Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.

Aims Now that we are in the deceleration phase of the COVID-19 pandemic, the focus has shifted to how to safely reinstate elective operating. Regional and speciality specific data is important to guide this decision-making process. This study aimed to review 30-day mortality for all patients undergoing orthopaedic surgery during the peak of the pandemic within our region. Methods This multicentre study reviewed data on all patients undergoing trauma and orthopaedic surgery in a region from 18 March 2020 to 27 April 2020. Information was collated from regional databases. Patients were COVID-19-positive if they had positive laboratory testing and/or imaging consistent with the infection. 30-day mortality was assessed for all patients. Secondly, 30-day mortality in fracture neck of femur patients was compared to the same time period in 2019. Results Overall, 496 operations were carried out in 484 patients. The overall 30-day mortality was 1.9%. Seven out of nine deceased patients underwent surgery for a fractured neck of femur. In all, 27 patients contracted COVID-19 in the peri-operative period; of these, four patients died within 30 days (14.8%). In addition, 21 of the 27 patients in this group had a fractured neck of femur, 22 were over the age of 70 years (81.5%). Patients with American Society of Anesthesiologists (ASA) grade > 3 and/or age > 75 years were at significantly higher risk of death if they contracted COVID-19 within the study period. Conclusion Overall 30-day postoperative mortality in trauma and orthopaedic surgery patients remains low at 1.9%. There was no 30-day mortality in patients ASA 1 or 2. Patients with significant comorbidities, increasing age, and ASA 3 or above remain at the highest risk. For patients with COVID-19 infection, postoperative 30-day mortality was 14.8%. The reintroduction of elective services should consider individual patient risk profile (including for ASA grade). Effective postoperative strategies should also be employed to try and reduce postoperative exposure to the virus. Cite this article: Bone Joint Open 2020;1-7:392–397.

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Aims To monitor the performance of services for developmental dysplasia of the hip (DDH) in Northern Ireland and identify potential improvements to enhance quality of service and plan for the future. Methods This was a prospective observational study, involving all infants treated for DDH between 2011 and 2017. Children underwent clinical assessment and radiological investigation as per the regional surveillance policy. The regional radiology data was interrogated to quantify the use of ultrasound and ionizing radiation for this population. Results Evidence-based changes were made to the Northern Ireland screening programme, including an increase in ultrasound scanning capacity and expansion of nurse-led screening clinics. The number of infant hip ultrasound scans increased from 4,788 in 2011, to approximately 7,000 in 2013 and subsequent years. The number of hip radiographs on infants of less than one year of age fell from 7,381 to 2,208 per year. There was a modest increase in the treatment rate from 10.9 to 14.3 per 1,000 live births but there was a significant reduction in the number of closed hip reductions. The incidence of infants diagnosed with DDH after one year of age was 0.30 per 1,000 live births over the entire period. Conclusion Improving compliance with the regional infant hip screening protocols led to reduction in operative procedures and reduced the number of pelvic radiographs of infants. We conclude that performance monitoring of screening programmes for DDH is essential to provide a quality service. Cite this article: Bone Joint J 2020;102-B(4):495–500.

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