Failing to Succeed: Advancing Mechanistic Understanding of Implementation Strategies Through Retrospective and...

Implementation strategies often fail to achieve their intended outcomes, yet limited methodological guidance exists for systematically understanding why strategies fail or how to adapt them for new contexts. Causal pathway diagrams (CPDs) are tools that map the mechanisms through which implementation strategies work. This study presents the first case study using CPDs both retrospectively to understand implementation failure in one context and prospectively to inform strategy adaptation for a new context.

We conducted a case study of three failed implementation strategies-electronic best practice alert and clinical decision support, provider education, and clinical champion-designed to improve metabolic-associated steatotic liver disease (MASLD) screening in a weight management clinic. Using mixed methods data and realist evaluation principles, we constructed CPDs guided by three theoretical frameworks (i-PARIHS, Theory of Planned Behavior, and Technology Acceptance Model) and post-intervention qualitative interviews to understand failure mechanisms. We then applied insights from these CPDs alongside qualitative interviews with primary care providers to develop predictive CPDs for implementing adapted strategies in the primary care setting.

The retrospective CPDs revealed specific failure points not apparent during initial planning. The clinical decision support strategy failed because fundamental preconditions were unmet: only 54.2% of patients had recent laboratory results needed for automated calculations, and the alert placement misaligned with provider workflows. Provider education and clinical champion strategies were undermined by universal moderators including mistrust in the FIB-4 screening tool and competing clinical priorities. The prospective primary care CPDs identified necessary adaptations including replacing best practice alerts with integrated health maintenance reminders, adding content about MASLD complications and treatments to provider education, and selecting multiple champions to ensure adequate coverage.

CPDs provide a systematic framework for transforming implementation failures into actionable insights for future intervention design. By distinguishing between preconditions necessary for mechanism activation and moderators that influence mechanism strength, CPDs enable precise identification of adaptation targets. The integration of realist evaluation principles with multi-theoretical CPD development offers a replicable methodology for mechanistic failure analysis and context-adapted implementation planning. This approach advances implementation science by moving beyond descriptive accounts toward rigorous understanding of how and why implementation strategies work across diverse settings.