3.1 Publication growth

All articles were published between 1975 and 2023 (Fig. 2).The first and only article we found regarding this topic was published in 1975, discussing a basic lesion in isthmic spondylolisthesis with its risk factor and the importance of early recognition of the condition for better outcomes, had 390 citations and was the top globally cited article. Scientific production fluctuated from 1975 to 2023. Despite fluctuations afterward, publications on this topic steadily rose, peaking in 2022 with a total of 36 publications. Despite a growth in publication numbers, biblioshiny's analysis of the number of citations for the publication tends to decrease.

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Fig. 2 Analysis of publication growth and average citations for 519 journals obtained from Biblioshiny. (a.) Scientific production in isthmic spondylolisthesis over the year. (b.) Average citations per year regarding article publication in isthmic spondylolisthesis. Fig. 2a displays the number of articles published over time, with the x-axis representing the year of publication and the y-axis representing the number of articles. In the inaugural year of publication, 1975, there were 2 articles published. The lowest publication count was 0 during the years 1977–1979, 1983, and 1986. Fig. 2b illustrates the average number of citations per year for publications related to isthmic spondylolisthesis. Here, the x-axis represents the year of citation and the y-axis shows the average citation rate. The highest average citation rate, 6.38, was recorded in 1975, the first year of publication. In contrast, the citation rate was 0 in 1987 (Fig. 2).

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3.2 Countries analysis

The United States has emerged as the leader in terms of published research (148 articles) on the current topic and the leading collaborator, partnering with 19 other countries. The published articles and IF of other remaining top 10 journals are as follows: European Spine Journal (n = 49, IF = 23), Journal of Spinal Disorders and Techniques (n = 25, IF = 18), Journal of Neurosurgery: Spine (n = 23, IF = 13), World Neurosurgery (n = 22, IF = 6), Spine Journal (n = 21, i = 15), International Journal of Spine Surgery (n = 13, i = 6), Spine Deformity (n = 12, i = 6), Orthopaedics and Traumatology: Surgery and Research (n = 11, i = 7), and Clinical Spine Surgery (n = 10, i = 5).

3.3 Author analysis

A total of 2047 contributing authors in the current topic. Mikko S. Poussa tops the prolific authors list with 17 articles with first publication in 1990 and the latest in 2019. Poussa's research focuses on isthmic spondylolisthesis in young patients. The remaining top 10 authors are: Dietrich K.A. Schlenzka (n = 16), Sangho Lee (n = 14), Seppo K. Seitsalo (n = 14), Kalevi E. Österman (n = 13), Rune Hedlund (n = 12), Jin-sung Luke Kim (n = 8), Kern Singh (n = 8), Alexander R. Vaccaro (n = 8), and Timo A. Yrjönen (n = 8). Poussa, Schlenzka, Seitsalo, Österman, and Yrjönen all come from Finland and frequently collaborate. Sangho Lee and Jin-sung Luke Kim are both from South Korea and have also collaborated. Singh and Vaccaro are both from the US.

3.4 Journal analysis

The topic isthmic spondylolisthesis was published in 143 different journals. Spine boasted the highest number of published articles (n = 72), highest citations (n = 5310) and highest impact factor (IF = 40). The published articles and IF of other remaining top 5 journals are as follows: European Spine Journal (n = 49, IF = 23), Journal of Spinal Disorders and Techniques (n = 25, IF = 18), Journal of Neurosurgery: Spine (n = 23, IF = 13), World Neurosurgery (n = 22, IF = 6).

3.5 Keywords & Topic trends

The majority of publications cover surgical procedures and the long-term outcome. Fig. 3a shows the author’s keywords to describe the content of their research paper. The most common term was isthmic spondylolisthesis (n = 161), followed by spondylolisthesis (n = 140). The rest are: spinal fusion (n = 75), an operative treatment for isthmic spondylolisthesis; lumbar spine (n = 53), a frequently affected region; spondylolysis (n = 48), a basic lesion on spondylolisthesis; other terms were related to operative treatments: TLIF (n = 49), ALIF (n = 40), PLIF (n = 35), and minimally invasive surgery (n = 28). Fig. 3b shows that certain topics have recently gained attention, suggesting a prior lack of discussion on these topics. Both spinal stenosis (n = 10) and endoscopic spine surgery (n = 13) appeared in 2020. However, only ESS has continued to garner interest up to this time. Minimally invasive spine surgery such as ESS has emerged as a preferred treatment for a wide range of spinal disorders, offering numerous advantages over traditional open procedures for various spinal conditions. PROMs (n = 11) first appeared in 2022 and have been the subject of ongoing research until now. PROMs are crucial for evaluating treatment effectiveness and care quality in spine surgery, ultimately aiming to improve patients' quality of life by reducing pain, enhancing function, and stabilizing the spine.

