Pseudarthrosis after spinal fusion: a bibliometric and thematic analysis of global research trends in neurosurgical spine practice

Abstract

AimThis study aimed to evaluate global research trends and the knowledge structure of pseudarthrosis after spinal fusion from a neurosurgical spine perspective.MethodsA bibliometric and thematic analysis was performed using the Web of Science Core Collection. The search strategy was TS=((pseudarthrosis OR pseudoarthrosis) AND ("spinal fusion" OR "spine fusion" OR "lumbar fusion" OR "cervical fusion" OR "thoracolumbar fusion")). English-language original articles indexed in SCI-EXPANDED and published between 2006 and 2025 were included. VOSviewer was used for keyword co-occurrence and overlay visualization analyses.ResultsA total of 571 articles were included. Annual publication output increased over time, peaking in 2025. The leading research area was Neurosciences Neurology, followed by Orthopedics and Surgery. The most productive journal was Spine, followed by The Spine Journal, European Spine Journal, World Neurosurgery, and Journal of Neurosurgery: Spine. The United States was the dominant contributing country, and the University of California System was the most productive affiliation. Lenke LG, Vaccaro AR, and Wang JC were the most prolific authors. Keyword analysis showed that the field was centered on pseudarthrosis, spinal fusion, lumbar fusion, smoking, nicotine, nonunion, osteoporosis, complications, and revision surgery. Overlay visualization indicated a temporal shift from fusion biology and graft-related topics toward revision surgery, reoperation, postoperative complications, and clinically oriented outcome research.ConclusionResearch on pseudarthrosis after spinal fusion has increased substantially and is primarily situated within neurosurgical and orthopedic spine surgery. Future studies are likely to focus on prevention, risk stratification, bone health optimization, and improved revision strategies.

Keywords

Introduction

Spinal fusion is widely performed for degenerative, deformity-related, traumatic, and instability-associated spinal disorders to achieve solid arthrodesis and durable segmental stability. Pseudarthrosis, or nonunion, represents failure of osseous fusion and remains a major cause of failed spinal fusion.¹ It is clinically important because it may cause persistent pain, implant failure, progressive deformity, neurological symptoms, and revision surgery, which is often technically demanding and associated with increased morbidity, higher costs, and less predictable outcomes.²
The development of pseudarthrosis is multifactorial and is influenced by both patient- and surgery-related factors. Older age, smoking, osteoporosis, metabolic disorders, and impaired bone healing are important patient-related factors, whereas the number of fused levels, instrumentation strategy, graft selection, fusion bed preparation, and biomechanical stability are key surgical factors.³ Smoking is one of the most consistently reported modifiable risk factors, and previous studies have shown that it significantly increases the risk of nonunion after both cervical and lumbar fusion.^4,5 Bone quality is also increasingly emphasized, as osteoporosis and osteopenia may compromise screw fixation, graft incorporation, and fusion biology, thereby increasing the risk of pseudarthrosis and revision surgery.⁶
Recent research has expanded beyond fusion biology and surgical technique toward revision spine surgery, minimally invasive approaches, biologics, osteoporosis-related complications, smoking cessation, and predictive risk modeling. Risk prediction models for pseudarthrosis after lumbar interbody fusion further highlight the growing interest in individualized risk stratification.⁷ However, the global research landscape of pseudarthrosis after spinal fusion has not yet been comprehensively mapped. Bibliometric analysis allows quantitative evaluation of publication trends, influential authors, leading journals, productive countries and institutions, citation patterns, and thematic structures.^8,9 Therefore, this study aimed to evaluate global research trends and the knowledge structure of pseudarthrosis after spinal fusion from a neurosurgical spine perspective.

