1 Introduction

Proximal femur fractures commonly known as hip fractures are a major healthcare burden with a profound impact on patients.¹ 4.5 million patients worldwide are affected by this pathology each year which is expected to increase to 6.26 million by 2050.^2,3 By the year 2040 projected costs related to hip fractures are $9.8 billion in the United States and $650 million in Canada.⁴ A hip fracture is a significant cause of morbidity and mortality, and mortality rates have been reported in the literature as high as 10.5 % thirty days after surgery and 27.3 % at one year post-operatively.⁵ Early surgical management is essential in order to lower the risk of morbidity and help reduce mortality rates.^6,7

Intracapsular neck of femur fractures are most commonly treated by performing a hip hemiarthroplasty.⁸ Different options are available when performing this surgery, unipolar and bipolar implants can be used along with cemented and cementless stems.⁹ Much debate exists within the literature around the use of cemented or cementless stems, unipolar or bipolar implants and what surgical approach to undertake.⁸

Citation count remains a quantifiable metric to assess the influence of certain articles. Analysing trends and research hotspots on the most cited articles within a given topic is known as a bibliometric analysis. Many bibliometric analysis have been conducted on various other Orthopaedic topics. To our knowledge this is the study conducted on hip hemiarthroplasty. Given how common this procedure is performed worldwide and how variable the management can be throughout different centres, this study aimed to analyse the most cited articles in this area to uncover any research trends and common characteristics shared between these studies. Our hypothesis was that most of the highly cited studies would be published from the USA and focus on different treatment options when performing a hip hemiarthroplasty. We also hypothesised that many of the articles would be published from the same journals and institutions.

2 METHODS

3 RESULTS

3.1

3.1 Literature search

The search strategy yielded 1241 studies, which were subsequently screened and filtered according to the selection criteria. After ranking by citation count, the top 118 studies underwent further evaluation, leading to the exclusion of 68. Ultimately, 50 full-text articles were included in the review (Fig. 1)

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Fig. 1 Search strategy.

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3.2

3.2 Study characteristics & patient demographics

Citation counts per study varied significantly, ranging from 38 to 300 citations. 22 % of the studies had more than 100 citations. Patient gender was reported in 43 studies, with 46,292 (28.4 %) male patients and 116,444 (71.6 %) female patients (Table .1). The main focus within the contained studies compared outcomes of cemented vs cementless stems with 12 of the 50 (24 %) included studies focusing on this, followed by 11 (22 %) studies comparing total hip arthroplasty vs hip hemiarthroplasty.

Table 1 Summary of bibliometric parameters of the top 50 cited studies.

Characteristic	Count
Number of citations total (range)	4068 (38–300)
No. of studies with ≥100 citations (% of total)	11 (22)
Patient
Total Number (No. of studies)	188696 (49)
Mean Age	79.5
Sex
Male (No. of studies)	46,292(46)
Female (No. of studies)	116,444 (46)

Publications increased from 2005 onward, peaking in 2011. The two most cited studies were published in 2006 and 2007 (Fig. 2). A significant proportion (44 %) of the top 50 studies were classified as Level I evidence (Fig. 3). Ponzer et al. from the Karolinska institution was the most highly cited author (Table .2), and this institution also led in total publications along with the University of Bergen and Haukeland University hospital (Table .3). Clinical Orthopaedics and Related Research was the most productive journal, publishing 11 studies (Table .4). USA produced the most articles with 8 studies (16 %) while England, Sweden and Norway followed closely with 7 studies each (Table .5).

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Fig. 2 Publication trends over time for the Top 50 cited articles.

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Fig. 3 Level of evidence compared to citation count and number of published articles.

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Table 2 The most Productive Authors.

Author	No. of articles
S Ponzer	6
R Blomfeldt	5
J Gjertsen	5
A Enocson	4
L Engesaeter	4
O Furnes	4
J Tidermark	4
H Tornkvist	4

Table 3 The top 5 most productive institutions.

