Bibliometric Analysis of the Orthopedic Literature

Materials and Methods

A total of 61 orthopedics-related journals were selected from the orthopedics category of the Science Citation Index Expanded (SCIE) database.³ A computerized literature search was conducted using the SCIE database on February 20, 2012, and the orthopedics articles published from January 2000 to December 2011 in these journals were retrieved. The full journal titles of the 61 journals were used to perform searches in the SCIE database.

Three methods were used to evaluate the quality of the research articles. First, the impact factor was generated according to Journal Citation Reports 2010. Second, the distribution of articles by authors’ country of origin and the total number of citations were analyzed. Third, the articles published in orthopedics journals with top-10 impact factors were also quantified.

Statistical analyses were performed using SAS version 9.1.3 statistical software (SAS Institute Inc, Cary, North Carolina). The nonparametric test for trends was used to determine significant changes in the total number of articles over the study period. The Kruskal-Wallis test was used to determine the differences in the proportion of yearly world contributions to orthopedics by the United States, the United Kingdom, Germany, Japan, China, and South Korea, and the rank sum test was used to detect the difference in the growth rate between China and the world, if needed. The test for significance was 2-sided, and a P value less than .05 was considered significant.⁴

Results

A total of 91,216 articles were published in the 61 orthopedics journals from 2000 to 2011. Table 1 shows the year-by-year output. The outputs in 2010 (10,276 articles) and 2011 (10,087 articles) were approximately twice that of 2000 (5161 articles), a growth rate of approximately 40%. In calculating the annual growth rate for each year, 2004 had the fastest growth (14.02%), followed by 2007 (11.39%) and 2006 (11.24%); 2001 had the lowest growth (1.88%), followed by 2009 (2.20%) and 2003 (2.70%).

Table 1: Number of Articles Per Year and Growth Rate, 2000–2011

Authors’ Countries of Origin

The contributions of authors from different countries were plotted, with a focus on the top 10 countries according to publication count and those in Asia.

From a total of 91,216 articles, the United States ranked first in output (36,222; 39.71%), followed by the United Kingdom (7745; 8.49%), Germany (6979; 7.65%), and Japan (5686; 6.23%). Japan ranked 1st in Asia, followed by South Korea, which ranked 10th in the world (2262; 2.48%). China ranked 12th in the world (1973; 2.16%) and 3rd in Asia (Table 2).

Table 2: Top 10 Countries According to Number of Articles Plus China, 2000–2011

Although authors from the United States contributed the largest number of articles, the proportion of US articles showed a declining trend between 2000 (43.64%) and 2011 (35.07%). Before 2008, little difference existed between Germany and Japan; after 2008, Germany (8.18%) exceeded the United Kingdom (7.99%) and ranked 2nd in the world (Table 3; Figure 1).

Table 3: Proportion of World Contribution to Orthopedics by Year, 2000–2011

Figure 1: Line graph showing publication counts between 2000 and 2011.

China showed an improvement in orthopedics research, with articles published in international journals increasing significantly during the study period. In 2010, China (3.41%) overtook South Korea (3.34%) to become 2nd in Asia. In 2011, China (5.05%) narrowed its gap with Japan (5.58%) to rank 5th in the world (Tables 3 and 4; Figure 1).

Table 4: Top 10 Countries According to Number of Articles per Year, 2000–2011

Citation analysis for the retrieved articles (Table 5; Figure 2) indicated that US-authored articles were cited the highest number of times (396,797), followed by the United Kingdom (71,129), Germany (52,644), Japan (43,900), South Korea (13,863), and China (9225). Articles by US authors had the highest average per-article citation (10.96), followed by the United Kingdom (9.18), Japan (7.72), Germany (7.54), South Korea (6.13), and China (4.68) (Tables 2 and 5).

Table 5: Total Citations of Articles per Year, 2000–2011

Figure 2: Line graph showing numbers of citations between 2000 and 2011.

