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Table 1 Characteristics of the included studies

From: The incidence of regression after the non-surgical treatment of symptomatic lumbar disc herniation: a systematic review and meta-analysis

Author Year Country Study type Qualitya LDH Levelb Measurement Imaging method Countingc Number of patients
Regression Total
El Barzouhi et al. [9] 2013 Netherlands RCT Low risk single Qualitative MRI A 88 95
Santilli et al. [10] 2006 Italy RCT Low risk single/multiple Qualitative MRI A 0 102
Fan et al. [11] 2015 China RCT Unclear risk Unknow Qualitative MRI A 0 158
Ahn et al. [12] 2002 Korea Prospective 11 single Qualitative MRI B 13 17
Maigne et al. [13] 1992 France Prospective 10 single Qualitative CT B 39 48
Benson et al. [14] 2010 UK Prospective 12 single Quantitative MRI B 28 32
Komori et al. [15] 1998 Japan Retrospective 12 single Qualitative MRI A 19 22
Modic et al. [16] 1995 USA Prospective 12 single/multiple Qualitative MRI B 4 16
Kamanli et al. [17] 2010 Turkey Prospective 8 Unknown Qualitative MRI A 5 26
Autio et al. [18] 2006 Finland Prospective 12 single Quantitative MRI A 51 55
Gallucci et al. [19] 1995 Italy Prospective 10 Unknown Qualitative MRI B 11 15
Ozturk et al. [20] 2006 Turkey RCT Low risk single/multiple Quantitative CT A 19 46
Ahn et al. [21] 2000 Korea Prospective 12 single Quantitative MRI A 25 36
Ilkko et al. [22] 1993 Finland Unknown 7 single/multiple Qualitative CT A 15 18
Delauche-Cavallier et al. [23] 1992 France Prospective 9 single Qualitative CT A 14 21
Buttermann et al. [24] 2002 USA Prospective 10 single Quantitative MRI A 52 58
Bozzao et al. [25] 1992 Italy Prospective 10 Unknow Qualitative MRI A 41 65
Broetz et al. [26] 2008 Germany Prospective 9 Unknow Qualitative MRI A 0 10
Jensen et al. [27] 2006 Denmark Prospective 10 Unknow Qualitative MRI A 65 139
Henmi et al. [28] 2002 Japan Unknown 11 single Quantitative MRI A 4 10
Takada et al. [29] 2001 Japan Prospective 9 single Qualitative MRI A 37 42
Cribb et al. [30] 2007 England Unknown 7 single Quantitative MRI A 14 15
Ellenberg et al. [31] 1993 USA Prospective 9 single/multiple Qualitative CT A 11 14
Demirel et al. [32] 2017 Turkey RCT Low risk single/multiple Quantitative MRI A 18 20
Hong et al. [33] 2016 Korea Retrospective 10 single Quantitative MRI A 24 28
Matsubara et al. [34] 1995 Japan Unknown 9 single Qualitative MRI B 20 32
Yukawa et al. [35] 1996 Japan Unknown 11 single Quantitative MRI A 17 30
Fagerlund et al. [36] 1990 Sweden Prospective 12 single Qualitative CT B 22 30
Kesikburun et al. [37] 2019 Turkey Prospective 12 single Quantitative MRI A 36 40
Teplick et al. [38] 1985 USA Unknown 7 Unknown Qualitative CT A 11 55
Shan et al. [39] 2014 China Retrospective 12 single Quantitative MRI A 24 30
Shin et al. [40] 2017 Korea Prospective 8 Unknown Qualitative MRI A 42 73
Komori et al. [41] 1996 Japan Retrospective 10 single Qualitative MRI A 49 77
Saal et al. [42] 1990 USA Unknown 8 Unknown Qualitative CT/MRI B 9 11
Bush et al. [43] 1992 UK Prospective 10 single/multiple Qualitative CT A 71 111
Iwabuchi et al. [44] 2010 Japan Prospective 10 single Qualitative MRI A 21 34
Yu et al. [45] 2014 China Unknown 10 single Qualitative MRI A 20 83
Lee et al. [46] 2017 Korea Retrospective 10 single Quantitative MRI A 486 505
  1. aQuality of non-randomized studies was assessed following the MINORS; the risk of bias of RCTs was evaluated using a tool from the Cochrane Collaboration
  2. bSome studies included only single-level SLDH patients and some studies included both single- and multiple-level SLDH patients
  3. cCounting. A. The number of patients with regression was reported and was extracted from the publication. B: For studies that recorded the number of patients by the regression proportion or size interval but did not define the interval of non-regression or report the number of patients without regression, we regarded the lowest interval as the no regression range, and the number of patients outside of this interval was considered the number of patients with regression