title: National representation in the spine literature: a bibliometric analysis of highly cited spine journals.
abstract: OBJECTIVE
  Significant progress has been seen in the field of spine in recent years as a consequence of worldwide contributions. However, the national productivity to the field of spine is still unclear. The aim of this study was to investigate the national contributions in the field of spine.
  
  
  METHODS
  Web of Science was searched for articles published in the five highly cited spine journals from 2009 to 2013, including The Spine Journal, European Spine Journal, Spine, Journal of Neurosurgery: Spine, and Journal of Spinal Disorders and Techniques. The number of total articles, the per capita numbers, impact factors, citations and funding source were recorded and analyzed.
  
  
  RESULTS
  A total number of 6920 articles were published in the five journals from 2009 to 2013 worldwide. North America, East Asia, and West Europe were the most productive world areas. High-income countries published 83.97% of articles, middle-income 16.01%, and lower-income just 0.01%. The United States published the most number of articles (35.79%), followed by China, Japan, South Korea, and Canada, and had the highest total impact factors and the highest total citations. However, when normalized to population size, Switzerland had the highest number of articles per million populations, followed by The Netherlands and Sweden.
  
  
  CONCLUSIONS
  The majority of the spine articles are published by authors from high-income countries while few publications from low-income countries. The United States is the most productive country in the field of spine. However, some European countries may be more productive when normalized to population size.
authors: Department of Orthopedics, Wuhan Pu'Ai Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 473 Hanzheng Street, Wuhan, 430033, China. orthopedist_dingf@163.com.
authors: Fan
authors: F
authors: Ding
authors: Graduate School, Second Military Medical University, No. 800 Xiangyin Road, Shanghai, 200433, China. jiazhiwei@139.com.
authors: Zhiwei
authors: Z
authors: Jia
authors: Department of Orthopedics, Wuhan Pu'Ai Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 473 Hanzheng Street, Wuhan, 430033, China. veteran-1972@sohu.com.
authors: Ming
authors: M
authors: Liu
mesh_terms: D015706:Bibliometrics; D006801:Humans; D055811:Journal Impact Factor; D009985:Orthopedics; D010506:Periodicals as Topic / Q000706:statistics & numerical data*; D011643:Publishing / Q000706:statistics & numerical data*; D013131:Spine
keywords: Bibliometric analysis; Spine