Abstract

Background: In this study, we aimed to examine the development of knowledge on pectus deformities through a meticulous analysis of the 100 most-cited articles published on this topic.

Methods: Publications related to pectus deformities from January 1975 to April 2020 were scanned using the Web of Science Core Collection database. The publications were ranked from maximum to minimum according to the number of citations and were examined in detail.

Results: The 100 articles were published in 27 different journals and received a total of 8,290 citations. The average of the impact factors of journals in 2018 was 4.441. The mean citation density of all articles was 5.1±3.8. In the past years, a surgical technique definition and experience transfer were more frequently used, while complications and technical details were started to be presented in recent years.

Conclusion: Our study results suggest that the studies of pectus deformities would continue and, from now on, issues such as complications and technical details would come to the forefront in the articles.

Repair surgeries of pectus deformities have continually advanced and become an important area of research interest due to their serious aesthetic issues and functional limitations. Many leading surgeons have described techniques and shared their experiences throughout the history. The first publication concerning pectus excavatum in the literature belongs to Bauhinus and Schenck von Grafenberg,[1] who described the case of a male patient in 1594; however, the first surgical intervention, a costal cartilage excision, was reported by Meyer in 1911.[2] To date, many articles have been written, many techniques have been defined, and experiences with these techniques have been shared frequently on pectus deformities, dating back to the early 20^th century in the field of surgery.

Bibliometric analyses are the studies which best show knowledge memory in a research area. In many areas, bibliometric analyses have been conducted, and the number of citations and articles has been shown to be useful in a particular area. In addition to general areas such as cardiac surgery and general thoracic surgery, bibliometric studies have been conducted on subspecialty issues, such as burns and rheumatoid arthritis.[3-6]

In the present study, we aimed to examine the development of knowledge on pectus deformities through a meticulous analysis of the 100 most-cited articles published on this topic.

Methods

Publications related to pectus deformities from January 1975 to April 2020 were scanned in the Web of Science Core Collection database. The key terms "chest wall" OR "pectus deformit*" OR "pectus carinatum" OR "pectus excavatum" were searched, and duplicate publications were excluded. The publications were ranked from maximum to minimum according to the number of citations, full-texts of the first 100 publications were obtained, and the publications were examined in detail. Articles that dealt with subjects other than pectus deformity or the main subject of another study, such as breast cancer, chest wall tumors, and Marfan syndrome were excluded from the study.

The names of the journals, number of citations, year of publication, citation density (citation number/time since publication), principal author and country, type of article and subject were examined for the 100 most-cited articles. The impact factors of journals in 2018 were examined.

Since this study is a bibliometric analysis and publicly available information was compiled, ethical approval was waived.

Statistical analysis
Statistical analysis was performed using the IBM SPSS version 25.0 software (IBM Corp., Armonk, NY, USA). The suitability of the data to normal distribution was checked using the Shapiro-Wilk- Francia test. The Spearman's rho test was used to examine the correlations among variables. A p value of <0.05 was considered statistically significant with 95% confidence interval (CI).

Results

General bibliometric results
Top-100 most-cited articles regarding pectus deformities were determined in order of the number of citations (Table 1). The articles were published in 27 different journals and received a total of 8.290 citations (min 43 - max 638). According to the addresses of their first authors, they were written by 69 authors from 21 countries. There were 29 articles whose average number of citations surpassed 82.9.

Table 1: Rankings of 100 most-cited articles

Table 1: Continued

Table 1: Continued

Table 1: Continued

"A 10-year review of a minimally invasive technique for the correction of pectus excavatum" published in the Journal of Pediatric Surgery in 1998 was the article having the highest total number -638 citations- and also registered the highest number of citations per year with 29.

Journals and impact factors
Of the 100 articles with the highest number of citations, the journal that published the most articles on pectus deformities was the Journal of Pediatric Surgery. While there were 36 publications in this journal, the total number of citations was 3.362. This number of citations constituted 40.5% of all citations received by the articles in the first 100 rankings. This was followed by the Annals of Thoracic Surgery (10 articles), which published the second most articles in the top 100 citation rankings about pectus deformities. The total number of citations in this journal was 698. The journal with the highest number of citations per article was the Journal of Bone and Joint Surgery- American Volume with an average of 177.6 citations.

The mean of the impact factors of the 27 journals with articles among the 100 most-cited in 2018 was 4.441 (1.062-16.494) (Table 2).

Table 2: Impact factors and citation numbers of top 10 journals

Citation density and years of publication
All articles were published between 1980 and 2013, and the mean citation density of all articles was 5.1±3.8 (min 1.2 - max 29). There were 33 articles above this average, and the citation density of the other 67 articles was below the mean density.

The article, with the highest citation density (n=29), was also the article with the highest number of citations: "A 10-year review of a minimally invasive technique for the correction of pectus excavatum".[7] This was followed by the third and seventh most-cited articles "The characteristics of thoracic insufficiency syndrome associated with fused ribs and congenital scoliosis" and "Twenty-One Years of Experience With Minimally Invasive Repair of Pectus Excavatum by the Nuss Procedure in 1,215 Patients" which had the second and third highest citation densities-16.88 and 16.3, respectively.[8,9]

When the articles were sorted by decades, most articles (n=68) in the top 100 were published between 2000 and 2009 (Figure 1). Years with more than three articles published were examined, and 2006 ranked the first (n=11) (Figure 2). The average number of citations for those 11 articles from 2006 was 57.9 (46-91).

