were identified. After removing duplicates, 1,525 citations were screened. Of these, 159 full text references were reviewed and 85 systematic reviews met predefined inclusion criteria. Five QA methods were most commonly employed: Newcastle-Ottawa Quality Assessment Scale (NOS) or modified NOS (28%); checklists developed by authors (15%); the Cochrane checklist or modified version (11%); modified checklists from other authors (5%); applying disease-specific QA tools (5%). The reliability and applicability of the most commonly employed tool in this research field, NOS, were questioned in included reviews, corresponding with concerns on the validity of the NOS reported in recently published literature of research methodology. ConClusions: The available evidence demonstrates a lack of consensus on the use of QA tools for non-RCTs assessing surgical interventions. Various methods have been adapted or newly developed by researchers, and the most commonly applied QA tool (NOS) may not be fit for purpose in this field of research. There is an urgent need for a validated QA tool to appraise the quality of evidence to help inform evidence-based decision making on the use of surgical devices and types of surgical approaches.

A715predominantly positive. However, experts refer to methodological deficits and only few would recommend the use of the instruments in practice. ConClusions: There are many questionnaires to assess workability and related concepts. However, only few seem to be scientifically sound and valid and at the same time applicable for a broad use in practice.

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23 items, accounting for 72.8% of variance. Internal reliability for the 3 domains was high (Cronbach's α .84-.96), as was test-retest reliability (intra-class correlation .81-.96). Concurrent validity was demonstrated through highly significant relationships with relevant domains of the SF-36 and the EQ-5D-5L. ConClusions: Preliminary results suggest that the Ox-PAQ is a short, valid and reliable measure of participation and activity. The measure will now be validated in a range of further conditions and additional properties, such as sensitivity to change and predictive validity, will also be assessed in the next phase of the instrument's development.