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. 2022 Dec 31;19(4):1093–1107. doi: 10.14245/ns.2244574.287

Global Trends and Hotspots in Endoscopic Discectomy: A Study Based on Bibliometric Analysis

Boyu Wu 1,✉,*, Lei Yang 1,*, Chengwei Fu 2, Yue Zhuo 1, Xiang Feng 1, Hui Xiong 1,✉
PMCID: PMC9816580  PMID: 36597660

Abstract

Objective

With the advancement of minimally invasive spine surgery, endoscopic discectomy (ED) has become a common technique for degenerative disease of the spine. The present study aimed to explore the knowledge structure, emerging trends, and future research hotspots in this field.

Methods

All relevant publications on ED from 2002 to 2021 were extracted from the Web of Science databases. Key bibliometric indicators, including countries/regions, institutions, authors, journals, references, and keywords were calculated and evaluated using VOSviewer and CiteSpace software.

Results

A total of 1,196 articles and reviews were included for analysis. The number of publications regarding ED increased yearly. From the quality and quantity viewpoint, China, South Korea, and the United States were the major contributors in this field. The most influential institution in the field of ED was Wooridul Spine Hospital. We identified 3,488 authors, among which Lee SH had the most significant number of papers, and Ruetten S was cocited most often. World Neurosurgery was the journal with the most papers, and Spine was the most commonly cocited journal. Keywords were stratified into 4 clusters by VOSviewer software: cluster 1 (clinical outcomes of ED in the treatment of lumbar disc herniation); cluster 2 (surgical technique of percutaneous endoscopic lumbar discectomy); cluster 3 (clinical outcomes of ED in the treatment of lumbar spinal stenosis); and cluster 4 (clinical outcomes of percutaneous endoscopic cervical discectomy). Several topics including lateral recess stenosis, spinal stenosis, and reoperation were considered as the next hotspot in ED research.

Conclusion

ED research has gained considerable attention over the last 2 decades. Our bibliometric findings illuminate the publication trends and research hotspots of the ED field, which may provide useful references for scholars and decision-makers interested in this field.

Keywords: Endoscopic discectomy, Bibliometric, VOSviewer, CiteSpace

INTRODUCTION

Since earlier work by Kambin [1] to adapt arthroscopy for lumbar disc herniation (LDH), endoscopic discectomy (ED) has experienced tremendous development in the past few decades. Multiple studies [2-5] have suggested the ED provides equivalent clinical outcomes to conventional microdiscectomy with fewer postoperative pain, shorter hospitalizations, less local tissue injury, and faster recovery. With growing experience and technological innovation, the indications of ED have been extended from lumbar degenerative diseases to degenerative diseases of the thoracic and cervical spine [6-8].

Bibliometrics is a multidisciplinary discipline that involves various disciplines such as mathematics, statistics, and philology [9,10]. It can not only quantitatively analyze the current state of a certain research domain through data visualization, but also identify current research hotspots and predict future research trends [11,12]. However, to our knowledge, there is currently no bibliometric analysis assessing the relevant status quo and trends regarding ED research have been performed.

In this study, we aimed to visually analyze publications about ED in the Web of Science (WoS) database over the past 20 years. We presented a statistical analysis of the current status of the ED field, including the annual publication, countries/regions, institutions, authors, journals, references, and keywords. We also analyzed the trends and hotspots of ED to provide a reference for scholars and decision-makers interested in this field.

MATERIALS AND METHODS

1. Data Sources and Search Strategies

A comprehensive online search was performed using the Science Citation Index Expanded in the Web of Science Core Collection database on April 29, 2022. The search formula was “TS=(endoscop*) AND ((TS=(discectomy)) OR TS=(diskectomy)).” The search was limited to the English language with a publication date restricted from January 1, 2002 to December 31, 2021. For literature types, only articles and reviews were included. Ultimately, 1,196 records were identified.

2. Data Extraction and Bibliometric Analysis

Records retrieved from WoS were extracted and downloaded in “plain text” format with “Full Record and Cited References” for subsequent bibliometric analysis.

