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Objectives: This study aims to compare early mortality after total knee arthroplasty (TKA) using conventional intramedullary instrumentation to TKA performed using technology-assisted (non-intramedullary) instrumentation., Design: Comparative observational study. Using data from a large national registry, the 30-day mortality after unilateral TKA performed for osteoarthritis was compared between procedures using conventional instrumentation and those using technology-assisted instrumentation. Firth logistic regression was used to calculate ORs, adjusting for age, sex, use of cement and procedure year for the whole period, and additionally adjusting for American Society of Anesthesiologists physical status classification system class and body mass index (BMI) for the period 2015 to 2019. This analysis was repeated for 7-day and 90-day mortality., Setting: National arthroplasty registry., Participants: People undergoing unilateral, elective TKA for osteoarthritis from 2003 to 2019 inclusive., Interventions: TKA performed using conventional intramedullary instrumentation or technology-assisted instrumentation., Main Outcome Measures: 30-day mortality (primary), and 7-day and 90-day mortality., Results: A total of 581 818 unilateral TKA procedures performed for osteoarthritis were included, of which 602 (0.10%) died within 30 days of surgery. The OR of death within 30 days following TKA performed with conventional instrumentation compared with technology-assisted instrumentation, adjusted for age, sex, cement use, procedure year, American Society of Anesthesiologists and BMI was 1.72 (95% CI, 1.23 to 2.41, p=0.001). The corresponding ORs for 7-day and 90-day mortality were 2.21 (96% CI, 1.34 to 3.66, p=0.002) and 1.35 (95% CI, 1.07 to 1.69, p=0.010), respectively., Conclusions: The use of conventional instrumentation during TKA is associated with higher odds of early postoperative death than when technology-assisted instrumentation is used. This difference may be explained by complications related to fat embolism secondary to intramedullary rods used in conventional instrumentation. Given the high number of TKA performed annually worldwide, increasing the use of technology-assisted instrumentation may reduce early post-operative mortality., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Controversy exists regarding the safety of bilateral simultaneous total knee arthroplasty (BSTKA). When conventional instrumentation is used, the increased fat emboli that result from the insertion of intramedullary rods may increase the risk of perioperative complications. We hypothesized that the use of technology-assisted instrumentation (avoiding intramedullary involvement) would be associated with a lower rate of early postoperative death compared with the use of conventional instrumentation., Methods: We compared the 30 and 90-day rates of mortality following BSTKA performed with conventional versus technology-assisted instrumentation from 2003 to 2019, with use of data from a large national registry. Firth logistic regression analysis was utilized, adjusting for age, sex, and procedure year for all BSTKAs performed during the study period. For procedures performed from 2015 to 2019, odds ratios were additionally adjusted for American Society of Anesthesiologists physical status classification and body mass index., Results: A total of 34,908 BSTKAs were identified. The proportion of cases utilizing technology-assisted instrumentation increased over the study period. The odds ratio of death within 30 days after technology-assisted BSTKA, adjusted for age, sex, and procedure year, was 0.26 (95% confidence interval [CI], 0.08 to 0.83; p = 0.02). The odds ratio, adjusted for age, sex, procedure year, American Society of Anesthesiologists classification, and body mass index, was 0.26 (95% CI, 0.09 to 0.74; p = 0.01). The corresponding odds ratios for 90-day mortality were 0.25 (95% CI, 0.09 to 0.72; p = 0.01) and 0.26 (95% CI, 0.10 to 0.67; p = 0.005), respectively., Conclusions: Technology-assisted BSTKA was associated with a significant reduction in early mortality compared with the use of conventional instrumentation. This difference may be explained by the reduced fat emboli associated with technology-assisted BSTKA and is likely to be clinically important on a population scale., Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/G714)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

1. Mutants produced by x-irradiation of fungal spores of Chaetomium globosum have been compared with those produced by ultraviolet irradiation. 2. The most striking difference between the mutants produced by x-irradiation and ultraviolet irradiation is the absence in x-ray experiments of the K mutant which is produced in large numbers at short ultraviolet wave lengths. 3. A comparison is made of the relation between x-ray dose and numbers of lethal mutants, and the relation between the short ultraviolet wave length 2804 dose and numbers of lethal mutants. Both are compared with theoretical curves for 1, 2, 5, and 8 quantum hits. 4. The production of lethal mutants by x-rays is shown to be consistent with the theoretical curve for five quantum hits on the sensitive spot of the spore, whereas the production of lethal mutants by the ultraviolet wave length 2804 A.u. is consistent with two quantum hits.