Orthopedics

Feature Articles 

Trends in Femoroacetabular Impingement Research Over 11 Years

Barak Haviv, MD; Alon Burg, MD; Steven Velkes, MD; Moshe Salai, MD; Israel Dudkiewicz, MD

Abstract

Femoroacetabular impingement is the abutment between the proximal femur and the rim of the acetabulum. It is a common cause of labral injury that has been identified as an early cause of hip osteoarthritis. The diagnosis of femoroacetabular impingement of the hip is currently well defined in orthopedic surgery but should attract the attention of physicians in other disciplines. Conversely, much less is known about the etiology and natural history of femoroacetabular impingement.

The goal of this study was to assess the number of articles published on femoroacetabular impingement over 11 years in orthopedic vs nonorthopedic medical journals, and to evaluate the quality of available evidence. PubMed and OvidSP databases were searched for articles on femoroacetabular impingement published from 1999 to 2009. Articles were characterized by publication type and journal type per year. Regression analysis was used to determine the effect of publication year on number of publications of each type. The search yielded 206 publications on femoroacetabular impingement during the evaluation period. Seventy-two percent were published in orthopedic journals. Overall, the number of publications increased exponentially with time. There was an increase in clinical trials over the course of the study period. However, studies with high-quality evidence were scarce. The increase in data from orthopedic and nonorthopedic disciplines is welcome. Nevertheless, high-quality evidence on femoroacetabular impingement is lacking. We believe the current trend toward evidence-based orthopedic surgery will impact future research on this relatively new disorder.

Femoroacetabular impingement of the hip is considered a relatively new entity in orthopedic surgery and has been investigated extensively in the past decade. It is the abutment between the proximal femur and the rim of the acetabulum, which is a common cause of labral injury and has been identified as an early cause of hip osteoarthritis.1,2 The diagnosis and surgical treatment of femoroacetabular impingement are currently well established,3,4 along with short- to long-term outcomes.5-7

Conversely, much less is known about the etiology and natural history of femoroacetabular impingement.8-10 Prior to the recognition of femoroacetabular impingement, many young patients with groin pain were misdiagnosed and referred to other treatments. Therefore, it is important that femoroacetabular impingement is described and published in medical disciplines other than orthopedic surgery (eg, primary care medicine). The goal of this study was to determine if current trends toward a greater number of publications in orthopedic surgery, and specifically research with a higher quality of evidence, apply to femoroacetabular impingement. Given that femoroacetabular impingement is a multidisciplinary disease (eg, family practice, orthopedic surgery, sports, and imaging), we also assessed portions of the literature relative to the disease published in orthopedic and nonorthopedic journals.

Using the keywords femoroacetabular impingement, we searched PubMed and OvidSP for all articles published from January 1, 1999, to December 31, 2009. To refine our search at OvidSP, we used the 5-star ranking (ie, all search concepts are present and complete). For each article identified, we recorded the year of publication and the type of publication as categorized by PubMed: randomized, controlled trial; meta-analysis; clinical trial; review; technical; and case report. We also verified that the categorization by PubMed was adequate by reviewing all summaries. Some overlap was noted: Randomized, controlled trials that were also listed as clinical trials or case reports combined with a review of the literature were sometimes listed as both case reports and reviews. We used regression analysis and Pearson coefficient of correlation to determine the effect of time on the number of publications of each type. A P value <.05 was considered statistically significant.

The PubMed search (which included all search results from OvidSP) yielded 206 articles on femoroacetabular impingement published in…

Abstract

Femoroacetabular impingement is the abutment between the proximal femur and the rim of the acetabulum. It is a common cause of labral injury that has been identified as an early cause of hip osteoarthritis. The diagnosis of femoroacetabular impingement of the hip is currently well defined in orthopedic surgery but should attract the attention of physicians in other disciplines. Conversely, much less is known about the etiology and natural history of femoroacetabular impingement.

