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The Top 100 Classic Papers in Lumbar Spine Surgery

Steinberger, Jeremy, MD*; Skovrlj, Branko, MD*; Caridi, John M., MD*; Cho, Samuel K., MD

doi: 10.1097/BRS.0000000000000847
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Study Design. Bibliometric review of the literature.

Objective. To analyze and quantify the most frequently cited papers in lumbar spine surgery and to measure their impact on the entire lumbar spine literature.

Summary of Background Data. Lumbar spine surgery is a dynamic and complex field. Basic science and clinical research remain paramount in understanding and advancing the field. While new literature is published at increasing rates, few studies make long-lasting impacts.

Methods. The Thomson Reuters Web of Knowledge was searched for citations of all papers relevant to lumbar spine surgery. The number of citations, authorship, year of publication, journal of publication, country of publication, and institution were recorded for each paper.

Results. The most cited paper was found to be the classic paper from 1990 by Boden et al that described magnetic resonance imaging findings in individuals without back pain, sciatica, and neurogenic claudication showing that spinal stenosis and herniated discs can be incidentally found when scanning patients. The second most cited study similarly showed that asymptomatic patients who underwent lumbar spine magnetic resonance imaging frequently had lumbar pathology. The third most cited paper was the 2000 publication of Fairbank and Pynsent reviewing the Oswestry Disability Index, the outcome-measure questionnaire most commonly used to evaluate low back pain. The majority of the papers originate in the United States (n = 58), and most were published in Spine (n = 63). Most papers were published in the 1990s (n = 49), and the 3 most common topics were low back pain, biomechanics, and disc degeneration.

Conclusion. This report identifies the top 100 papers in lumbar spine surgery and acknowledges those individuals who have contributed the most to the advancement of the study of the lumbar spine and the body of knowledge used to guide evidence-based clinical decision making in lumbar spine surgery today.

Level of Evidence: 3

Lumbar spine surgery is a dynamic field that owes its development to the work and visions of many dedicated individuals. This article's identification of the top 100 lumbar papers gives us an insight into the development and trends in the 20th and early 21st centuries.

From the Departments of *Neurosurgery and

Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, New York, NY.

Address correspondence and reprint requests to Samuel K. Cho, MD, Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, 5 E 98th St, Box 1188, New York, NY 10029; E-mail: samuel.cho@mountsinai.org

Acknowledgment date: October 31, 2014. First revision date: January 2, 2015. Acceptance date: January 10, 2015.

The manuscript submitted does not contain information about medical device(s)/drug(s).

No funds were received in support of this work.

Relevant financial activities outside the submitted work: consultancy, grants/grants pending.

Surgery for various conditions in the lumbar spine is common. Despite its prevalence, our knowledge of the underlying pathological mechanisms remains limited and the indications for surgical treatment remain controversial in many areas. Basic science and clinical research remain paramount in the understanding and advancement of the field of lumbar spine. Although new literature is published at increasing rates, few studies make long-lasting impacts on the field. This is the first study to analyze and quantify the most frequently cited papers in lumbar spine surgery and to measure their impact on the entire lumbar spine literature.

A citation is an expression that acknowledges the relevance given by the author to the work of others on a topic of interest in which the citation appears.1 The primary goal of a citation is to credit the author of the work that has been previously published. The greater the number of citations an author has, the more influential that author becomes in his or her particular area of expertise. Citation analysis is used to determine the relative importance of medical journals by means of the impact factor, which is determined from the ratio of the number of citations in the current year to articles published in the journal in the 2 preceding years, divided by the number of citable items published in the same 2 years.2–4 The impact factor has emerged as a marker of the quality and rank of a journal.

The goal of this study was to identify the 100 most cited papers relevant to lumbar spinal surgery and published in spine-related journals through an extensive search of the literature using methods validated in other similar, previously published studies in other areas.5–7 In doing so, trends, controversies, successes, and novelties that have defined lumbar spine surgery can be readily identified.

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MATERIALS AND METHODS

The Thomson Reuters Web of Science, a research platform that provides bibliographic database services and ranks journals according to impact factor, was used to search for papers for this study. The subject of the search was “lumbar spine surgery,” with a year range of 1900 to 2014. The results were organized from most cited to least cited and those with implications in lumbar spine surgery were selected for the study, whether they were published in surgical or nonsurgical journals.

The 100 articles that matched the search criteria were then further analyzed, and the title, first author, journal and year of publication, number of citations, and country and institution of origin were recorded.