WoS was applied to describe the characteristics of the publications, including annual publications, countries/regions, institutions, authors, journals, funding sources, citation frequency, and Hirsch index (H-index). In addition, the journal impact factor (IF) and quartile ranks were extracted from the Journal Citation Reports 2021. The information extraction process was performed by 2 researchers independently, and any discrepancies were resolved through consensus.

Then, the VOSviewer 1.6.18 (Leiden University, Leiden, The Netherlands) and CiteSpace 5.8.R3 (Drexel University, Philadelphia, PA, USA) were applied to perform the bibliometric and visualization analysis. VOSviewer was applied to generate knowledge maps of the identified influential authors, contributing countries and institutions, core journals, high-quality papers, co-occurring keywords and cocited references. CiteSpace was used to extract keywords and references from publications with high-citation bursts and generate a dual-map overlay for journals. The flow diagram of literature search and analysis are presented in Fig. 1.

Fig. 1.

Fig. 1.

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The flow diagram of literature search and analysis. WoSCC, Web of Science Core Collection; SCIE, Science Citation Index Expanded.

RESULTS

1. The Publication and Citation Trends

A total of 1,196 publications were identified from WoS, including 1,038 articles and 158 reviews. Fig. 2 shows the publications and citations in the field of ED between 2002 and 2021. In general, the annual number of publications and citations showed an overall increasing trend over the years. The evolution of the annual number of publications in the ED field can be separated into 2 stages: a slow and steady growth phase from 2002–2015, followed by a rapid and high-yield growth phase from 2016–2021. As of the search date, these publications received 20,633 citations, an average of 17.25 citations per publication, and an H-index of 66.

Fig. 2.

Fig. 2.

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The global trend of annual publications and citations related to endoscopic discectomy research from 2002 to 2021.

2. Countries/Regions, Institutions, and Funding Agencies

The ED is a research hotspot worldwide, with a total of 53 countries/regions contributed to this field. The top 10 most productive countries/regions in ED are shown in Table 1 and Fig. 3A. China published the largest number of papers (521), followed by South Korea (241), and the United States (181). South Korea accounted for 5,409 citations with an H-index of 40, which both ranked first among all involved countries/regions. The number of citations of publications from the United States was 5,013 with an H-index of 37, which both ranked second. Notably, though the number of citations and H-index from China both ranked third, the average number of citations ranked last in the top 10 countries/regions. The VOSviewer was employed to analyze the network visualization of coauthorship between countries/regions. The United States and China occupied the central place of the network, and there were active collaborations among these countries/regions (Fig. 3B).

Table 1.

Top 10 largest contributing countries/regions in the field of endoscopic discectomy research

Rank Country/region No. Citations Average article citations H-index
1 China 521 3,985 7.65 28
2 South Korea 241 5,409 22.44 40
3 USA 181 5,013 27.7 37
4 Germany 65 2,408 37.05 22
5 Japan 63 721 11.44 14
6 Taiwan 44 623 14.16 12
7 Turkey 31 316 10.19 10
8 India 26 271 10.42 10
9 Netherlands 20 671 33.55 13
10 Italy 19 264 13.89 8
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Fig. 3.

Fig. 3.

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(A) The annual number of publications in the top 10 countries/regions from 2002 to 2021. (B) The coauthorship map of countries/regions involved in percutaneous endoscopic discectomy research (generated by VOSviewer). (C) The coauthorship map of institutions involved in endoscopic discectomy research (generated by VOSviewer); The size of the node indicates the number of documents in the countries/regions or institutions, and the thickness of the line between the nodes indicates the collaborative intensity between countries/regions or institutions. (D) The top 10 most active funding agencies involved in endoscopic discectomy research.

As for institutions, the top 10 most productive institutions are listed in Table 2. Among the top 10 most productive institutions, 5 were from China, 4 from South Korea, and 1 from the United States. Wooridul Spine Hospital contributed the most publications with 57 papers published, followed by the Tongji University (48 publications), and The Catholic University of Korea (31 publications). In terms of other parameters, the H-index of Wooridul Spine Hospital ranked first (32), followed by that of Army Medical University (15) and Tongji University (13). The citation frequency of papers from Wooridul Spine Hospital ranked first (2,895 times), followed by that from The Catholic University of Korea (673 times) and Army Medical University (526 times). The Wooridul Spine Hospital had the highest average citations of 50.79 per paper, followed by Leon Wiltse Memorial Hospital (22.86) and The Catholic University of Korea (21.71). The institutional coauthorship network map was conducted by VOSviewer and illustrated in Fig. 3C. There was an active collaboration among leading institutions.