Materials and Methods

Study DesignThis study was designed as a bibliometric and thematic analysis of global research trends and knowledge structure in pseudarthrosis after spinal fusion. The analysis was based on bibliographic records retrieved from the Web of Science Core Collection database. Publication trends, research areas, journals, countries, institutions, authors, citation patterns, and keyword-based thematic structures were evaluated. This bibliometric and thematic analysis was reported in accordance with the BIBLIO checklist for bibliometric reviews of the biomedical literature.Data Source and Search StrategyThe Web of Science Core Collection database was used as the data source. The database was searched on June 9, 2026. The search was performed using the following strategy: TS=((pseudarthrosis OR pseudoarthrosis) AND ("spinal fusion" OR "spine fusion" OR "lumbar fusion" OR "cervical fusion" OR "thoracolumbar fusion"))
The search was limited to articles indexed in SCI-EXPANDED, published in English, and classified as original articles. The publication period was restricted to 2006–2025. The initial search yielded 1,341 records. After limiting the dataset to SCI-EXPANDED records, 1,128 records remained. Restriction to original articles reduced the dataset to 970 records. After excluding non-English publications, 954 records remained. Finally, after applying the publication year restriction, 571 articles were included in the final bibliometric analysis.
The inclusion criteria were as follows: English-language original articles, publication between 2006 and 2025, indexing in SCI-EXPANDED, and relevance to pseudarthrosis or pseudoarthrosis after spinal fusion. Reviews, editorials, letters, meeting abstracts, proceedings papers, book chapters, corrections, early access records not assigned to the selected publication period, non-English records, and non-SCI-EXPANDED publications were excluded.
Following database export, the records were screened for eligibility according to document type, language, index, publication year, and relevance to pseudarthrosis after spinal fusion. The exported dataset was checked for duplicate records using the Web of Science unique accession numbers, article titles, authors, and digital object identifiers. No duplicate records were retained in the final dataset. Data cleaning was performed before analysis by reviewing incomplete records, standardizing synonymous keywords and spelling variants, and harmonizing country, institution, and journal names where appropriate. The titles and bibliographic metadata of potentially eligible records were independently reviewed by two authors. Any disagreements were resolved through discussion and consensus.Data ExtractionAll eligible records were exported from Web of Science Core Collection as plain text files using the Full Record and Cited References option. The exported data included article titles, authors, publication years, source titles, Web of Science categories, research areas, countries/regions, institutional affiliations, author keywords, Keywords Plus, citation counts, and cited references. The exported files were checked for completeness before bibliometric mapping and visualization.Bibliometric IndicatorsDescriptive bibliometric analyses were performed using the final dataset of 571 articles. The following indicators were evaluated: annual publication output, Web of Science categories, research areas, leading journals, most productive countries/regions, most productive institutions, most productive authors, open access status, and most-cited documents. Publication counts and percentages were calculated according to the total number of included articles.Bibliometric Mapping and VisualizationBibliometric mapping and visualization were performed using VOSviewer software, version 1.6.20 (Centre for Science and Technology Studies, Leiden University, Leiden, the Netherlands). VOSviewer is a freely available software tool developed for constructing and visualizing bibliometric networks, including networks based on citation, bibliographic coupling, co-citation, co-authorship, and keyword co-occurrence relationships. VOSviewer version 1.6.20 was released on October 31, 2023.¹⁰
Keyword co-occurrence analysis was conducted to identify the conceptual structure and thematic clusters of pseudarthrosis research after spinal fusion. The unit of analysis was all keywords, and the full counting method was used. A thesaurus file was applied to merge synonymous terms and spelling variants, including “pseudoarthrosis” and “pseudarthrosis.” Network visualization was used to identify major keyword clusters, whereas overlay visualization was used to evaluate the temporal evolution of research themes according to the average publication year of keywords.
In the VOSviewer maps, each node represented a keyword. Node size reflected the frequency of keyword occurrence, links represented co-occurrence relationships between keywords, and link strength indicated the degree of association between terms. In overlay visualization, node color represented the average publication year, allowing identification of older and more recent research themes.Statistical AnalysisOnly descriptive bibliometric analyses were performed. Publication counts, percentages, citation counts, and keyword frequencies were summarized descriptively. Bibliometric network analyses, including keyword co-occurrence and overlay visualization, were conducted using VOSviewer. No inferential statistical analyses, hypothesis tests, confidence intervals, or regression analyses were applied.Ethical ApprovalThis study was based entirely on publicly available bibliographic data and did not involve human participants. Therefore, ethics committee approval and informed consent were not required.

