Table 1.

Summary of the stages of surgical innovation according to the IDEAL framework

Stage of innovation	Description	No. of patients	Proposed method of investigation	Studies included in this review
0: idea (preclinical)	Feasibility and definition of procedure	None	Simulated, cadaver, animal, modelling	Preclinical studies in animals (in vivo and post-mortem models) and in vitro
1: idea	Proof of concept; first in human	Very few	Case reports, small case series	Case reports, small case series, occupational health and safety studies; data relate to safety and technical feasibility
2a: development	Therapy evolving; refining and modifying the technique	Usually < 30	Prospective development studies	Larger case series, non-randomized studies; prospective and retrospective case series; single centre
2b: exploration	Learning curves progressing, indication expanding	Many	Prospective series, multisite, feasibility RCT	Large multicentre case series, studies looking at new indication
3: assessment	Procedure has clear definition and used by many surgeons but needs to be tested against standard of care	Many	RCT	RCT and RCT protocols
4: long-term	Long-term follow-up with registry data, to monitor late/rare complications	Many	Registry, late/rare case reports	NA

RCT, randomized clinical trial; NA, not applicable.