Comprehensive Analysis of the Biomechanical Research of Pelvic Organ Prolapse: A Scientometric Approach

Introduction

The pelvic floor consists of complex and supportive connective tissue and muscles which are intended to counteract gravity and intra-abdominal pressure while providing support for the pelvic organs. When this system is damaged, it is possible to develop pelvic floor dysfunction (PFD), including pelvic organ prolapse (POP).^1,2 The International Urogynecological Association (IUGA) and the International Continence Society (ICS) define POP as the descent or displacement of one or more of the anterior vaginal wall, posterior vaginal wall, or apex of the vagina (uterus/cervix or vaginal cuff scar after hysterectomy).³ The incidence of POP is on an upward trend year by year, with approximately 50% of mothers presenting with POP-related symptoms and 30–50% of adult women being affected by POP.^4,5 About 13% of women have undergone prolapse surgery in their lifetime.⁶ Due to the complexity and variability of the female pelvic floor anatomy, the pathophysiological mechanisms of POP are very complex. Although numerous studies have shown that the occurrence of POP is closely related to the damage of paravaginal support structures and the morphological changes of the uterus and vagina.⁷ However, due to the complex and variable anatomy of the female pelvic floor structure, we are not very specific on the mechanisms responsible for the occurrence of POP. With the wide application of finite element (FE) analysis, researchers have also started to perform mechanical analysis of pelvic floor organs and soft tissues by computer. Although the application of FE analysis to soft tissues is still in its early stages, with the development of computers, medical radiology imaging and image processing software, and the intersection of various disciplines, this field has now emerged as a popular research area.

FE analysis is a modern computer simulation method that divides complex objects into a limited number of small units and replaces the original complex objects by setting different material properties for each small unit. The mechanical analysis of the FE model can be used to observe the displacement, stress, and strain of its internal and external structure under the action of external forces.^8,9 Due to the deep anatomy of the pelvic organs, the interaction of the supporting structures is still highly controversial. Radiology examinations (such as ultrasound, CT, MRI etc) combined with 3D reconstruction technology to establish FE analysis can well simulate the motion deformation and stress of pelvic tissues and organs, which can accurately reflect both regional information and overall characteristics. This method is helpful in guiding the preoperative design and postoperative outcome assessment.^10–12 However, the current problem of pelvic floor FE analysis is that the soft tissues of the pelvic floor are not visible in various radiology examinations, which results in manual modeling errors and reduces the accuracy of the finite element model simulation. Meanwhile, incomplete knowledge of the structural relationships and material parameters of tissues and organs limits the accuracy of the model.^13,14 The application of the FE analysis to pelvic floor studies can establish a close relationship between engineering and medical disciplines to better understand the mechanics of the supporting structures of the female pelvic system and the POP mechanism.

The field of bibliometrics serves as a research methodology capable of quantitatively analyzing and visually representing extensive literature data, thereby unveiling the developmental trends and evolutionary patterns within specific research domains.^15–17 By employing bibliometric visualization techniques, researchers can efficiently identify key investigators, research institutions, countries, and journals within the field of POP biomechanics. This approach not only elucidates the interrelationships among researchers, institutions, and countries but also provides a comprehensive overview of developments, emerging research frontiers, and future trends within the field. It enables a deeper understanding of the historical evolution, current landscape, and future directions in this domain, highlighting areas that warrant further investigation and offering valuable insights to guide upcoming research endeavors.

Despite the abundance of studies conducted in the field of POP biomechanics, a comprehensive and systematic approach to reviewing all existing research in this area is still lacking. Although Yu et al conducted a bibliometric analysis of the mechanism of POP, they did not analyze the biomechanical mechanisms that have recently garnered attention in this field.¹⁸ Meanwhile, given the extensive and rapid advancements in research within this domain, this paper presented a comprehensive bibliometric analysis of the biomechanics of POP with the aim of providing a holistic overview of the subject by investigating dynamic trends in research focus within this field. Based on this premise, we conducted a literature review to investigate the previous advancements and current research focal points in this domain, while also proposing future research trends and directions. The objective of this study was to utilize the biomechanical research literature on POP published in the Web of Science Core Collection (WoSCC) database over the past two decades as the primary focus of investigation, aiming to delineate the research force network within the realm of knowledge and ascertain focal areas of research and evolutionary trajectories in the domain of POP biomechanics. We believe that our findings may offer valuable references and novel perspectives for future research.