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Fig. 3 Biblioshiny analysis was conducted using the author’s keywords. (a.) WordCloud of Top 50 Author’s Keywords of articles related to isthmic spondylolisthesis. (b.) Trend Topics in Isthmic Spondylolisthesis. The parameters for the keyword analysis are set as follows: the time range spans from 1975 to 2024, with a minimum word frequency threshold of 5 and an average of 3 keywords per year. In Fig. 3a, the size of each word corresponds to its frequency, with larger words appearing more often. In Fig. 3b, the line indicates the years a keyword appeared, and the size of the circle represents its frequency (Fig. 3).

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3.6 Co-occurrence cluster

The author's keyword co-occurrence network (Fig. 4a) revealed six distinct clusters. Cluster 1 (red) contains 33 keywords, Cluster 2 (green) includes 30 keywords, and Cluster 3 (blue) comprises 13 keywords. Cluster 4 (yellow) has 10 keywords, Cluster 5 (purple) features 8 keywords, and Cluster 6 (gray) consists of just 1 keyword. The overlay visualization in Fig. 4b and c illustrate the mean publication years and the average citations per keyword, respectively.

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Fig. 4 Network visualization of author’s keyword co-occurrence on articles covering isthmic spondylolisthesis. (a.) Co-occurrence clusters of the author’s keyword. The circle's size correlates with keyword frequency, while its thickness reflects co-occurrence strength. (b.) Mapping of keywords according to the mean frequency of appearance between 2010 and 2020; keywords in blue appeared earlier (2010 or earlier) than those in yellow (2020 or later). (c.) Mapping of keywords according to the mean frequency of citation per keyword; keywords in blue cited less (10; zero) than those in yellow (50 or more).Using VOSviewer, we performed a bibliometric analysis to generate network and overlay visualizations for research on isthmic spondylolisthesis. We employed a co-occurrence analysis with a full counting method, focusing on author’s keywords. Keywords appearing at least 3 times were included in the analysis, resulting in 97 of the 857 keywords meeting this criterion. The layout settings were configured with an attraction value of 2 and a repulsion value of 1. For clustering, we set the resolution to 0.60 and the minimum cluster size to 1 (Fig. 4).

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3.7 Strategic diagram

3.7.1

3.7.1 First period

Fig. 5a's strategic diagram shows 8 themes from 2002 to 2012. Keywords across themes lack diversification, making differentiation challenging.

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Fig. 5 Strategic diagram of author’s keyword in isthmic spondylolisthesis. The 'Walktrap' algorithm was used for clustering, with a minimum cluster frequency of 5 and a weight index of 0.06. The time slices chosen were 2002 and 2012 because publications began increasing in 2002, and 2012 serves as a midpoint to assess advancements. (a) Diagram of the first period; representing keywords between 2002 and 2012. (b) Diagram of the second period; representing keywords from 2013 until 2024. The diagrams are divided into 4 quadrants: Motor themes (Quadrant 1/upper-right quadrant), Niche themes (Quadrant 2/upper-left quadrant), Emerging or declining themes (Quadrant 3/lower-left quadrant), and Basic themes (Quadrant 4/lower-right quadrant) (Fig. 5).

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4.1 Publication growth

Scientific production fluctuated but showed an overall upward trend reflecting the growing interest and engagement from researchers, peaking in 2022. Most research focuses on surgical techniques such as comparing different techniques or evaluating their short-term and long-term outcomes. This proliferation of studies likely stems from the ongoing controversy surrounding the optimal surgical approach for this condition. However, publications are expected to decline in 2024, currently showing only five related publications. Despite its status as the second most common type among spondylolisthesis cases, its incidence in the general population which ranges only from 4 % to 8 % might explain the current waning of research interest.²

4.2 Countries

The United States has played a pivotal role in advancing spine science since 1829, as evidenced by the significant contributions of American surgeons and the establishment of numerous spine-related medical societies in America.⁸ The Cervical Spine Research Society (CSRS), founded in 1973, focuses on advancing surgical techniques, diagnosis, and treatment for cervical spine disorders. In similar spirit, the Lumbar Spine Research Society started in 2008. North American Spine Society (NASS), established in 1985, leads efforts to advance knowledge, excellence, and patient outcomes in spine health.

The leading contribution of certain countries to publications on this topic may be supported by a large number of funding sponsors. Further analysis shows many institutional funders are based in the US and China. However, this conclusion remains uncertain due to the presence of many undefined institutional funders.

4.3 Author and journal analysis

There is a correlation between the top prolific authors, locations, and collaboration; where the majority come from the same country and have collaborated. This should encourage collaboration in future research. Spine is a pioneering journal founded in 1976 and dedicated exclusively to spinal research, which has led to its highest publication record in isthmic spondylolisthesis. Its legacy continued with the launch of the Journal of Spinal Disorders and Techniques (1988), which ranks third. Additionally, the European Spine Journal (1991), holds the second position. Since then, numerous spine-focused journals have emerged with more anticipated in the future. These findings offer valuable guidance for researchers to decide where to publish, as higher impact factors are typically esteemed.