Table 2.

Top 10 most productive institutions in the field of endoscopic discectomy research

Rank Institutions Country No. Citations Average no. of citations H-index
1 Wooridul Spine Hospital South Korea 57 2,895 50.79 32
2 Tongji University China 48 461 9.6 13
3 The Catholic University of Korea South Korea 31 673 21.71 12
4 Army Medical University China 30 526 17.53 15
5 Brown University USA 27 408 15.11 12
6 Southern Medical University China 24 101 4.21 6
7 Chongqing Medical University China 23 244 10.61 9
8 Leon Wiltse Memorial Hospital South Korea 22 503 22.86 12
9 Capital Medical University China 21 54 2.57 4
10 Gachon University South Korea 21 206 9.81 8
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The top 10 most active funding agencies are shown in Table 3 and Fig. 3D, 7 were from China, and the other 3 were from South Korea. The National Natural Science Foundation of China financed 96 studies in the ED field (ranked first, 8.027%), followed by the Wooridul Spine Foundation (16 studies, 1.338%) and the Korea Health Technology R D Project through the Korea Health Industry Development Institute Khidi Ministry of Health Welfare Republic of Korea (8 studies, 0.669%).

Table 3.

Top 10 most active funding agencies in the field of endoscopic discectomy research

Rank Funding Source Country No. % of 1,196
1 National Natural Science Foundation of China China 96 8.027
2 Wooridul Spine Foundation South Korea 16 1.338
3 Korea Health Technology R D Project Through The Korea Health Industry Development Institute Khidi Ministry of Health Welfare Republic of Korea South Korea 8 0.669
4 China Postdoctoral Science Foundation China 6 0.502
5 Natural Science Foundation of Zhejiang Province China 6 0.502
6 Chinese Ministry of Health China 5 0.418
7 Foundation for Leading Talent in Traditional Chinese Medicine of Jiangsu Province China 5 0.418
8 Ministry of Education Science and Technology Republic of Korea South Korea 5 0.418
9 National Key R D Program of China China 5 0.418
10 National Key Research and Development Program of China China 5 0.418
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3. Authors and Cocited Authors

A total of 3,488 authors contributed to the publications on ED research. The top 10 most productive authors and the top 10 cocited authors are presented in Table 4. Among the top 10 authors, 5 were from South Korea, 4 from China, and 1 from the United States. Lee SH published the most papers (66) and ranked first, followed by Ahn Y (43) and Kim HS (41). The coauthorship network of authors was performed by VOSviewer and illustrated in Fig. 4A. In this network, different colors represent different clusters. It found that authors in the same cluster have relatively close cooperation. Nevertheless, the collaboration between authors from different clusters was weak, indicating little cooperation between different research teams. Additionally, we also use VOSviewer to perform author cocitation analysis. In cocited author network analysis (Fig. 4B), Ruetten S (1,113 times) had the highest citation frequency and ranked first, followed by Ahn Y (850 times) and Kambin P (675 times).

Table 4.

Top10 most productive authors and the top 10 cocited authors in the field of endoscopic discectomy research

Rank Author Country No. Total citations H-index Cocited author Country Citations
1 Lee SH South Korea 66 2,916 32 Ruetten S Germany 1,113
2 Ahn Y South Korea 43 1,816 24 Ahn Y South Korea 850
3 Kim HS South Korea 41 459 14 Kambin P USA 675
4 Kim JS South Korea 38 948 15 Yeung AT USA 494
5 He SS China 31 302 11 Choi G South Korea 485
6 Zhou Y China 27 520 15 Choi KC South Korea 407
7 Jang IT South Korea 26 286 8 Lee SH South Korea 294
8 Telfeian AE USA 25 397 12 Hoogland T Germany 256
9 Gu X China 23 242 10 Kim CH South Korea 247
10 Fan GX China 23 235 10 Kim HS South Korea 240
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Fig. 4.

Fig. 4.

