One hundred twenty-one and 425 studies were identified from Medline and Scopus, respectively (Fig. 1); 97 studies were duplicates, leaving 449 studies for review of titles and abstracts. Of these, 30 studies were reviewed and data extracted. Characteristics of the 30 studies are described in Table 1. Thirteen studies were transdiscal PECD and 17 studies were transcoporeal PECD. Twenty-six were retrospective cohort studies and three studies were prospective cohort and one study was a RCT study. Twenty-four studies were reported outcomes of disc herniation, four studies reported outcomes of radiculopathy, one study reported outcomes of myelopathy and one study reported outcomes of cervical disc diseases. Neck disability score using the neck disability index in 8 studies (4 studies were transdiscal PECD and 4 studies were transcorporeal PECD) and visual analog scale score neck and arm pain were reported in 21 studies (11 studies were transdiscal PECD and 10 studies were transcorporeal PECD) and 10 studies (4 studies were transdiscal PECD and 6 studies were transcorporeal PECD). Complications, reoperation rates and modified Mcnab questionnaire were reported in 30 (12 studies were transdiscal PECD and 18 studies were transcorporeal PECD), 30 (12 studies were transdiscal PECD and 18 studies were transcoporeal PECD) and 10 studies (6 studies were transdiscal PECD and 4 studies were transcoporeal PECD), respectively. Mean age and mean follow up of participants varied from 37 to 62 years, and 3 to 45.7 months respectively. Percentages of male gender and cervical disc level L5-6 ranged from 43 to 95 percent and 12.5 to 55 percent.
Table 1
Characteristics of the included studies NC: n transcoporeal; ND: n transdiscal; RCT: randomized controlled trial; NDI: neck disability score
Author | Year | Design | ND | NC | Diseases | Age (mean) | N (Male %) | FU (months) | C5-6 (%) | Outcome |
Choi G | 2007 | Prospective | - | 20 | Radiculopathy | 48.7 | - | 16.7 | 0.20 | VAS arm and neck, NDI, complications and reoperations |
Ruetten S | 2009 | RCT | 60 | - | Disc Herniation | - | - | - | - | VAS arm and neck, complications and reoperations |
Sakai T | 2009 | Retrospective | - | 20 | Disc Herniation | 50.3 | 0.95 | - | - | VAS neck and arm, complications and reoperations |
Shim CS | 2009 | Retrospective | - | 1 | Disc Herniation | 68 | - | - | - | Complications and reoperations |
Choi G | 2010 | Retrospective | - | 30 | Disc Herniation | 52.4 | 0.67 | 35.7 | - | VAS arm and neck, complications and reoperations |
Kim JS | 2011 | Retrospective | - | 8 | Disc Herniation | 58.9 | 0.63 | 8.5 | 0.50 | Complications and reoperations |
Tzaan WC | 2011 | Retrospective | 107 | - | Disc Herniation | 38 | 0.55 | 12 | 0.50 | VAS arm and neck, NDI, Mcnab, complications and reoperations |
Deukmedjian AJ | 2012 | Retrospective | 142 | - | Cervical disc diseases | - | - | - | - | Complications |
Takeuchi M | 2012 | Retrospective | - | 118 | Disc Herniation | 52 | 0.8 | 20 | - | VAS neck, complications and reoperations |
Umebayashi D | 2013 | Retrospective | - | 34 | Disc Herniation | 55.2 | 0.74 | 40 | 0.49 | Complications and reoperations |
Lee JH | 2014 | Retrospective | 37 | - | Disc Herniation | - | 0.54 | 45.5 | - | VAS neck and arm, NDI, complications and reoperations |
Yang JS | 2014 | Retrospective | 42 | - | Disc Herniation | 41.3 | 0.62 | - | 0.55 | VAS neck and arm, Mcnab, complications and reoperations |
