Influences of osteoarthritis and osteoporosis on the electrical properties of human bones as in vivo electrets produced due to Wolff's law.

We characterized the electrical properties of living bone obtained from patients who had undergone total hip arthroplasty (THA) or hemiarthroplasty by means of analysis of the electrically polarized and nonpolarized bone specimens, and we discussed the role of an organic and inorganic matrix of human bone in bone piezoelectricity. We used human femoral neck bone that was harvested during THA for advanced osteoarthritis of the hip joint (OA group) and hemiarthroplasty for femoral neck fracture (FNF group). The specimens were scanned to evaluate the cancellous bone structures using micro-computed tomography, and we quantified the carbonic acid by attenuated total reflection (ATR) spectra to estimate carbonate apatite. The stored electrical charge in the electrically polarized and nonpolarized bone specimens were calculated using thermally stimulated depolarized current (TSDC) measurements. Each TSDC curve in the groups had peaks at 100 degrees C, 300 degrees C and 500 degrees C, which may be attributed to collagen, carbonate apatite and hydroxyapatite, respectively. It is suggested that organic substances are more effectively electrically polarized than apatite minerals by the polarization at room temperature and that the stored charge in living bone may be affected not only by total bone mass but also by bone quality, including 3-dimensional structure and structural component.