Trends in Breast Augmentation Research: A Bibliometric Analysis

Background Breast augmentation is one of the most demanded procedures in plastic surgery and one of the most commonly performed by plastic surgeons. However, a bibliometric analysis of breast augmentation has not been published in recent years. The current study aimed to use a bibliometric analysis to conduct a qualitative and quantitative evaluation of breast augmentation research and provide the research trends and hotspots in this field. Methods Publications on breast augmentation research were extracted from the Web of Science core collection database. VOSviewer 1.6.18 was used to assess co-authorship, co-occurrence, citation of countries, institutions, authors, and journals, as well as hotspot keywords. Results On February 8, 2022, 4637 records of breast augmentation research published from 1985 to 2021 were collected. The bulk of the retrieved studies were original research articles (n = 2235, 48.20%). A total of 1053 (22.71%) papers were open access. The annual publication output increased annually. The USA was the driving force in this field and had a strong academic reputation. The top-contributing institution was the University of Texas MD Anderson Cancer Center (2.37%, with 110 publications). Plastic and reconstructive surgery (998 publications, 21.52%) published the most research in this field and was also the most frequently co-cited journal (22,351 citations, total link strength (TLS): 409,301). Clemens MW (68 publications, 1.47%) was the most prolific author, and Spear SL (1456 citations, TLS: 27,231) was the most frequently co-cited author. The research hotspots included the following four aspects: safety and effectiveness of breast implants, implant-based breast reconstruction, breast cancer incidence after breast implantation, and breast implant-associated anaplastic large-cell lymphoma (BIA-ALCL). The research trends were BIA-ALCL, implant-based breast reconstruction, BREAST-Q, acellular dermal matrix, capsular contracture, and autologous fat grafting. Conclusion The present study provides a panoramic view of breast augmentation research in plastic and reconstructive surgery. This novel comprehensive bibliometric analysis can help researchers and nonresearchers alike to rapidly identify the potential partners, research hotspots, and research trends within their areas of interest. Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.


Introduction
Breast augmentation is one of the most demanded procedures in plastic surgery [1][2][3][4][5] and one of the most commonly performed procedures by plastic surgeons [6].
Reports of breast augmentation surgery date back to 1895, when a lipoma was successfully transplanted from the back to the breast defect in a mastectomy patient [6][7][8][9]. In the 1930s, implantation of a glass ball into a patient's breast was the first implant-based breast augmentation [8]. The first modern breast implant was developed in 1961, and since then, there have been significant developments in implant composition and design [10].
Many reviews have summarized the clinical applications and experimental studies of breast augmentation in aesthetic plastic and reconstructive surgery [1,5,6,[10][11][12][13]. However, due to the rapid growth of scientific literature, it is difficult to generate a comprehensive assessment of this field. Manually compiling and systematically reviewing all publications in this field would be time-consuming, if not impossible.
Bibliometric analysis is a subject that quantitatively describes the current status, research hotspots, and trend information of science and technology based on the unique parameters of the published literature (such as countries, institutions, and authors), using a combination of mathematical and statistical methods. Both researchers and nonresearchers can use this information to quickly achieve specific aims in their area of interest (for example, to identify active partners, research topics, landmark documents, or other useful information) [14].
Bibliometric analysis was first applied by Pritchard in the 1960s and has been widely used in medicine and more recently in the plastic surgery literature [15][16][17].
In recent years, there have been many studies on breast augmentation, but a bibliometric analysis of breast augmentation has not been published recently. Therefore, we used a bibliometric analysis to conduct a qualitative and quantitative evaluation of breast augmentation research, and on this basis, we expect to identify emerging trends and hotspots in this field and predict future research priorities.

Methods
The Web of Science core collection online database was queried with the following search string: Tl = (((breast augmentation)) OR (augmentation mammaplasty)) OR (breast implants)) OR (breast lipoaugmentation). Only original articles and reviews written in English and published from 1985 to 2021 were included.
Two investigators independently screened the literature, collected information, and cross-checked the references, and disagreements were resolved by a third author. VOSviewer 1.6.18 was used to assess the co-authorship, cooccurrence, citation of countries, institutions, authors, journals, and hotspot keywords. The size of the node represents the occurrence frequency of the relevant parameters, the thickness of the connection between nodes represents the degree of association, and the different colors represent different modules in the visualization mapping. The total link strength (TLS) attribute indicates the total strength of the co-authorship links of a given researcher with other researchers. The journal impact factor (IF) was obtained from the Journal Citation Reports by Thomson Reuters on January 30, 2021.

