Table 1.

Literature overview of classification systems and the corresponding evidence of each criterion

Author	Years	Type of study	Oxford	New classification	Use of a classification	Recurrence rating	Morphology	Size	Risk factors	Surgical procedure
Ammaturo and Bassi [51]	2005	Case series	4	X			X	X
Chevrel and Rath [52]	2000	Expert opinion	5	X
Chowbey et al. [53]	2006	Expert opinion	5	X
Conze et al. [54]	2005	Experimental	5				X			X
Conze et al. [55]	2007	Case series	4				X			X
Dietz et al. [56]	2007	Expert opinion	5	X
Dietz et al. [57]	2012	Retrospective case–control	3		X	X	X	X	X
Hadeed et al. [58]	2011	Case series	4	X
Höer et al. [59]	2002	Outcome study	2c						X
Jenkins et al. [14]	2010	Case series	4				X	X	X
Kaafarani et al. [60]	2009	RCT	2B			X
Kaafarani et al. [21]	2010	RCT	2B			X		X
Kingsnorth [61]	2006	Review	5							X
Klinge et al. [62]	2001	Experimental	5						X
Korenkov et al. [63]	2001	Expert opinion	5	X
Leblanc et al. [64]	2001	Retrospective cohort	4					X
Licheri et al. [65]	2008	Case series	4		X		X
Losanoff et al. [66]	2007	Review	5				X			X
Martínez-Serrano et al. [67]	2010	Retrospective cohort	3						X
Moreno-Egea et al. [68]	2007	Review	5				X
Moreno-Egea et al. [69]	2008	NR-controlled trial	3				X
Muysoms et al. [70]	2009	Expert opinion	5	X	X	X	X	X	X
Muysoms et al. [71]	2012	Expert opinion	5		X				X
Parker et al. [72]	2011	Retrospective cohort	4					X
Piardi et al. [73]	2010	Retrospective cohort	4				X	X	X
Sanchez et al. [74]	2011	Review	5						X
Sørensen et al. [75]	2005	Retrospective cohort	3						X
Varnell et al. [15]	2008	Case series	4			X	X	X
Veljkovic et al. [76]	2009	Case series	4						X
Winkler et al. [77]	2008	Review	5		X	X	X	X		X

RCT randomized controlled trial, NR nonrandomized