A Bibliometric Analysis and Visualization of Current Research Trends in the Treatment of Plantar Fasciitis


 Plantar fasciitis has become a common health problem. Both in theory and in therapy of plantar fasciitis has progressed rapidly in the past few decades, but there were no bibliometric studies regarding plantar fasciitis. This study aimed to illustrate the overall knowledge structure and development trends of plantar fasciitis. The research datasets were collected from the Web of Science, limited to articles published before Dec 16, 2020. VOS viewer and Citespace software were provided to analyze the data and generate visualization knowledge maps, including annual trends of publications, distribution, h-Index status, citations status, co-authorship status and research hotspots. 1429 publications met the requirement. The number of publications showed an upward trend with a stable rise in recent years. In the fields of plantar fasciitis, the United States published most papers (493, 34.50%), both total citations (13268) and h-index (65) ranked first of all the countries; the most productive institution was La Trobe University (30); Foot & Ankle International (122) published the most papers. Growth factor, wave therapy, corticosteroid, foot function index and physical therapy were the research hotspots in the recent years. Indeed, this study provides great insights to the growth and development of plantar fasciitis. Moreover, it will contribute to the growth of the international frontier of plantar fasciitis. Level of Evidence II.


Introduction
Plantar fasciitis (PF), occurring in 11% to 15% of adults, has become a common public health concern.
Mechanical overload, whether the result of biomechanical faults, obesity, or work habits of prolonged standing and running, contributes most to PF. 1,2 The damage from overloading leads to aseptic in ammation of the fascia or tendon. 3,4Patients usually feel painful on initiation of weight bearing, and the plantar heel pain usually occurring at the origin of the plantar fascia from the medial tubercle of the calcaneus.The pain tends to decrease after a few minutes` adaptation.PF has progressed in the past few decades both in theory and in therapy, but many topics still remain controversial, such as the natural history of PF, scoring system to evaluate the severity of PF, objective judgment to choose between conservative and surgical treatment, predictors of treatment outcome, and so on. 5,6bliometrics is a special type of quantitative and qualitative analysis in knowledge elds, using mathematics, statistics, philology, and other professional knowledge and methods to analyze the research achievement distribution of a current status comprehensively.9][10] However, to our knowledge, bibliometric studies concerning the trend of the published literature of articles published in the eld of PF has not yet been reported.This study aimed to intuitively show the research framework, overall knowledge structure, and development trends of the eld of PF.We hope that this study will help scienti c researchers better understand the research status and frontier trends.
Furthermore, the results can also provide useful information and references for further investigation and publication.

Search strategy and re ned data
The data for this study were collected from the Web of Science (WOS).WOS is the most widely accepted tool for the subsequent bibliometric analysis due to its strict evaluation process.The search term was *plantar fasciitis*.The literature search was limited to articles published before Dec 16, 2020.Original articles and reviews were included in this study, while letter, editorial material, basic research article and correction were excluded in our nalized dataset.Two independent researchers respectively reviewed and evaluated the cited articles to perfect the research.All different opinions were discussed until consensus was reached.

Data analysis
All data were extracted and imported into Microsoft Excel 2017.Annual trends of publications, distribution, citation and H-Index status, co-authorship status, research hotspots and co-citation status were quantitatively and qualitatively.All statistical analyses were performed using SPSS 20.0.Statistical signi cance was considered at P < 0.05.VOS viewer and Citespace are software tools for creating maps based on various layouts data and for visualizing and exploring the maps.[13] 3. Results

The Current Status and Annual Trend of Study
A total of 1429 articles were identi ed in WOS database and analyzed with an additional manual screening according to the inclusion criteria, among which 180 are reviews and 1048 are original articles.Fig. 1A shows the selection ow chart.The sum number of citation is 31204 (19336 without selfcitations).The average citation of all the papers is 21.84 times.The H-index of all the publications is 85.Fig. 1B shows the annual trends of publication numbers.Overall, there was an upward trend with a stable rise of the number of publications since 1995.There was a peak in the number of studies from 2018 to 2020.A total of 107 (7.49%) articles were published in 2018, the highest in all years, followed by the year 2020 (106, 7.42%) and the year 2019(100, 7.00%).The result indicated that more and more efforts and exploration had been made on PF.