The goal of this study was to assess the number of articles published on femoroacetabular impingement over 11 years in orthopedic vs nonorthopedic medical journals, and to evaluate the quality of available evidence. PubMed and OvidSP databases were searched for articles on femoroacetabular impingement published from 1999 to 2009. Articles were characterized by publication type and journal type per year. Regression analysis was used to determine the effect of publication year on number of publications of each type. The search yielded 206 publications on femoroacetabular impingement during the evaluation period. Seventy-two percent were published in orthopedic journals. Overall, the number of publications increased exponentially with time. There was an increase in clinical trials over the course of the study period. However, studies with high-quality evidence were scarce. The increase in data from orthopedic and nonorthopedic disciplines is welcome. Nevertheless, high-quality evidence on femoroacetabular impingement is lacking. We believe the current trend toward evidence-based orthopedic surgery will impact future research on this relatively new disorder.

Femoroacetabular impingement of the hip is considered a relatively new entity in orthopedic surgery and has been investigated extensively in the past decade. It is the abutment between the proximal femur and the rim of the acetabulum, which is a common cause of labral injury and has been identified as an early cause of hip osteoarthritis.1,2 The diagnosis and surgical treatment of femoroacetabular impingement are currently well established,3,4 along with short- to long-term outcomes.5-7

Conversely, much less is known about the etiology and natural history of femoroacetabular impingement.8-10 Prior to the recognition of femoroacetabular impingement, many young patients with groin pain were misdiagnosed and referred to other treatments. Therefore, it is important that femoroacetabular impingement is described and published in medical disciplines other than orthopedic surgery (eg, primary care medicine). The goal of this study was to determine if current trends toward a greater number of publications in orthopedic surgery, and specifically research with a higher quality of evidence, apply to femoroacetabular impingement. Given that femoroacetabular impingement is a multidisciplinary disease (eg, family practice, orthopedic surgery, sports, and imaging), we also assessed portions of the literature relative to the disease published in orthopedic and nonorthopedic journals.

Materials and Methods

Using the keywords femoroacetabular impingement, we searched PubMed and OvidSP for all articles published from January 1, 1999, to December 31, 2009. To refine our search at OvidSP, we used the 5-star ranking (ie, all search concepts are present and complete). For each article identified, we recorded the year of publication and the type of publication as categorized by PubMed: randomized, controlled trial; meta-analysis; clinical trial; review; technical; and case report. We also verified that the categorization by PubMed was adequate by reviewing all summaries. Some overlap was noted: Randomized, controlled trials that were also listed as clinical trials or case reports combined with a review of the literature were sometimes listed as both case reports and reviews. We used regression analysis and Pearson coefficient of correlation to determine the effect of time on the number of publications of each type. A P value <.05 was considered statistically significant.

Results

The PubMed search (which included all search results from OvidSP) yielded 206 articles on femoroacetabular impingement published in the past 11 years in the medical literature; of these, 149 (72%) were published in orthopedic journals. From 1999 there was an exponential increase over time in the total number of publications on femoroacetabular impingement in the medical literature. Further analysis by journal type (orthopedic vs nonorthopedic) revealed an increase in the proportion of articles published in nonorthopedic journals, along with a continuous growth of articles published in orthopedic journals (Figure). There was a linear correlation between the year of publication to the number of annual published articles, both in orthopedic (Pearson correlation coefficient r=0.79, P=.004) and nonorthopedic (r=0.85, P=.001) journals.

Figure: Number of publications on femoroacetabular impingement per year per journal type
Figure: Number of publications on femoroacetabular impingement per year per journal type: orthopedic vs nonorthopedic journals (Abbreviations: Ortho, orthopedic journals; Non-Ortho, nonorthopedic journals).

We analyzed the articles by publication type, starting with publications with higher quality of evidence (Table 1). As mentioned, the numbers of articles in the specific categories do not necessarily add up because of categorization overlaps by PubMed. The current gold standard in evidence-based medicine is systematic reviews, which are not included in the PubMed categorization. Therefore, we conducted a parallel online search for systematic reviews on the Cochrane Library. We found no systematic reviews using the term femoroacetabular impingement on the Cochrane Library. Overall, in 2009, there were a substantial number of articles on femoroacetabular impingement in all types of publications compared to previous years. The publications of randomized, controlled trials and meta-analyses on femoroacetabular impingement over the years were scarce. There was a significant increase in the number of clinical trials and case reports since 2007 and of reviews since 2006. Excluding 2009, the number of technical reports and cadaver research remained between 1 to 2 annual articles since 2003.