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The network visualization map of authors’ coauthorship (A) and cocitation (B). In the authors’ coauthorship map, the node’s size represents the number of papers published by the author, and the thickness of the line between the nodes indicates the collaborative intensity between authors. In authors’ cocitation map, the size of the node represents the citation frequency, and the line between 2 nodes means that both were cited by one author.

4. Journals and Cocited Journals

A total of 174 journals published papers on ED research. The top 10 journals with the greatest number of publications are listed in Table 5 and Fig. 5A. Among the top 10 journals, 7 were from the United States, and the other 3 were from Germany, England, and South Korea. World Neurosurgery published the most papers (179), followed by Pain Physician (75) and Medicine (53). Spine has the largest number of total citations (3,406 times) and highest value of H-index (27), and Pain Physician has the highest IF (2021 IF, 4.396). The journal cocitation analysis was conducted via VOSviewer. As shown in Fig. 5B, the top 5 cocited journals were Spine (6,326 times), European Spine Journal (2,097 times), Neurosurgery (1,528 times), World Neurosurgery (1,336 times), and Journal of Neurosurgery-Spine (1,269 times).

Table 5.

Top 10 journals with the greatest number of publications in the field of endoscopic discectomy research

Rank Journal title No. Country Citations H-index IF (2021) JCR (2021)
1 World Neurosurgery 179 USA 1,578 18 2.210 Q3/Q4
2 Pain Physician 75 USA 1,293 21 4.396 Q2
3 Medicine 53 USA 187 7 1.817 Q3
4 Spine 47 USA 3,406 27 3.241 Q2/Q3
5 European Spine Journal 46 Germany 1,511 22 2.721 Q2/Q3
6 Journal of Neurosurgery-Spine 38 USA 1,143 18 3.467 Q1/Q2
7 Neurospine 35 South Korea 259 9 3.374 Q2/Q3
8 Journal of Neurological Surgery Part A-Central European Neurosurgery 34 USA 180 8 0.984 Q4
9 Biomed Research International 29 USA 260 10 3.246 Q3
10 Journal of Orthopaedic Surgery and Research 26 UK 177 9 2.677 Q2
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IF, impact factor; JCR, Journal Citation Report; Q, quartile.

Fig. 5.

Fig. 5.

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(A) The top 10 journals with the greatest number of publications. (B) The network visualization map of journal cocitation analysis using VOSviewer. The size of the node represents the citation frequency, and the line between 2 nodes means that both were cited by 1 journal. (C) A dual-map overlay of journals on endoscopic discectomy research was generated by CiteSpace. The labels represent different disciplines covered by the journals. The citing journals are on the left half, the cited journals are on the right half, and the colored path represents the citation relationship.

A dual-map overlay of journals was generated using CiteSpace (Fig. 5C). We found that there were 3 main citation paths. The published articles were mainly focused on journals in the field of neurology, sports, and ophthalmology, whereas most of the cited articles were published in journals in the field of health, nursing, medicine, sports, rehabilitation, sport, psychology, education, and social.

5. Cocited Reference and Reference Burst

We used VOSviewer to analyze the cocited references and create a network map (Fig. 6A). The top 10 most cocited references are presented in Table 6. The most cocited reference was an article published in Spine by Yeung and Tsou [13] with 308 citations in 2002, entitled “Posterolateral endoscopic excision for lumbar disc herniation: surgical technique, outcome, and complications in 307 consecutive cases.” Among the top 10 references, 9 articles focused on the surgical technique and outcome of ED.

Fig. 6.

Fig. 6.

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(A) The cocitation network map of references on endoscopic discectomy. The size of the node represents the citation frequency, and the line between 2 nodes means that both were cited by 1 paper. (B) The top 25 references with the highest burst value (generated by CiteSpace). The blue bars indicate the time interval, and the red bars indicate the active time.

Table 6.