Figure 1: Articles sorted by decades.

Figure 2: Years with more than three articles published.

Authors and countries
Kelly was the principal author having the highest number of articles with six. The principal author with the most citations per article was Nuss with 285. The highest numbers of cited publications by country were from the United States (n=55), Germany (n=7), Canada (n=6), and South Korea (n=5) (Figure 3).

Figure 3: World map of top 100 most-cited articles.

Subject
The most discussed topic, with 3,304 citations in 35 articles, was experience transfer regarding results of surgical techniques (Nuss and Ravitch procedures and modifications). In the second place, 10 articles with 786 citations discussed complications following pectus deformity surgery (Table 3).

Table 3: Number of article and citation according to top 10 subject

Technical details and experience transfer related to a surgical technique showed an increasing trend over the last two decades. The articles related to the complications of surgery started to receive high citations after 2000s. Studies on cardiopulmonary functions were found to be highly cited in every period (Table 4).

Table 4: Distribution of the subjects by decades

Types of articles
The article types were classified as 82 original articles (48 retrospective articles, 34 prospective articles), eight review articles, seven case reports, and three meta-analyses.

There was no statistically significant relationship between the impact factor and the number of articles, the number of citations, and the average number of citations (p=0.965, p=0.571, and p=0.372, respectively) (Table 5). However, there was a strong positive correlation (r=0.886) between the number of articles in a journal and the number of citations, which was statistically significant (p<0.001). As the number of published articles increased, the number of citations increased accordingly (Table 6, Figure 4).

Table 5: Relationship between the impact factor and the number of articles, the number of citations, and the average number of citations (n=27)

Table 6: Correlation between the number of articles in a journal and the number of citations

Figure 4: As the number of published articles increases, the number of citations increases accordingly.

Discussion

Bibliometric analyses show what kinds of articles are published on a topic within a historical period, allowing a comprehensive understanding of the parts of a subject having global interest. In this study, we attempted to understand what were done on chest wall deformities over the years, which studies were most cited in other researches, and what was became the gold standard. We found a positive correlation between the number of articles and the number of citations in a journal, suggesting that high-value articles were consistently published. The lack of a statistical relationship between the impact factor and the number of articles in a journal proves that qualitative rather than quantitative values are reflected by the impact factor. The fact that 100 articles were published in 27 different journals by 69 different first authors from 21 countries is an indication that the interest in pectus deformities is quite extensive and meaningful. The average of the impact factors for these journals was also found to be quite high.

The number of citations objectively reflects the strength of the impact of a scientific article and is considered an academic evaluation criterion for researchers. The number of citations is known as the best criterion for analyzing the impact of a journal or of a single article; however, annual citation density is important to compare two articles in a bibliometric study. In this study, the articles ranked the first, third, and seventh in number of citations were the top three according to the citation density. Thus, we consider that the density of citations should be taken into consideration in addition to the number of citations in a bibliometric study.

The fact that 17 authors who published more than one article on the list also underscores the importance of the average number of citations per article. While Kelly authored the most articles, the author with the highest average number of citations per article was Nuss, showing that not only the number of articles should be taken into account. Of note, the Ravitch's articles, which were groundbreaking in pectus deformities by defining an important surgical technique and frequently defining it in comparison with the Nuss procedure in two-technique comparisons, as noted above, remained out of this study, as they were published long before 1975.[10,11]

Sixty-eight of the top 100 articles cited were published between 2000 and 2009. In this peak period, a "golden age" of academic studies related to pectus deformities, mainly experienced with a single surgical technique (n=25), complications (n=9), and cardiopulmonary function (n=7) were studied and presented on the academic platform.

The articles designed prospectively constitute 41.4% of the original articles, while the retrospective studies were on experience transfer in the form of larger series of cases with long follow-up.

The main limitation of this study is that only Web of Science Core Collection data and post-1975 data were evaluated. However, Web of Science is a generally accepted database that scans SCI-EXPANDED, SSCI, A & HCI, CPCI-S, CPCI-SSH, BKCI-S, BKCI-SSH, ESCI indexes and contains the majority of the citations available.

In conclusion, bibliometric analyses play an important role in determining the non-contact points of a subject, understanding the most controversial issues, and even choosing the journal to which an article would be submitted. According to the number and density of citations, a surgical or non-surgical technique begins to be undertaken as a routine or the gold standard in practice and is the pioneer of successive articles in this regard. Our study results suggest that the studies of pectus deformities would continue and, from now on, issues such as complications and technical details would come to the forefront in the articles.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
The authors received no financial support for the research and/or authorship of this article.

References

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11) Ravitch MM. Operative correction of Pectus Carinatum (pigeon breast). Ann Surg 1960;151:705-14.