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
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
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
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
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: orthopedic vs
nonorthopedic journals (Abbreviations: Ortho, orthopedic journals; Non-Ortho,
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.
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).
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.
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
evidencenamely systematic reviews; meta-analyses; randomized, controlled
trials; and clinical guidelineswere 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
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.
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.
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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 (firstname.lastname@example.org).