The Distribution and Co-authorship Analysis of Countries
A total of 59 countries contributed to the eld of PF research.But the majority of the papers were published in only a few countries.Fig. 2A shows the top 10 most productive countries in PF eld.There were 950 papers (66.5%) published in the top 5 countries.The United States published the largest number of articles (493, 34.50%), followed by China (129, 9.03%), Germany (117, 8.19%), UK (109, 7.63%), and Australia (102,7.14%).H-index is a reliable and authentic parameter for academic evaluation.The H-index of USA ranked rst (65), followed by Germany (34), UK (31), and Australia(31).Furthermore, the number of citations can re ect the quality of a paper.Articles from USA were cited 13268 times, ranked rst of all the countries, followed by Germany (3325) and Australia (3320).The result shows that USA is the country with the highest productivity, not only in qualities, but also in quantities.China, Germany, UK and Australia are the other most contributing countries.Fig. 2C shows a map of worldwide research productivity, only countries published more than 10 articles were included.It shows that research on PF was concentrated in only a few countries during recent decades, more regions hadn`t participated in the eld of PF yet.The Citespace viewer software was employed to analyze the network visualization of co-authorship relationship.(Fig. 2B) USA was at the center of research, the cooperation between countries were relatively weak.

The Distribution and Co-authorship Analysis of Institutions
A total of 1691 institutions contributed to the eld of PF research.The top 10 most productive institutions in the PF eld are summarized in Fig. 3A.La Trobe University published the largest number of articles (30), follow by Harvard University (18) and Hong Kong Polytech University (18).The H-index of La Trobe University and University Munich ranked rst (12), followed by Harvard University (11) and Hong Kong Polytech University (10).The sum of times cited of La Trobe University ranked rst of all the institutions (791), follow by Hong Kong Polytech University (719) and University Munich (663).Fig. 3B is the co-authorship relationship analysis of institutions.It shows that Harvard University and Natl Taiwan University had closely collaborated with their a liated hospitals and research centers.In general, cooperation between the institutions were relatively weak.(Fig. 3B)

The Distribution and Co-authorship Analysis of Authors
The top 8 most productive authors in PF eld are shown in Fig. 4A.Rompe JD published the largest number of articles (23), follow by Landorf KB (22), Maffulli N ( 14), Menz HB (14) and Schmitz C (13).The cited time of Rompe JD ranked rst (1115), followed by Landorf KB (764) and Maffulli N (600).The Hindex of Rompe JD (18) ranked rst of all the authors, follow byLandorf KB (14) and Schmitz C (10).Fig. 4B shows the co-authorship relationship analysis of authors.Only authors cited a minimum of 20 times were included.95 authors met the threshold and were selected for analyzing.It shows that authors in the same country have relatively close collaboration.Nevertheless, cooperation between authors from different country is weak.

The Distribution and Co-authorship Analysis of Published Journals
All publications were published in 367 journals.Only 32 (8.72%) journals published more than 10 papers.The top 10 journals that published the most papers are showed in Fig. 5A.The journal with the greatest number of publications was Foot & Ankle International, with a total of 122 (8.54%) papers.At the second position was Journal of the American Podiatric Medical Association with 61 (4.27%) paper, followed by Journal of Foot & Ankle Surgery with 59 (4.13%),American Family Physician with 29 (3.15%) and Journal of Orthopaedic & Sports Physical Therapy with 28(1.96%).These top 5 journals account for 20.9% of all the papers.The H-index of Foot & Ankle International ranked rst (36), followed by Journal of the American Podiatric Medical Association (19), American Journal of Sports Medicine( 16), Journal of Orthopaedic & Sports Physical therapy (14) and Journal of Bone and Joint Surgery-American Volume (13).The cited time of Foot & Ankle International (3771), followed by Journal of Bone and Joint Surgery-American Volume (1524) and British Journal of Sports Medicine (1327).Fig. 5B plots the co-authorship relationship of journals.Only journals cited a minimum of 100 times were included.67 journals met the threshold and selected for analyzing.Foot & Ankle International, Journal of Bone and Joint Surgery-American Volume and American Journal of Sports Medicine were at the center of research.In general, cooperation between journals is relatively weak.
Table 1 shows the top 10 cited articles in terms of title, journal, authors, years and citation numbers.The highest and the lowest number of citations for an article was 844 and 200.Two of these top ten cited articles were published in Foot & Ankle International.All the 10 papers were in English.8 papers were coauthored.

The Keywords Analysis of Research Hotspots on Study
Keywords co-occurrence can effectively re ect the research hotspots and provide support for the research.Keywords and research focuses related to PF was visualized by VOS viewer and shown in Fig. 6.The bigger nodes and darker color show a larger weight of the keyword.There were 6 clusters with highfrequency in the eld of PF.The cluster name was re ned according to the keywords contained in each cluster.The six cluster are mainly about diagnose, treatment, injury site, cause of disease, related diseases and examine.
Table 2 shows the 25 meaningful keywords with the strongest citation burst, which represented the research frontiers.The red and blue bars represented the frequently-and infrequently-cited keywords, respectively.Fig. 7 shows the keywords timeline view of publications.The results indicated that growth factor, wave therapy, corticosteroid, foot function index and physical therapy are the research hotspots in the recent years.

