The influence of COVID-19 epidemic on the number of orthopaedic surgeries in Japan.

BACKGROUND: There is limited data on the impact of COVID-19 epidemic on the number of orthopaedic surgeries in Japan. METHODS: We conducted a nationwide hospital survey asking for the monthly number of orthopaedic surgeries performed at each facility from January 2019 to June 2021. Those facilities that had performed at least 100 surgeries in 2019 were included for analyses. The facilities were further grouped by prefecture and by hospital characteristics. A brief health economic evaluation was also performed. Risk ratios were compared using univariate analyses with P < 0.05 considered statistically significant. RESULTS: Questionnaire was sent to 1988 hospitals with 1671 hospitals (84%) responding. The survey data indicated a total number of orthopaedic surgeries decreased in 2020 compared to 2019 (1,061,541 vs 1,119,955 P < 0.01), and also for the first six months of 2021 compared to the same period in 2019 (530,388 vs 550,378 P < 0.01). In 2020, over 50% of all facilities in nearly all of the prefectures saw a decline in surgical procedures. The risk of incurring more than a 25% decease in the number of surgeries was significantly higher in 2020 for class I designated medical institutions compared to those that were not designated for any types of infectious diseases among the institutions with a tertiary emergency medical center in 2020 (crude risk ratio 2.9: 95% CI 1.2-7.4, p = 0.02) and in 2021 (crude risk ratio 4.7: 95% CI 1 0.9-12.1, p < 0.01). The estimated total nationwide decrease of revenue were in the range of approximately ¥29.2 to ¥116.8 billion per year for orthopaedic surgeries alone. CONCLUSION: There was a statistically significant decrease in the number of orthopaedic surgeries in Japan. The magnitude of the decline varied by prefectures and hospital characteristics, with the greater impact imposed on medical institutions with higher classification functions. The estimated immediate health economic impact was sizable.

Experimental determination of the minimum onset temperature of runaway reaction from a radioactive salt disposal in asphalt.

In order to clarify the reason for the most hazardous explosion in the history of the Japanese nuclear power development by a radioactive salt disposal in asphalt, an adiabatic process was developed using a Dewar vessel to minimize the temperature difference between the reactants and the surroundings. By this means, the heat evolution from a reaction which is readily lost can be detected at a lower temperature imitating the accidental condition. A series of ambient temperature-tracking Dewar experiments on asphalt salt mixtures were conducted under different initial ambient temperatures, such as 230, 210, 190, and 170 degrees C, respectively. As a result, it was observed that from 190 degrees C the sample's temperature rose until a runaway reaction occurred. The minimum onset temperature for the runaway reaction of the asphalt salt mixture was determined to be 190 degrees C, which is close to the initial temperature of approximately 180 degrees C, the same temperature as the real accident. This implies that at near this operational temperature, initial faint chemical reactions may occur and lead to further rapid reactions if heat is accumulated at this stage.

Evaluation on thermal explosion induced by slightly exothermic interface reaction.

An asphalt-salt mixture (ASM), which once caused a fire and explosion in a reprocessing plant, was prepared by imitating the real bituminization process of waste on a lab scale to evaluate its actual thermal hazards. Heat flux reaction calorimeters were used to measure the release of heat for the simulated ASM at a constant heating rate and at a constant temperature, respectively. Experimental results show that the reaction in the ASM below about 250 degrees C is a slightly exothermic interface reaction between the asphalt and the salt particles contained in the asphalt, and that the heat release rate increases sharply above about 250 degrees C due to melting of the salt particles. The reaction rates were formulated on the basis of an assumed reaction model, and the kinetic parameters were determined. Using the model with the kinetic parameters, temperature changes with time and drum-radius axes for the ASM-filled drum were numerically simulated assuming a one-dimensional infinite cylinder system, where the drum was being cooled at an ambient temperature of 50 degrees C. The minimum filling temperature, at which the runaway reaction (MFTRR) can occur for the simulated ASM in the drum is about 194 degrees C. Furthermore, a very good linear correlation exists between this MFTRR and the initial radius of salt particles formed in the bituminization product. The critical filling temperature to the runaway reaction is about 162 degrees C for the asphalt-salt mixture, containing zero-size salt particles, filled in the same drum at an ambient temperature of 50 degrees C. Thus, the runaway reaction will never occur in the drum filled with the asphalt-salt mixture under the conditions of the filling temperature below 162 degrees C and a constant ambient temperature of 50 degrees C. As a consequence, the ASM explosion occurred in the reprocessing plant likely was due to a slightly exothermically reaction and self heating.