Number of Publications on Femoroacetabular Impingement per Year per Journal Type

According to the level of evidence rating currently used by leading scientific journals,11 nine articles were level V, 85 were level IV, 22 were level III, 15 were level II, and 2 were level I. In addition, 75 reviews were not considered systematic reviews of level I to III studies and therefore can be categorized as level IV.

The leading journals reporting femoroacetabular impingement were those considered the most popular in orthopedic surgery (ie, with a higher impact factor) and several journals from the imaging field (Table 2).

Leading Journals in Femoroacetabular Impingement Studies<sup>a</sup>

Most studies were written by authors from North America (89 from the United States and 8 from Canada) and Europe (56 from Switzerland, 13 from Germany, and 10 from England).

Femoroacetabular impingement is treated surgically, either with open hip dislocation or by hip arthroscopy. Open hip dislocation was mentioned in 43 studies and hip arthroscopy in 56, while 22 included both techniques and 85 did not report on specific surgical technique.

Discussion

Our study shows that the number of publications on femoroacetabular impingement in the medical literature has increased steadily over 11 years. The increase was attributable to an increase in the appearance of articles in nonorthopedic as well as orthopedic literature. This finding emphasizes the multidisciplinary nature of femoroacetabular impingement, which has aspects relevant to family practitioners, radiologists, physiotherapists, sports physicians, and orthopedic surgeons. Moreover, the fact that most studies originated from just a few countries may reflect a universal lack of knowledge regarding femoroacetabular impingement. However, the presence of several major reports in high-impact orthopedic journals reflects the growing interest in femoroacetabular impingement in the orthopedic community.

At the same time, the increase in the number of publications was largely accounted for by an increase in articles of lower levels of scientific evidence, such as case reports and reviews. This was previously noted by Leunig et al.9 Publications representing the highest level of scientific evidence—namely systematic reviews; meta-analyses; randomized, controlled trials; and clinical guidelines—were few to none in number overall, with no change in recent years. The only 2 randomized, controlled trials were cadaveric studies on the approach and limitations of cam-type femoroacetabular impingement resection technique.12,13 Although the number of clinical trials has increased exponentially, many were inconsistent in their design and methodology. This was emphasized in a recent search of the literature by Clohisy et al,14 who found only 11 studies with clinical outcome data and minimum 2-year follow-up. However, most were level IV evidence studies with substantial limitations that primarily result from the inadequate number of publications, heterogeneous study methods, and surgical techniques used.

The shortage of high-quality studies may have several explanations. Symptomatic femoroacetabular impingement is not a common entity. For instance, the reported incidence of femoral deformity in osteoarthritic population is 0.6% in Japan.15 We found no reports on the prevalence of symptomatic femoroacetabular impingement in the general population. This makes it difficult for clinicians to conduct large-scale randomized, controlled trials. A byproduct of the low number of randomized, controlled trials is the lack of meta-analyses and clinical guidelines. Furthermore, because symptomatic femoroacetabular impingement is also a mechanical disturbance requiring surgical correction, it is not ethically possible to conduct comparative trials of true interventions vs placebo. This problem was exacerbated by the lack, until recently, of a consistent classification of disease stages16 and the therapeutic response.

Conclusion

The past 11 years have witnessed a significant increase in published data on femoroacetabular impingement. The growing amount of data published in journals from nonorthopedic fields is a welcome contribution, and a multidisciplinary approach will broaden our understanding on the pathogenesis of femoroacetabular impingement. The current trend should aim toward high-quality evidence-based studies.