Publication Output
From 1985 to 2021, a total of 4637 publications were identified from the Web of Science core collection online database (2022.2.8). These included 2235 (48.20%) original research articles, 747 (16.11%) letters, 552 (11.90%) meeting abstracts, 546 (11.77%) editorial materials, 234 (5.05%) review articles, 168 (3.62%) proceedings papers, and 155 (3.34%) other articles, including early access papers, among other publications (Fig. 1). A total of 1053 (22.71%) papers were open access. The growth of the annual publication output is shown in Fig. 2. Of these, 457 (9.86%) papers were published in 2021, and 412 (8.89%) papers were published in 2020. The annual publication output increased annually and increased to 457 in 2021 to more than two times the annual publication output in 2011.

Analysis of Countries/Regions
All publications were distributed among 78 countries/regions. The annual national publication output of the ten most productive countries/regions is shown in Fig. 3. Since 2017, the annual growth rate of publication output has increased in England, followed by China, Germany, and Brazil. The ten most productive countries/regions are shown in Table 1. The USA had the highest output, with 1682 publications (36.27% of 4637 publications), followed by England (9.08%, with 421 publications), Italy (7.85%, with 364 publications), Canada (4.72%, with 219 publications), China (4.27%, with 198 publications), and Germany (4.23%, with 196 publications). The international collaboration network analysis is shown in Fig. 4. The size of the node indicates the number of publications issued in a specific country/region, and lines represent the frequency of cooperation between countries. Ten clusters were obtained based on this information. As shown in Fig. 4, the USA was the main driving force with a high academic reputation in breast augmentation research, which was confirmed by the following characteristics: number of publications (1682), H-index value (81), number of partners (45), total number of citations (31099), and TLS (388). Brazil had the highest number of citations per publication (CPP: 28.47). The total number of research publications from other countries, such as England, Italy, Canada, Germany, France, and Australia, was relatively low. However, their publication output still reflected the considerable progress made by these countries in this field, which was closely related to their collaborations with the USA.

Analysis of Institutions
All publications were distributed among 3450 institutions. The ten most productive institutions are shown in Table 2  The network visualization map of cooperative institutions related to this research field is shown in Fig. 5. The nodes represent institutions, and lines between the nodes represent cooperative relationships. As shown in Fig. 5

Analysis of Journals and Co-cited Journals
The ten most productive and co-cited journals are listed in Tables 3, 4. A total of 520 journals published the relevant publications, of which 100 journals published more than five publications. In total, 2663 publications were published in the top ten active journals, which accounted for half of the publications on the Web of Science core collection online database. Plastic and reconstructive surgery (998 publications, 21.52%) published the most research in this field and had an IF of 4.73 in 2021, followed by Aesthetic Plastic Surgery (481 publications, 10.37%), Aesthetic Surgery Journal (391 publications, 8.43%), Journal of Plastic Reconstructive and Aesthetic Surgery (240 publications, 5.18%), and Annals of Plastic Surgery (233 publications, 5.02%). Among the top ten most productive journals, International Journal of Radiation   (70). More than half of the top ten co-cited journals were in Q1. Plastic and reconstructive surgery was recognized as a breast augmentation research resource and had an important influence on this research field.

Analysis of Authors and Co-cited Authors
A total of 13,320 authors have published papers on breast augmentation. The ten most productive authors and the ten top co-cited authors are shown in Table 5. Clemens MW (68 publications, 1.47%) published the most publications,   According to Fig. 8, the size of the node represents the number of specific publications that have been cited. The more the literature is cited, the larger the diameter of the node. Table 6 summarizes the top 100 most-cited   We found that the research hotspots included the following four aspects: safety and effectiveness of breast implants (Cluster 1, red zone), implant-based breast reconstruction (Cluster 2, green zone), breast cancer incidence after breast implantation (Cluster 3, blue zone), and breast implant-associated

