We conducted a comprehensive search using the advanced search feature of the WOSCC database Pubmed database and Embase database to collate literature pertaining to free flaps in plastic surgery procedures.

Our analysis was restricted to literature published from January 1, 2004 to July 23, 2025, identifying a total of 1,438 articles. We further refined the selection to include only “articles” or “reviews”. Utilizing CiteSpace software, we thoroughly reviewed titles and abstracts to eliminate any irrelevant or duplicate articles, resulting in a final tally of 1,407 articles. The complete record for each article was downloaded. The detailed methodology and search strategy is outlined in Figure 1 and Supplementary Figure S1.

For visualizing geographical distribution of publications, tools such as the Scimago Graphica (version 1.0.36) and Microsoft Charticulator (https://charticulator.com/) were employed. Besides, analysis of authors and co-cited authors, journals, institutions, references, and keywords mainly involved software and websites like VOS viewer (version 1.6.20) (13), bibliometrix (14), and Citespace (version 6.2.R6).

Figure 2A illustrates the publication trends, revealing a consistent upward trajectory in publication volume. In 2022, a total of 109 publications were recorded, representing a substantial increase—approximately three to four times the publication count in 2004—indicating a period of explosive growth from 2019 to 2025. To further assess the progress of research in this field, we excluded incomplete data for 2025 and performed a linear regression analysis using publication data from 2004 to 2024, as shown in Figure 2B. The results indicate a steady increase in the number of publications, with the fitted equation given by: y = 4.170x − 8335, R² = 0.8954.

Research in this field involves contributions from 69 countries. Figure 3A illustrates the global distribution of publications in this domain, with darker blue shades indicating a higher volume of publications. To provide further detail, we consolidated the publication data from each country, with Table 1 enumerating the top 10 countries with the highest research output. The United States leads with 900 articles, accounting for 63.97% of the total publications, and holds the highest citation count at 6,318. Germany follows with 436 articles. As shown in Figure 3C, the steeper slopes of the purple, brown, and red lines suggest that the United States, Germany, and China are experiencing pronounced growth in publication numbers, highlighting their strong potential for future scientific contributions.

The chord diagram in Figure 3B illustrates the collaborative networks among countries, with Germany, the United States, Italy, and China being key players in international research partnerships. Lastly, Figure 3D reveals that France was one of the pioneering countries in this field, while Switzerland, through its close international collaborations, demonstrates significant scientific research potential.

This study identified 1,175 institutions actively engaged in research within this field. As shown in Figure 4A, the top 24 contributing institutions are listed, with the University of Texas System leading with 58 publications. Ongoing monitoring of this institution's research output may provide valuable insights into emerging trends and directions in the field.

To further examine institutional collaboration, a co-authorship network map was generated based on total link strength (Figure 4B). The University of Michigan and Heidelberg University were the most influential institutions, with total link strengths of 1,618 and 1,540, respectively.

A total of 6,273 authors were identified as contributors to research on free flap procedures in plastic surgery. Among them, KNESER U (32 publications) and HORCH RE (17 publications) were the most prolific. To evaluate academic impact, the H-index—a metric that reflects both productivity and citation impact—was used to identify the top 10 most influential authors (15). These authors are visualized in Figure 4C, and their H-index values are listed in Table 2. Their publication records and citation metrics underscore their significant academic influence in the field.

Author co-citation analysis, which identifies authors cited together in the same reference list, is depicted in Figure 4D. KOSHIMA I (172 citations) and WEI FC (122 citations) were the most frequently co-cited authors. This analysis illustrates the intellectual structure and scholarly interconnectedness of the research community focused on free flap reconstruction.

As shown in the three-field plot (Figure 5A), the United States leads in research output, with its contributions broadly distributed across the top 10 journals. American scholars predominantly publish in Annals of Plastic Surgery and Journal of Plastic, Reconstructive & Aesthetic Surgery, the latter also receiving substantial input from the United Kingdom and exerting considerable disciplinary influence.

A dual-map overlay of journals (Figure 5B) illustrates citation trajectories across research fields. Colored paths trace citation flows, primarily along two routes: from HEALTH, NURSING, MEDICINE and DERMATOLOGY, DENTISTRY, SURGERY to MEDICINE, MEDICAL, CLINICAL and NEUROLOGY, SPORTS, OPHTHALMOLOGY; and within the originating domains themselves.

Table 3 ranks the top 10 journals by citation frequency and publication volume. According to Journal Citation Reports (JCR), several are Q1 journals, including Plastic and Reconstructive Surgery, Head and Neck, Journal of Plastic Reconstructive and Aesthetic Surgery, Journal of Clinical Medicine, and Journal of Periodontology. Among them, Journal of Plastic Reconstructive and Aesthetic Surgery leads in both publication count (199 articles) and citations (6,423), underscoring its prominence. Annals of Plastic Surgery follows with 89 publications. Figure 5C presents publication trends in the top five journals, highlighting their growing influence.

Co-citation analysis revealed 31,657 entities, forming six major clusters (Figure 5D). Plastic and Reconstructive Surgery had the strongest link strength (148,591), reflecting close collaboration with Annals of Plastic Surgery and Journal of Plastic Reconstructive and Aesthetic Surgery.

