018) increased after 122 days of frozen storage. Hydration for one hour after the 15-day storage period significantly decreased density compared to fresh (p=0.0407) and frozen-stored (p=0.0008) specimens. In the 122-day storage experiment, hydration for three hours significantly decreased density compared to the frozen- stored bones, both between (p=0.0059) and within samples (p=0.0270). Hydration did not significantly alter the density of bones frozen for 831 days. Hydration of bones frozen for 122-days decreased yield strain (p=0.0100) and strain at failure (p=0.0214) compared to fresh bones. Plastic strain (p=0.0474) and strain at failure (p=0.00116) both increased and Young’s modulus decreased for hydrated bones compared to frozen-stored bones. Bones frozen for 831 days and hydrated for either one hour or three hours showed an increase in plastic strain (p=0.0469) with the longer hydration time. These results indicate frozen storage for up to 122 days does not affect bone density, but does alter the biomechanical behavior of the rat femoral neck for storage periods as short as 34 days. Hydration decreases density in bones frozen for up to 122 days, but extending the frozen storage period to 831 days prevents additional dehydration of stored bones. The biomechanical bahavior of the rat femoral neck is affected by hydration for bones frozen for both 122 and 831 days.
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