Analysis of Author Keywords and Keyword Cooccurrence Clusters
The annual keyword publication output of breast augmentation research is shown in Fig. 9. A total of 3316 keywords were considered in the analysis. Figure 10 shows a network map of keyword co-occurrence, where there are    210 items (occurrence [5) and 2253 links. Each item represents the frequency of a keyword appearing in the topic articles of our research. The larger the item is, the more clinical research on the subject surrounding the specific keyword. The thicker the line between the keywords, the higher the frequency of this group of keywords appearing in the clinical articles. The rapid identification of these keywords can help us quickly identify the hot topics studied in the literature. In addition, there are 12 clusters in total, and the name of each cluster is determined according to the number of items. After this analysis, we can further determine specific categories with an overview of this study derived from all keywords. The clinical significance of the co-occurrence keyword cluster map is that each cluster contains several different keywords for the subtheme of the study. Therefore, it can provide a convenient approach to help researchers who are concerned about the subtheme of this research field to quickly identify which other relevant keywords are contained in the subline they are concerned about from a global perspective.   (Fig. 11).
The timing diagram showed that the research trends focused on breast implant-associated anaplastic large cell lymphoma (BIA-ALCL), implant-based breast reconstruction, and autologous fat grafting (Fig. 11).

Discussion
Breast augmentation is one of the most commonly performed aesthetic surgeries every year [1]. This study identified 4637 publications related to breast augmentation research through the Web of Science core collection database from 1985 to 2021. This is probably the first bibliometric analysis in the available literature evaluating articles published on breast augmentation. During 2016-2021, the annual publication output increased steadily, and the USA was the main driving force with a high academic reputation in breast augmentation research. Furthermore, plastic and reconstructive surgery (USA) was recognized as a breast augmentation research resource and had an important influence on this research field. Clemens MW from the University of Texas MD Anderson Cancer Center published the most publications (68 publications, 1.47%). His most-cited article mainly reported that surgical management with complete surgical resection is necessary to achieve optimal event-free survival in patients with BIA-ALCL [18].
Spear SL from the Department of Plastic Surgery at Georgetown University Hospital (USA) ranked first among all co-cited authors. His three most-cited articles focused on the safety and effectiveness of silicone breast implants and capsular contracture after prosthetic breast reconstruction [19][20][21]. These articles have been considered reliable reference resources for subsequent research.
Additionally, the paper entitled ''Anaplastic T-cell lymphoma in proximity to a saline-filled breast implant'' published in Plastic and Reconstructive Surgery was the most co-cited reference, which focused on the causal relationship between the presence of saline-filled breast implants and the development of non-Hodgkin's lymphoma involving the breast. In this study, the researchers were involved in the care of a young woman with anaplastic T-cell lymphoma in proximity to saline-filled breast implants, in whom antineoplastic therapy was successfully accomplished without necessitating removal of the breast implants; the authors considered the presence of implants not to be an obstacle to the delivery of effective radiation therapy. A causal relationship between the presence of a saline-filled breast implant and the development of non-Hodgkin's lymphoma involving the breast was not demonstrated [22]. Therefore, this article may provide insights for the study of the association of inflammatory or neoplastic diseases associated with saline-filled breast implants.
The second most-cited article was ''Cell-assisted lipotransfer for cosmetic breast augmentation: supportive use of adipose-derived stem/stromal cells'' published in Aesthetic Plastic Surgery. This article assessed the cell-assisted lipotransfer known as a strategy to overcome the problems with lipoinjection [23]. Lipoinjection is a promising treatment but has some problems, such as unpredictability and a low rate of graft survival due to partial necrosis. Yoshimura et al. used autologous adipose-derived stem cells in combination with lipoinjection and reported preliminary results suggesting that cell-assisted lipotransfer was effective and safe for soft tissue augmentation and superior to conventional lipoinjection [23].
The third most-cited article assessed long-term trends in rates and types of immediate breast reconstruction. Albornoz et al. suggested that the significant rise in immediate breast reconstruction rates in the USA correlated closely to an increase in implant use, and the reason for the increase in implant use was changes in mastectomy patterns, such as increased bilateral mastectomies [24].