Most Prolific Authors

An author analysis was conducted for the retrieved articles to determine the top 100 authors according to publication counts. Researchers were ranked based on their number of articles and citations (Tables 6–8). Among the top 100 most prolific authors, 43 were American, 19 were Japanese, 6 were Korean, 5 were German, 4 were English, and 23 were from other countries. Table 7 shows that among the top 10 most published authors, 4 were American, 2 were English, 2 were Japanese, 1 was Canadian, and 1 was Korean. The number of publications for the top 10 authors ranged from 258 (1st place) to 185 (10th place). Table 8 shows the citation ranking of the top 10 authors, ranging from 4672 (1st) to 2261 (10th).

Table 6: Country Distribution of Top Authors According to Number of Articles, 2000–2011

Table 7: Top 10 Authors According to Number of Articles, 2000–2011

Table 8: Top 10 Authors According to Number of Citations, 2000–2011

P.V. Giannoudis, from the United Kingdom, was the most prolific author, publishing 258 articles during the study period; Freddie Fu, from the United States, was the most-cited author (4672 citations). The top 5 prolific authors all had citations within the top 10, including P.V. Giannoudis (United Kingdom), J. Parvizi (United States), A.R. Vaccaro (United States), M. Bhandari (Canada), and L.G. Lenke (United States). Citation rates for authors not in the top 10 were not necessarily low. For example, the 112 articles by R. Ganz (Switzerland) ranked him in 35th place overall, but his articles ranked 3rd in total number of citations (n=4447). K.H. Bridwell (United States) ranked 16th (n=169) in number of articles and 4th (n=3728) in total number of citations.

Most Prolific Institutions

An analysis of academic institutions was conducted for the retrieved articles to determine the top 100 institutions according to publication counts. The institutions were ranked according to the numbers of articles and citations (Tables 9–11).

Table 9: Country Distribution of Top Affiliations According to Number of Articles, 2000–2011

Table 10: Top 10 Institutions According to Number of Articles, 2000–2011

Table 11: Ranking of Top 10 Institutions According to Citation, 2000–2011

Among the top 100 most prolific institutions, 59 were in the United States, 5 in Germany, 5 in the United Kingdom, 4 in Japan, 2 in South Korea, and 1 in China (Table 9). Table 10 shows that the 10 most prolific institutions were all in the United States. The number of publications by the top 10 institutions ranged from 1258 (1st place) to 640 (10th place). Table 11 shows the rankings of the top 10 institutions according to their total citations, which ranged from 17,752 to 9107. The Hospital for Special Surgery (United States) was the most prolific institutional source of orthopedic articles, with 1258 articles about orthopedics, whereas the University of Pittsburgh ranked first in total number of citations (n=17,752). Total number of citations for the top 5 most prolific institutions—the Hospital for Special Surgery, Harvard University, the Mayo Clinic, Washington University (St Louis), and the University of Pittsburgh—were all in the top 10.

However, the total citations for institutions outside of the top 10 were not necessarily low. For example, the University of Bern (Switzerland) ranked 25th in number of articles (n=453) and 8th in total number of citations (n=9737).

Journal Distribution: Most Popular Orthopedic Journals

A source publication analysis was conducted for the retrieved articles to determine the top 10 most popular journals according to publication counts (Table 12). Spine ranked the first in number of articles (n=7902; impact factor, 2.51), Clinical Orthopedics and Related Research ranked second (n=6243; impact factor, 2.116), and the Journal of Bone and Joint Surgery, British Volume ranked third (n=5662; impact factor, 2.967).

Table 12: Top 10 Journals According to Number of Articles, 2000–2011

High-impact Orthopedic Journals

The 61 journals were ranked according to their impact factor, and the number of articles published in the top 10 journals was analyzed according to the authors’ country of origin (Table 13). Osteoarthritis and Cartilage had the highest impact factor (3.953), the American Journal of Sports Medicine ranked 2nd (3.821), and Arthroscopy ranked 3rd (3.317). As shown in Table 13, authors from the United States published the most articles (n=15,835) in the journals with a top 10 impact factor, followed by those from Japan (n=1928) and the United Kingdom (n=1359).

