Abstract
Introduction:
Meniscus has always been the focus of sport medicine with thousands of articles published annually. Few study has tried to analyze these papers with bibliometric methods. The purpose of this study is to statistically analyze the output of meniscus research and determine emerging research trends and hot spots.
Methods:
Papers related to the meniscus published from 2010 to 2019 were downloaded from the Web of Science Core Collection. Information about annual publications and journal distribution was analyzed by Excel 2016. Co-occurrence analysis of the countries/regions, institutions, authors, and keywords were performed with CiteSpace V, which was also used to perform a co-cited analysis of the references and generate corresponding knowledge maps as well as detect burst keywords.
Results:
A total of 10,066 articles regarding meniscus were published between 2010 and 2019. The number of articles annual about meniscus increased from 786 to 1300. Knee Surgery Sports Traumatology Arthroscopy, the United States, University of Pittsburgh, and LaPrade RF were journal, country, institution, and author with the most publications, respectively. Makris EA et al. in 2011 was the most cited articles, with a citation of 198. Osteoarthritis, tear repair, anterior cruciate ligament, and articular cartilage were keywords with occurrence of more than 500. Meniscal extrusion, scaffold, and tissue engineering were terms with most burst strength.
Conclusions:
Meniscus-related publications showed a gradual rising trend from 2010 to 2019. Osteoarthritis, tear repairs, and the anterior cruciate ligament are the current research hot spots. Extrusion and scaffolds may be the frontiers of meniscus research in the next few years.
Level of evidence:
IV.
Introduction
The meniscus plays an important role in maintaining both normal function and long-term health of the knee joint. The functions performed by the meniscus include load transmission, shock absorption, and stability maintenance. However, the meniscus is also easily injured, especially in athletic populations. Meniscal injuries of the knee, mainly referring to meniscus tears, are the most common adult musculoskeletal soft tissue injuries, with an average incidence of 60–70/100,000 per year. 1,2 Thus, studies about the meniscus, ranging from prevention, prevalence, injury mechanism, and treatment, have been performed through the past decade, and thousands of articles have been published. To address the difficulties faced by researchers in finding hot spots and research frontiers in this field, a bibliometric analysis was performed in this study.
Bibliometric theory and technology have been developed and are widely used in the social sciences and natural sciences to unearth hidden information regarding the hundreds of articles published. 3 CiteSpace, the most common analysis software, was first developed by Chaomei Chen in 2004 and performs functions such as country, institution, author, and co-citation reference analyses with a convenient operation process. 4 Therefore, CiteSpace was used in this study to perform a bibliometric analysis of the publications on meniscus research.
Materials and methods
Data collection
The articles regarding the meniscus published from 2010 to 2019 were retrieved from the Web of Science Core Collection (WoSCC) with the following retrieval strategy: =Topic:(meniscus) OR Topic:(menisci) OR Title:(meniscus) OR Title:(menisci) AND LANGUAGE=English; indexes: SCI-EXPANDED, CCR-EXPANDED, IC; time span: 2010–2019. The document type was not restricted. Finally, a total of 10,066 articles were retrieved and sent to CiteSpace V in “Plain Text” form. In addition, 8130 unique articles were used for further analysis, and the duplicates removed by the software.
Statistical analysis
Information about the publications, including annual publications and journal distribution, was obtained from literature analysis reports from the WoSCC database. Excel 2016 was used to generate publication trends with a polynomial model. CiteSpace V was used to perform co-occurrence analyses of countries, institutions, authors, keywords, and related knowledge maps. In addition, co-cited analyses of the authors and references and burst keyword detection were also performed by CiteSpace V.
Results
Basic information
Of all the included papers, 7237 (89.02%) are original articles and 648 (7.97%) are reviews. Besides, 6076 (74.74%) are clinical papers and the other parts are nonclinical papers. However, only 342 (4.20%) papers are randomized comparison clinical trial (RCT) which are of great clinical value.
The number of annual articles about the meniscus increased from 786 to 1300 in the past decade according to the WoSCC database. To display the trends clearly, a clustered column chart with a trend line (Figure 1) was generated with Excel 2016. An obvious increasing trend can be seen in the chart, indicating that meniscus research has developed rapidly during the past decade.
The number of articles regarding the meniscus published per year from 2010 to 2019 and a red trend line based on fitting the polynomial model.
Distribution of journals
The number of journals that published articles regarding the meniscus was as high as 2015, and the top 10 journals with most publications are listed in Table 1. Of these journals, Knee Surgery Sports Traumatology Arthroscopy from Germany published the most articles (360 publications, 4.40%), followed by Osteoarthritis and Cartilage (296 publications, 3.62%) and the American Journal of Sports Medicine (285 publications, 3.48%). In addition, 50% of the top 10 journals were from the United States, indicating strong scientific research strength. Arthroscopy Techniques was the only journal from the Emerging Sources Citation Index, and the Proceedings of SPIE was the only conference proceedings.
The top 10 journals in the meniscus research field from 2010 to 2019.