Materials and Methods

Data Source and Search Strategy

This study utilized the WoSCC database, which comprises sub-databases such as SCIE and CCR-EXPANDED. These databases serve as the primary sources of data for this research and encompass scholarly articles from reputable journals.¹⁹ By ensuring the quality of literature while conducting a comprehensive search for core publications in this field, we aimed to ensure the precision and consistency of the data. To achieve this, all literature searches and data extraction were performed simultaneously on the same day by three authors. The search strategy integrated MeSH terms with free words to establish a comprehensive retrieval approach. The specific search formula was as follows: ((((TS = (Pelvic organ prolapse OR pelvic organ prolapse OR pelvic organ prolapses)) AND TS = (biomechanical OR biomechanics OR biomechanic OR finite element)) AND DT = (Article OR Review)) AND LA = (English)) AND DOP = (2003–01-01/2022-12-31).

Bibliometric Analysis

Export the literature that fulfills the selection criteria in a plain text format, ensuring a complete record and citation of references. Import the file into VosViewer 1.6.18, CiteSpace 6.2, and Scimago Graphica software for further scientific knowledge map visualization. The normalization method in VosViewer is set to correlation strength, with minimum thresholds of 5 for countries, institutions, and authors’ publications. For authors, journals, and keywords the minimum thresholds are adjusted to 100, 200, and 15 respectively. In CiteSpace, the time range is set from January 2003 to December 2022, with each slice representing a year. The selected node types include keywords and citations, based on the criterion of the top 50 for each slice. To ensure precision while maintaining default settings, pruning techniques such as Pathfinder, slicing networks, and merging networks are employed. In the analysis of Countries/Regions, Institutions, Authors, Journals, and References, the H-index serves as a quantitative metric for evaluating both the quantity and quality of academic output. Generally, a higher H-index indicates greater academic influence. Similarly, TLS reflects the degree of interconnectedness between a node and other nodes, with higher TLS values suggesting more extensive collaborative relationships for that specific node.^20–22

Results

Analysis of Annual Publications

This study encompassed a total of 292 pertinent literature pieces in the realm of biomechanics in POP, comprising 252 research articles (constituting 86.3% of all articles) and 40 review articles (constituting 13.7% of all articles). As depicted in Figure 1, a consistent upward trend can be observed in the number of annual publications over the past two decades. After analyzing the overall development of this field, we observe a consistent upward trend in its progress. The number of articles has significantly increased from 1 in 2003 to 17 in 2023, representing a seventeen-fold rise. Although this field has developed over the past 20 years, the total number of publications remains below one thousand. This indicates that further research by more scholars is needed to enhance its academic impact. Among them, the United States and China are the two countries with the highest number of publications in this field. As depicted in this figure, both nations have exhibited a consistent upward trend in their publication numbers. The cumulative count of publications from the United States (111 articles, 38%) surpasses that of China (30 articles, 10%), and it also commenced at a higher baseline within this domain. Nevertheless, China’s publication volume has steadily increased over time and is now comparable to that of the United States. The present findings suggest that despite the growing research interest and awareness in this field, the overall publication volume remains relatively limited, indicating its status as an emerging field that requires further exploration by a broader range of scholars.

Figure 1 Annual publications chart of biomechanical research on POP.

Analysis of Countries/Regions

Figure 2 depicts a knowledge graph showcasing the cooperative networks established among various countries/regions. Each colored block represents a country/region, with its size proportionate to the quantity of publications. The lines depict collaborative relationships between countries/regions, and the thickness and darkness of the lines signify the frequency of cooperation.^23–25 As depicted in the graph, the United States exhibits the highest number of publications in this particular field and maintains robust collaborations with multiple countries. However, Belgium emerges as the country engaging in the most extensive collaboration, fostering close connections with the Czech Republic, Switzerland, and Portugal. Furthermore, Table 1 presents pertinent information regarding the top 10 countries/regions in terms of publication volume. Among them, the United States (111 articles, 38%), China (30 articles, 10%), and Portugal (30 articles, 10%) collectively contribute to a significant proportion of the overall publication volume, accounting for approximately 58%, thus establishing themselves as prominent contributors within this domain. The United States leads significantly in terms of total citations (TC=2931) and H-index (29), while Switzerland, despite ranking tenth in total publications, exhibits the highest average citation per publication (ACPP=29.31). Portugal and Belgium share the top spot for total link strength (TLS=44).

Table 1 Top 10 Countries/Regions Ranked by Number of Publications

Figure 2 National/regional cooperative network knowledge graph.

Analysis of Institutions

Figure 3 depicts the collaborative efforts among institutions with a publication count exceeding 5 in this particular field, along with their average publication year. Based on this figure, it is evident that the University of Michigan, University of Auckland, University of Sydney, University of Zaragoza, and University of Texas Southwestern Medical Center at Dallas have demonstrated early contributions in this field. Conversely, there has been a recent increase in research activity from the University of Amsterdam, Radboud University Nijmegen, Cleveland Clinic, Louis Stokes Cleveland VA Medical Center, Cleveland Clinic, Tulane University, and Virginia Polytechnic Institute and State University. The top ten institutions in terms of the number of published articles in this field are presented in Table 2. The University of Porto exhibits the highest publication count (27 articles, 9%), followed by Magee Woman Research Institution (22 articles, 8%) and the University of Pittsburgh (20 articles, 7%). The University of Michigan is at the forefront in terms of TC (TC=806), while Magee Woman Research Institution and the University of Pittsburgh have achieved the highest H-index, both being 14. Conversely, the University of Porto holds a significant lead in TLS (TLS=40). Among the top ten institutions ranked by publication volume, the majority are located in the United States, consistent with the results of the country analysis. While China and Portugal rank second in publication volume within this field, no institutions from China are included in the top ten.

