Background: The focus of clinical trials is typically intervention efficacy, or whether they attain their desired outcomes. Comparatively less attention is focused on understanding how or why interventions succeed, or fail to attain, those outcomes. This may be particularly important in trials of complex interventions such as surgery or physiotherapy, which are multifaceted and often tailored to individual participants, providers, or settings, increasing the potential for variations in intervention delivery and effects. The correspondence between the intervention that was planned and what was actually delivered in a trial is its intervention fidelity. Several benefits for high levels of intervention fidelity have been proposed. However, a lack of a uniform definition for fidelity and its key components may hinder intervention delivery in clinical trials and the translation of evidence-based interventions to clinical practice. Methods: In this study, we undertook systematic review, and Best-fit framework synthesis to develop an empirically-based intervention fidelity framework for complex interventions in rehabilitation. Results: The resulting CONSIDER (Complex iNterventionS Design dElivery Recepit) framework is first integrated fidelity framework developed specifically for clinical trials of for complex interventions rehabiliation. CONSIDER consists of three main components, Design, Delivery and Receipt and the factors moderating them. Design encompasses the core elements of the intervention and the protocol for the clinical trial to evaluate its effectiveness. Delivery encompasses the actual implementation of the protocol and treatment integrity. It is focused primarily on the actions of the intervention providers. Receipt addresses the exposure of the trial participants to the intervention and their response to it. Conclusions: This fidelity framework is the first designed suit the unique complexities and challenges presented by physical complex interventions. It can help promote transparency and reproducibility and helps researchers design clinical trials that reduce waste, enable uptake into clinical practice, and benefit the practice and evidencing of physiotherapy, surgery and other physical complex interventions. Keywords: intervention fidelity, adherence, compliance, integrity, framework, complex interventions, rehabilitation

The authors have declared no competing interest.

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42019135957

This study did not receive any funding

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