The “ Golden Age ” of quadriceps tendon grafts for the anterior cruciate ligament: a bibliometric analysis

Importance: Bibliometric research is a statistical analysis of publications to measure the scienti ﬁ c output in a speci ﬁ c ﬁ eld in order to highlight medical developments or knowledge gaps and to direct future scienti ﬁ c research. The quantity of orthopedic papers on the internet is astounding and is steadily growing as a result of recent advancements in technology and medicine. This is why choosing the right information is essential


INTRODUCTION
The occurrence of anterior cruciate ligament (ACL) rupture is prevalent among people who engage in physical activities, with an estimated yearly frequency of approximately 1 in 3500 individuals in the United States [1].Due to ongoing and substantial research efforts and advancements in surgical techniques, ACL reconstruction (ACL-R) has gained widespread acceptance as the preferred treatment modality for ACL injuries in recent decades [2].
Currently, a range of autograft and allograft choices, such as hamstring (HT), bone patellar-tendon-bone (BPTB), quadriceps tendon (QT), and other alternatives, have been effectively employed in clinical and surgical practices for ACL-R [3].The QT was initially proposed as a potential graft choice for ACL-R in the late 1970s [3].However, its adoption was limited due to the initial emergence of several postoperative complications, such as elevated anterior laxity, weakness in the extensor mechanism, and positive pivot shift in approximately 20% of the treated cases [4].Consequently, the utilization of the QT as a graft option for ACL-R did not gain widespread acceptance and was largely discontinued.However, it is not unexpected that these outcomes were observed, given that the initial treatments involved the extraction of a substantial segment of the QT, together with sections of the prepatellar retinaculum and patellar tendon, resulting in considerable soft tissue damage [4].In recent decades, BPTB and HT autografts have consistently emerged as the predominant choices for grafting in ACL-R surgeries on a global scale [5].Nevertheless, the resurgence of the QT in the clinical and research domains can be attributed to advancements in harvesting procedures and devices, coupled with notable enhancements in surgical techniques.These advancements have been accompanied by substantial research and a multitude of clinical studies, which have reported favorable outcomes [4].Consequently, the QT is presently acknowledged as a feasible option for transplantation, offering a durable and mechanically advantageous graft.An increasing number of studies are providing evidence of the therapeutic potential and biomechanical features of QT autografts, highlighting their numerous benefits [4].The rise in usage potential of the ACL Study organization has been acknowledged by experts in the field, leading to the establishment of the International Quadriceps Tendon Interest Group (IQTI) in 2017 [6].The primary objective of this expert organization is to promote the adoption of the QT as a viable graft option.According to the findings of the 2018 study conducted by the IQTI expert group, it is advised to increase the frequency of employing QT autografts.This recommendation is based on the superior anatomical and biomechanical characteristics exhibited by the QT autograft when compared to other autograft options that have been traditionally utilized [6].
Bibliometric research is a statistical analysis of publications to measure the scientific output in a specific field in order to highlight medical developments or knowledge gaps and to direct future scientific research.The quantity of orthopedic papers on the internet is astounding and is steadily growing as a result of recent advancements in technology and medicine.This is why choosing the right information is essential [7,8].
One bibliometric measure used to assess an article's scholarly effect is the quantity of citations it has received.While this does not equate to quality, it does show the degree of attention and impact an item has in a particular sector [7,8].No previous bibliometric analysis of ACL-R with the quadriceps has been found, according to an examination of the current literature.Therefore, the purpose of this study was to analyze the trends of publications on anterior cruciate ligament reconstruction using the quadriceps as a graft in the current literature.We hypothesized that publications on this topic have quickly increased in recent years due to increased knowledge of both clinical and radiological pathology.