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RESULTS

The search yielded a total of 65,014 papers, 16,532 of which more precisely matched the search criteria. Of those, 322 were cited 100 times or more. The top 100 papers, their first author, and their corresponding number of citations are shown in Table 1. The top paper was cited 3315 times, the 100th paper 176 times, and the mean number of citations for the top 100 papers was 293. The papers were published between 1949 and 2010. The oldest paper was by Nicoll,99 which was published in 1949. The most recent paper was published in 2010 by Deyo et al.91 Seventy-six percent of the top 100 cited papers were published after 1980, with the 1990s producing the largest number of highly cited papers (49%) (Table 2). The top 100 papers were published in 17 journals, with the top 3 journals publishing 75% of the articles (Table 3). The top journal was Spine with 63 papers, followed by the Journal of Bone and Joint Surgery American Volume with 7 papers and the Journal of Bone and Joint Surgery British Volume with 5 papers. The three most popular categories published were low back pain (LBP) with 23 papers, biomechanics with 16 papers, and disc degeneration with 9 papers (Table 4). Eighty-three first authors contributed to the top 100 papers. Ten authors contributed more than once, 3 of whom were credited with 4 or more publications and only one author, Deyo et al, had 5 publications in the top 100 (Table 5). The top papers originated from 14 different countries, with the United States (58%) being the most prolific (Table 6). There were 61 institutions responsible for the top cited papers, with the University of Washington contributing the most papers with 6 publications in the top 100 (Table 7).

TABLE 1

TABLE 1

TABLE 2

TABLE 2

TABLE 3

TABLE 3

TABLE 4

TABLE 4

TABLE 5

TABLE 5

TABLE 6

TABLE 6

Table 7

Table 7

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DISCUSSION

This study identifies the authors and topics that have had the most impact on the field of lumbar spine surgery during the course of the last century and the beginning of this century. Through the identification of these classic works, we gain an insight into the history, development, and current trends in lumbar spine surgery. The findings of this study identify the papers responsible for many important developments in this field.

The most cited paper in lumbar spine surgery is the classic 1990 work by Boden et al 8 describing magnetic resonance imaging (MRI) findings in 67 individuals without back pain, sciatica, and neurogenic claudication. This seminal study showed that common indications for surgery (e.g., herniated discs, spinal stenosis) can be incidentally found when scanning patients without neurological symptoms. The study also showed that as patients aged, these incidental findings increased in frequency. The study implied correctly that to recommend surgery for a patient, there should be a clear correlation of symptoms and radiographical findings and certainly should not be based on radiographical findings alone. Indications should be clear and unambiguous prior to surgery.

Similarly, the second most referenced study was a radiographical study of degenerative disc disease findings in asymptomatic individuals. In this study by Jensen et al,9 98 asymptomatic patients underwent lumbar spine MRI, with 52% having a bulge at 1 level, 26% having a protrusion, and 1% having a disc extrusion. The paper noted an increased amount of disc bulges with aging and the relatively common finding of a Schmorl node, a herniation of nucleus pulposus through the bony and cartilaginous endplate into the vertebral body. This paper aimed to correlate LBP with disc pathology, concluding “bulges or protrusions in people with low back pain may frequently be coincidental.”

The third most cited paper was the 2000 publication of Fairbank and Pynsent10 reviewing the Oswestry Disability Index, the outcome-measure questionnaire most commonly used to evaluate LBP. The Oswestry Disability Index is a self-administered questionnaire detailing activities of daily living that takes less than 5 minutes to complete. Published originally in 1980 and since translated into many other languages, it has become an often-used tool in spine research and in evaluating standards of medical care worldwide.

The oldest paper, published in 1949, was by Nicoll,99 which described the relationship of traumatic lumbar instability with the posterior ligament complex. This paper is one of the building blocks that led to the 3-column model of Denis,108 frequently used to determine post-traumatic lumbar spine instability. If 2 or more of the columns (anterior, middle, and posterior) are damaged, then the spine is deemed to be “unstable.”

The most recent paper, published in 2010, was by Deyo et al,91 which described the trends and complications of surgery for spinal stenosis in Medicare patients from 2002 to 2007. The study demonstrated the increased rate of fusion surgical procedures for spinal stenosis during the study time span and the increased morbidity rates of fusion over simple decompression. The 100th paper on the list by Weinhoffer et al 107 was a biomechanical study revealing that intradiscal pressures increased significantly during flexion in discs above an instrumented spinal segment. The intradiscal pressure increased as the number of levels involved in the fusion increased. Because intradiscal pressure at the segment adjacent to the fusion is associated with adjacent segment disease,109 this study contributed to the evolving and controversial topic of predicting and evaluating adjacent segment disease.