Top 10 cocited references in the field of endoscopic discectomy research

Rank First author Title Year Source Citations
1 Yeung AT Posterolateral endoscopic excision for lumbar disc herniation: surgical technique, outcome, and complications in 307 consecutive cases 2002 Spine 308
2 Ruetten S Full-endoscopic interlaminar and transforaminal lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study 2008 Spine 274
3 Mayer HM Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy 1993 Journal of Neurosurgery 143
4 Macnab I Negative disc exploration: an analysis of the causes of nerve-root involvement in sixty-eight patients 1971 The Journal of Bone and Joint Surgery 139
5 Hoogland T Transforaminal posterolateral endoscopic discectomy with or without the combination of a low-dose chymopapain: a prospective randomized study in 280 consecutive cases 2006 Spine 137
6 Ahn Y Percutaneous endoscopic lumbar discectomy for recurrent disc herniation: surgical technique, outcome, and prognostic factors of 43 consecutive cases 2004 Spine 133
7 Ruetten S Use of newly developed instruments and endoscopes: full-endoscopic resection of lumbar disc herniations via the interlaminar and lateral transforaminal approach 2007 Journal of Neurosurgery-Spine 132
8 Hermantin FU A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy 1999 The Journal of Bone and Joint Surgery 129
9 Choi G Percutaneous endoscopic approach for highly migrated intracanal disc herniations by foraminoplastic technique using rigid working channel endoscope 2008 Spine 110
10 Ruetten S A new full-endoscopic technique for the interlaminar operation of lumbar disc herniations using 6-mm endoscopes: prospective 2-year results of 331 patients 2006 Minimally Invasive Neurosurgery 108
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The ‘Burstness’ tool of the Citespace software was used to identify the publications that received widespread attention from related researchers during a certain period of time [14,15]. Fig. 6B presents the top 25 references with the strongest citation bursts. The strongest burst reference was an article published in Spine by Ruetten et al. [16] (2010–2013, strength 19.2), entitled “Full-endoscopic interlaminar and transforaminal lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study.” In addition, the articles of Liu et al. [17] and Komp et al. [18] were the most recent high-citation reference with a citation burst.

6. Keywords Analysis of Research Hotspots

Research hotspots and frontiers of the ED field can be revealed through keyword co-occurrence analysis and burst detection. In this study, VOSviewer was applied to present the keyword co-occurrence and cluster analysis (Fig. 7A). We merged some keywords with the same meaning to get a better perspective. According to the criteria that the co-occurrence of the keywords was at least 15 times, we totally introduced 84 keywords into the analysis. The top 5 keywords identified were “discectomy,” “surgery,” “disc herniation,” “lumbar disc herniation,” and “endoscopy,” which is consistent with our research topic. In addition, the inclusion keywords could be classified into 4 clusters: (1) clinical outcomes of ED in the treatment of LDH, green frames; (2) clinical outcomes of ED in the treatment of LDH, blue frames; (3) clinical outcomes of ED in the treatment of lumbar spinal stenosis (LSS), yellow frames; (4) clinical outcomes of percutaneous endoscopic cervical discectomy (PECD), red frames.

Fig. 7.

Fig. 7.

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(A) Keyword co-occurrence analysis on endoscopic discectomy research using the VOSviewer. The size of the node represents the occurrence times of keywords, the line between 2 nodes represents the co-occurrence of keywords, and different colors represent different clusters. (B) The top 25 keywords with the highest burst value (generated by CiteSpace). The blue bars indicate the time interval, and the red bars indicate the active time.

We also used CiteSpace to detect burst keywords (Fig. 7B). Among these words, “surgical technique” (2008–2012, strength 7.49) was the strongest burst keyword. Notably, the citation burst time of keywords including “lateral recess stenosis” (2018–2021), “spinal stenosis” (2019–2021), and “reoperation” (2019–2021) has continued to 2021, and the bursts are still ongoing, indicating that these research directions have received great attention recently.

DISCUSSION

In the past 20 years, ED has been extensively researched, and the overall number of publications has also increased yearly. From 2002 to 2015, the relatively small amount of paper in this period suggests that the study of ED is in its infancy. From 2016 to 2021, the number of papers showed rapid growth, demonstrating that the ED has been attracting increasing interest from scholars in the last years. Therefore, the topic of ED possibly remains a research hotspot in the field of spinal surgery, and the number of publications on ED may increase in the upcoming years.