Table 13: Top 10 Journals According to Impact Factor and Number of Articles, 2000–2011

Discussion

According to classical bibliometric theory, an increase or decrease in the publication of scientific literature indicates the speed of progress of science and technology, and the period needed for the doubling of scientific literature can be used to measure scientific development. An acute change in the number of published articles likely reflects a turning point in the development of the science.⁵ The current study found that the number of orthopedics articles published dramatically increased between 2000 and 2011, when the number doubled, indicating an important turning point for the rapid development of orthopedics and the achievements that have been made. Another reason for the increase is the increase of orthopedics journals found in the SCIE database.

The geographic and language distributions of scientific literature can mirror the research capabilities and technological developments of different countries.⁵ This study found that the top 10 countries’ authors published 81.39% of the total orthopedics articles, indicating that the worldwide research efforts in orthopedics were actually concentrated, with the United States publishing the most articles and making the greatest contribution, followed by the United Kingdom and Germany.

The contribution rankings of countries underwent variation in the past decade, but the variation was mild. The United States still ranked first but showed a declining trend year by year, a trend that was also true for other traditionally strong countries, such as the United Kingdom and Japan. However, Germany, Korea, and China showed an increase in orthopedics publishing. In 2011, China ranked 5th in the world, with the proportion increasing from 0.64% in 2000 to 5.05% in 2011.

Researchers believe that the total citation rate for an article can reflect the quality and value of the research it reports. Citation analysis can thus be used to evaluate and compare the academic position of different countries and research institutions.⁵ An investigation of the citation rates for the orthopedic articles under analysis showed that the United States ranked first in terms of total citations and average citations per article. Although the number of articles published by Japanese authors was lower than those published by German authors, their total citations and average citations per article were both higher than those of German authors, indicating a stronger influence for Japanese articles. China also witnessed a rapid increase in the number of published orthopedics articles, but its total citations and average citations per article were small.

An analysis of prolific authors in orthopedics showed that the United States and Japan had the most prolific authors because these 2 countries had the most-cited orthopedics researchers. Analysis of the top research institutions found that the United States had the greatest number of top research institutions for orthopedics, demonstrating that the United States is currently the strongest power in orthopedics research. If the impact factor is the most important quality indicator for scientific journals, then US authors published the most articles in the top 10 orthopedics journals.

The results of the analyses of number of articles, citation status, top researchers, and top institutions all showed that the United States is the strongest country in orthopedics research, and the United Kingdom, Germany, and Japan were always within the world’s top 4 in terms of number of articles and citation status. China has shown a rapid increase and is now ranked fifth in terms of number of articles. However, China is lagging behind in terms of citations per article, top research institutions, and most prolific authors.

Current changes in Chinese orthopedic research are due to several factors. First, the number of research institutions has grown and clinical orthopedic practice and research capabilities have improved with recent advances in China’s economy. Chinese orthopedic researchers now have more chances to communicate with their international partners.⁶ Second, the Chinese government and various academic and research institutions now regard the number of articles indexed in the SCIE database as an important indicator of the research ability and achievements of a researcher or an institution, and these evaluation outcomes are now typically related to an author’s technical title, salary, bonus, and other important benefits, which stimulates an interest in research. However, these changes seem to have resulted only in an increase in number of articles and not in their quality, as indicated by the current citation rates for Chinese-authored articles.

One of the limitations of this study is that only the 61 orthopedics journals covered by the SCIE database were analyzed; some orthopedics articles are also published in multispecialty medical journals.

Conclusion

This bibliometric analysis showed that orthopedics research witnessed rapid development between 2000 and 2011. The United States is the strongest country in terms of orthopedic research: US authors published the greatest number of orthopedics articles, and those articles have the highest total number of citations and average citations per article. Moreover, the United States has the most prolific authors and the most top research institutions. Japan is the strongest country in Asia in terms of published orthopedic research. China demonstrates rapid progress in orthopedic research thanks to its rapid economic development and growth in research funding.

The purpose of this study was to evaluate the scientific productivity of orthopedics research by bibliometric methods. Among the benefits of this study is the potential for the professional orthopedics community to discover a new perspective on their own discipline and its subfields. The authors’ work in this area is ongoing.