LBP was the most popular topic in the top 100 papers, with 23 papers dedicated to it. It is highly prevalent in society and has significant impact in health care, with a cost ranging from $84 billion to $625 billion annually.110 Of all physical and mental health conditions, it is the fourth largest productivity burden for US employers.111 It affects up to 80% of the population. One-half of working Americans have back pain symptoms every year.112 It is the leading care of disability in Americans younger than 45 years and the second most common reason to see a doctor in the United States.112 Effective treatment of LBP is limited by its poorly understood pathogenesis. The number of posterior fusions has increased dramatically during the past decades. In 1996, the Food and Drug Administration approved intervertebral fusion cages. At this point, the increased rate of fusion took a noticeable jump.113 From 1998 to 2008, the number of posterior fusions per year increased 3-fold.114 , 115 Three of the top 100 most cited papers revolve around the popular and controversial issue of surgical fusion versus conservative management for chronic LBP. The trial of Fritzell et al 18 (14th most cited paper) suggested an advantage of fusion over nonsurgical care for degenerative discs in 2001 and is often cited in lumbar spine surgery. However, other studies in the top 100 have not shown this advantage, including the studies by Brox et al 54 and Fairbank et al,87 and showed no clear evidence that spinal fusion was more beneficial than intensive rehabilitation using cognitive behavior principles for chronic LBP.

Three of the authors were credited with 4 or more publications. Deyo was the most prolific of all of the authors on the top 100 list. First author on 5 publications, his name appears as a contributing author on 9 of the top 100 papers. His papers focus on outcomes, quality of life, role of physical examination, surgical indications, and morbidity surrounding surgery in the lumbar spine. Boden had 4 works in the top 100 focusing on bone morphogenetic protein, spinal fusion, imaging for patients with LBP, and operative decision making for patients with herniated lumbar discs. Weinstein focused on operative decision making, spinal stenosis, and trends of spinal surgery over time. Interestingly, in 2006, all 3 of the aforementioned most prolific authors contributed to 1 study, the SPORT (Spine Patient Outcomes Research Trial) study (28th most cited article). In this study that spanned 13 spine clinics in 11 states, patients with sciatica from lumbar disc herniation were divided into standard discectomy versus usual nonoperative care groups. The intent-to-treat analyses showed that improvements were in favor of surgery but were small and not statistically significant for the primary outcomes.

Of the top cited papers, only 4 were published before 1980. Previous studies have suggested that older papers are more likely to be cited.116 However, this may be misleading due to the phenomenon of “obliteration by incorporation,” the process whereby data from truly classic papers are cited less frequently as they are absorbed into the body of current knowledge.111 In this study, the journal Spine produced the largest number of articles in the top 100 list. It must be noted that when evaluating contributions by various journals, those journals with bimonthly publications and those that have been in circulation for the longest time have more chance of being cited by other authors.

This study has several limitations. Although Thomson Reuters Web of Knowledge helped identify commonly cited lumbar spine surgery papers, it was difficult to determine the true “lead” author of each paper. For this reason, the first author was assumed to be the primary contributor to the work and this was used to create the ranking of authors according to the number of publications. Another limitation to this study is the problem of “incomplete citing,” which is described as the erroneous manner in which some citations are made in an effort to convince or persuade the readership of that particular journal, instead of giving credit to those who most significantly influenced the work. Using the impact factor as a marker for quality and rank of a journal is a possible limitation of our study. The impact factor is published annually by Thomson Reuters and is broadly based on the number of citations for a given journal. It is frequently used as an indicator of the importance of a journal to its field (although it should not be used as an indicator of a specific article's significance). The strengths and weakness of the impact factor have been discussed widely in the literature. One notable weakness is the short time frame (2 yr) that is factored into its calculation, putting fields that take longer to accumulate citations at a disadvantage.117 Another weakness is the inclusion of noncitable items in the calculation for the impact factor, including letters, book reviews, and news items.118 Eugene Garfield, the man who created the impact factor, stated that although it “is not a perfect tool to measure the quality of articles ... there is nothing better ... and is, therefore, a good technique for scientific evaluation.”119 Another limitation is the subjective nature of choosing which papers are relevant to include in the top 100 list and which should be excluded because of irrelevance to lumbar spine surgery. Finally, because the key word “lumbar spine surgery” was searched, it is possible that important contributions were missed if they did not include this specific word used for the database query, constituting another weakness.

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CONCLUSION

To our knowledge, this study is the first to identify the 100 most cited papers in lumbar spine surgery. It provides an insight into the development and trends within this challenging subspecialty. This paper identifies those individuals whose contributions to the ever-growing body of knowledge have provided guidance and suggestions for further investigation.

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Key Points

  • The most cited article was found to be the classic paper from 1990 by Boden et al that described MRI findings in individuals without back pain, sciatica, and neurogenic claudication showing that spinal stenosis and herniated discs can be incidentally found when scanning patients.
  • The second most cited study similarly showed that asymptomatic patients who underwent lumbar spine MRI frequently had lumbar pathology.
  • The third most cited paper was the 2000 publication of Fairbank and Pynsent10 reviewing the Oswestry Disability Index, the outcome-measure questionnaire most commonly used to evaluate LBP.
  • The majority of the papers originate in the United States (n = 58) and most were published in Spine (n = 63).
  • Most papers were published in the 1990s (n = 49), and the 3 most common topics were LBP, lumbar spine biomechanics, and disc degeneration.
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                                                        Keywords:

                                                        top 100; classic; most cited; lumbar spine; spine surgery

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