From the current study, China had the largest number of publications in the ED field, followed by South Korea. Of course, this is closely associated with the local funding agencies, and the top ten funding agencies were all from China and South Korea. South Korea, the United States, and China ranked in the top three regarding the total number of citations and H-index. Of note, China ranked first for the number of publications, while it ranked third for the total number of citations and H-index. This suggests that although China has an advantage in the number of publications, the quality of the publication is relatively low, resulting in a low average article citation. The possible reasons might be (1) The research on ED started late in China, with only 32 papers published from 2002–2015 (South Korea, 79 papers; United States, 75 papers). It is only since 2016 that China has gradually become a leading country in terms of the annual number of publications. (2) The type of studies published in China is primarily case-control studies and case series, while there are relatively few high-quality randomized control trials. (3) There may be certain language barriers, and China has less cooperation with top countries such as South Korea and the United States. Thus, it is urgent to promote the quality of papers for Chinese scholars in the future. Among the top 10 productive institutions, 5 were from China, and 4 were from South Korea. This may be the reason why China and South Korea have published most papers on the ED field. It is noteworthy that Wooridul Spine Hospital ranks first regarding the number of publications, the total number of citations, and H-index. This indicates that Wooridul Spine Hospital might be the top research institution in this field, and scholars interested in ED may cooperate with this institution.

According to the authors and cocited authors in Table 4, the top 3 most prolific authors were all from South Korea (Lee SH, Ahn Y, and Kim HS). This indicates that scholars from South Korea is leading in the field of ED, and there will be more papers on this field to be published on these scholars and their teams in the future. As for cocited authors, the publications of 3 authors were cocited more than 500 times, with Ruetten S having the highest citation frequency, followed by Ahn Y, and Kambin P. Notably, Ahn Y was ranked second in both the number of publications and cocitation frequency, indicating that the papers published by him and his team are excellent in both quantity and quality. The chief contribution of Ruetten S was first proposing the use of percutaneous endoscopic interlaminar discectomy for the treatment of LDH, and his team subsequently had done a lot of investigations for clinical promotion and application of this technique [16,19-21].

Professor Kambin P is one of the top experts in the ED field from the United States. Through extensive clinical and cadaver studies, he proposed “safe working zone” for the transforaminal approach, which has been robustly cited and widely utilized in percutaneous transforaminal endoscopic discectomy (PTED) [22,23].

As for journal analysis, the journals with the most papers about ED were World Neurosurgery, followed by Pain Physician, Medicine. Thus, it suggests that more studies on this field would also be preferentially published in the listed journals. From the perspective of cocited journals, Spine was the journal with the highest citations, followed by the European Spine Journal, Neurosurgery, indicating the important influence of these journals in this field. Subsequently, researchers interested in ED should pay more attention to these journals as mentioned above.

As shown in Table 6, the most cocited article in this field was Yeung and Tsou [13] published in 2002, which mainly introduced ‘inside-out’ technique of posterolateral endoscopic lumbar discectomy, called YESS technique. Subsequently, a substantial number of novel techniques based on the YESS technique have constantly emerged, which vastly promotes the development of PTED. Of note, a total of 3 publications within the list of top 10 cocited papers were reported by Ruetten S, which also explained why he was the author with the highest cocitation frequency. Burst references are those that are frequently cited over a period of time [14,15]. Among these references, the references with the strongest citation bursts are published by Ruetten et al. [21] with burst duration from 2010 to 2013. In this study, Ruetten et al. used a prospective randomized controlled trial design to compare the clinical results of lumbar discectomies in full-endoscopic transforaminal and interlaminar approach with the conventional microdiscectomy. They concluded that the full-endoscopic technique is equivalent in efficacy to conventional microdiscectomy, with the advantage of operation technique and reduced traumatization. More importantly, among the top 25 references with the strongest citation burst, 2 references are still in burstness, indicating that this topic has received sustained attention in recent years.

In bibliometrics, the analysis of frequently appearing keywords is used to identify the research direction. As illustrated in the keywords clustering map in Fig. 7A, all the included keywords in the ED research could separate into 4 main clusters.

(1) Clinical outcomes of ED in the treatment of LDH: At the beginning of the development of the ED technique, most of the studies focused on exploring whether the percutaneous endoscopic lumbar discectomy (PELD) was effective. At present, many studies have shown that PELD has the same effect as conventional microdiscectomy with the advantages of minimal trauma, fast recovery, and less pain [3,24-26].

