Deep Vein Thrombosis

The events of interest in this study were AESIs that might need evaluation after covid-19 vaccination. This list of outcomes was based on the protocol published by the FDA Center for Biologics Evaluation and Research, the prioritised covid-19 vaccine AESI list by the Brighton Collaboration, and previous studies.4
17 We included 15 events: non-haemorrhagic and haemorrhagic stroke, acute myocardial infarction, deep vein thrombosis, pulmonary embolism, anaphylaxis, Bell’s palsy, myocarditis or pericarditis, narcolepsy, appendicitis, immune thrombocytopenia, disseminated intravascular coagulation, encephalomyelitis (including acute disseminated encephalomyelitis), Guillain-Barré syndrome, and transverse myelitis.4
Events were identified by records of the occurrence of conditions based on predefined phenotyping algorithms (eg, diagnosis codes from claims or diagnosis codes and problem lists from electronic health records). Definitions for encephalomyelitis, non-haemorrhagic and haemorrhagic stroke, and acute myocardial infarction also required the record to occur within an inpatient setting in any diagnosis positions, whereas the definition for Guillain-Barré syndrome required the condition to be recorded in an inpatient setting in the primary position. Appendix tables 2 and 3 present the full specifications of all phenotype definitions, including source codes (original codes used in the database) and standard concepts (normative expressions used to represent a unique clinical entity within the Observational Medical Outcomes Partnership common data model, which were mostly SNOMED (Systematized Nomenclature of Medicine) codes in this study).
We defined a “clean window” period before each index date, during which qualifying events (AESIs) could not be observed. If an AESI was observed during this period, the participant did not enter the study cohort for that event. If an individual had a qualified event during follow-up, this participant would contribute to the person time of that event cohort after the clean window continually until censored from the cohort.
Figure 1 shows the cohort entry, follow-up, and event definitions. In keeping with the FDA protocol, the clean window was 365 days for all events except anaphylaxis (30 days) and facial nerve palsy and encephalomyelitis (183 days).4
As the CPRD-GOLD (UK), IQVIA (France, Germany, and Australia), and IPCI (the Netherlands) databases only included primary care data, we did not use them for events where definition required an inpatient diagnosis.

This was a retrospective cohort study on prospectively collected data of a sample of consecutive patients undergoing total knee arthroplasty due to end-stage osteoarthritis unresponsive to conservative treatments at a single facility by a fellowship-trained joint reconstructive surgeon. The study period was between June 2018 and March 2021. Institutional Review Board (IRB) exemption was obtained prior to study initiation. Waiver of informed consent was issued by the same IRB. There were 89 patients (121 knees) treated with 1G and 98 patients (123 knees) treated with 2G who consented to be enrolled for the study. The surgeon switched from 1G to 2G prostheses once the new implants were available to order. No changes in patient selection strategies were made once the new generations were implanted. Patients were excluded from the study if they had a history of metabolic bone disease (such as Paget’s disease of bone, severe osteoporosis), systemic conditions affecting bone density (e.g. renal osteodystrophy; inflammatory arthritis), bony defects requiring grafting, a poorly functioning contralateral TKA or revision regardless of function.
All TKAs were performed via a medial parapatellar approach using an intramedullary femoral alignment guide set at five-degrees and an extramedullary tibial alignment guide set at neutral in the coronal plane with a neutral posterior slope in the sagittal plane. All TKAs were cemented (Palacos^®, Heraeus Medical, Hanau, Germany). The postoperative protocol was the same in all cases including deep vein thrombosis prophylaxis, prophylactic antibiotics, and follow-up schedule (8 weeks, 6 months, 1 year, and every 1 to 2 years thereafter). Physical therapy was initiated on the day of operation. Each exam was performed by the attending physician.
As per the study protocol, the surgeon switched from 1G to 2G a year into the study period. Data for demographic parameters including age, gender, race, and body mass index (BMI) were collected preoperatively. Scores from patient-reported outcome measures such as the Knee Injury and Osteoarthritis Outcome Survey-Joint Replacement (KOOS-JR) [10 (link)] and Knee Society clinical and radiographic scoring system (KSS) were collected at each office visit [11 (link)]. Scores from different components of KSS were reported separately. These components were objective knee score, functional score, patient satisfaction and expectation score. Intra- and post-operative complications, as well as any revisions, reoperations, and returns to operating room, were diligently recorded. All data were collected prospectively in an institutional database. This study represents a retrospective review of these prospectively collected data.