Institution	Country	No. of articles
Haukeland University hospital	Norway	5
Karolinska Institute	Sweden	5
University of Bergen	Norway	5
Södersjukhuset Hospital	Sweden	4
Saint Göran Hospital	Sweden	3

Table 4 Top 5 most productive journals with impact factor.

Journal	No. of studies	Impact Factor
Clinical Orthopaedics and Related Research	11	4.2
Journal of Bone and Joint Surgery – British Volume	6	4.6
Journal of Bone and Joint Surgery-American Volume	6	4.6
Acta Orthopaedica	4	2.5
Injury- International journal of the care of the injured	4	2.1

Table 5 The top 5 countries with frequently cited articles.

Country	No. of articles
USA	8
England	7
Sweden	7
Norway	7
Netherlands	4

3.3

3.3 Institutional and author coupling analysis

A coupling analysis of institutions revealed that ten institutions met the threshold of at least two articles. The University of Bergen and the Haukeland hospital had the strongest link strength (LS) with 5 publications each, 388 citations each, and a LS of 23 each. It was followed by Södersjukhuset with 3 articles (291 citations, LS = 15) and University of Aberdeen and University of Edinburgh (400 citations, LS = 12), each with two articles(Fig. 4A).

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Fig. 4 Bibliographic coupling analysis of publication institutions (A) and authors (B) (≥2 published articles).

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In the author coupling analysis, 30 authors met the threshold of having at least two articles. The author with the strongest link strength was S.Ponzer, with four publications and 352 citations (LS = 17), followed by R. Blomfeldt (LS = 14), G. Lapidus (LS = 14), J. Tidermark (LS = 14), H. Tornkvist (LS = 14) all with three publications(Fig. 4B).

3.4

3.4 Keyword analysis

A total of 202 keywords were analysed for their frequency of occurrence. The five most frequently used keywords were "replacement" (n = 21, LS = 77), "bipolar hemiarthroplasty" (n = 20, LS = 69), "internal-fixation" (n = 15, LS = 56), "prosthesis" (n = 11, LS = 46), and "femur" (n = 14, LS = 43)(Fig. 5).

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Fig. 5 Co-occurrence analysis of keywords.

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3.5

3.5 Co-citation analysis

Using a minimum of 5 citations, 56 authors were included in the co-citation analysis (Fig. 6). The top five authors based on link strength were MJ Parker (44 citations, LS = 589), J. Tidermark (26 citations, LS = 460), M. Bhandari (22 citations, LS = 354), R. Blomfeldt (21 citations, LS = 354), and C. Rogmark (20 citations, LS = 337).

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Fig. 6 Co-citation analysis of authors.

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4 Discussion

The most important finding is that the most cited studies within the hip hemiarthroplasty litreature is of high scientific quality, with a large proportion of studies representing Level I evidence and focusing on the use of cementless or cemented stems. The majority of the most cited studies are published within a limited number of journals with a significant proportion of patients being female.

The purpose of a bibliometric analysis is to explore research trends in a specific field and highlight possible directions for future research. This is particularly useful for topics with a large body of literature, as it helps identify the most influential areas and highlights questions that are not yet answered within that field. In a topic such as hip hemiarthroplasty which is a very commonly performed procedure, it is encouraging that a significant proportion of the highly cited studies are of Level I evidence. This is not uniform throughout Orthopaedic with many bibliometric analyses showing that much of the litreature and practice is guided by Level IV evidence.^10–13

The decision to use cemented or uncemented stems for hip hemiarthroplasty has been long debated within Orthopaedics and is unsuprising that this is a major focus of the most cited studies. A recent meta analysis of randomized controlled trials by Feng et al. found that cemented hemiarthroplasty leads to superior outcomes with lower rates of 1-year mortality, postoperative periprosthetic fracture, loosening aswell as lower rates of intraoperative periprosthetic fracture.¹⁴ However, authors have found that cemented hemiarthroplasty leads to increase operative time and increased blood loss.^15,16 Pritto et al. has shown an increase in the rates of embolic events and pulmonary insult when using cement during the procedure, while further articles have shown higher perioperative mortality rates associated with cement use.¹⁷ Given that the majority of patients who require a hip hemiarthroplaty are frail, elderly patients with multiple comorbidities it is not suprising that the potential for a quicker operation with less physisological toll on patients that may be associated with a cementless proceudre is widely investigated.