METHODS
The current bibliometric analysis follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.PubMed was searched on August 28, 2023 by two orthopedic surgeons experienced in knee surgery (SBK and RD) (Appendix 1) [9].
The references were collected from PubMed, and trends were analyzed using this information.
No time limit has been set for the bibliometric analysis.This retrieved 830 articles on human and animal studies.The bibliometric analysis encompassed solely those studies that examined the utilization of the quadriceps as a graft for ACL reconstructions leaving 405 articles for analysis.
A flow chart of the article selection process is presented in Fig. 1 [10].
We analyzed the top 10 authors and journals in terms of publication numbers, citation numbers, and citations per year.The PubMed-by-year feature was used to compare the number of publications on ACL reconstruction with the quadriceps with all publications in PubMed.
Data mining was performed using the Orange software, Mac version 3.32.0(https://orangedatamining.com/), from the titles of all articles [11].The output is presented as word clouds.Most of the analysis was What are the new findings?
By utilizing a variety of indicators, including the impact factor and the H-index, bibliometric approaches assist in the quantitative evaluation of publications and are best known for their efforts to assess the importance of scientific research.These indicators are being used more frequently by reviewers and policy-makers to assess the impact of research since such analyses are more objective than peer reviews.Global trend analysis suggests that research on anterior cruciate ligament reconstruction with the quadriceps has significantly increased in the last 5 years and that the number of papers on this topic is increasing steadily.

What is already known
Quadriceps Tendon autograft shows superior anatomical and biomechanical characteristics when compared to other autograft options that have been traditionally utilized.The quantity of orthopedic papers on the internet is astounding and is steadily growing as a result of recent advancements in technology and medicine.performed using the output from PubMed (yearly publications, citations per publication, top authors, top journals).A word cloud analysis of titles from different periods (before 2017, after 2017, and journals before and after 2018) was performed.A word cloud analysis of the authors (before and after 2018) was also performed.

RESULTS
The number of yearly publications averaged 10 or less up to 2018 from 1982 when the first paper on the QT was published.However, the number of publications increased from 2018.While the total number of publications on this topic was 405, 260 were published from 2018 alone.This amounts to 64% of all publications in just the last six years.There has been a large surge in interest in this topic in recent years.The number of citations was 8262 in total over all years.It is expected that the last five years' publications, especially those for the last year, will be low in number, as it takes time for the citations to accrue.The maximum number of citations showed that the year interest in this topic started increasing in 2018 (Fig. 2).
The most cited article results to be "Vertical femoral tunnel placement results in rotational knee laxity after anterior cruciate ligament reconstruction," published in 2007 in Arthroscopy with 187 citations.The 50 most cited articles are resumed in Table 1.
The number of citations of ACL-R with the quadriceps compared to all publications in PubMed, noting a precipitous rise from 2018 (Fig. 3).
The journal Arthroscopy published the most articles on this topic, with 57 papers and 1884 citations, followed by the American Journal of Sports Medicine, with 39 articles and 1576 citations.The top three journals on this topic were Arthroscopy: The Journal of Arthroscopic and Related Surgery; The American Journal of Sports Medicine; and Knee Surgery, Sports Traumatology, Arthroscopy, official journal of the ESSKA (Fig. 4).
When we analyzed the number of citations per publication for the journals, The Orthopedic Clinics of North America, The Journal of the American Academy of Orthopedic Surgeons and British Journal of Sports Medicine were the top three journals, with 63, 56 and 50.5 citations per publication, respectively.Each of these journals had equal to or less than five publications published (Table 2).
There were a total of 1508 authors with 304 unique first authors.The most published author was Musahl V (with 24 articles), and the most cited author was Xerogeanes JW (with 570 citations).The top 10 authors arranged in order of the number of publications are given in Fig. 5.The top 10 authors by number of published articles and citations are given in the figure.Musahl V was the top published author, with 24 articles and 319 citations.Xerogeanes JW was the most cited, with 570 citations and 20 publications.The top three published authors included Musahl V, Xerogeanes JW, and Fink C.
Word clouds for titles, journals, and authors, including differences before and after 2018 for authors and titles, are given in Appendix 2 and Figures S1 to S5.