Table 2 Top 10 Institutions Ranked by Number of Publications

Figure 3 Institutions cooperative network knowledge graph.

Analysis of Authors

The collaboration network and average publication time of authors who have published no fewer than five articles in this field are illustrated in Figure 4. Notably, in the early stages of research in this field, prominent scholars such as Feola A, Abramowitch S, and Mascarenhas T played a pivotal role. However, recent studies have witnessed the emergence of scholars like Guler Z and De Vita R who have made significant contributions. The specific details of the top ten authors with the highest publication volume in this field are presented in Table 3. As shown in this table, Moali PA is the most prolific author, with a publication record of 27 publications (9%). He demonstrates strong performance in terms of TC (TC = 1098), ACPP (ACPP = 40.67), and H-index (18). In contrast, Deprest J holds a prominent position in TLS (TLS=53).

Table 3 Top 10 Authors Ranked by Number of Publications

Figure 4 Authors cooperative network knowledge graph.

Analysis of Journals

The top ten journals in this field, ranked by publication volume and sorted based on the number of publications, are presented in Table 4. The Int Urogynecol J holds the first position with a significantly higher publication volume (51 articles, 17%) compared to other journals. Moreover, it exhibits TC value (TC=1219) and H-index (20). However, the Am J Obstet Gynecol boasts the highest impact factor among its peers, with an impressive ACPP score of 37.81 and an IF rating of 9.8, placing it in the top quartile (Q1) for scholarly publications among these top ten journals. The co-citation relationships among these journals are depicted in Figure 5 and Table 5, where Int Urogynecol J, Am J Obstet Gynecol, and Obstet Gynecol exhibit significantly higher citation frequency and TLS compared to other journals.

Table 4 Top 10 Journals Ranked by Number of Publications

Table 5 Top 10 Co-Cited Journals Ranked by Citation Frequency

Figure 5 Journal co-citation network knowledge graph.

Analysis of References

The co-citation relationships among 28 publications, which have received a minimum of 50 citations, are illustrated in Figure 6. Additionally, Table 6 provides comprehensive details on the top 10 most frequently cited publications. According to the study conducted by Summer et al published in 2006 in the American Journal of Obstetrics and Gynecology, their work has received the highest number of citations within the field. Conversely, Lei et al’s publication in 2006 in the International Urogynecology Journal holds the record for having achieved the highest TLS (TLS=61). By defining the minimum duration of an outbreak as 3 years, a total of 30 reference articles reporting high-intensity outbreaks were identified, as depicted in Figure 7. The term “citation burst” refers to papers that experience a high frequency of citations within a specific time frame.^26,27 The time interval is represented by the blue line in this figure, while the duration of the outbreak is indicated by the red line. “Strength” refers to the magnitude of the eruption, and “Begin” and “End” respectively denote the initiation and termination time of the eruption.^25,28 We can discern that the developmental emphasis in this domain fluctuates over different epochs. The literature that has garnered attention focuses on electron microscopy examination of biopsy specimens from various supportive structures of the pelvic floor to elucidate their composition or biomechanical measurements for determining their material parameters.^29–32 In the mid-term of this field, scholars have increasingly turned their attention to conducting FE analysis on various supporting structures of the pelvic floor in order to enhance our understanding of the biomechanical mechanisms underlying POP.^33–35 In recent years, the literature in this field has increasingly focused on developing diverse mesh-based FE models to investigate the repair outcomes of POP and examine the comparative effects of different materials on these repairs.^35–37

Table 6 Top 10 Co-Cited References Ranked by Citation Frequency

Figure 6 References co-citation network knowledge graph.

Figure 7 Top 30 co-cited references ranked by citation frequency.