4.4 The most productive and recent keywords

Fig. 3b highlights current trending topics: ESS and PROMs. Open spinal surgery has a long recovery time, and has several complications. Minimally invasive techniques such as ESS have emerged as an alternative, with reduced tissue damage and improved patient outcomes.⁹ Initially used for lumbar discectomy and simple nerve decompression, ESS is now possible to safely achieve spinal fusion due to the advancement of percutaneous screw fixation systems.^10–13 However, the efficacy of ESS for spinal fusion has not been conclusively shown to yield superior outcomes.¹⁴ Publications regarding the application of endoscopic spine surgery in isthmic spondylolisthesis remain a developing trend and are still relatively few. PROMs assess an individual's health perception using questionnaires. It remains a prominent topic, with numerous publications comparing clinical outcomes across various methods.

4.5 Keyword Co-occurrence cluster

Cluster 1 (red) (Fig. 4a) revolves around the general characteristics of spondylolisthesis. It commonly occurs in the L5-S1 due to higher mechanical stress compared to above portion.¹⁵ Instability in spondylolisthesis causes symptoms such as hamstring tightness, lower back pain, or buttock pain exacerbated by spinal extension.^16,17 Low-back pain, the predominant symptom, can be evaluated using The Oswestry Disability Index (ODI).¹⁸ Lateral lumbar plain radiographs are recommended for their quick results, affordability, and availability.¹⁹ Radiculopathy may also occur, warranting MRI evaluation.²⁰

Cluster 2 (green) (Fig. 4a) revolves around operative treatment for isthmic spondylolisthesis. Surgical management is an option in cases with high slippage risk, symptomatic, or not achieving satisfactory results after conservative treatment. The mainstay of surgical principles are decompression, stabilization and fusion.²¹ Spino-pelvic parameters can be assessed using whole standing postero-anterior and lateral radiographs. This aims to analyze postoperative spinal alignment and aids surgical planning. PLF and LIF are the most popular fusion techniques.²² PLIF is widely utilized and associated with higher fusion rates compared to PLF.^22–25 Circumferential fusion effectively treats all grades of isthmic spondylolisthesis with an acceptable complication rate.^26–28 However, the optimal surgical approach for isthmic spondylolisthesis remains contentious due to its varying advantages and disadvantages.

Cluster 3 (Blue) (Fig. 4a) revolves around ALIF. By providing direct midline view of the disc space and extensive lateral exposure of the vertebral body, ALIF facilitates aggressive correction of lordosis and restoration of foraminal height.²⁹ ALIF can be considered as an option to directly decompress foraminal stenosis in adults with low-grade isthmic spondylolisthesis, and may be superior in terms of radiographic measures than TLIF.^30,31 However, approach-related complications such as retrograde ejaculation, and visceral and vascular injury are associated with ALIF.²⁹

Cluster 4 (yellow) (Fig. 4a) mainly revolves around identifying and diagnosing spondylolisthesis. Understanding epidemiology can assist medical practitioners in identifying potential diagnoses through a patient's medical history and physical examination. Differentiating the type and grading of the slip angle guides further management. Dysplastic spondylolisthesis is a congenital defect which is present from birth. While the isthmic, the defect is usually present by the age of 7, but the slip may appear only some years later.¹ Grade I-II are low-grade spondylolisthesis and grade III-IV are high-grade spondylolisthesis.

Cluster 5 (purple) (Fig. 4a) revolves around FEA. FEA helps to determine how organs and tissues react to loads, enhancing the understanding of biomechanics in healthy or pathological conditions.³² It is useful for evaluating biomaterials for implant design, predicting mechanical stress distribution and helping prevent future pathologies caused by incorrect implant positioning.^33,34 FEA can analyze spine biomechanics before and after surgery, allowing surgeons to analyze the pros and cons of different internal fixation methods for spine repair.^35,36

Cluster 6 (gray) (Fig. 4a) contains only one keyword, "discography”. Discography is a diagnostic test for identifying intervertebral discs pathological feature, involves injecting a contrast agent into the disc's nucleus pulposus under X-ray, CT, or MRI.³⁷ It is is now rarely used due to the risk of the procedure and its complications, which may explain its infrequent mention.

4.6 Strategic diagram

4.7 Limitations

While the bibliometric research method offers an overview of discussions on isthmic spondylolisthesis, readers need a basic understanding of the topic for better comprehension. The current bibliometric study we only incorporated one database. While Scopus being the largest and renowned database and missing keywords may be covered by the number of articles included, this might still reduce the robustness of the results. In addition, we excluded non-English articles, which may introduce bias and reduce the generalizability.

Guardian/patient's consent

There are no human subjects in this article and informed consent is not applicable. This manuscript titled “Research Topics and Trends of Isthmic Spondylolisthesis: A Bibliometric Analysis and Review of Literature” is a bibliometric analysis that uses sample data from the Scopus database in the form of articles related to isthmic spondylolisthesis.