DISCUSSION
The main findings of our study reveal that there has been a steady growth in the number of publications regarding anterior cruciate ligament reconstruction using quadriceps grafting in the last 5 years (from 2018 to 2023), with an upsurge in publications.Our analysis demonstrated that Arthroscopy: The Journal of Arthroscopic Related Surgery is the most impactful journal and that Musahl V is the most impactful author on the topic of anterior cruciate ligament reconstruction using the quadriceps.Xerogeanes JW is currently the author with the most citations on the topic (570).
Currently, this is the first article in the literature to analyze PubMed in detail regarding publication trends and bibliometric data regarding anterior cruciate ligament reconstruction with the QT.
The reason why this tendon has experienced a resurgence in recent years is attributable to several and varied factors [6].In ACL-R, QT autografts are significantly less prevalent than HT and BPTB grafts [12].According to historical research, the QT autograft was linked to unacceptably high rates of residual rotatory knee laxity and quadriceps weakness, and it had worse biomechanical qualities than the native ACL [2].The behavior of a "substitution" graft harvest approach, which entailed a thorough dissection of a 13 cm segment of extensor mechanism tissue made up of the QT, prepatellar retinaculum, and patellar tendon tissue, served as a major basis for these results [13].Additionally, it was found that, in terms of ultimate load assessments, the graft obtained via the substitution procedure was 14%-21% weaker than the native ACL [2].The substitute approach of autograft harvesting in ACL-R has been linked to a 20% rate of postoperative pivot shift.Significant quadriceps weakness is still linked to the substitute graft harvest procedure, especially in women.As a result, prior claims that the QT autograft was less effective in ACL-R were mostly supported by data from an out-of-date graft harvesting method [14].
Contemporary methods for harvesting QT autografts consistently provide a substantial amount of soft tissue while reducing the risk of donor site morbidity and/or deficiencies in quadriceps strength.Regarding the suitability of QT autografts for primary and revision knee ligament restoration, encouraging clinical data continue to come to light [14].
It is recommended to choose a graft based on individual characteristics in contemporary ACLR; there is no one graft that is suitable for all individuals.When selecting the most suitable graft for each patient, the surgeon must take into account several patient-specific, physician-specific, and graft-specific criteria.The factors to be taken into account are   the accessibility of tissue, any previous or simultaneous injury, the presence of other medical conditions in the patient, and the level of expertise of the surgeon.The ideal graft will provide a quick and efficient harvest with few complications, rapid integration into the body, and mechanical and structural characteristics that are comparable to the natural ACL.Nevertheless, each graft alternative possesses distinct anatomical and biomechanical features, leading to specific benefits and drawbacks [15].Several recent clinical studies and reviews support the use of the QT as a primary graft choice [16][17][18].
Dai et al. in 2021 analyzed 7 RCTs and 17 observational studies for a total of 19,584, hypothesizing that QT had comparable graft survival as well as clinical function and pain outcomes with respect to HTs and bonepatellar-tendon-bone grafts.The authors concluded that the QT autograft had comparable graft survival, functional outcomes, and stability outcomes compared with BPTB and HT autografts.However, donor site morbidity was significantly lower with QT autografts than with BPTB and HT autografts [19].
Similarly, Mourabes et al. performed a systematic review and metaanalysis and found that QT autografts had comparable clinical and functional outcomes and graft survival rates compared with BPTB and HT autografts.However, QT autografting resulted in significantly less harvest site pain than BPTB autografting and better functional outcome scores than HT autografting [15].
The "new life" application of the QT for ACL reconstruction not only involves primary ACL surgery but also concerns revision surgery, and the number of publications is increasing, supported by clinical studies.In fact, recently, Ashy et al. performed a systematic review and meta-Fig.3. The graph shows the number of citations for ACL-R using quadriceps graft, compared to all PubMed publications (per 100,000 PubMed publications) in Y axis, over the years in X axis.analysis of revision ACL-R (RACLR) with the QT and compared its patient outcomes to those of RACLR with HT and BTB autografts.RACLR with QT autografting yields satisfactory patient-reported outcomes, satisfactory improvement in knee laxity, and expected return to sport rates and has an overall 7.6% failure rate.Outcomes are comparable to those of the HT and BTB, making the QT an acceptable graft choice for RACLR [20].
One of the reasons this tendon was abandoned for years, scientifically and clinically, was due to the number of complications.It has been seen, however, especially in recent years that these are negligible or at least comparable to those of other grafts.
Even though QT ACL-R results are similar, problems do occur and have been documented in a number of studies over the years.Thankfully, the majority of significant issues affect only a tiny proportion of patients, and the majority of complications are mild.These comprise the standard hazards of ACL-R that are related to any kind of transplant, such as graft failure, infection, and venous thromboembolism [6,14].In contrast to BTB or HS ACL-R, Lind et al. discovered a much greater revision rate in the Danish Knee Ligament Registry after QT ACL-R.However, after more investigation, they found that the higher revision rate only occurred in centers that performed fewer than 100 procedures over an 8-year span.This highlights the fact that there is a learning curve for QT ACL-R and that, similar to many other surgical techniques, better results come with more practice [21,22].
