Table 2.

Summary of Idea, Exploration, Assessment, Long-term study and recommendations IDEAL-framework [17]

	1 Idea	2A Development	2B Evaluation	3 Assessment	4 Long-term study
Purpose	Proof of concept	Establish technical details and replicate early results	Learning	Assessment	Surveillance
Design	Structured case report	Prospective case series	Prospective comparative case series, feasibility RCT	RCT	Audit, registry, database
Number of patients	1	< 30	> 30	Guided by sample size calculation	Often large number
Inclusion criteria	Highly selected	Selected	Widening	Wide	Wide
Technical modifications	Report success and failures	Modifications allowed	Modifications allowed	No further modifications	No further modifications
Considered innovative procedure	Yes	Yes	Yes	No	No
Surgeon and center expertise	Details of pre-human work	Details of surgeon training	Details of mentoring and learning curve	Surgeons should be past the learning curve	Surgeons should be past the learning curve
Outcomes	Proof of concept; technical achievement, dramatic success, adverse events, surgeon view of the procedure	Mainly safety: technical and procedural success	Safety; clinical outcomes, short term patient centered outcomes, feasibility outcomes	Clinical outcomes, potential patient reported outcomes, health economic outcomes	Rare event, long term outcomes, quality assurance