Analysis of Keywords

Summarizing the entire research content in this field through keywords analysis can provide valuable insights into the primary research topics and current issues, facilitating an exploration of the developmental status and emerging trends within this domain.^38–40 Figure 8 depicts the collaborative relationships, occurrence frequency, and average appearance time of keywords that have a minimum frequency of 15 occurrences. In this figure, larger nodes represent keywords with higher frequencies of occurrence, while the connections between nodes indicate their collaborative relationships. Generally, thicker connections imply stronger collaboration among the keywords. To enhance the precision of this study, we manually processed all instances of “Stress urinary-incontinence” and “Mechanical-properties” keywords, as these terms possess similar connotations across various literature but are expressed differently. Consequently, we revised them to “Stress urinary incontinence” and “biomechanical properties”. From this graph, it is evident that keywords such as “prolapse”, “stress urinary incontinence” and “vaginal tissue” have emerged prominently in this domain. Conversely, keywords like “biomechanical properties”, “implantation” and “impact” have gained significant attention in recent years. Furthermore, Table 7 presents the top 20 high-frequency keywords along with their TLS, which partially reflects the predominant research themes and emerging trends in this particular domain. This study also employs keywords clustering to derive 5 cluster labels, which are then visualized in the form of a keyword timeline graph (Figure 9). This visualization enables a comprehensive examination of the temporal evolution characteristics exhibited by each clustered field. The term “emerging keywords” refers to key terms that frequently occur within a specific time frame, and analyzing them can unveil research hotspots and development trends in a particular field.²² By setting the minimum duration of an outbreak at 3 years, we detected the top 20 keywords with the highest outbreak intensity. Among them, tissue engineering and extracellular matrix will continue to be prominent until 2023 or later (Figure 10), thus reflecting recent research focuses to some extent.

Table 7 Top 20 Keywords Ranked by Number of Publications

Figure 8 Keywords co-citation network knowledge graph.

Figure 9 Keywords timeline graph.

Figure 10 Top 20 keywords ranked by burst strength.

Discussion

In the past two decades, researchers have dedicated significant efforts to the field of biomechanics in POP and achieved remarkable progress, thereby making substantial contributions to this domain. This present study employs a bibliometric analysis of biomechanical research pertaining to the WoSCC database and POP over the past two decades, effectively illustrating the current state of research in this field through a comprehensive graphical representation.

With the advancement of solid biomechanics, biofluid mechanics, and movement biomechanics, along with continuous progress in radiographic imaging and computer technology, this field has demonstrated a steady upward trajectory in overall development. However, the current publication volume in this field remains relatively low, indicating its nascent stage but with significant potential. In the future, we anticipate a substantial increase in high-quality research publications. In recent years, compared to the initial research achievements in 2003, there has been a twenty-fold increase. The United States leads the world in terms of published research, making a substantial contribution to this field and accounting for 38% of total publications. It holds the top position in TC, h-index, and TLS, highlighting its substantial academic influence and prominent status in this research domain, while maintaining strong collaborations with other countries and regions. Amidst the wave of enhanced collaboration, Portugal, Belgium, the Czech Republic, and Switzerland have established robust connections in this domain, emerging as pivotal contributors alongside the United States and China - the leading nations in terms of publication output. Meanwhile, Switzerland’s lower publication output is counterbalanced by its highest ACPP, indicating widespread recognition and citation of its research achievements among peers. It is noteworthy that 70% of the top ten high-productivity countries/regions are predominantly concentrated in North America and Europe, underscoring their prominent status as primary research hubs in this field.

The University of Porto, situated in Portugal, stands out as the institution with the highest number of published papers and TLS. This indicates its exceptional productivity in this field and its robust collaborative network with other institutions. The publication with the highest citation rate in this institution employed the FE method to simulate the complete process of vaginal delivery in early-stage research, investigating the impact of the fetal head on pelvic floor muscles during vaginal delivery. The findings of this study suggest that the levator ani muscle and the pubococcygeus muscle undergo significant stretching and strain during vaginal delivery, with a potential risk for pelvic floor muscle injury in the second stage of labor.⁴¹ The University of Michigan, situated in the United States, is widely regarded as the foremost institution in the field concerning TC and ACPP. Meanwhile, both the University of Pittsburgh and Magee Woman Research Institution, also based in the United States, are acknowledged for their exceptional H-index among institutions within this domain. These accomplishments reflect America’s robust research capabilities within this discipline and have garnered significant attention from scholars in this field. The University of Michigan’s highly influential publication provides a biomechanical perspective on the correlation between the anterior compartment (bladder) and the apical compartment (cervix). The findings suggest that approximately 50% of the observed variability in anterior compartment support can be attributed to apical support, thus establishing a theoretical framework for comprehending the underlying mechanism of POP.⁴² The University of Pittsburgh’s most influential publication is a comprehensive review article that critically examines the extensive research conducted in 2009, providing an insightful synthesis of diverse animal models, anatomical manifestations, and biochemical constituents pertaining to POP. Furthermore, it delves into the intricate structure and biomechanical properties of vaginal supportive connective tissues.⁴³ The most influential publications from Magee Women’s Research Institution primarily focus on organizational remodeling and biochemical evidence pertaining to advancements in POP. This research suggests that vaginal collagen fibers exhibit a whorled pattern, predominantly composed of type III collagen. In comparison to women without prolapse, those with prolapse demonstrate elevated levels of total collagen protein and increased activity of MMP-9 within the vagina.⁴⁴ The University of Porto maintains strong collaborations with prominent institutions such as the University of Pittsburgh, Katholieke Universiteit Leuven, and Monash University, among others. It is noteworthy that Royal Hallamshire Hospital exhibits the most extensive collaboration with the University of Sheffield among all institutions in this field. In their collaborative research, the most influential articles focused on assessing the in vivo response of alternative materials (polypropylene (PPL), polyvinylidene fluoride (PVDF), poly-lactic acid (PLA), and polyurethane (PU) mesh implants)) for the management of stress urinary incontinence and POP in rabbits over a three-month duration. This study revealed that PLA and PU mesh implants demonstrate superior host tissue integration, whereas commercial PPL and PVDF mesh implants exhibit a heightened level of sustained inflammation in comparison to the former.³⁷ It is evident that the majority of highly productive and influential institutions are concentrated in Europe and the United States, indicating a predominant research presence in Western countries, consistent with our country/region analysis.

