Global Scientific Outputs of Microsurgery Publications: A Bibliometric Approach About Yesterday, Today, and Tomorrow

Introduction Although there have been important developments in microsurgery in recent years, there is no current and comprehensive bibliometric study in the literature. In this study, we aimed to present a summary of the articles published on microsurgery between 1980 and 2019 with bibliometric analysis. Methods Articles published on microsurgery between 1980 and 2019 were withdrawn from the Web of Science database and analyzed by bibliometric methods. Citation analysis was performed to identify effective journals and articles. Keyword cluster and trends analyses were performed for a detailed analysis of the researched topics. Relationships between the article numbers of the countries and gross domestic product (GDP) and human development index (HDI) values were investigated using Spearman’s correlation coefficient. A linear regression analysis was used to estimate the number of articles to be published in the future. Results A total of 3,537 publications related to microsurgery were found. Bibliometric analyses were performed in 2,063 articles (58.3%) of these publications. The most active countries in publishing were the United States (504), Germany (286), and Italy (154), respectively. A statistically significant correlation was found between the article numbers and the GDP and HDI sizes of the countries (r = 0.758, p <0.001, r = 0.659, p <0.001). Conclusion The economic size and development levels of the countries were an important factor in academic productivity in microsurgery. Undeveloped countries should be encouraged by performing multidisciplinary studies in this regard.


Introduction
Microsurgery is a term used to describe the surgical techniques that require surgical microscopy and the necessary special instrumentation (microscopes, microstrums, and micro-sutures) to perform sensitive operations on small structures in our body [1]. It specializes in many clinical disciplines including microsurgical orthopedics, otorhinolaryngology, ophthalmology, neurosurgery, plastic surgery, transplantation surgery, oncology, gynecology, and urology [2]. There are highly efficient microsurgery applications in orthopedic surgery [3].
Although there have been important developments in microsurgery in recent years, there is no current and comprehensive bibliometric study in the literature.
In this study, we aimed to present a summary of the articles published on microsurgery between 1980 and 2019 with bibliometric analysis. In addition, we aimed to reveal the most cited effective publications, active journals, countries, institutions, and authors; identify international collaborations; and discuss keyword analysis and trending research topics. We also aimed to determine the development of publications over the years and the factors affecting the productivity of the publication with correlation and regression analysis.

Materials And Methods
The literature review was performed using the Web of Science (WoS; Clarivate Analytics, Philadelphia, Pennsylvania) database (access date: May 10, 2020). All articles published on microsurgery were searched. All the publications with the keywords "microsurgery/micro surgery/micro-surgery" in the title and published between 1980 and 2019 were pulled from the WoS database and analyzed by bibliometric methods. The codes for repeatability were as follows: Title: ("micro-surgery") OR Title: ("micro surgery") OR Title: (microsurgery) and Document Types: (Article) Timespan = 1980-2019. Indexes = SCI-Expanded, SSCI, A & HCI, CPCI-S, CPCI-SSH, BKCI-S, BKCI-SSH, ESCI). Bibliometric network visualizations were performed using the VOSviewer (Version 1.6.15; Centre for Science and Technology Studies, The Netherlands) package program [11].
Statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) (Version 22.0, IBM Corp., Armonk, NY) package programming. The normality of data distribution was tested using the Shapiro-Wilk test. The correlation between the number of articles produced by countries and gross domestic product (GDP) (data obtained from the World Bank Group website) [12] and human development index (HDI) (data from the United Nations Development Program Human Development Report 2019) [13] was determined using Spearman's correlation coefficient in accordance with the data distribution. Linear regression analysis was used to estimate the number of articles to be published in the future. A p-value of <0.05 was considered significant.

Development of publications
The distribution of articles by year is presented in Figure 1. The number of publications for the next five years predicted by regression analysis is also shown in Figure 1 with 95% confidence intervals. The

Trend topics
A total of 2,628 different keywords were used in 2,063 articles. Approximately 76 keywords used in at least eight different articles from these keywords are listed in Table 1. The network visualization map obtained according to the citation analysis of the articles containing the keywords is shown in Figure 2.   Footnote: The number of citations taken by keyword increases from blue to red (blue-green-yellow-red). The size of the circles indicates that the keyword is used frequently. The thickness of the lines indicates the strength of the relationship.

Active organization
The 16 organizations and organizations-enhanced that published the most articles on microsurgery are presented in Table 2.

Active journals
A total of 636 journals with 2,063 articles were published. Among these journals, 74 published at least six articles on this subject. The first 74 journals that produced the most publications are presented in Table 3.
The table lists the total number of citations and the average number of citations per article.