The most cited article found in this study is titled “Randomized comparison of reduction and fixation, bipolar hemiarthroplasty, and total hip arthroplasty - Treatment of displaced intracapsular hip fractures in healthy older patients” by Keating et al., which was published in the Journal of Bone and Joint Surgery-American Volume in 2006.¹⁸ This study compared outcomes following treatment with either reduction and fixation, bipolar hemiarthroplasty with cement, and total hip replacement with cement. Interestingly, the findings of this study suggest that while reduction and fixation is a cheaper initial treatment method it is assocatied with a higher overall cost when compared to arthroplasty due to higher rates of readmission and reoperation. It also found that 2 year functional outcomes are superior for patients managed with total hip arthroplasty. This article represents another major focus of the most cited studies on hip hemiarthroplasty with 22 % of included studies comparing total hip arthroplasty to hip hemiarthroplasty.

Previous studies have shown that citation counts vary across different orthopaedic subspecialties.^19–22 Interestingly, the most cited study on hip hemiarthroplasty had only 300 citations. This study aligns with previous findings that different orthopaedic subspecalities contribute to the Orthopaedic litreature in variable quantities, which could be explained due to greater research focus on elective preactice compared to the trauma setting.²³

Previous authors have criticised the purpose of examining the most highly cited articles, questioning the relevance that citation count has in measuring the impact of an article and believe it doesn't offer a reliable measure of their quality.^24–26 Previous studies may align with this viewpoint with a large number of the included studies being of a low quality of evidence.^10–13 However, this study demonstrates that the most impactful studies with the greatest contribution to the hip hemiarthroplasty literature are of high scientific quality. This correlates with recent studies which suggest that the scientific quality of Orthoapedic litreature is improving.^27,28

Clinical Orthopaedics and Related Research are the most prominent journal in the hip hemiarthroplasty literature, followed by the Journal of Bone and Joint Surgery. This aligns with Callaham et al.’s viewpoint that higher citation counts are influenced by the higher the impact factor of the journal.²⁹ The US had the most contributions to the literature and this has been seen in many other bibliometic analyses, which could be explained due to available resources.^10,30–33

5 Conclusion

The most cited studies within the hip hemiarthroplasty litreature is of high scientific quality, with a large proportion of studies representing Level I evidence and focusing on the use of cementless or cemented stems. The majority of the most cited studies are published within a limited number of journals with a significant proportion of patients being female.

CRediT authorship contribution statement

Conor J. Kilkenny: Investigation, Writing – original draft, Visualization. Conor Farrell: Investigation, Methodology, Writing – review & editing. Conor Medlar: Investigation, Writing – review & editing. Martin S. Davey: Methodology, Writing – review & editing. Fahad Farooq: Formal analysis, Writing – review & editing. John F. Quinlan: Conceptualization, Writing – review & editing, Supervision.

Informed consent

Not applicable.

Declarations

•The authors did not receive support from any organization for the submitted work.

•The authors have no relevant financial or non-financial interests to disclose.

Human ethics and consent to participate declarations

Not applicable.

Data, materials and/or code availability

N/A.

Ethical statement

Hereby, I Conor J Kilkenny assure that for the manuscript “Uncovering Research Trends in hip hemiarthroplasty: A Citation and Publication Analysis” the following is fulfilled.1)This material is the authors' own original work, which has not been previously published elsewhere.2)The paper is not currently being considered for publication elsewhere.3)The paper reflects the authors' own research and analysis in a truthful and complete manner.4)The paper properly credits the meaningful contributions of co-authors and co-researchers.5)The results are appropriately placed in the context of prior and existing research.6)All sources used are properly disclosed (correct citation). Literally copying of text must be indicated as such by using quotation marks and giving proper reference.7)All authors have been personally and actively involved in substantial work leading to the paper, and will take public responsibility for its content.

Funding

The authors have no relevant financial or non-financial interests to disclose.