Assessment of simulated and functional disuse on cortical bone by nuclear magnetic resonance Original Research Article

A nuclear magnetic resonance (NMR) spin (T2) relaxation technique has been described for determining water distribution changes on turkey cortical bone tissue of simulated weightlessness (disuse) in vitro. The advantages of using NMR T2 relaxation techniques for bone water distribution are illustrated. The Carr–Purcell–Meiboom–Gill (CPMG) T2 relaxation data can be used to determine the porosity of bone, and can be inverted to T2 relaxation distribution, and this distribution then can be transformed to a pore size distribution with the longer relaxation times corresponding to larger pores. The free induction delay (FID) T2 relaxation data can be inverted to T2 relaxation distribution and this distribution then can be transformed to bound and mobile water distribution with the longest relaxation time corresponding to mobile water and the middle relaxation time corresponding to bound water. The technique is applied to quantify apparent changes in porosity, bound and mobile water in normal and disuse cortical bone. Overall bone porosity is determined using the calibrated NMR fluid volume from the proton relaxation data divided by overall bone volume. The NMR bound and mobile water changes were determined from cortical bone specimens obtained from normal and disuse turkey bones. Differences in porosity and water distribution were found between specimens from normal and disuse. Our results show that the ratio of the average bound to mobile water in bone from normal turkey is higher than in bone from disuse turkey, and the porosity is lower in normal than in disuse turkey. We also show that the average bone porosity multiplied by the ratio of bound to mobile water may be constant for both normal and disuse bone groups. Currently, the influence of water removal on the strength and toughness of cortical bone has been studied by some researchers. Therefore, the porosity, bound and mobile water distribution changes could provide further information directly related to bone quality and be used for further bone mechanical studies.