The increasing trends of publications regarding ACL-R with the QT have also occurred because in the last ten years, there has been a sharp increase in publications worldwide [23].This shows a significant growth in scientific interest in these minimally invasive techniques.Arthroscopic procedures enable a faster healing process after surgery, which enables patients to resume sporting and professional activities sooner than after  conventional surgery.In addition to a general increase in the number of publications in medicine, the rising publication rate can be explained by, among other things, increasing technical and technological progress, resulting in increased procedural options and novel indications [24].Bibliometric techniques are most known for their efforts to measure the significance of scientific research using many indicators, including the impact factor and the Hirsch (H)-index, and for their assistance in the quantitative evaluation of publications [25].Due to their greater objectivity than that of peer reviews, reviewers and policy-makers are increasingly employing these indicators to assess the impact of research.However, assessors may employ bibliometric indicators erroneously due to a lack of clarity regarding their functionality [25].The most common mistake is probably estimating an article's importance based only on its impact factor, which is inaccurate because only 10%-30% of papers published in journals receive the majority of the citations (also known as "skewed publications") that journals use to determine their impact factor [25].
There are significant differences in citation counts between different topic fields; hence, it is incorrect to compare the impact factor or an author's H-index values between disciplines.The third common mistake assessors make is not taking time into account.Citations accumulate slowly at first, but they also continue to accumulate over time.Studies have shown that papers need to have received enough citations for two or three years after publication for bibliometric indicators to be reliable.This suggests that the most recent papers considered in any institutional evaluation, including bibliometric markers, should have been published no less than two years previously [26,27].
Regarding the impact of bibliometric analysis, a recent article examined a series of papers from top-ranked orthopedic journals with respect to the number of citations over a 10-year observation period to identify factors that lead to high citation rates and thereby identify what makes an orthopedic publication highly citable.The authors found a statistical correlation between the number of citations and the number of authors, number of keywords and number of references.In addition, the top 20% of papers showed a largely constant citation trend after two years for up to at least ten years.Randomized clinical trials (RCTs) and reviews are cited most frequently [28].
Our study presents some limitations.First, only terms from the titles were used for the analysis.This has the following drawback: if a term was not included in the title, the analysis would not incorporate it.Some data may be missing because standardizing the names of manuscripts-such as RCTs and systematic reviews-is a relatively new requirement that authors and publishers have not all followed consistently.
Veterinary journal publications were among the ones examined.Since the majority of fundamental science research on the ligament was conducted on animals and some of these articles may have been published in veterinary journals, we did not attempt to separate the veterinary literature.Our study relied on PubMed, which, similar to all bibliometric databases, is not exhaustive.For instance, PubMed does not show all the articles published in different databases (WoS or Scopus).Nevertheless, it is most commonly used and freely available.
We selected one of the most popular databases, but there is no single one that is unquestionably better.Since citations are a dynamic phenomenon, the articles and search results we found today represent the state of the field; a search conducted later may provide different results, or the quantity of citations may change.
Last, the quality and quantity of evidence in the papers is another constraint; even though a study is frequently mentioned, it may only be a level 5 paper.
Despite the abovementioned possible limitations, we believe the approach utilized in this study is appropriate for the type of research.Research trends and hotspots can be easily seen using bibliometrical and visual analysis.This can help figure out the best future directions for basic and clinical research and boost research skills in the field of ACL reconstruction.

Conclusions
Global trend analysis suggests that research on anterior cruciate ligament reconstruction with the QT has significantly increased in the last 5 years and that the number of papers on the topic is increasing steadily.We found that the publications and citations presented a rising trend: Arthroscopy: The Journal of Arthroscopic and Related Surgery, is the most impactful journal, and Musahl V is the most impactful author on the topic; Xerogeanes JW is currently the author with the most citations on the topic.The promising clinical results of anterior cruciate ligament reconstruction with quadriceps have attracted the most research interest.

Ethical committee approval
Not needed, being a literature review and not involving any human intervention.

Funding
None.

Fig. 1 .
Fig. 1.PRISMA type chart of the analysis of articles and summary of the methodology.

Fig. 4 .
Fig. 4. Top ten journals for publications and citations.

Table 2
Top 10 journals arranged as per citations per publication for journals.