Citation and co-citation analyses offer critical insights into the foundational literature of a research field (16). A reference co-citation network was constructed, as shown in Figure 6A, highlighting the seminal works of Hidalgo DA (17), Koshima I (18), and Song (19) as the most influential. Notably, these cornerstone studies represent distinct publication types: a case report, a research article, and a review, respectively (Table 4).

The timeline view in Figure 6B illustrates the evolutionary path of research in this domain. Clustering analysis of cited references indicates two primary research hotspots in the application of free flaps in plastic surgery. The first centers on novel clinical indications—such as gingival recession—reflecting the expanding scope of free flap procedures. The second involves technological and procedural advancements aimed at improving flap survival and aesthetic outcomes. These include refinements to established techniques, such as microvascular surgery and flap thinning (20), as well as the integration of emerging technologies like robotic microsurgery and 3D printing, which further enhance the precision and efficacy of flap transplantation (Figure 6C).

Visual keyword analysis enables the identification of key clinical focus areas in the application of free flaps within plastic surgery. In the co-occurrence map (Figure 7A), core terms such as “reconstruction,” “complication,” and “microsurgery” emerge prominently, reflecting the central themes in this field. Keyword clusters are organized into distinct thematic groups. The dark blue and light blue clusters primarily represent mature clinical applications, such as managing complex limb trauma caused by open fractures and procedures like urethroplasty. The temporal sequence shown in the timeline map (Figure 7B) further supports the maturity of these themes.

By contrast, the green and red clusters denote rapidly evolving research areas, including reconstruction of the head, face, and neck, as well as post-oncologic or post-mastectomy chest wall and local soft tissue reconstruction. The purple cluster highlights recent technological innovations, such as robotic-assisted microsurgery, which is receiving growing attention. These developments are further validated by their temporal progression in Figure 7B.

To provide a longitudinal perspective, we constructed a keyword cluster timeline visualization (Figure 7C). After excluding broad terms like “free flap,” the visualization still emphasizes two major thematic axes: clinical applications and technological advancements. The clinical axis includes terms such as “breast reconstruction” and “gingival recession,” while the technological axis features innovations like “robotic microsurgery.” In addition, keywords related to postoperative complications and aesthetic outcomes underscore an increasing emphasis on patient-centered care in reconstructive surgery.

A keyword burst analysis (Figures 7D,E) further illustrates emerging research hotspots and their respective timeframes. Early interest in “muscle flap” (2006–2013) highlights the clinical focus during that period on muscle-based flap techniques. More recently, terms such as “neck reconstruction” (2017–2018), “mandibular reconstruction” (2020–2022), and “breast reconstruction” (2024–2025) have gained traction. Notably, “robotic microsurgery” (2023–2025) has emerged as a significant focus area, consistent with the growing integration of advanced technologies into surgical practice.

To further examine the disciplinary breadth of this research, a domain-based overlay analysis was conducted (Figure 7F). Among the 1,407 articles analyzed, 65 unique subject areas were identified. Surgery emerged as the dominant category (n = 921), followed by Dentistry, Oral Surgery & Medicine (n = 157), Otorhinolaryngology (n = 129), and Oncology (n = 71). Forensic-facial reconstruction and post-oncologic repair remain core applications of free flaps. Notably, the overlay map reveals significant intersections between medical disciplines and technology-driven fields: Multidisciplinary Sciences and Biomedical Engineering (green cluster), Computer Science and Robotics (red cluster), and Health Care Sciences (blue cluster). These intersections suggest an encouraging trend toward cross-disciplinary integration, pointing to a future where industrial technologies play an increasing role in surgical innovation.

Over the past two decades, both the variety of free flaps and the scope of research on their clinical applications have expanded significantly. Notably, global research on free flaps for plastic reconstruction has surged, especially between 2019 and 2022, a trend likely driven by the increasing prevalence of cancer.

In terms of publication output, the United States leads, nearly doubling the output of Germany, and excels in total citations while maintaining a high average citation per paper. This reflects the substantial academic impact and high quality of its research. China has demonstrated impressive research momentum, surpassing previous leaders such as Germany and the United Kingdom in growth rate. Both the U.S. and China exhibit robust national collaborations, with the U.S. also showcasing a strong institutional presence, though Germany remains notable for its contributions. South Korea, China, and the United Kingdom, despite their significant research outputs, still face challenges in enhancing their institutional influence.

Among the 6,273 researchers, Kneser U and Horch RE stand out with the highest research outputs, H-index, and g-index, guiding future research directions. The co-authorship network reveals a strong preference for domestic collaboration, highlighting the need for more international partnerships to foster knowledge exchange, resource sharing, and innovation.

Regarding journal publications, The Journal of Plastic, Reconstructive & Aesthetic Surgery and The Annals of Plastic Surgery lead in article volume, with publications increasing annually. The U.S. and the U.K. contribute the highest number of articles. Despite fewer publications, Plastic and Reconstructive Surgery—a Q1 journal—holds the highest local citations and co-citations, underscoring its significant influence and reputation.

The results from keyword extraction and analysis indicate that free flaps are a current research hotspot in the field of plastic surgery, reflecting the latest trends in the field. Current studies predominantly fall into two main categories: the practical clinical applications of free flaps and the technologies related to free flaps.

Our study possesses several limitations. Firstly, by selecting only the WOSCC database, Pubmed database and Embase databases, we cannot ensure comprehensive coverage of literature on free flaps within plastic surgery. Secondly, we restricted our analysis to literature written in English, which introduces a potential language bias.