• Juay Seng Tan and Sasidhar Uppuganti.
• Department of Biomedical Engineering, University of Akron, Akron, OH 44325, USA. juayseng@gmail.com
• Spine. 2012 Sep 15;37(20):E1238-42.

Study DesignAn in vitro biomechanical study on 3-dimensional flexibility of human lumbosacral motion segments after multiple freeze-thaw cycles and cumulative testing.ObjectiveTo determine the significance of multiple freeze-thaw cycles and extended testing duration on between-day and within-day variations in motion segment flexibility.Summary Of Background DataPrevious studies have found no significant effect of single freeze-thaw cycle on creep behavior of human spinal motion segments. Up to 3 freeze-thaw cycles were found to not affect flexibility of porcine spines and viscoelastic properties of human tendons, but more than 5 freeze-thaw cycles resulted in declined structural properties of human tendons.MethodsThree lumbosacral motion segments were subjected to repeated flexibility tests to determine both the effects of within-day ambient exposure and between-day multiple freeze-thaw cycles on range of motion (ROM) and neutral zone (NZ). Repeated measures analysis of variance was carried out to evaluate within-day and between-day effects at α = .05.ResultsSignificant between-day effects were found for intervertebral ROM and NZ in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) (all P < 0.001). Post hoc analysis indicated that significant differences from test day 1 become apparent after 4 freeze-thaw cycles with cumulative testing. There were no within-day variations from repeated testing on intervertebral FE ROM (P = 0.10), LB ROM (P = 0.36), AR ROM (P = 0.46), FE NZ (P = 0.83), LB NZ (P = 0.42), and AR NZ (P = 0.72).ConclusionThe flexibility of the human cadaveric lumbosacral motion segments between test days was significantly affected after repeated freeze-thaw and cumulative testing cycles. Multiple freeze-thaw cycles and cumulative testing, however, does not affect flexibility data for tests carried out within a single test day.

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