References

  1. Ganz R, Parvizi J, Beck M, Leunig M, Nötzli H, Siebenrock KA. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003; (417):112-120.
  2. Ganz R, Leunig M, Leunig-Ganz K, Harris WH. The etiology of osteoarthritis of the hip: an integrated mechanical concept [published online ahead of print January 10, 2008]. Clin Orthop Relat Res. 2008; 466(2):264-272.
  3. Kuhlman GS, Domb BG. Hip impingement: identifying and treating a common cause of hip pain. Am Fam Physician. 2009; 80(12):1429-1434.
  4. Byrd JW, Jones KS. Arthroscopic management of femoroacetabular impingement. Instr Course Lect. 2009; (58):231-239.
  5. Byrd JW, Jones KS. Arthroscopic femoroplasty in the management of cam-type femoroacetabular impingement [published online ahead of print December 19, 2008]. Clin Orthop Relat Res. 2009; 467(3):739-746.
  6. Beck M, Leunig M, Parvizi J, Boutier V, Wyss D, Ganz R. Anterior femoroacetabular impingement: part II. Midterm results of surgical treatment. Clin Orthop Relat Res. 2004; (418):67-73.
  7. Philippon MJ, Briggs KK, Yen YM, Kuppersmith DA. Outcomes following hip arthroscopy for femoroacetabular impingement with associated chondrolabral dysfunction: minimum two-year follow-up. J Bone Joint Surg Br. 2009; 91(1):16-23.
  8. Leunig M, Ganz R. FAI—concept and etiology [in German]. Orthopade. 2009; 38(5):394-401.
  9. Leunig M, Beaulé PE, Ganz R. The concept of femoroacetabular impingement: current status and future perspectives [published online ahead of print December 10, 2008]. Clin Orthop Relat Res. 2009; 467(3):616-622.
  10. Sierra RJ, Trousdale RT, Ganz R, Leunig M. Hip disease in the young, active patient: evaluation and nonarthroplasty surgical options. J Am Acad Orthop Surg. 2008; 16(12):689-703.
  11. Wright JG, Swiontkowski MF, Heckman JD. Introducing levels of evidence to the journal. J Bone Joint Surg Am. 2003; 85(1):1-3.
  12. Sussmann PS, Ranawat AS, Lipman J, Lorich DG, Padgett DE, Kelly BT. Arthroscopic versus open osteoplasty of the head-neck junction: a cadaveric investigation [published online ahead of print October 29, 2007]. Arthroscopy. 2007; 23(12):1257-1264.
  13. Mardones RM, Gonzalez C, Chen Q, Zobitz M, Kaufman KR, Trousdale RT. Surgical treatment of femoroacetabular impingement: evaluation of the effect of the size of the resection. J Bone Joint Surg Am. 2005; 87(2):273-279.
  14. Clohisy JC, St John LC, Schutz AL. Surgical treatment of femoroacetabular impingement: a systematic review of the literature. Clin Orthop Relat Res. 2010; 468(2):555-564.
  15. Takeyama A, Naito M, Shiramizu K, Kiyama T. Prevalence of femoroacetabular impingement in Asian patients with osteoarthritis of the hip [published online ahead of print March 11, 2009]. Int Orthop. 2009; 33(5):1229-1232.
  16. Pollard TC, Villar RN, Norton MR, et al. Femoroacetabular impingement and classification of the cam deformity: the reference interval in normal hips. Acta Orthop. 2010; 81(1):134-141.

Authors

Dr Haviv is from the Arthroscopy and Sports Injuries Unit and the Department of Orthopedic Surgery, and Drs Burg and Velkes are from the Department of Orthopedic Surgery, Rabin Medical Center, Petah Tikva, and Dr Salai is from the Department of Orthopedic Surgery, and Dr Dudkiewicz is from the Orthopedic Rehabilitation Unit, Department of Rehabilitation, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.

Drs Haviv, Burg, Velkes, Salai, and Dudkiewicz have no relevant financial relationships to disclose.

Correspondence should be addressed to: Barak Haviv, MD, Department of Orthopedic Surgery, Rabin Medical Center, 39 Jabotinski St, Petah Tikva 49100, Israel (barak_haviv69@hotmail.com).

doi: 10.3928/01477447-20110317-04

10.3928/01477447-20110317-04

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