Moali PA, affiliated with Magee Women’s Research Institution, emerges as the most prolific author in this field, surpassing other researchers in terms of his TC, ACPP, and H-index. This not only highlights his exceptional academic accomplishments and influence but also underscores his extensive collaborations with scholars such as Abramowitch S, Feola A, Jallah Z, and Shand SH. This scholar’s research, aligned with the work conducted by their affiliated institution, highlights their significant contributions and respected status within both the academic field and their organization. Deprest J from Katholieke Universiteit Leuven emerges as a leading scholar in this field, boasting the highest TLS. He demonstrates an impressive publication record, along with high TC, ACPP, and H-index rankings. These accolades attest to his respected standing within the academic community and exemplary collaboration with fellow scholars, rendering him an indispensable pillar for advancing the progress of this discipline. His highly cited article primarily focuses on the biomechanical performance and incidence of associated complications in comparing vaginal and abdominal mesh implantation. This study revealed a significant correlation between the size of vaginal mesh pores and transplant-related complications, based on research involving 20 sheep. Furthermore, it demonstrated that the biomechanical performance of extraperitoneal implants is comparable to that of abdominal implants.⁴⁵

Int Urogynecol J, Am J Obstet Gynecol, and J Mech Behav Biomed are highly productive and influential journals with a strong co-citation network in this field. Therefore, when disseminating research findings or conducting literature searches, these five journals should be prioritized. It is noteworthy that among the top ten high-productivity journals, only those originating from Europe and the United States are included, with 70% of them being affiliated with institutions in the United States and the United Kingdom. This indicates that the journals of these countries have made significant contributions to this field, garnering extensive attention and recognition from researchers worldwide. Consequently, they are regarded as valuable platforms for disseminating and accessing high-level research accomplishments.