Distribution of countries and institutions
In the past decade, 5650 institutions from 100 countries have published articles regarding the meniscus. The country with the most publications was the United States (2749 publications, 33.59%), followed by China (978 publications, 11.95%) and Germany (676 publications, 8.26%). The University of Pittsburgh (109 publications, 1.33%), University of California San Francisco (98 publications, 1.20%), and Boston University (97 publications, 1.19%) were the top three institutions with the most publications. Countries and institutions with publications ranking top 10 are listed in Table 2.
Ranking of countries and institutions contributing publications in study of meniscus from 2010 to 2019.
Analysis of authors and co-cited authors
A total of 21,909 authors have published papers related to the meniscus, and the top 10 contributive authors are listed in Table 3. The author with the most publications was Laprade RF (72 publications), followed by Guermazi A (62 publications) and Link TM (53 publications). In addition, the authors with the top 10 citations are also listed in Table 3. Interestingly, only one of the top 10 cited authors (1/10) was from a top 10 contributive author, suggesting that the article quality was as important as quantity.
Ranking of the top 10 authors and co-cited authors in study of meniscus from 2010 to 2019.
Analysis of references, hot spots, and frontiers
The articles with the top 20 citations are listed in Table 4, and the article with the most citation was published in Biomaterials in 2011 by Makris EA. The top 10 research hot spots and frontiers in meniscal study were list in Table 5, with scaffold and meniscal extrusion being the first hot spots and frontiers, respectively.
Top 20 co-cited articles in meniscal study from 2010 to 2019.
Top 10 keywords with most counts and top 10 burst terms from 2010 to 2019.
Discussion
General information
As indicated by the trend line in the annual publications chart, an increasing number of papers have been published each year from 2010 to 2019. Accordingly, great progress has been made during the past decade in the meniscus research field. Moreover, as the trend line implies, meniscus research will probably continually develop in the coming years. According to the available knowledge, many reasons contribute to the rapid progression of meniscal research. One of the important factors may be the popularization of arthroscopy technique in the past decades, making meniscus surgery a common treatment. 5 Besides, the high rate of incidence of meniscus injury in physically active population maintains meniscal study the focus of researchers. 6 Moreover, the increasing momentum of meniscal research is also greatly related with the understanding function of meniscal and protection mechanism to the cartilage. 7
In addition, papers published in the top 10 journals account for 21.41% of all publications, suggesting that these are core journals in the meniscus research field. These journal may warrant prior consideration whenever scholars want to publish manuscripts or search for valuable articles.
As the country that accounts for 50% of the top 10 journals and 33.59% of all publications, the United States undoubtedly has the strongest research strength in the meniscus research. Many factors account for the current situation. On the one hand, the United States has traditionally been scientific research power with thousands of research institutions. On the other hand, the strong research strength is build on its big gross domestic product, which is a good explanation to great development of China in meniscal study.
Citation information
Dr Laprade was the author with the most publication. A large part of his articles focusing on meniscal root, including cadaveric anatomic study and biomechanics study. 8 As authors with the most citation, Dr Englund M have two articles ranking top 20 of all cited papers. One of Englund M’s article entitled “Incidental Meniscal Findings on Knee MRI in Middle-Aged and Elderly Persons” came to a conclusion that meniscus injury was common in elder and middle-aged population irrespective of knee symptoms after a large sample study. 9 This viewpoint has challenged the previous standpoint and thus has great influence on meniscal research.
The top 20 cited papers had between 64 and 198 citations, indicating that these articles have great influence in meniscus research. An analysis of these articles will probably help us understand this research field. Interestingly, nine of these articles (45%) focused on arthroscopic partial meniscectomy, a widely used operation method in the treatment of meniscus tears. Paxton ES et al. performed a systematic literature review comparing the long-term clinical outcomes and reoperation rates after partial meniscectomy and meniscal repair, and the authors found that compared to meniscal repair, partial meniscectomy had worse long-term outcomes but a lower reoperation rate. 10 In addition, Stein T et al. also found that arthroscopic meniscal repair provided better results during long-term osteoarthritis prevention compared with partial meniscectomy. 11 In a trial involving patients with symptoms of medial meniscus tears without knee osteoarthritis, Sihvonen R found that the outcomes of partial meniscectomy were no better than those of a sham surgical procedure. 12 In addition, in a prospective randomized trial comparing the clinical outcomes of a collagen meniscus with those of partial meniscectomy, Rodkey WG reported patients with chronic meniscal injuries regained more lost activity after receiving a collagen meniscus implant than undergoing partial meniscectomy. Thus, the results of arthroscopic partial meniscectomy are controversial, especially since osteoarthritis prophylaxis and collagen meniscus implants may be alternative choices.
Research hot spots
Since the keywords of an article are selected by authors and editors to represent the main idea of the article, those that commonly occur can be considered research hot spots to some extent. The following keywords occurred more than 500 times: Osteoarthritis, tear repair, anterior cruciate ligament, and articular cartilage; these keywords are summarized in the following three research hot spots based on professional knowledge.