Trends of publications related to PF
Bibliometric analysis is a mature tool to quantify the characteristics and scholarly impact, and it has been applied vastly to assess the merits of a speci c eld. 14,15 PF research has made great progress in recent years.In this article, we identi ed and summarized the papers related to PF, and compared the papers from different countries, institutes and journals, and showed the global trends of researches by visual tools.The result will be helpful in guiding researchers in selecting relevant topics, nding suitable teams to collaborate with and research platforms to use for their research.
There is a stable rising trend both in the number of published papers and relative research interest in the past 20 years.It suggests that the development of PF research has a rapid stage of progress and attracted more attention in the global medical eld.More achievements had also been made.The study found that 66.5% of total articles were published by the top ve productive countries (the United States, China, Germany, UK and Australia), and the top productive institutions were all from these countries.It indicated that worldwide research results of PF were concentrated in America, West Europe, East Asia and Australia.
USA made the most academic contributions to this area having the highest total publications (493, 34.50%) and H-index (65), suggesting that USA dominates studies of PF.The most possible reasons for USA's great contributions may be related to technological, economic and academic advantages.In addition, substantial research funds are invested in medical research to increase the quality of researches.Nevertheless, the qualities of researches of China is relatively low, need to improve its qualities of publications concerning PF.China has an advantage in recruitment of participants because of the large population and high prevalence of lumbar degenerative disorders, but China is still a developing country with relatively backward technological strength.Furthermore, the amount of government funds is much lower than USA.For example, Chinese government funds in medical research only account for 2-3% of the total governments funds.For all this, China`s research in uence is still more signi cant than the other counties and cannot be ignored.La Trobe University is the most productive organizations in the eld of PF.La Trobe University and University Munich ranked rst side by side in H-index.La Trobe University ranked rst in total citation numbers.It suggesting that the signi cant studies related to PF are more likely to be published by these institutions, and researchers who are interested in PF may cooperate with these institutions.Regarding the productive journals, Foot & Ankle International ranked rst in total publications, H-index and cited time.This was a re ection of the great in uence of Foot & Ankle International and its leading position in the eld of PF.There is no doubt that authors interested in PF should pay more attention to La Trobe University and Foot & Ankle International.
Co-authorship research is an important content of bibliometrics and the level of research collaboration is an index to assess the current research status.The network map revealed that the centrality and density value of this study was not high.The interaction between countries, institutions, journals and authors were relatively weak.Therefore, it is urgent to strengthen the international academic cooperation between countries/regions and institutions.Furthermore, forming an academic community is bene cial to the development of research in the future.

Studies focused on PF
Under normal circumstances, doctors can differentiate causes of plantar fasciitis during the patient history and physical examination.To diagnose objectively, MRI is the only imaging method that can precisely visualize lesions of the plantar fasciitis, whether they be musculoaponeurositides, enthesopathies or tears, and whether they be acute or chronic, with or without complications at present.By its direct visualization of the lesion, MRI enables an accurate assessment of the injury to be made and thereby better orients the therapeutic strategy.Currently, the clinical e cacy of treatment for PF is controversial.The relationship between individual patient's characteristics and its potential predictive value on outcomes has not been studied.[18] In past decades, most physicians only paid attention to patients' improvement of symptoms and signs.But with the transformation of medical model to "bio-psycho-social medical model", physicians should consider the whole body, including patients' psychological, spiritual and social adaptability, that is, to emphasize the improvement of patients' quality of life.Through the assessment of quality of life, physicians will have more understanding of the patients' physical, psychological and social functions, carry out effective psychological guidance, so that they can truly achieve the purpose of treating diseases, reducing trauma, recovering functions and improving the quality of life. 19,20

Strengths and
To the best of our knowledge, the current study is the rst to analyze the quality and quantity of researches using bibliometric analysis and visualization tool in the eld of PF.To guarantee the objectivity and comprehensiveness, we conducted a systematic literature search in the WOS, which could offer powerful data from various aspects with a high and powerful recognition.Although these notable strengths, this study also has some limitations.First, bibliometric analyses only contain the published literature in WOS database, the unpublished and non-English articles were not included.Second, bibliometric data are changing over time, the delay of the indexation may account for the slight difference in the results retrieved.Third, all citations were treated in the same way whether it was cited for its positive contribution or for its negative impact or poor quality.Also the authors might tend to cite papers from the journals in which they hoped to publish their research.

Conclusions
This study provided a basic worldwide overview of research publications and relative research interest on PF.The number of publications showed an upward trend with a stable rise in recent years.USA is the country with the highest productivity, not only in quality, but also in quantity.La Trobe University has been the largest contributor in this eld.Foot & Ankle International is the best journal related to PF.Growth factor, wave therapy, corticosteroid, foot function index and physical therapy are the research hotspots in the recent years.Indeed, this study provides great insights to the growth and development of PF.
Moreover, it will contribute to the growth of the international frontier of PF.