Determination of cortical bone porosity and pore size distribution using a low field pulsed NMR approach

Abstract

The objective of this study was first to prove the concept of a low field pulsed nuclear magnetic resonance (NMR) process for assessing the cortical porosity and pore size distribution of human bone in vitro, and then to apply the technique to detect age-related changes of bone in these parameters. The Carr-~Purcell--Meiboom-Gill NMR spin echo train method is used to determine the porosity, and an inversion NMR spin-spin relaxation (T2) spectrum is used to assess the pore size distribution in cortical bone. Using these techniques, cortical porosity and pore size distribution of 19 specimens of human cadaveric bone, ranging from 16 to 89 years of age, were assessed. The NMR results were compared with the histomorphometric data of the same bone samples to verify the efficacy of the NMR approach. Moreover, a coefficient (surface relaxivity) relating the pore size to the T2 relaxation time was determined empirically for the Haversian canals and the osteocytic lacunae. The results of this study demonstrate that the in vitro NMR approach using T2 relaxation techniques can directly assess the porosity and pore size distribution (Haversian canals and osteocytic lacunae) in human cortical bone. In addition, this study indicates that the age-related changes in cortical porosity relate predominantly to Haversian canals, whereas the porosity of osteocytic lacunae appears to be independent of age.

Measurements of mobile and bound water by nuclear magnetic resonance correlate with mechanical properties of bone

“…While mobile water is likely a measure of porosity in bone [40], bound water as presently quantified by NMR does not clearly relate to a specific property of bone because only a few compositional parameter were presently examined, with PE being weakly correlated ( Table 2). The bulk measure of mineral-to-collagen was originally thought to influence bound water since mineral displaces water from collagen and collagen provides a number of sites for water to bind.…”

“…While both NMR and magnetic resonance imaging (MRI) have been used to characterize bone in a number of studies [40,45,[48][49][50][51][52][53][54][55][56], the present work is the first to quantify water distribution in bone for two age groups. A previous study had actually characterized water distribution in dentin samples from a 20 year, 35 year, and 50 year old donor [50].…”

Nuclear magnetic resonance cryoporometry

“…Evans et al highlighted this point, suggesting NMR cryoporometry and gas adsorption as ideal calibration tools for NMR relaxometry (Evans et al, 2005). The wide range of porosities probed by the NMR relaxometry measurement can lead to incorrect analysis if calibrated against limited techniques such as bone histomorphometry (an optical measurement) (Wang and Ni, 2003). Fig.…”

Use of low-field NMR for the characterization of gels and biological tissues

“…The capability of estimating the pore size distribution rendered LF-NMR a valuable approach also in the biomedical field. Indeed, many authors employed LF-NMR to characterize bones [15][16][17][18], a very particular porous material, while Grassi et al [19] and Fiorentino et al [20] focussed on the characterization of polymeric scaffolds for tissue engineering. Finally, Abrami et al [21] dealt with a very new application of LF-NMR concerning the characterization of expectorate of patients affected by chronic pulmonary diseases like cystic fibrosis (CF).…”