3.1 The Current Status and Annual Trend of Study
A total of 1429 articles were identified 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 flow chart. The sum number of citation is 31204 (19336 without self-citations). 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.
3.2 The Distribution and Co-authorship Analysis of Countries
A total of 59 countries contributed to the field 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 field. 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 first (65), followed by Germany (34), UK (31), and Australia(31). Furthermore, the number of citations can reflect the quality of a paper. Articles from USA were cited 13268 times, ranked first 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 field 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.
3.3 The Distribution and Co-authorship Analysis of Institutions
A total of 1691 institutions contributed to the field of PF research. The top 10 most productive institutions in the PF field 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 first (12), followed by Harvard University (11) and Hong Kong Polytech University (10). The sum of times cited of La Trobe University ranked first 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 affiliated hospitals and research centers. In general, cooperation between the institutions were relatively weak. (Fig.3B)
3.4 The Distribution and Co-authorship Analysis of Authors
The top 8 most productive authors in PF field 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 first (1115), followed by Landorf KB (764) and Maffulli N (600). The H-index of Rompe JD (18) ranked first 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.
3.5 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 first (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 co-authored.
3.6 The Keywords Analysis of Research Hotspots on Study
Keywords co-occurrence can effectively reflect 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 high-frequency in the field of PF. The cluster name was refined 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.