medRxiv preprint Contribution: All authors have seen and approved the manuscript, and contributed significantly to the work.Key points: By propensity score matching analysis, the average treatment effect of corticosteroids on 70 patients with severe COVID-19 pneumonia was estimated.Corticosteroid therapy lowered the risk of intubation with a risk difference of -47.1% (95% confidence interval -71.8% to -22.5%).

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New sterilization methods for human bone are likely to affect the mechanical properties of human cancellous grafts. These mechanical properties dictate the short- and mid-term results of the orthopedic procedure. The aim of this study was to compare the effects on bone mechanical properties, as assessed by ultrasound velocity, of different sterilization methods used under similar conditions: bleach and sublimation, humid heat, successive baths of physiological saline with osmotic detersion, and CO(2) in the supercritical phase. Alterations in mechanical properties were small with CO(2) (velocity change: -2%) and humid heat (-2.5%). Osmotic detersion had a significant but moderate effect (-4.7%). The -9% change with the protocol involving bleach suggested a greater than 30% decrease in load to failure, based on earlier studies. Gamma irradiation of defatted trabecular allografts, in a dose of 10 or 25 KGy, produced no significant changes in ultrasound velocity. Powerful protein denaturants used in sterilization protocols substantially alter the mechanical resistance of the grafts, which may jeopardize the orthopedic procedure.

New sterilization methods for human bone allografts may lead to alterations in bone mechanical properties, which strongly influence short- and medium-term outcomes. In many sterilization procedures, bone allografts are subjected to gamma irradiation, usually with 25 KGy, after treatment and packaging. We used speed-of-sound (SOS) measurements to evaluate the effects of gamma irradiation on bone. All bone specimens were subjected to the same microbial inactivation procedure. They were then separated into three groups, of which one was treated and not irradiated and two were exposed to 10 and 25 KGy of gamma radiation, respectively. SOS was measured using high- and low-frequency ultrasound beams in each orthogonal direction. SOS and Young modulus were altered significantly in the three groups, compared to native untreated bone. Exposure to 10 or 25 KGy had no noticeable effect on the study variables. The impact of irradiation was small compared to the effects of physical or chemical defatting. Reducing the radiation dose used in everyday practice failed to improve graft mechanical properties in this study.