Osteoarthritis: The meniscus has a protective role in the knee, and meniscus injuries accelerate the development of osteoarthritis. According to a recent systematic review, meniscal injuries and combined injuries to both the anterior cruciate ligament (ACL) and meniscus are associated with a sixfold higher incidence of osteoarthritis than that in with noninjured knees. 13 Lohmander LS also reported that 50% of people diagnosed with ACL injuries or meniscus tears had osteoarthritis 10 to 20 years later. 14 However, the methods for treating meniscus treatments, especially partial meniscectomy, have not been successful in delaying the progression of osteoarthritis. Over five RCTs reported that partial meniscectomy had no additional benefits compared with nonoperative treatment. 15 –19 Thus, a number of researchers have focused on the mechanism of osteoarthritis and prevention strategies after meniscus injury.
Tear repair: Meniscus tears are the most common type of injury to the meniscus. Meniscus tears are classified as traumatic tears and degenerative tears based on the tear pattern. 20 Although the therapeutic schedule may vary among tear patterns, meniscus repair and partial meniscectomy have always been the main two treatment choices. Previous publications geared more to meniscus resection for faster recovery and to avoid reoperation. However, with enhanced understanding of the meniscus and its physiological function, an increasing number of physicians have realized that the meniscus should be preserved whenever possible. 21 Besides, the long-term results of recent papers emphasized the importance of attempt to save meniscus for prevention of cartilage degradation and full-blown osteoarthritis of knee. According to a report, the rate of meniscal repair increased by 37% from 2004 to 2012, and the indications and criteria of meniscal repair were expanded. 22 However, previous research reported a substantial percentage of failed meniscal repairs with an average 8.9% of patients needing a subsequent meniscectomy. 23 Thus, a number of studies have been performed to determine the risk factors for meniscus repair failure and to improve the surgical techniques.
Anterior cruciate ligament: A close relationship exists between the meniscus and ACL. On one hand, meniscus injuries are always combined with ACL injuries, and meniscus injuries are common in patients with ACL tears. 24 On the other hand, a significantly more meniscus injuries are observed in ACL-deficient knees. 25 The ruptured ACL should be reconstructed within 12 months of the injury to avoid a secondary injury to the meniscus. 26
Research frontiers
Research frontiers, the emerging changes in research topics, were effectively determined by burst keyword analysis. The following keywords had abrupt increases in occurrence frequency: meniscal extrusion, scaffold, tissue engineering, pressure distribution, and imbibition; these keywords were considered research frontiers to some extent. After setting limits based on the length of the article, the terms with scientific research significance were identified and are discussed below.
Extrusion: Meniscus extrusion refers to the incompatibility between the outer edge of the meniscus and outer edge of the articular cartilage of the tibial plateau. 27 Meniscus extrusion is strongly associated with knee osteoarthritis. 28 In addition, meniscus extrusion was discovered in many physiological and pathological conditions or during procedures, such as meniscus tear, meniscus repair, meniscus transplantation, and even age-related meniscus degeneration. Currently, meniscus extrusion is also found to related with outcome of meniscal allograft transplantation. A systematic review has been conducted to comprehensively evaluate postoperative meniscus transplant extrusion. Two of the included studies found nonanatomic placement of lateral meniscus transplants and suture fixation of medial and lateral transplants were associated with greater extrusion. 29 Finally, the authors concluded that a postoperative more than 3-mm extrusion on MRI imaging suggested technique and/or implant sizing problems that required correction. 30 In view of the universality of meniscus extrusion, current studies have focused on the radiographic evaluation of meniscal extrusion and the role of extrusion in the progression of knee osteoarthritis. With increased understanding of meniscus extrusion, we may potentially learn the relationship between the meniscus and osteoarthritis.
Scaffold: Scaffolds are an essential element of tissue-engineered menisci that provide a novel choice for treating severe meniscus injuries. 31 Scaffolds, including those constructed from natural biomaterials and synthetic polymer and biological composite tissue-engineered scaffolds, present promising fundamental results and have attracted attention in research. 32 Currently, synthetic scaffolds and collagen-based implants have entered the market, although mixed results have been observed. 33 The rate of failure ranged from 0% to 31.8% in different studies. 34 In a recent systematic review, the overall treatment failure occurred in 9.9% of synthetic scaffold meniscus transplantation while 6.7% in collagen-based implants. 35 These studies have proven the feasibility of partial or even total meniscus replacement.
Conclusions
Studies regarding the meniscus published from 2010 to 2019 were comprehensively analyzed with CiteSpace V. Great progress has been made in the meniscus research field with an increasing number of publications each year. Knee Surgery Sports Traumatology Arthroscopy, Osteoarthritis and Cartilage, and the American Journal of Sports Medicine were the core journals in this field. The United States was the country with the most publications. Of the main topics in this research field, osteoarthritis, tear repair, and the ACL were research hot spots, and extrusion and scaffolds were likely research frontiers.
Footnotes
Authors’ note
TZ and YX contributed equally to the manuscript and they are the co-first authors.
Author contributions
TZ and YX wrote the manuscript and WX reread the manuscript.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