Highly cited publications serve as a reflection of the research status and focal points within a specific field, enabling an analysis that aids in summarizing significant research accomplishments. This analysis provides valuable theoretical guidance for conducting future in-depth investigations.^46–48 One of the most frequently cited studies is a 2006 publication by Summer A et al in the journal Am J Obstet Gynecol, widely regarded as a highly influential piece of research originating from the University of Michigan. Similarly, the paper published by Abramowitch SD et al in 2009 holds the second highest citation count and is widely acknowledged as a highly influential publication at The University of Pittsburgh. These findings suggest that both universities played a pioneering role in the nascent stages of this field and made substantial contributions to its advancement, aligning with institutional analysis. Additionally, Ashton-Miller et al conducted a pioneering research, utilizing MRI to model the pelvic floor region and investigate the specific biomechanical mechanisms underlying pelvic floor injury resulting from vaginal childbirth, thereby providing an unprecedented understanding of the functional anatomy and daily load on the female pelvic floor in everyday life.⁴⁹ This study suggests that muscle damage occurs in the region experiencing the greatest stretch during the second stage of labor, and there is a significant correlation between forceps usage and levator ani muscle injury. The urogenital hiatus undergoes forced dilation due to increased intraabdominal pressure, resulting in distal vaginal exposure to a pressure differential, apical descent, and cystocele formation. Amongst the major pelvic floor nerves, the anal sphincter nerve experiences the highest level of pressure during the second stage of labor. However, further investigation is warranted to explore the impact of pregnancy on the constitutive behavior and failure characteristics of pelvic floor tissues. Fourthly, the study conducted by Moalli et al in 2005 focused on the histological and biochemical evidence of vaginal connective tissue remodeling in patients with prolapse. This study is also one of the most influential research conducted by the Magee-Womens Research Institute. In contrast to the highly influential publications from the University of Michigan, Chen et al’s 2006 study specifically examined the interaction between the anterior vaginal wall and its supporting system with respect to the levator ani muscle.⁵⁰ The research findings revealed that the degree of anterior vaginal wall prolapse is a result of combined damage to both pubovisceral muscle, uterosacral, and/or cardinal ligament (“apical supports”) impairment under increased intra-abdominal pressure. Once a certain level of visceral damage to the pubovisceral is reached, it leads to genital hiatus opening and subsequent prolapse development. The severity of anterior wall prolapse increases with a greater extent of pubovisceral injury. By comparing this study with the research conducted by Summers et al, we can enhance our comprehensive understanding of the intricate interrelationships among diverse supporting structures within the pelvic floor.⁴² The study conducted by Liang et al in 2013 aimed to investigate the impact of synthetic meshes with varying stiffness (The prototype prolapse mesh Gynemesh PS was compared to two new generation lower stiffness meshes, UltraPro and SmartMesh) on vaginal morphology and structural composition.⁵¹ The findings suggest that the implantation of mesh has a detrimental impact on vaginal morphology and connective tissue remodeling. It is possible that the utilization of more rigid mesh results in an upregulation of collagenase activity, a decrease in collagen and elastin content, and an increase in GAG content, all of which have negative effects on the structural integrity of the vagina. It is noteworthy that Feola et al, in a study published in the same year, conducted a biomechanical analysis of Liang et al’s research and arrived at an identical conclusion.⁵² To comprehensively validate these findings, further research from multiple perspectives is warranted to investigate the impact of various synthetic mesh patches on vaginal functionality and elucidate the molecular and biomechanical mechanisms underlying these changes. The study conducted by Lei et al in 2006 involved pathological biopsies of vaginal tissues in 43 patients with varying degrees of menopausal status and prolapse after transvaginal hysterectomy.³¹ This study revealed that pre- and postmenopausal patients with POP exhibit reduced vaginal connective tissue elasticity and increased stiffness compared to the general population. Substantial variations in biomechanical properties were observed between mild and moderate types, as well as between mild type and severe type. However, no significant difference was found between moderate type and severe type. Rahn et al investigated the alterations in biomechanical properties of the vaginal wall induced by pregnancy and childbirth using Fibulin-5 knockout (Fbln5^−/−) mice model, both with and without POP.⁵³ From an animal model perspective, this study has shown that pregnancy can induce changes in the vaginal wall similar to those observed in POP, including increased distensibility, decreased stiffness, and reduced maximum pressure. These alterations may contribute to the poorer durability of many restorative surgical procedures for POP. The 2011 publication by Chen et al is a comprehensive review that extensively explores the impact of collagen/elastin and extracellular matrix metabolism on the urinary reproductive system, with a specific focus on stress urinary incontinence.⁵⁴ Furthermore, this study provides an overview of the influence of genetics and reproductive hormones on extracellular matrix metabolism, encompassing collagen, elastin, and transforming growth factor-β. The aforementioned highly cited articles serve as a fundamental research foundation with substantial academic influence and reference value in this field. By interpreting and exploring these articles, we can enhance our comprehension of the developmental trends within this field and identify potential directions for future research.

The term “Citation burst” typically denotes the literature that garnered significant attention during a specific timeframe. Analyzing these publications from various periods can facilitate comprehension of research trends prevalent in the field at that particular time and enable the identification of prospective avenues for future research.^55–57 To comprehensively capture the current research trends and anticipate future developments in this field, this study will primarily focus on the literature that continues to generate significant interest until 2024 or later. In the field of research, only one article garnered significant attention until 2024, which was authored by Paul et al from the Hudson Institute of Medical Research in 2019.³⁵ This study represents a pioneering application of 3D printing technology for the fabrication of endometrial mesenchymal stem/stromal cells (eMSCs) onto a mesh, aiming at targeted repair of POP in the vaginal wall. The study was conducted in three stages, including the fabrication of a melt electrospun (MES) mesh, bioprinting eMSCs into a Ca²⁺ free Aloe Vera-Alginate (AV-Alg) based hydrogel, and in vivo study. The result demonstrated that AV-ALG hydrogel has the potential to suppress the foreign body response, and the additional incorporation of eMSCs induced a significant influx of anti-inflammatory CD206+ M2 macrophages. This study represents a significant breakthrough in the field of tissue engineering and bioprinting for POP treatment, providing an alternative approach to overcome the challenges posed by non-degradable knitted meshes currently used. This method has important implications for future advancements in this field. By analyzing highly cited and “Citation burst” research, it can be inferred that the primary research areas in this field encompass the development and validation of three-dimensional FE models for pelvic floor structures, investigation into the interplay among diverse supporting systems within the pelvic floor, verification of the impact of vaginal delivery on various supportive structures, analysis of different mesh or 3D printing materials’ effects on POP repair, remodeling of vaginal connective tissue in patients with prolapse conditions, and biomechanical performance assessment of pelvic floor tissues in individuals with prolapse disorders.