Results

A total of 571 English-language original articles indexed in the Web of Science Core Collection were included in the final analysis. Annual publication output gradually increased over the study period, with a more evident rise after 2015 and the highest number of publications recorded in 2025. The annual distribution of publications is presented in Figure 1.
Research area analysis showed that pseudarthrosis after spinal fusion was mainly studied within spine-related neurosurgical and orthopedic disciplines. Neurosciences Neurology was the leading research area with 417 records (73.03%), followed by Orthopedics with 354 records (62.00%) and Surgery with 174 records (30.47%). Similarly, Clinical Neurology was the most represented Web of Science category with 415 records (72.68%), followed by Orthopedics and Surgery.
The most productive journal was Spine, with 104 publications (18.21%), followed by The Spine Journal with 49 publications (8.58%), European Spine Journal with 48 publications (8.41%), World Neurosurgery with 43 publications (7.53%), and Journal of Neurosurgery: Spine with 29 publications (5.08%). Other productive journals included Clinical Spine Surgery, Global Spine Journal, Journal of Spinal Disorders & Techniques, Journal of Clinical Neuroscience, and BMC Musculoskeletal Disorders. The top 10 journals are listed in Table 1.
Country-level analysis showed that the United States was the dominant contributor, with 358 publications (62.70%). It was followed by South Korea with 44 publications (7.71%), China with 38 publications (6.66%), Japan with 36 publications (6.31%), Germany with 21 publications (3.68%), and France with 20 publications (3.50%). Türkiye appeared as 5 records under “Turkiye” and 4 records under “Turkey,” indicating the need for country name standardization. The top contributing countries and regions are presented in Table 2.
The most productive affiliation was the University of California System, with 45 publications (7.88%), followed by Washington University/WUSTL with 31 publications (5.43%), Thomas Jefferson University and University of California San Francisco with 24 publications each (4.20%), and Johns Hopkins University with 22 publications (3.85%). Other leading institutions included the University System of Ohio, Rothman Institute, Barrow Neurological Institute, Hospital for Special Surgery, Mayo Clinic, Baylor College of Medicine, and Rush University. However, 246 records (43.08%) lacked department-level affiliation data.
Author-level productivity analysis showed that Lenke LG, Vaccaro AR, and Wang JC were the most prolific contributors, each with 15 publications (2.63%). They were followed by Bridwell KH and Reece EM with 12 publications each (2.10%), and Bydon M, Kepler CK, Ropper AE, and Schroeder GD with 11 publications each (1.93%). Hilibrand AS ranked next with 10 publications (1.75%). The most productive authors are illustrated in Figure 2.
The most-cited document was the randomized trial by Ghogawala et al., Laminectomy plus Fusion versus Laminectomy Alone for Lumbar Spondylolisthesis, with 666 citations. The second most-cited article was by Martin et al., with 390 citations, followed by Patel et al., with 359 citations. Overall, the most influential documents were mainly related to lumbar fusion, reoperation, perioperative complications, adult spinal deformity surgery, osteoporosis-related complications, and cervical fusion techniques. The top 10 most-cited documents are listed in Table 3.
Keyword co-occurrence and overlay visualization showed that the field was mainly organized around “pseudarthrosis,” “spinal fusion,” “lumbar fusion,” “fusion,” “arthrodesis,” “smoking,” “nicotine,” “nonunion,” “osteoporosis,” “complications,” “revision,” and “adjacent segment disease.” Pseudarthrosis occupied a central position in the network, while closely related terms indicated a strong focus on fusion-related failure, particularly in the lumbar spine.
The network demonstrated three main thematic clusters: fusion biology and risk factors; lumbar fusion, bone quality, and graft-related factors; and revision-related clinical consequences. Overlay visualization showed a temporal shift from earlier themes such as fusion, arthrodesis, and demineralized bone matrix toward more recent themes including revision, reoperation, and postoperative complications. These findings indicate that the field has evolved from a mainly technical and biological focus toward clinically oriented outcome and revision research. The keyword co-occurrence and temporal overlay visualization is presented in Figure 3.