Correlation analysis
A statistically significant correlation was found between the number of articles published by countries on microsurgery and the GDP and HDI sizes of countries (r = 0.758, p <0.001, r = 0.659, p <0.001). Scatter plots of correlations are presented in Figure 4.

FIGURE 4: Scatter plot between the number of articles produced by country on microsurgery and log (GDP) and HDI values
Footnote: GDP: gross domestic product, HDI: human development index

Co-citation analysis
In the references section of 2,063 articles, 29,387 publications were referred. Among these were eight publications that received more than 50 citations. These most cited publications were Buess (1984)

Citation analysis
When the analyzed articles were evaluated according to the total number of citations and the average number of citations per year, the most cited study was Anderson et al.'s study titled "Selective photothermolysis -precise microsurgery by selective absorption of pulsed radiation" published in Science in 1983 [22]. The remaining most cited articles were performed by Sylla et al. [23], Haughey et al. [24], Hutson et al. [25], and Bach et al. [26], respectively. The articles were ranked according to the average number of citations per year, and the first five articles are presented in Table 4 [22][23][24][25][26]. The total citation numbers of the articles are also provided in the

Discussion
According to our comprehensive statistical analysis findings with 2,063 articles, a significant increase was observed in the number of articles on microsurgery especially after 2005. The number of articles published ranged from 21 to 60 per year between 1980 and 2009. The number of articles exceeded 60 in 2010 and reached 122 in 2019. When the regression analysis results were evaluated, we observed that the number of articles published will continue to increase.
When the results of the keyword analysis were evaluated, the top 10 topics related to microsurgery investigated were transanal endoscopic microsurgery (TEM), rectal cancer/adenoma, transoral laser microsurgery, local excision, vestibular schwannoma, endoscopy, quality of life, endodontic microsurgery, minimally invasive surgery, and larynx. According to the results of cluster analysis, four major primary clusters were formed based on the topics used in similar articles: microsurgery, transanal endoscopic microsurgery/rectal cancer/local excision, transoral laser microsurgery/quality of life, and vestibular schwannoma/acoustic neuroma. The literature on microsurgery developed four main clusters, with a total of eight different clusters.
According to the results of trend analysis to determine the current research topics, issues related to transanal endoscopic microsurgery, rectal carcinoma/tumors, laser microsurgery, endoscopy, transsphenoidal surgery, gamma knife, and pituitary adenoma were initially studied; in the following years, acoustic neuroma, stereotactic radiosurgery, radiotherapy, arteriovenous malformation, local excision, When the publication distributions of the world countries were analyzed, we found that developed countries produce the most publications in microsurgery (US, Germany, Italy, UK, France, Japan, Switzerland, Canada, Spain, Netherlands, South Korea, Belgium, Australia, Austria, Taiwan, and Israel) or developing countries with large economies (China, Brazil, Turkey, and Russia). When the relation graph plotted for the correlations was evaluated, countries with HDI 0.88 and above provided remarkable article contributions. Countries with a log (GDP) value of more than 5.6 (about 400,000 GDP) contributed significantly to the attention. Some studies conducted in the literature reported that the economic size or development levels of the countries had a significant effect on academic publication productivity [4][5]. Some cutting points were discussed in our study. When co-authoring cooperation of countries was evaluated, we found that geographical regional neighborhood is an important factor in cooperation.
In our study, comprehensive bibliometric analyses, such as keyword analysis, citation analysis for articles and journals, international collaborations, and correlation analyses, were performed for the first time in this study. Our study is the most comprehensive research in the literature in which the most articles are analyzed on this subject.
This study has some limitations. It only reviewed the articles published in the WoS database. The PubMed and Scopus databases were not included for analysis. In the bibliometric studies where many articles were analyzed, if multiple databases are used, the same articles (there maybe thousands) in different databases can be included in the analysis twice. This will negatively affect the reliability of the results.

Conclusions
As a result of our study on microsurgery, which has an increase in the number of articles every day in the literature, summary information of 2,063 articles published between 1980 and 2019 was presented. The most active publishing countries were the US, Germany, and Italy. There was a significant correlation between article numbers and countries' GDP and HDI sizes. The top three journals to publish articles were the Journal of Reconstructive Microsurgery, Microsurgery, and Surgical Endoscopy and Other Interventional Techniques. The most active institution was University Gottingen.
The researchers will be able to get ideas for new studies on this subject by evaluating the development of the topics studied by year, the trending topics, and the topics that received more citations. Hence, this study will be a useful guide for clinicians and scientists on the global outcomes of studies on microsurgery.

Additional Information Disclosures
Human subjects: All authors have confirmed that this study did not involve human participants or tissue. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue.

Conflicts of interest:
In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.