Research Hotspots
As shown in the network map of co-cited references (Fig. 8), the research hotspots included the following four aspects: safety and effectiveness of breast implants, implant-based breast reconstruction, breast cancer incidence after breast implantation, and breast implant-associated anaplastic large-cell lymphoma (BIA-ALCL).
''Safety and effectiveness of breast implants'' (Cluster 1) included the most publications and indicated that the most common local complication was capsular contracture. In the sixth and tenth most-cited articles, Handel N et al. noted that the longer the implant was in place, the greater the cumulative risk of developing capsular contracture, and textured breast implants were better than smooth breast implants in decreasing the rate of capsular contracture [20,21,[25][26][27][28][29].
''Implant-based breast reconstruction'' (Cluster 2) indicated that the significant increase in immediate implantbased breast reconstruction rates was closely related to the expansion of implant use [19,30]. The fourth, eighth, and ninth most-cited articles assessed implant-based reconstruction and additional options for this treatment [31][32][33].The fifth and seventh most-cited articles evaluated complications and clinical risk factors following implant breast reconstruction [34,35].
''Breast cancer incidence after breast implantation'' (Cluster 3) indicated the possibility that women who received implant-based breast augmentation for cosmetic purposes had an increased long-term risk of developing cancer. Janowsky EC et al. mentioned that there was no evidence of an association between silicone-gel-filled breast implants and any of the individual connective tissue diseases, all defined connective tissue diseases combined, or other autoimmune or rheumatic diseases [36,37]. Brisson J et al. mentioned that women undergoing breast augmentation do not appear to have an increased long-term risk of developing cancer [38,39].
''Breast implant-associated anaplastic large-cell lymphoma'' (Cluster 4) showed that the association between breast implants and BIA-ALCL has been confirmed [22,[40][41][42][43][44][45]. The eleventh most-cited article by De Jong D in 2008 discussed whether the risk of anaplastic large T-cell lymphoma was associated with breast implants [41]. This article was seminal in this field, as evidenced by publication in JAMA-Journal of the American Medical Association, a high-impact factor medical journal. BIA-ALCL is a rare cancer in patients with breast implants, but the incidence is increasing [46,47]. The nineteenth mostcited article by Hu H in 2016 identified bacterial biofilms in BIA-ALCL. Bacterial biofilms and a distinct microbiome found in BIA-ALCL samples suggest a possible cause of infection, and thus strategies to reduce their contamination should be more widely studied and practiced [42]. The twenty-second and twenty-eighth most-cited articles detailed that high-surface-area textured implants had been shown to significantly increase the risk of BIA-ALCL [43,48]. The overall incidence of BIA-ALCL was 1.15 per 1000 textured implants and 1.79 per 1000 patients with textured implants, and the median time to diagnosis was 10.3 years (range, 6.4-15.5 years) [49]. The National Comprehensive Cancer Network (NCCN) guidelines on BIA-ALCL have been endorsed by the FDA and widely advocated by national professional societies, and the consensus guidelines have helped establish standardization of treatment for BIA-ALCL at all stages of the disease [50]. The treatment includes capsulectomy and implant removal at an early stage. However, systemic therapy is needed to include chemotherapy, radiation therapy (residual disease), and brentuximab vedotin at stages II to IV; complete capsular removal is the most important factor, and most patients can be cured [51].