Discussion

This bibliometric and thematic analysis provides an overview of global research trends and the knowledge structure of pseudarthrosis after spinal fusion from a neurosurgical spine perspective. The final dataset included 571 English-language original articles indexed in SCI-EXPANDED between 2006 and 2025. Publication output increased over time, especially after 2015, and reached its highest level in 2025, suggesting growing academic interest in this topic.
Pseudarthrosis after spinal fusion was mainly positioned at the intersection of neurosurgery, orthopedics, and general spine surgery. Neurosciences Neurology was the leading research area, followed by Orthopedics and Surgery. The most productive journals also included both orthopedic spine journals, such as Spine, The Spine Journal, and European Spine Journal, and neurosurgical journals, such as World Neurosurgery and Journal of Neurosurgery: Spine, reflecting the multidisciplinary nature of the field.
The United States was the dominant contributing country, followed by South Korea, China, Japan, Germany, and France. Leading institutions included the University of California System, Washington University, Thomas Jefferson University, UCSF, Johns Hopkins University, Rothman Institute, Barrow Neurological Institute, Hospital for Special Surgery, and Mayo Clinic. These findings suggest that pseudarthrosis research is concentrated in countries and institutions with high-volume spine surgery centers and strong academic infrastructures.
Author-level analysis showed that Lenke LG, Vaccaro AR, and Wang JC were the most productive authors, followed by Bridwell KH, Reece EM, Bydon M, Kepler CK, Ropper AE, Schroeder GD, and Hilibrand AS. These authors are closely associated with spinal fusion, adult spinal deformity, cervical and lumbar fusion techniques, and revision surgery, indicating that pseudarthrosis research is embedded within broader spinal fusion and deformity surgery literature.
The most-cited documents were mainly related to lumbar fusion, reoperation, perioperative complications, obesity, adult spinal deformity, osteoporosis-related complications, and cervical fusion techniques. This suggests that the intellectual base of the field extends beyond nonunion itself and is closely linked to spinal fusion outcomes and revision surgery. Reoperation after lumbar spine surgery remains a major concern, and revision procedures have been reported to have higher rates of subsequent reoperation than primary lumbar fusion.¹¹
Keyword co-occurrence analysis identified “pseudarthrosis” as the central conceptual hub, with close connections to “spinal fusion,” “lumbar fusion,” “fusion,” “arthrodesis,” “smoking,” “nicotine,” “nonunion,” “osteoporosis,” “complications,” and “revision.” These terms indicate three major thematic areas: fusion biology and risk factors, lumbar fusion and bone quality, and revision-related clinical consequences. Smoking and nicotine were prominent keywords, consistent with evidence showing that smoking significantly increases the risk of pseudarthrosis after lumbar and cervical fusion.⁴
Osteoporosis and bone quality-related terms also represented an important research direction. Successful spinal fusion depends on surgical technique, instrumentation, biological fusion capacity, and host bone quality. Recent evidence has identified age, smoking status, and the number of fused levels as important risk factors for pseudarthrosis after lumbar fusion.³ These findings suggest that the field has evolved from technical fusion failure toward a broader understanding of patient-related, biological, and biomechanical risk factors.
Overlay visualization demonstrated a temporal shift in research priorities. Earlier studies were more closely related to fusion terminology, arthrodesis, demineralized bone matrix, instrumentation, and animal model research. In contrast, recent terms were associated with revision, reoperation, postoperative complications, lumbar spinal fusion, and minimally invasive spine surgery, indicating a shift toward clinically oriented topics such as revision burden, postoperative outcomes, and risk mitigation.
The increasing emphasis on revision surgery is clinically understandable. Revision fusion for symptomatic pseudarthrosis can improve pain, disability, and quality of life, although outcomes may remain less predictable than primary surgery.¹² Outcomes may also vary according to the underlying indication, with some studies reporting worse results in degenerative disc disease than in spondylolisthesis despite successful repair of nonunion.¹³
From a neurosurgical perspective, pseudarthrosis should be considered not only a radiological endpoint but also a clinically relevant cause of persistent symptoms, mechanical failure, and revision surgery. Modifiable risk factors such as smoking, poor bone health, vitamin D deficiency, and metabolic status should be addressed during preoperative planning. Future research will likely focus on individualized risk prediction, prevention of nonunion, and improved revision outcomes.
Finally, this study highlights the value of bibliometric methods in identifying the conceptual evolution of a surgical field. Bibliometric analysis allows quantitative assessment of publication trends, leading contributors, influential documents, and keyword networks. Recent methodological publications have emphasized the usefulness of Web of Science data, VOSviewer mapping, and keyword co-occurrence analysis for identifying hotspots and thematic structures in biomedical research.¹⁴ In the present study, this approach showed that pseudarthrosis after spinal fusion has evolved from a fusion biology-centered topic into a broader clinical research field involving complications, revision surgery, risk factors, and outcome optimization.

Limitations

Several limitations should be acknowledged. First, the analysis was limited to English-language original articles indexed in the Web of Science Core Collection and SCI-EXPANDED; therefore, relevant studies indexed in PubMed, Scopus, Embase, Google Scholar, or non-English sources may have been missed. Second, citation counts may favor older publications because they have had more time to accumulate citations. Third, bibliometric analyses depend on the accuracy of database indexing, author names, institutional affiliations, and keyword standardization. Although thesaurus-based cleaning was applied to merge synonymous terms such as “pseudarthrosis” and “pseudoarthrosis,” residual terminology variation may remain. Finally, bibliometric analysis describes publication patterns and thematic structures but does not assess the methodological quality, risk of bias, or clinical validity of individual studies.

Conclusion

In conclusion, this bibliometric and thematic analysis showed that research on pseudarthrosis after spinal fusion has increased over the last two decades and remains centered within neurosurgical and orthopedic spine surgery, with keyword and temporal analyses revealing a shift from fusion biology and graft-related topics toward clinically oriented outcome research, prevention, risk stratification, bone health optimization, and improved revision strategies.

Declarations

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