Conclusion
The comprehensive process evaluation at hand was theoretically based on the CFIR, complements the outcome evaluation of the SDM implementation trial, and adds to our understanding of influencing factors on SDM implementation. To our knowledge this is the first SDM implementation trial following a stepped-wedge cluster randomized design including such a thorough a priori planned process evaluation. Major influencing factors were found for all domains of the CFIR, and strong interrelations between those factors were evident. The identified influencing factors can be used for planning, conducting, and evaluating future SDM implementation. Further studies should investigate which of the influencing factors are predictors for implementation success, and how the interrelations can be taken into account successfully. This knowledge, in turn, may support the implementation of SDM in routine care in the future.