Lowry DW | 2015 | Retrospective | - | 42 | Disc Herniation | 50.6 | - | 12 | - | VAS arm and neck, NDI, complications and reoperations |
Deng ZL | 2016 | Retrospective | - | 1 | Disc Herniation | 37 | - | 3 | - | Complications and reoperations |
Gushcha AO | 2016 | Retrospective | - | 25 | Disc Herniation | - | - | - | - | VAS arm and neck, complications and reoperations |
Nadkarni SM | 2017 | Retrospective | 20 | - | Disc Herniation | - | 0.7 | 6 | - | VAS neck, NDI, complications and reoperations |
Oh HS | 2017 | Retrospective | 101 | - | Disc Herniation | 46.1 | 0.64 | 34 | 0.45 | VAS neck and arm, NDI, Mcnab, complications and reoperations |
Chu L | 2018 | Retrospective | - | 5 | Radiculopathy | - | - | 6 | - | VAS neck and arm, complications and reoperations |
Du Q | 2018 | Retrospective | - | 36 | Radiculopathy | 48.33 | 0.58 | 12 | 0.33 | VAS neck and arm, complications and reoperations |
Nakamura S | 2018 | Retrospective | 42 | - | Disc Herniation | 45 | 0.73 | 13.8 | - | VAS neck, complications and reoperations |
Quillo-Olvera | 2018 | Retrospective | - | 3 | Myelopathy | 65 | - | 3 | - | Complications and reoperations |
Yu KX | 2019 | Retrospective | - | 35 | Disc Herniation | 50.26 | 0.66 | 24 | 0.46 | VAS arm and neck, complications and reoperations |
Nakai S | 2000 | Retrospective | - | 24 | Radiculopathy | 46.8 | 0.625 | 45.7 | 0.125 | Complications and reoperations |
Hong WJ | 2006 | Retrospective | - | 20 | Disc Herniation | 46.6 | - | - | - | Mcnab, complications and reoperations |
Leon JFR | 2020 | Retrospective | 293 | - | Disc Herniation | 55.9 | 0.43 | - | - | VAS neck, Mcnab, complications and reoperations |
Jiang Z | 2020 | Retrospective | 36 | - | Disc Herniation | 59.89 | 0.64 | 24 | - | VAS neck, complications and reoperations |
Ren Y | 2020 | Prospective | 42 | - | Disc herniation | 41.3 | 0.62 | 24 | 0.55 | VAS arm and neck, complications and reoperations |
Ren Y | 2020 | Prospective | - | 77 | Disc herniation | 50.3 | 0.66 | 24 | 0.21 | VAS arm and neck, complications and reoperations |
Haijun M | 2021 | Retrospective | 56 | - | Disc herniation | 62.12 | 0.43 | 12 | 0.41 | VAS neck, complications and reoperations |
Chen X | 2021 | Retrospective | - | 26 | Disc herniation | 49.14 | 0.62 | 19.6 | 0.46 | VAS neck, complications reoperations |
Outcomes
Visual Analog Score (neck pain)
Eleven studies reported mean VAS back pain between post and pre-operative transdiscal and transcorporeal PECD surgery with 836 and 414 patients. The pooled unstandardized mean difference varied highly across studies (Chi-square = 296.75 d.f. = 10, p < 0.001, I2 = 99.28%) -4.52 (95%CI: -6.35 to -2.69) and (Chi-square = 309.17 d.f. = 9, p < 0.001, I2 = 98.44%) -4.86 (95%CI: -6.87 to -2.84), indicating that postoperative transdiscal and transcorporeal PECD surgery had VAS neck pain scores showing statistically significant improvement of about 4.5 and 4.9 scores when compared to preoperatively (Table 2, Fig. 2). The pooled unstandardized mean difference between transdiscal and transcorporeal PECD varied highly across studies (I2 = 99.05) were − 0.33 (95%CI: -3.05 to 2.39), indicating that postoperative transdiscal PECD surgery had VAS neck pain scores that improved 0.33 scores when compared to transcorporeal PECD surgery. However, there was no statistically significant difference between groups. None of the co-variables could explain the heterogeneity. There was no evidence of publication bias on Egger’s test or contour funnel plot.
Table 2
Comparisons of VAS back pain, VAS leg pain and NDI between pre and post-operative of transcoporeal and transdiscal endoscopic discectomy surgery
Author | A) A) VAS neck pain transdiscal endoscopic discectomy |
Preoperative | Postoperative |
N | Mean | S.D. | N | Mean | S.D. |
Ruetten S | 60 | 1.8 | 0.09 | 60 | 1.5 | 0.09 |
Tzaan WC | 107 | 6.9 | 2.3 | 107 | 1.4 | 1.1 |
Lee JH | 37 | 6.3 | 2.15 | 37 | 2.7 | 2.15 |
Yang JS | 42 | 7.9 | 1.7 | 42 | 0.8 | 0.17 |
Oh HS | 101 | 6.75 | 2 | 101 | 0.9 | 2 |
Nadkarni SM | 20 | 9.125 | 2.2 | 20 | 0.5 | 2.2 |
Nakamura S | 42 | 2.085 | 1.79 | 42 | 0.38 | 0.289 |
Leon JFR | 293 | 7.8 | 2.16 | 293 | 2.2 | 2.16 |
Ren Y | 42 | 3.7 | 0.1 | 42 | 2.6 | 0.1 |
Jiang Z | 36 | 6.26 | 0.68 | 36 | 0.49 | 0.42 |
Haijun M | 56 | 6.41 | 1.29 | 56 | 1.33 | 0.57 |
All group the UMD (95% CI) of (Chi-square = 296.75 d.f. = 10, p < 0.001, I2 = 99.28%) -4.52 (95%CI: -6.35 to -2.69) |
B) B) VAS neck pain transcoporeal endoscopic discectomy |
Choi G | 20 | 3.2 | 1.9 | 20 | 1.1 | 1.1 |
Choi G | 30 | 4.05 | 0.84 | 30 | 1.23 | 0.84 |
Takeuchi M | 118 | 7.8 | 2.04 | 118 | 1 | 0.81 |
Lowry DW | 42 | 5.5 | 3.1 | 42 | 0.6 | 0.8 |
Gushcha AO | 25 | 4.5 | 1.19 | 25 | 1.25 | 2.15 |
Chu L | 5 | 7.2 | 0.8 | 5 | 1.6 | 1.1 |
Du Q | 36 | 6.5 | 1.44 | 36 | 0.83 | 0.77 |
Yu KX | 35 | 7.26 | 0.61 | 35 | 1.14 | 0.6 |
Ren Y | 77 | 3.7 | 0.1 | 77 | 2.6 | 0.1 |
Chen X | 26 | 6.55 | 1.45 | 26 | 0.72 | 0.7 |
All group the UMD (95% CI) of (Chi-square = 309.17 d.f. = 9, p < 0.001, I2 = 98.44%) -4.86 (95%CI: -6.87 to -2.84) |
C) C) VAS arm pain transdiscal endoscopic discectomy |
Ruetten S | 60 | 8.2 | 2.31 | 60 | 0.8 | 2.31 |
Lee JH | 37 | 7.5 | 2.9 | 37 | 2.6 | 2.9 |
Oh HS | 101 | 7.8 | 1.5 | 101 | 1.1 | 1.5 |
Ren Y | 42 | 6.1 | 0.5 | 42 | 1.1 | 0.2 |
All group the UMD (95% CI) of (Chi-square = 239.46 d.f. = 3, p < 0.001, I2 = 99.58%) -5.51 (95%CI: -10.40 to -0.62) |
D) D) VAS arm pain transcoporeal endoscopic discectomy |
Choi G | 20 | 7.8 | 0.9 | 20 | 0.6 | 0.8 |
Choi G | 30 | 8.15 | 2.11 | 30 | 1.05 | 2.11 |
Lowry DW | 42 | 7 | 2.4 | 42 | 0.7 | 1.4 |
Gushcha AO | 25 | 5.75 | 1.45 | 25 | 1.5 | 1.19 |
Du Q | 36 | 6.72 | 1.52 | 36 | 0.81 | 0.67 |
Ren Y | 77 | 6.3 | 0.6 | 77 | 1.1 | 0.3 |
All group the UMD (95% CI) of (Chi-square = 150.00 d.f. = 5, p < 0.001, I2 = 97.89%) -5.58 (95%CI: -8.17 to -3.00) |
E) E) NDI transdiscal endoscopic discectomy | | | | |
Tzaan WC | 107 | 19.6 | 8.7 | 107 | 6.8 | 3 |
Lee JH | 37 | 46.8 | 17.4 | 37 | 17.2 | 17.4 |
Oh HS | 101 | 64.5 | 12.3 | 101 | 30 | 12.3 |
Nadkarni SM | 20 | 96 | 33 | 20 | 3 | 1 |
All groups the UMD (95%CI) of (Chi-square = 24.64 d.f. = 3, p < 0.001, I2 = 92.61%) -2.51 (95%CI: -3.39 to -1.62) |
F) F) NDI transcoporeal endoscopic discectomy |
Choi G | 20 | 55.6 | 16.2 | 20 | 4 | 3.7 |
Choi G | 30 | 55.16 | 14.6 | 30 | 5.82 | 14.6 |
Lowry DW | 42 | 20 | 10.4 | 42 | 2.7 | 3.9 |
Gushcha AO | 25 | 14 | 5.8 | 25 | 22 | 7.02 |
All group the UMD (95% CI) of (Chi-square = 131.76 d.f. = 3, p < 0.001, I2 = 97.77%) -2.13 (95%CI: -4.49 to 0.24) |
*P-value < 0.05 statistically significant difference |
Table 3
Comparisons of Complications, Re-operation and modified Mcnab questionnaire between transdiscal and transcoporeal anterior endoscopic discectomy surgery
Author | Complications, Re-operation and modified Mcnab questionnaire |
Complications | Reoperation | Modified Mcnab questionnaire (good and excellent) |
Yes | No | Yes | No | Yes | No |
Ruetten S | 2 | 58 | 1 | 59 | 56 | 4 |
Tzaan WC | 0 | 107 | 1 | 106 | 101 | 6 |
Deukmedjian AJ | 0 | 142 | 0 | 142 | - | - |
Lee JH | 0 | 37 | 0 | 37 | - | - |
Yang JS | 2 | 40 | 1 | 41 | 40 | 2 |
Oh HS | 0 | 101 | 12 | 89 | 95 | 6 |
Nadkarni SM | 0 | 20 | 0 | 20 | - | - |
Nakamura S | 0 | 42 | 0 | 42 | - | - |
Leon JFR | 8 | 285 | 10 | 283 | 275 | 18 |
Ren Y | 0 | 42 | 2 | 40 | - | - |
Jiang Z | 2 | 34 | 2 | 34 | 34 | 2 |
Haijun M | 0 | 56 | 0 | 56 | - | - |
Prevalence of transdiscal (95%CI) 0.031 (95%CI: 0.014 to 0.047) 0.025 (95%CI: 0.013 to 0.037) 0.941 (95%CI: 0.923 to 0.959) |
Nakai S | 2 | 22 | 2 | 22 | 19 | 5 |
Hong WJ | 0 | 20 | 0 | 20 | 20 | 0 |
Choi G | 0 | 20 | 0 | 20 | - | - |
Sakai T | 0 | 20 | 0 | 20 | - | - |
Shim CS | 0 | 1 | 0 | 1 | - | - |
Choi G | 0 | 30 | 0 | 30 | - | - |
Kim JS | 0 | 8 | 0 | 8 | - | - |
Takeuchi M | 0 | 118 | 0 | 118 | - | - |
Umebayashi D | 0 | 34 | 0 | 34 | - | - |
Lowry DW | 0 | 42 | 2 | 40 | - | - |
Deng ZL | 0 | 1 | 0 | 1 | - | - |
Gushcha AO | 0 | 25 | 1 | 24 | - | - |
Quillo-Olvera | 0 | 3 | 0 | 3 | - | - |
Chu L | 0 | 5 | 0 | 5 | - | - |
Du Q | 0 | 36 | 0 | 36 | 33 | 3 |
Yu KX | 0 | 35 | 0 | 35 | - | - |
Ren Y | 0 | 77 | 3 | 74 | - | - |
Chen X | 0 | 26 | 0 | 26 | 24 | 2 |
Prevalence of transcoporeal 0.083 (95%CI: 0 to 0.194) 0.045 (95%CI: 0.014 to 0.076) 0.901 (95%CI: 0.838 to 0.963) |
IRR (95%CI) transd vs tranc 0.64 (95%CI: 0.34 to 1.18) 0.72 (95%CI: 0.35 to 1.46) 1.05 (95%CI: 0.85 to 1.30) |
Visual Analog Score (arm pain)
Four studies reported mean VAS arm pain between post and preoperative transdiscal and transcorporeal PECD surgery with 240 and 230 patients. The pooled unstandardized mean difference varied highly across studies (Chi-square = 239.46 d.f. = 3, p < 0.001, I2 = 99.58%) -5.51 (95%CI: -10.40 to -0.62) and (Chi-square = 150.00 d.f. = 5, p < 0.001, I2 = 97.89%) -5.58 (95%CI: -8.17 to -3.00), indicating that postoperative transdiscal and transcorporeal PECD surgery had VAS arm pain scores that showed statistically significant improvement of about 5.5 and 5.6 scores when compared to preoperatively (Table 2, Fig. 2). The pooled unstandardized mean difference between transdiscal and transcorporeal PECD varied highly across studies (I2 = 99.01) were − 0.14 (95%CI: -5.15 to 4.88), indicating that postoperative transdiscal PECD surgery had VAS arm pain score improvement of about 0.14 scores when compared to transcorporeal PECD surgery. However there was no statistically significant difference between groups. None of the co-variables could explain the heterogeneity. There was no evidence of publication bias on Egger’s test or contour funnel plot.
Neck Disability Index
Four studies reported mean NDI between post and preoperative transdiscal and transcorporeal PECD surgery with 265 and 117 patients. The pooled unstandardized mean difference varied highly across studies (Chi-square = 24.64 d.f. = 3, p < 0.001, I2 = 92.61%) -2.51 (95%CI: -3.39 to -1.62) and (Chi-square = 131.76 d.f. = 3, p < 0.001, I2 = 97.77%) -2.13 (95%CI: -4.49 to 0.24) scores, indicating that postoperative transdiscal and transcorporeal PECD surgery had disability scores showing statistically significant improvement of about 2.5 and 2.1 scores when compared to preoperatively (Table 2, Fig. 2). The pooled unstandardized mean difference between transdiscal and transcorporeal PECD varied highly across studies (I2 = 97.57) and was 0.46 (95%CI: -2.08 to 2.99), indicating that there was no statistically significant difference of disability scores between the two groups. None of the co-variables could explain the heterogeneity. There was no evidence of publication bias on Egger’s test or contour funnel plot.
Complications, reoperation rates and modified Mcnab questionnaire
The prevalence of complications (neurological deficit, dysphagia and vascular injury) and reoperation of PECD in the transdiscal group were 0.03 (95%CI: 0.01 to 0.05) and 0.03 (95%CI: 0.01 to 0.04) respectively while the complications and reoperation rates in the transcorporeal PECD group were 0.08 (95%CI: 0 to 0.19) and 0.045 (95%CI: 0.01 to 0.08) respectively. Results by the modified Macnab’s criteria showed an excellent and good outcome, with a success rate of 0.94 (95%CI: 0.92 to 0.96) % in the transdiscal PECD group and 0.90 (95%CI: 0.84 to 0.96) % in the transcorporeal PECD group. Risk of complications and reoperation were lower in the transdiscal PECD group with a pooled RR of 0.64 (95% CI: 0.34, 1.18) and 0.72 (95%CI: 0.35 to 1.46) times when compared to the transcorporeal PECD group, indicating that the chance of having postoperative complications and reoperation were lower by approximately 36 and 28 percent in the transdiscal PECD group when compared to the transcorporeal PECD group. However, there was no statistically significant difference. In terms of the Mcnab questionnaire satisfisfactoryoutcomes (good and excellent), this was higher in the transdiscal PECD group with a pooled RR of 1.05 (95%CI: 0.85 to 1.30) when compared to the transcorporeal PECD group, indicating that the chance of patient satisfaction with good and excellent outcomes was approximately 5 percent higher in the transdiscal PECD group when compared to the transcorporeal PECD group.