Hydroxyapatite (Ca 10 (PO 4) 6 (OH) 2 ; HAp) is widely used as a biomaterial due to its high biocompatibility. However, biological apatite present in bone and teeth contains various ions in the HAp crystal structure. Thus, biological apatite has many strains and defects, which may impart high osteoconductivity to apatite. To clarify the effects of the strain and/or defects in the HAp crystal structure on the bioactivity, nitrogen-doped (N-doped) HAp ceramics were fabricated by heating pure HAp ceramics. This N-doped method is well-known as a technique to modify the chemical structure at the surface. Some properties of the N-doped HAp ceramics were examined for optimization of the heating temperature. N-doped HAp ceramics fabricated by heating at 850°C in an NH 3 atmosphere had N 2 O molecules in the crystal structure. Therefore, the N-doped HAp ceramics fabricated by the N-doping method have a rare moleculesubstitution structure. In conclusion, we have developed the N-doped HAp ceramics which have a rare molecule-substitution structure.

Introduction: Magnetic resonance imaging (MRI) is widely used in orthopedics, but orthopedic surgeons, including spine surgeons, do not have detailed knowledge of MRI-related accidents. We, as orthopedic surgeons, investigated the details of medical accidents related to ferromagnetic objects brought into the MRI room using a national multicenter database. Methods:We conducted an exploratory analysis of accidents involving MRI ferromagnets based on the Japanese database of adverse medical occurrences. From a total of 104,659 accident reports over nine years, 172 involving the presence of ferromagnetic objects in the MRI room were extracted and analyzed. Results:The accident reports frequently involved children and the elderly. Nurses filed the highest number of reports (44.8%) by occupation, which was more than twice as many as physicians (19.8%). The most common ferromagnetic devices brought into the MRI rooms were pacemakers (n = 22). There were also large magnetic objects such as oxygen cylinders (n = 12) and IV stands (n = 7). In the field of orthopedics, ankle weights (n = 4), pedometers (n = 3), and artificial limbs (n = 2) were brought in. "Failure to check" was the most common cause of accidents (69%). Actual harm to patients occurred in 9% of cases, with no fatalities.