Research Trends
According to analysis of the most frequently used keywords and the timing diagram (Fig. 8), the research trends were as follows: breast implant-associated anaplastic large cell lymphoma (BIA-ALCL), implant-based breast reconstruction, BREAST-Q, acellular dermal matrix (ADM), capsular contracture, and autologous fat grafting.
The paper entitled ''Prepectoral Implant-Based Breast Reconstruction: Rationale, Indications, and Preliminary Results'' authored by Sigalove S and published in 2017 is the most frequently cited article associated with implant-based breast reconstruction among recently published publications. In this study, Sigalove S reported that by placing the implant prepectorally, problems related to pectoralis muscle elevation could be avoided [52]. Breast implant pocket locations are subglandular, subpectoral, subfascial, partially retropectoral, totally submuscular, and dual plane. Shen Z reported that the subfascial and subpectoral planes were safe and effective for controlling the overall complication rate and achieving a high satisfaction rate. The muscles of the chest, which are related to the optimal placement of implants, play an important role in breast augmentation surgery. The amount of muscle varies from patient to patient and may be a factor in determining whether submuscular or subglandular placement is best [53,54]. Tebbetts JB mentioned that dual-plane augmentation mammaplasty adjusts the relationship between the implant and tissue to ensure adequate soft tissue coverage while optimizing implant-soft-tissue dynamics to offer more benefits than a single pocket location for various breast types [55].
The BREAST-Q can be used to study the impact and effectiveness of breast surgery from the patient's perspective. The BREAST-Q has the potential to support advocacy, quality metrics, and an evidence-based approach to surgical practice by quantifying satisfaction and healthrelated quality of life [56].
Acellular dermal matrix (ADM) is developed from human skin (such as FlexHD, AlloMax, AlloDerm) or animal skin (such as SurgiMend), from which the cells are removed and the support structure is retained [57]. ADM has been widely used as an adjunct material for tissueexpander or implant-based breast reconstruction [34]. Implant-based breast reconstruction has been enhanced by ADM, and immediate single-stage direct-to-implant breast reconstruction with ADM may achieve aesthetic optimization by preserving the mastectomy skin envelope [30,34]. Some researchers have demonstrated that human cadaveric skin-based products such as FlexHD, Derma-Matrix, and ready-to-use AlloDerm have a similar risk of complications compared with those of freeze-dried Allo-Derm, which has been used longer [57]. Another researcher mentioned that ADM was related to a greater risk of major complications from immediate implant-based breast reconstruction, especially in patients with a high BMI [58]. However, further investigation is needed. Capsular contracture is a common complication of breast augmentation, and many techniques for prevention and treatment have been reported with inconsistent or variable results. Wagner DS mentioned that surgical capsectomy, prosthesis replacement, and acellular dermal matrix placement are effective methods for the treatment of capsular contracture after breast augmentation [59]. Some investigators suggest that adherence to a surgical technique focused on minimizing bacterial contamination of implants has greater clinical significance than implant surface characteristics when discussing capsular contracture. [60].
Autologous fat grafting for breast augmentation is a growing field, and the safety of this technique has been extensively evaluated [61]. Many authors have explored the effectiveness and safety of breast lipoaugmentation, focusing on volume change, fat retention, overall cosmetic improvement, and patient satisfaction [62]. Li FC mentioned that liposuction and autologous fat grafting were suitable approaches for breast augmentation [63]. Maione L described that the combination of high-profile round implants and fat grafting in breast augmentation can eliminate the risk of implant rotation to improve the aesthetic outcome and patient satisfaction [64,65]. Cell-assisted lipotransfer (CAL) is a novel and promising technique for breast augmentation [66]. In cell-assisted lipotransfer, autologous adipose-derived stem (stromal) cells (ASCs) are used in combination with lipoinjection. This process converts relatively ASC-poor aspirated fat to ASC-enriched fat [67]. ASCs-enriched fat grafts had significantly higher retention rates than conventional fat grafts [68] and these results suggested that cell-assisted lipotransfer is superior to conventional lipotransfer for improving the fat survival rate in breast augmentation [69]. No serious or unexpected adverse events in autologous fat grafting for breast augmentation were reported, and all procedures were found to be safe and well-tolerated in all patients [70]. Time will prove whether these studies, as we mentioned above, will be real trends. There may be shortcomings from insufficient data or analysis, and more progressive studies are needed in the future.

Conclusions
The highest number of publications was from the USA, followed by England, Italy, Canada, and China. The primary collaborators with the USA were England, Italy, Canada, Germany, France, and Australia.
The University of Texas MD Anderson Cancer Center and Spear SL from the Department of Plastic Surgery at Georgetown University Hospital (USA) were the mostcited institution and author, respectively. The most-cited journal was plastic and reconstructive surgery.
The research hotspots included the following four aspects: safety and effectiveness of breast implants, implant-based breast reconstruction, breast cancer incidence after breast implantation, and breast implant-associated anaplastic large cell lymphoma (BIA-ALCL).
This novel comprehensive bibliometric analysis of breast augmentation research can help researchers and nonresearchers alike to rapidly identify the potential partners, research hotspots, and research trends within their areas of interest.
Author Contributions Conceptualization was done by CR and MZ; investigation was carried out by CR and JY; data curation was done by CR, MZ, and JM; writing-original draft preparation were done by CR; writing-review and editing were done by CR, MZ, and JY; supervision and project administration were done by CR and JY. All authors have read and agreed to the published version of the manuscript.
Funding This research received no funding from any public or private organizations/institutions.

Declarations
Conflict of interest The authors declare that they have no conflicts of interest to disclose.
Ethical Approval No ethical approval is required for such studies, as patients are not involved.
Human and Animal Rights This article does not contain any studies with human participants or animals performed by any of the authors.
Informed Consent For this type of study, informed consent is not required.
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