(2) Surgical technique of PELD: As the PELD technique has been gradually accepted by surgeon and patient, some scholars have started to focus on improving surgical techniques. Recently, numerous attempts have been made to simplify the operation, reduce the procedure time, and shorten the learning curve [27-31]. For example, Ao et al. [32] designed a novel targeted foraminoplasty device with the specially designed double-cannulas for PELD; their results showed that this novel technique is a safe and effective procedure for LDH, and provides more advantages than the traditional TESSYS technique in reducing the difficulty of PELD learning, minimizing radiation exposure, and decreasing intraoperative pain associated with foraminoplasty.

(3) Clinical outcomes of ED in the treatment of LSS: LSS is a common spinal disorder in the elderly, which is classified into central spinal stenosis, lateral recess stenosis, and foraminal stenosis [33]. In the past, the indication for ED was mainly soft disc herniation, and only a few physicians could use ED to manage LSS [34,35]. With the rapid developments of surgical techniques and instruments, the indication of ED has expanded from soft disc herniation to LSS. Various studies have confirmed the safety and efficacy of ED in the treatment of LSS [36-39]. Study carried out by Li et al. [40] showed that ED is a safe and effective technique for the treatment of LSS in the elderly, with the advantages of less traumatic, fewer anesthesia-related complications, and fast postoperative recovery.

(4) Clinical outcomes of PECD: Currently, PECD has been developed as an effective surgical alternative for cervical disc herniation or radiculopathy [41-44]. PECD can be performed using an anterior or posterior approach, which depends on the localization of pathology [45]. With the aid of laser and high-speed drills, PECD can complete the resection of central, paracentral, or foraminal soft disc herniations [46-48]. Compared with anterior cervical discectomy and fusion or posterior microdiscectomy, the most significant benefits of PECD are clearer surgical field, less tissue damage, and quicker recovery [49,50].

As shown in the keyword burst detection results, lateral recess stenosis, spinal stenosis, and reoperation are the latest burst terms in recent years, which indicate that these research topics might be considered as the next hotspot in ED research. Additionally, it identifies promising directions for research, which is of interest to scholars and funding agencies. Therefore, it suggests that scientific breakthroughs regarding these research topics may be possible within the next few years.

Publications on ED research evaluated in the current study are reviewed from the WoS database. To our knowledge, this is the first-ever bibliometric study to analyze publications of ED around the world, providing a valuable reference for further exploration in this field. Despite our comprehensive and systematic analysis of ED research in this study, there are some limitations that require discussion. First of all, the bibliometric analysis was limited to English language publications, and thus we may have missed some important papers published in other languages. As far as we know, most of the non-English papers lack English abstract or references, unable to meet the requirements of bibliometric analysis [51]. Secondly, the data analyzed in this study originated only from the WoS database, and some papers from other databases might have been missed. However, it should be noted that the WoS database is the most commonly used tool for bibliometric analysis [52]. Finally, the publications in 2022 were not included in our study as the WoS database is constantly updated, and the data for this year is incomplete. Nevertheless, we believe that this study has included the vast majority of publications from 2002, and our conclusions would not be affected even with these updated data.

CONCLUSION

In conclusion, the annual number of publications regarding ED has been constantly growing since 2002. From the quality and quantity viewpoint, China, South Korea, and the United States were the major contributors in this field. According to keywords analysis, 4 research directions were identified: (1) clinical outcomes of ED in the treatment of LDH, (2) surgical technique of PELD, (3) clinical outcomes of ED in the treatment of LSS, (4) clinical outcomes of PECD. More focus will be placed on lateral recess stenosis, spinal stenosis, and reoperation, which may be the next hotspot in ED research.

Footnotes

Conflict of Interest

The authors have nothing to disclose.

Funding/Support

This work is supported by the Postgraduate Scientific Research Innovation Project of Hunan Province (No. CX20210703 and CX20210683).

Author Contribution

Conceptualization: BW, HX; Data curation: CF, YZ; Formal analysis: LY, XF; Funding acquisition: HX; Methodology: CF; Visualization: YZ, XF; Writing - original draft: BW, LY; Writing - review & editing: BW, HX.

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