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  • SAGE Publications  (2)
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  • SAGE Publications  (2)
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  • 1
    Online Resource
    Online Resource
    SAGE Publications ; 2017
    In:  Statistical Methods in Medical Research Vol. 26, No. 1 ( 2017-02), p. 508-524
    In: Statistical Methods in Medical Research, SAGE Publications, Vol. 26, No. 1 ( 2017-02), p. 508-524
    Abstract: Multi-arm multi-stage trials can improve the efficiency of the drug development process when multiple new treatments are available for testing. A group-sequential approach can be used in order to design multi-arm multi-stage trials, using an extension to Dunnett’s multiple-testing procedure. The actual sample size used in such a trial is a random variable that has high variability. This can cause problems when applying for funding as the cost will also be generally highly variable. This motivates a type of design that provides the efficiency advantages of a group-sequential multi-arm multi-stage design, but has a fixed sample size. One such design is the two-stage drop-the-losers design, in which a number of experimental treatments, and a control treatment, are assessed at a prescheduled interim analysis. The best-performing experimental treatment and the control treatment then continue to a second stage. In this paper, we discuss extending this design to have more than two stages, which is shown to considerably reduce the sample size required. We also compare the resulting sample size requirements to the sample size distribution of analogous group-sequential multi-arm multi-stage designs. The sample size required for a multi-stage drop-the-losers design is usually higher than, but close to, the median sample size of a group-sequential multi-arm multi-stage trial. In many practical scenarios, the disadvantage of a slight loss in average efficiency would be overcome by the huge advantage of a fixed sample size. We assess the impact of delay between recruitment and assessment as well as unknown variance on the drop-the-losers designs.
    Type of Medium: Online Resource
    ISSN: 0962-2802 , 1477-0334
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2017
    detail.hit.zdb_id: 2001539-2
    detail.hit.zdb_id: 1136948-6
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  • 2
    Online Resource
    Online Resource
    SAGE Publications ; 2021
    In:  Foot & Ankle International Vol. 42, No. 10 ( 2021-10), p. 1254-1259
    In: Foot & Ankle International, SAGE Publications, Vol. 42, No. 10 ( 2021-10), p. 1254-1259
    Abstract: The number of ankle and revision ankle replacements performed is increasing. There is limited research into functional outcomes, especially in revision ankle replacements. The primary aim of this cohort study was to determine the functional improvements following primary and revision ankle replacements and compare which gave the greatest improvement in functional scores. Methods: A single-center prospective cohort study was undertaken between 2015 and 2018. All patients were followed up for a minimum of 2 years. Patients undertook a preoperative and 2-year Manchester Oxford Foot Questionnaire (MoxFQ) score. The Mann Whitney test was undertaken. Results: A total of 33 primary and 23 revision ankle replacements were performed between 2015 and 2018. The mean age was 69.3 years for primary replacements and 64.7 years for revision replacements. All primary replacements were the Infinity ankle replacement. Revision replacements were either the Inbone II or Invision. The indication for revision was 9 aseptic loosening, 6 infections, 5 cysts, and 3 malposition. Seventeen were performed as a single stage and 6 as a 2-stage revision. The overall MoxFQ improved by a mean of 48.8 for primaries and 20.2 for revisions ( P = .024). The walking/standing domain improved by 57.5 for primaries and 22.5 for revisions ( P = .016), the pain score improved by 43.0 and 32.3 ( P = .009), and the social interaction improved by 40.0 and 11.7 ( P = .128). Conclusion: Both primary and revision ankle replacements result in improved functional scores. In this relatively small cohort with the implants used, primary ankle replacements though have a significantly greater improvement in functional scores compared to revision ankle replacements. Level of Evidence: Level II, prospective cohort study.
    Type of Medium: Online Resource
    ISSN: 1071-1007 , 1944-7876
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2129503-7
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