Through the analysis of keyword co-occurrence relationships, clustering, and bursts, we have identified that the predominant research topics in this field encompass POP, biomechanical properties, women, stress urinary incontinence (SUI), and prolapse. These topics exhibit a significantly high frequency of occurrence. The 5 clustering labels, encompassing #0 pelvic floor, #1 polypropylene mesh, #2 tissue engineering, #3 pregnancy, #4 animal models, and #5 fecal incontinence to some extent reflect the predominant research themes within this field. Among them, the research field of tissue engineering and extracellular matrix, which are emerging keywords with durations ending in 2022 or later, has gained prominence in recent years. It has attracted great attention from the scientific community and is expected to become the focus of future research in this field. A comprehensive analysis of all articles in this field reveals that the focus of research shifts across different stages of the field’s development. Early biomechanical research on POP primarily centered on identifying and understanding the anatomical and mechanical properties of the pelvic floor and associated structures contributing to POP. Researchers recognized that biomechanical alterations in pelvic tissues, such as changes in tensile strength, elasticity, and extensibility, are crucial factors in the onset of prolapse.⁵⁸ An early discovery highlighted the role of vaginal tissue mechanics in POP. Studies by Rubod et al demonstrated that vaginal tissues in prolapse patients exhibit distinct biomechanical characteristics, such as hyperelasticity and increased deformation prior to rupture, compared to individuals without POP.⁵⁹ These insights laid the groundwork for subsequent research focused on quantifying mechanical behavior and refining surgical interventions for POP. Early studies also identified collagen, particularly types I and III, as fundamental to maintaining the structural integrity of the pelvic floor, noting that prolapsed tissues exhibit an altered collagen composition.⁶⁰ Furthermore, the connective tissue properties of the uterosacral ligaments and other supporting structures became a focal point in studies investigating why some individuals are more prone to developing POP. Many research highlighted that a combination of genetic predisposition and external factors could weaken these support structures, thereby increasing susceptibility to POP.^49,61 In the early stages of research in this field, numerous studies were conducted to elucidate the mechanisms underlying the occurrence of POP. Most of these studies focused on mechanical testing of cadaveric and animal models, in vitro evaluations of organs, and assessments of various implant materials used in pelvic floor repair surgeries. Additional research included in vitro mechanical testing of tissues and organs from living human subjects and analyzing the mechanical properties of collagen fibers in different tissues. In the mid-stage of biomechanical research on POP, attention shifted to the development of biomechanical FE models to simulate pelvic floor mechanics. Biomechanical modeling emerged as a prominent tool in understanding POP pathophysiology during this period. Advanced techniques, including FE analysis and computational simulation, were employed to replicate the mechanical environment of the pelvic floor. For instance, Yang et al used FE analysis to assess how mechanical forces affect the pelvic floor musculature and connective tissues under various loading conditions.¹⁰ This modeling enabled researchers to simulate and predict the progression of prolapse and evaluate the effectiveness of different surgical interventions in restoring pelvic support. Studies in this phase also revealed the importance of muscular support, particularly the role of the levator ani muscle complex. These muscles, particularly the pubovisceral component, were identified as essential in counteracting pelvic organ descent. The work of researchers like Jing highlighted how weakening or damage to these muscles during childbirth could predispose individuals to prolapse later in life, further emphasizing the need for protective interventions during childbirth.⁶² The use of high-resolution imaging techniques, such as MRI and ultrasound, has allowed for more accurate assessments of pelvic floor anatomy and biomechanical properties. For example, Brandão utilized MRI to quantify parameters like the moment of inertia of pelvic structures, providing insights into the anatomical changes associated with POP.⁶³ These imaging techniques facilitate early diagnosis, allowing for preventive measures and tailored interventions.

