Effect of the COVID-19 pandemic on surgery for indeterminate thyroid nodules (THYCOVID): a retrospective, international, multicentre, cross-sectional study

Background Since its outbreak in early 2020, the COVID-19 pandemic has diverted resources from non-urgent and elective procedures, leading to diagnosis and treatment delays, with an increased number of neoplasms at advanced stages worldwide. The aims of this study were to quantify the reduction in surgical activity for indeterminate thyroid nodules during the COVID-19 pandemic; and to evaluate whether delays in surgery led to an increased occurrence of aggressive tumours.Methods In this retrospective, international, cross-sectional study, centres were invited to participate in June 22, 2022; each centre joining the study was asked to provide data from medical records on all surgical thyroidectomies consecutively performed from Jan 1, 2019, to Dec 31, 2021. Patients with indeterminate thyroid nodules were divided into three groups according to when they underwent surgery: from Jan 1, 2019, to Feb 29, 2020 (global prepandemic phase), from March 1, 2020, to May 31, 2021 (pandemic escalation phase), and from June 1 to Dec 31, 2021 (pandemic decrease phase). The main outcomes were, for each phase, the number of surgeries for indeterminate thyroid nodules, and in patients with a postoperative diagnosis of thyroid cancers, the occurrence of tumours larger than 10 mm, extrathyroidal extension, lymph node metastases, vascular invasion, distant metastases, and tumours at high risk of structural disease recurrence. Univariate analysis was used to compare the probability of aggressive thyroid features between the first and third study phases. The study was registered on ClinicalTrials.gov, NCT05178186.Findings Data from 157 centres (n=49 countries) on 87 467 patients who underwent surgery for benign and malignant thyroid disease were collected, of whom 22 974 patients (18 052 [78 center dot 6%] female patients and 4922 [21 center dot 4%] male patients) received surgery for indeterminate thyroid nodules. We observed a significant reduction in surgery for indeterminate thyroid nodules during the pandemic escalation phase (median monthly surgeries per centre, 1 center dot 4 [IQR 0 center dot 6-3 center dot 4]) compared with the prepandemic phase (2 center dot 0 [0 center dot 9-3 center dot 7]; p<0 center dot 0001) and pandemic decrease phase (2 center dot 3 [1 center dot 0-5 center dot 0]; p<0 center dot 0001). Compared with the prepandemic phase, in the pandemic decrease phase we observed an increased occurrence of thyroid tumours larger than 10 mm (2554 [69 center dot 0%] of 3704 vs 1515 [71 center dot 5%] of 2119; OR 1 center dot 1 [95% CI 1 center dot 0-1 center dot 3]; p=0 center dot 042), lymph node metastases (343 [9 center dot 3%] vs 264 [12 center dot 5%]; OR 1 center dot 4 [1 center dot 2-1 center dot 7]; p=0 center dot 0001), and tumours at high risk of structural disease recurrence (203 [5 center dot 7%] of 3584 vs 155 [7 center dot 7%] of 2006; OR 1 center dot 4 [1 center dot 1-1 center dot 7]; p=0 center dot 0039).Interpretation Our study suggests that the reduction in surgical activity for indeterminate thyroid nodules during the COVID-19 pandemic period could have led to an increased occurrence of aggressive thyroid tumours. However, other compelling hypotheses, including increased selection of patients with aggressive malignancies during this period, should be considered. We suggest that surgery for indeterminate thyroid nodules should no longer be postponed even in future instances of pandemic escalation.Funding None.Copyright (c) 2023 Published by Elsevier Ltd. All rights reserved

Degradation of high loaded oscillating bearings: Numerical analysis and comparison with experimental observations

Nowadays mechanical systems are expected to sustain extreme working conditions, due to the increase of the involved power and the optimized design. Moreover special applications like aeronautics, space engineering and robotics require the reduction of the contact area in the contact pairs, which allow the relative motion between components, by increasing the power transmitted per unit of contact area. As a consequence the joint degradations are between the main issues, resulting in possible failures or increase of consumption and maintenance costs. This paper addresses the analysis of the degradation mechanism of oscillating ball bearings subjected to high loads. These bearings, needed to assure the repetitive relative rotation between two members of the mechanical system (e.g. repetitive motions of assembling and manufacturing robots, ship helms, aircraft flaps, etc.), can reach extreme contact pressures at the ball-race contact surfaces; the oscillations of the bearings provide a fatigue loading of the contact area due to the repetitive rotation of the balls between the races. This work is aimed to calculate the contact stress distributions due to the specific boundary conditions, in order to relate them with the bearing degradation. A numerical model is presented to reproduce the loading conditions and calculate the contact stress and strain distributions in order to correlate them with the damages observed experimentally; results obtained by 2D modelling and 3D modelling, for both elastic and plastic properties of the bearing material, are reported and compared. The numerical results and the comparison with tribological observations of a degraded bearing, after cyclic load application, suggest a possible degradation scenario that brings to the failure of the bearing due to subsurface damages. © 2014 Elsevier B.V

Experimental damage analysis in high loaded oscillating bearings

Several industrial applications require rolling bearings to operate under both high load and oscillating motion. While the oscillating motion does not allow for EHD regime, the high load applied induces high contact pressures. Even if many works in the literature deal with rotating bearings, few works address high loaded oscillating bearings. The degradation scenario of high loaded oscillating bearings is here analysed step by step for both greased and ungreased bearings. Subsurface plastic damage of the balls was found to be at the origin of greased bearing degradation, while progressive superficial degradation lead to a faster degradation of ungreased bearings

Numerical analysis of contact stress and strain distributions for greased and ungreased high loaded oscillating bearings

Nowadays rolling bearings are subject to extreme operating conditions due to the increasing of the transmitted power and the optimized design. Consequently, the reduction of the bearing dimensions can lead to a reduction of the contact area and an increasing of the power transmitted per unit of contact area. Some special applications as space engineering, robotics, aeronautics and wind energy require rolling bearings subjected to high contact pressure while the movement is governed by an oscillating motion; such extreme conditions can lead to degradation and failure scenarios which are not linked to classical contact fatigue and are not completely understood yet. The aim of this work is to investigate the contact stress and strain distribution of rolling bearings under high loaded oscillating motion, i.e. high contact pressure and deformation. 3D finite element simulations with elasto-plastic material law have been carried out and a comparison of the results with the classical elastic law is presented. The effect of the friction coefficient, the radial load and the surface conformity have been investigated. The numerical results have been compared with the tribological observations of the degraded bearings under the same load conditions. The presented results contribute to the tribological and physical interpretation of the degradation scenario, for greased and ungreased bearings, by a mechanical point of view

Roller bearing under high loaded oscillations: Life evolution and accommodation mechanisms

High loaded oscillating bearings are used on several industrial fields such as robotics, wind power, aeronautics and aerospace. These bearings are subjected to extremely high local contact pressures and relatively low oscillatory speed. In this work, endurance tests on commercial single row spherical roller bearings enable to propose a degradation scenario for the bearing lifecycle. Topographical analyses carried out at each phase of the bearing life allowed to understand the degradation evolution at the interface between the inner-ring raceway and rolling elements. The analysis of the experimental results, with the support of numerical stress analysis, led to the understanding of the involved accommodation mechanisms. Then, a comparison with the wear processes in deep-groove ball bearings is provided

Etude et realisation d'un multiplexeur a 12x140 bits: architecture et fonctionnement

SIGLECNRS RP 252 (273) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc