Table 1

List of endoscopy studies included into the meta-analysis with brief summary of study highlights.

No.	Authors	Year	Title	Reference	Study Highlights
1.	Ahn Y, Keum HJ, et al⁵	2019	Transforaminal endoscopic decompression for lumbar lateral recess stenosis: an advanced surgical technique and clinical outcomes	World Neurosurg. 2019;125:e916–e924.	Retrospective 2-y follow-up study on 45 patients treated with transforaminal endoscopic decompression for lumbar lateral recess stenosis.
2.	Ahn Y, Lee SG, et al¹⁰²	2019	Transforaminal endoscopic lumbar discectomy vs open lumbar microdiscectomy: a comparative cohort study with a 5-year follow-up	Pain Physician. 2019;22:295–304.	Long-term prospective outcome analysis of PELD vs microdiscectomy on 335 with 5-y follow-up.
3.	Bai YB, Xu L, et al¹⁰³	2012	Diagnosis and treatment of lumbar disc herniation by discography and percutaneous transforaminal endoscopic surgery	Zhonghua Yi Xue Za Zhi. 2012;92:3350–3353.	Retrospective analysis (26 mo) of 119 LDH patients by discography and transforaminal PELD surgery.
4.	Choi G, Lee SH, et al¹⁰⁴	2007	Percutaneous endoscopic discectomy for extraforaminal lumbar disc herniations: extraforaminal targeted fragmentectomy technique using working channel endoscope	Spine (Phila Pa 1976). 2007;32:E93–E99.	A retrospective analysis (34.1 mo follow-up) of 41 patients with soft lumbar extraforaminal disc herniations treated by endoscopic extraforaminal approach under local anesthesia.
5.	Choi G, Modi HN, et al¹⁰⁵	2013	Clinical results of XMR-assisted percutaneous transforaminal endoscopic lumbar discectomy	J Orthop Surg Res. 2013;8:14.	Prospective study on 89 patients (2-y follow-up) undergoing PELD for LDH in an operative suite equipment with fluoroscopic and magnetic resonance imaging.
6.	Choi KC, Kim JS, et al¹⁰⁶	2016	Percutaneous endoscopic lumbar discectomy as an alternative to open lumbar microdiscectomy for large lumbar disc herniation	Pain Physician. 2016;19:E291–E300.	Retrospective observational study (2-y follow-up) on 20 endoscopic and 23 open lumbar discectomy patients.
7.	Choi KC and Park CK¹⁰⁷	2016	Percutaneous endoscopic lumbar discectomy for L5-S1 disc herniation: consideration of the relation between the iliac crest and L5-S1 disc	Pain Physician. 2016;19:E301–E308.	Retrospective study on 51 patients (2-y follow-up) treated either with transforaminal PELD or interlaminar PELD.
8.	Chung J, Kong C, et al⁷	2019	Percutaneous endoscopic lumbar foraminoplasty for lumbar foraminal stenosis of elderly patients with unilateral radiculopathy: radiographic changes in magnetic resonance images	J Neurol Surg A Cent Eur Neurosurg. 2019;80:302–311.	Retrospective study (2-y follow-up) of 24 patients over 65 y of age who underwent percutaneous endoscopic lumbar foraminoplasty to treat unilateral radiculopathy caused by lumbar foraminal stenosis.
9.	Dey PC and Nanda SN¹⁰⁸	2019	Functional outcome after endoscopic lumbar discectomy by Destandau’s technique: a prospective study of 614 patients	Asian Spine J. 2019;13:786–792.	Retrospective study on 614 patients who underwent endoscopic lumbar discectomy using Destandau endospine system after a minimum follow-up of 12 mo and maximum up to 54 mo.
10.	Eun SS, Lee SH, et al¹⁰⁹	2018	Transforaminal percutaneous endoscopic lumbar diskectomy for downmigrated disk herniations: lever-up, rotate, and tilt technique	J Neurol Surg A Cent Eur Neurosurg. 2018;79:163–168.	Retrospective study (2-y follow-up) of 18 patients who underwent transforaminal PELD.
11.	Gibson JNA, et al¹¹⁰	2017	A randomized controlled trial of transforaminal endoscopic discectomy vs microdiscectomy	Eur Spine J. 2017;26:847–856.	Prospective trial on 143 patients, age 25–70 y with single-level lumbar prolapse and radiculopathy with 70 randomized transforaminal PELD under conscious sedation and another 70 patients to microdiscectomy under general anesthesia.
12.	Kim HS, Adsul N, et al¹¹¹	2018	A mobile outside-in technique of transforaminal lumbar endoscopy for lumbar disc herniations	J Vis Exp. 2018;(138):57999.	Prospective study on mobile outside-in treatment of LDH in 184 consecutive patients with unilateral lower limb radiculopathy—19 ± 6 mo follow-up.
13.	Kim JE and Choi DJ¹¹²	2018	Biportal arthroscopic spinal surgery (BASS) with 30 degrees arthroscopy for far lateral approach of L5-S1 - technical note	J Orthop. 2018;15:354–358.	Retrospective study on 12 patients with far lateral approach of biportal arthroscopic technique using 30 degrees arthroscopy for foraminal decompression of L5-S1.
14.	Komp M, Hahn P, et al¹¹³	2014	Operation of lumbar zygoapophyseal joint cysts using a full-endoscopic interlaminar and transforaminal approach: prospective 2-year results of 74 patients	Surg Innov. 2014;21:605–614.	Prospective study (2-y follow-up) of 74 full-endoscopic interlaminar and transforaminal PELD patients treat for lumbar z-joint cysts.
15.	Lee SH and Kang HS³⁰	2010	Percutaneous endoscopic laser annuloplasty for discogenic low back pain	World Neurosurg. 2010;73:198–206.	Retrospective study on 37 patients treated at a single-level laser-assisted spinal endoscopy vs percutaneous endoscopic laser annuloplasty with a mean follow-up of 9.7 mo.
16.	Lewandrowski KU, de Carvalho PST, et al¹²⁷	2020	Outcomes with transforaminal endoscopic vs percutaneous laser decompression for contained lumbar herniated disc: a survival analysis of treatment benefit	J Spine Surg. 2020;6:S84–S99.	Retrospective study of 248 patients consisting of 162 patients in the endoscopic group and 86 patients in the laser discectomy group with average 43.5 mo follow-up.
17.	Li H, Jiang C, et al¹¹⁴	2018	Comparison of MED and PELD in the treatment of adolescent lumbar disc herniation: A 5-year retrospective follow-up	World Neurosurg. 2018;112:e255–e260.	Retrospective study (48 mo follow-up) comparing the efficacy and safety of MED (30 patients) and PELD (48 patients) in the treatment of ALDH.
18.	Liu C, Chu L, et al¹¹⁵	2017	Percutaneous endoscopic lumbar discectomy for highly migrated lumbar disc herniation	Pain Physician. 2017;20:E75–E84.	Retrospective study (3 mo follow-up) on 73 patients with highly migrated LDH treated with PELD comparing 3 approaches.
19.	Pan F, Shen B, et al¹¹⁶	2016	Transforaminal endoscopic system technique for discogenic low back pain: a prospective cohort study	Int J Surg 2016;35:134–138.	Retrospective consecutive case series with 62 patients with 1-level discogenic low back pain with 26.8 ± 4.2 mo follow-up.
20.	Soliman HM¹¹⁷	2013	Irrigation endoscopic discectomy: a novel percutaneous approach for lumbar disc prolapse	Eur Spine J. 2013;22:1037–1044.	Prospective case series of 43 patients with uncontained LDH underwent irrigation endoscopic discectomy surgery with 24 mo follow-up.
21.	Song H, Hu W, et al¹¹⁸	2017	Percutaneous endoscopic interlaminar discectomy of L5-S1 disc herniation: a comparison between intermittent endoscopy technique and full endoscopy technique	J Orthop Surg Res. 2017;12:162.	Retrospective study comparing full endoscopy technique (65 patients) or intermittent endoscopy technique (61 patients) with average 27 mo follow-up.
22.	Teli M, Lovi A, et al¹¹⁹	2017	Higher risk of dural tears and recurrent herniation with lumbar microendoscopic discectomy	Eur Spine J. 2010;19:443–450.	Randomized controlled trial of 240 patients was randomized to microendoscopic (group 1), micro (group 2), or open (group 3) discectomy with minimum 2-y follow-up.
23.	Tu Z, Li YW, et al¹²⁰	2010	Clinical outcome of full-endoscopic interlaminar discectomy for single-level lumbar disc herniation: a minimum of 5-year follow-up	Pain Physician. 2017;20:E425–E430.	Retrospective study of 152 patients with single-level LDH located at either L4-L5 or L5-S1 who underwent either FEID (72 patients) or MED (80 patients) with >5-y follow-up.
24.	Tu Z, Wang B, et al¹²¹	2018	Early experience of full-endoscopic interlaminar discectomy for adolescent lumbar disc herniation with sciatic scoliosis	Pain Physician. 2018;21:E63–E70.	Retrospective case series of patients under age 20 with single-level ALDH with and without scoliosis treated with FEID. Average follow-up 39 mo.
25.	Wang Y, Zhang W, et al¹²²	2018	Transforaminal endoscopic discectomy for treatment of central disc herniation: surgical techniques and clinical outcome	Pain Physician. 2018;21:E113–E123.	Retrospective 2-y follow-up study of 69 consecutive patients treated with transforaminal PELD central disc herniation.
26.	Wang YP, Zhang W, et al¹²³	2016	Evaluation of transforaminal endoscopic discectomy in treatment of obese patients with lumbar disc herniation	Med Sci Monit. 2016;22:2513–2519.	Prospective study of 69 obese patients with LDH (35 men and 34 women; age range, 24–43 y) treated for LDH with PELD.
27.	Xu B, Xu H, et al¹²⁴	2018	Bilateral decompression and intervertebral fusion via unilateral fenestration for complex lumbar spinal stenosis with a mobile microendoscopic technique	Medicine (Baltimore). 2018;97:e9715.	Retrospective 3-y follow-up study on 61 patients with complex lumbar spinal stenosis (lumbar canal stenosis combined with degenerative spondylolisthesis, instability, and scoliosis) treated with Destandau-type mobile microendoscopic discectomy.
28.	Youn MS, Shin JK, et al¹²⁵	2018	Endoscopic posterior decompression under local anesthesia for degenerative lumbar spinal stenosis	J Neurosurg Spine. 2018;29:661–666.	Retrospective study of 50 patients (28 women and 22 men) treated for LDH with endoscopic posterior decompression under local anesthesia followed up to 24 mo postoperatively.
29.	Zhang B, Kong Q, et al¹²⁶	2019	Short-term effectiveness of percutaneous endoscopic transforaminal bilateral decompression for severe central lumbar spinal stenosis	Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2019;33:1399–1405.	Retrospective study on effectiveness and safety of bilateral transforaminal bilateral PELD decompression for severe central lumbar spinal stenosis in 44 patients with average follow-up of 24.8 mo.

ALDH, adolescent lumbar disc herniation; FEID, full-endoscopic interlaminar discectomy; LDH, lumbar disc herniation; MED, minimally endoscopic discectomy; PELD, percutaneous endoscopic lumbar discectomy.