The integration of these imaging modalities into FEA models allows clinicians to predict patient-specific outcomes more accurately and adjust surgical approaches based on individualized risk factors. However, during this stage, most FE analyses were based on models that included only one or a few pelvic tissues or organs, lacking a comprehensive model encompassing all pelvic floor tissues and organs. Such a complete model is needed to more accurately reflect the real development of POP and the mechanical performance of various materials used in POP repair. In recent years, biomechanical research on POP has adopted a more integrative approach, combining biomechanics, imaging, and genetic analysis to understand the complex interactions that contribute to prolapse. These trends reflect the progression toward personalized medicine and improved clinical interventions. Predictive FE modeling has become an area of great interest, as it allows for the identification of patients at high risk of developing POP. By inputting data on tissue and organ composition, mechanical properties, and load patterns, these models can simulate the long-term effects of repetitive mechanical stress on the pelvic floor. For example, studies by Gong et al have suggested that combining genetic information on collagen and ECM remodeling with FE analysis could enhance the predictive power of these models, providing a multi-faceted approach to risk assessment.⁶⁴ This predictive capability is instrumental in proactive management and may reduce the need for invasive interventions by targeting preventive measures in high-risk individuals. Additionally, this field has recently shifted attention toward using FE analysis to optimize mesh placement strategies for improved outcomes in POP repair. By simulating various attachment points and tension levels, researchers can predict which placements offer the best support while minimizing tissue strain. Alperin et al demonstrated that mesh anchored at specific pelvic ligaments could reduce tension and lower the likelihood of mesh failure or displacement.⁶⁵ This optimization has implications for reducing recurrence rates and improving patient outcomes post-surgery. In recent years, numerous comprehensive models of POP have emerged, with a growing body of research focusing on simulating pelvic floor muscles in puerperal women across various stages of labor, exploring interactions between pelvic organs and tissues in large-scale models, analyzing the stress-strain relationships of various implants under real-life conditions, and biomechanical alterations in organs treated with hormone therapy and mesenchymal stem cells.^66–69 This progress offers a more precise and innovative framework for enhancing the understanding of POP mechanisms. Notably, Egorov et al developed a novel comprehensive scoring system for female pelvic floor biomechanics, known as the Biomechanical Index (BI) score.⁷⁰ This score was subdivided into five categories to characterize (1) tissue elasticity, (2) pelvic support, (3) pelvic muscle contraction, (4) involuntary muscle relaxation, and (5) pelvic muscle mobility. Although this scoring system has shown strong reliability in recent validation studies, further large-sample clinical research is needed to evaluate its accuracy, and additional, more detailed scoring methods will be essential for future developments.^71,72

Based on the above analysis, future research is anticipated to concentrate on the development of personalized and regenerative therapeutic strategies. Advancing multi-scale, multi-modal, and personalized modeling for various populations with pelvic organ prolapse (POP) will likely become a trend to meet individualized clinical needs in this field. In the future, artificial intelligence (AI) and machine learning (ML) techniques may be integrated into finite element analysis (FEA) models, enabling early screening and predictive analysis of high-risk individuals by training models on extensive patient data. Simultaneously, further optimization of regenerative medicine and biomaterials, as well as FEA-based preventive treatments and risk assessments, are also expected to become significant directions for future development.

Strengths and Limitations

The present study represents the first comprehensive and systematic analysis of the existing literature on the biomechanics of POP using bibliometric and visualization techniques. Bibliometrics is an interdisciplinary field that integrates mathematics, statistics, and library science to leverage bibliometric features and research accomplishments in specific journals and disciplines. Its primary focus lies in quantifying comprehensive knowledge systems, particularly through the application of information visualization techniques and methodologies. This facilitates an intuitive presentation of the research development process, current status, emerging topics, and trends within a particular domain.^73–76 The present study, however, is subject to certain limitations. Firstly, although the WoSCC database is widely utilized in bibliometrics research, our study exclusively focused on SCI-Expanded within the WoSCC database, potentially excluding pertinent research findings. Secondly, our analysis may underestimate some recently published high-quality studies due to limited citation frequencies. Third, our study only considered the analysis of English-language publications, which may introduce a certain degree of bias to the findings. Lastly, as a result of continuous updates to the database, the dataset of 2024 remains incomplete and was therefore not included in this study. Despite certain limitations, this pioneering bibliometric study holds significant scholarly value as the first of its kind in this field. It offers valuable insights into the current state of development and serves as a guiding reference for future research endeavors.

Conclusion

Over the past two decades, there has been a substantial increase in the number of publications on biomechanics in POP, drawing growing scholarly attention to this field. The United States has emerged as the leading nation in terms of productivity, with the University of Porto making a significant contribution. All nations and institutions maintain robust collaborative partnerships. The current primary research areas in this field encompass the establishment and validation of three-dimensional FE models for pelvic floor analysis, investigation into the interplay between different support systems within the pelvic floor, assessment of the impact of vaginal delivery on various supporting structures, analysis of the effects of diverse meshes or 3D printing materials on POP repair, evaluation of connective tissue remodeling in patients with prolapse, and biomechanical performance assessment of pelvic floor tissues in individuals with obstructed defecation. Future research trends are anticipated to concentrate on the development of more intricate pelvic floor FE methodologies, integrating “tissue engineering” and “extracellular matrix” as key components for multidimensional biomechanical analysis of POP. In conclusion, advancing multi-scale, multi-modal, and personalized modeling for POP is expected to play a critical role in addressing individualized clinical needs within this field. The integration of artificial intelligence and machine learning into FE models, along with advancements in regenerative medicine, biomaterials, and the optimization of FE-based preventive treatments and risk assessment, represents a promising direction for future development. These emerging research trends are expected to introduce novel ideas and methodologies for the investigation and personalized clinical management of POP, thereby facilitating accelerated advancements in this domain.