Decreasing reimbursement, increasing surgical volumes, and prohibitive institutional review board polices potentially deter
residents from entering the subspecialty of joint replacement, while also inhibiting research production by existing surgeons.
Our hypothesis is that there has been a decline in total hip arthroplasty (THA) and total knee arthroplasty (TKA) research
in the United States relative to other countries over the past decade.
All original research involving THA and TKA published in
The Journal of Bone and Joint Surgery, American Volume,
Journal of Arthroplasty, and
Clinical Orthopaedics and Related Research over the past decade was queried. Country of origin and level of evidence of each publication were documented. From January
1999 to December 2008, 1724 original peer-reviewed research studies involving THA and TKA were identified. The percentage
of publications from US institutions steadily declined from 65.8% in 1999 to 46.9% in 2008. The percentage of Level I and
II studies from the United States increased from 9.7% in 1999 to 23.3% in 2008, which parallels the increase seen from all
countries from 7.8% to 24.8% during the same decade.
Despite the improving levels of evidence, the relative percentage of publications from the United States on THA and TKA has
declined over the past 10 years. In contrast to the relatively constant number from the United States, publications on THA
and TKA from non-US institutions have increased over the past decade. These trends may have significant implications for future
THA and TKA research in the United States.
Dr Meneghini is from the Department of Orthopedic Surgery, Indiana University Health Physicians, Indiana University School
of Medicine, Indianapolis, Indiana; and Mr Russo and Dr Lieberman are from the New England Musculoskeletal Institute, Department
of Orthopedic Surgery, University of Connecticut Health Center, Farmington, Connecticut.
Dr Meneghini receives consulting fees from Stryker and Convatec and royalties from Nemcomed. Mr Russo have no relevant financial
relationships to disclose. Dr Lieberman receives consulting fees from DePuy.
Correspondence should be addressed to: R. Michael Meneghini, MD, Indiana University Health Physicians, 200 W 103rd St, Ste
1400, Indianapolis, IN 46290 (firstname.lastname@example.org).
Since the development of total hip arthroplasty (THA) and total knee arthroplasty (TKA) approximately 4 decades ago, more
total joint arthroplasties have been performed in the United States than in any other country. Orthopedic surgeons in the
United States have made significant contributions to joint arthroplasty research, which has led to improved outcomes for patients.
However, it is more difficult to perform research now because of the stringent requirements of institutional review boards,
which are essential to maintain patient safety. In addition, there has been a substantial change in THA and TKA practice over
the past decade that has included a growing demand for the procedures, as well as a decline in physician reimbursement. This
has created an environment of increasing demand for higher surgical and practice volumes, as well as the need for increased
efficiency with respect to patient care delivery.
There has also been a decrease in the number of orthopedic surgery residents who select fellowship training in adult hip
and knee reconstruction.
Together, all of these factors have not only made it more difficult to perform research, but may have led to a decrease in
the number of surgeons who have the time and the resources to conduct clinical research in THA and TKA in this country.
The hypothesis of this study is that there has been a decline in the published clinical research on THA and TKA from US institutions
relative to other countries over the past decade.
Materials and Methods
All original research published in
The Journal of Bone and Joint Surgery, American Volume (JBJS-Am),
Journal of Arthroplasty (JOA), and
Clinical Orthopaedics and Related Research (CORR) from January 1999 to December 2008 was queried. Every article in every issue during that time period was examined,
and all original research involving THA and TKA was identified and examined in detail. Research manuscript inclusion criteria
included original clinical or basic science research involving primary or revision THA or TKA. Research involving epidemiology,
resource use, or cost analysis of THA and TKA was included. Additional topics selected included unicompartmental knee arthroplasty
and hip resurfacing. If the manuscript involved treatment of the proximal femur, it was only included if THA was used in at
least part of the study. Manuscripts isolated to hemiarthroplasty or internal fixation of proximal femoral fractures were
excluded. In addition, supplements of meeting proceedings and surgical techniques were excluded due to the altered peer-review
process and selection bias that is typically involved with those particular publications.
The proceedings of the Hip and Knee Society and the annual American Association of Hip and Knee Surgeons were reported as
well, but addressed separately because the manuscripts are invited and may introduce bias by virtue of the disproportionate
number of members from the United States in those respective societies. Review articles and opinion publications were excluded.
Each manuscript that met the inclusion criteria was examined in detail through review of the abstract and all pertinent accompanying
manuscript information. The research country of origin was identified and documented. In addition, each manuscript was examined
for the level of evidence to provide a more objective classification of the research quality. The manuscript on clinical research
was assigned 1 of the following levels of evidence: Level I (randomized, prospective), Level II (lesser quality randomized,
prospective), Level III (case control study), and Level IV (case series). If a manuscript included a level of evidence classification
assigned to it by that particular journal and peer-review process, that level of evidence classification was accepted and
recorded. All manuscripts that did not have a documented level of evidence were carefully reviewed and a level of evidence
was assigned based on the established classification criteria of JBJS-Am.
Manuscripts dealing with basic science, such as cadaver or biomechanical studies, were classified as “basic science” and
were not classified with the levels of evidence for clinical studies.
All information was recorded into a database for statistical analysis. The absolute number of manuscripts published annually
was determined and examined with respect to country of origin and level of evidence. The number of publications from the United
States and from non-US countries as a percentage of total annual research publications was determined in addition to the level
of evidence and compared.
From January 1999 to December 2008, 2272 original peer-reviewed research studies involving THA and TKA were identified. After
exclusion of the annual Hip Society and Knee Society meetings and the American Association of Hip and Knee Surgeons annual
meeting proceedings’ studies to minimize bias, 1724 original research publications remained and were analyzed. There were
399 articles published in JBJS-Am, 329 articles in CORR, and 996 articles in JOA. The topic distribution included 767 primary
THA articles, 727 primary TKA articles, 89 revision THA articles, and 33 revision TKA articles, with the remaining 108 articles
including both THA and TKA. Examined on an annual basis, the number of overall THA and TKA publications in all 3 journals
steadily increased from 146 articles in 1999 to 194 articles in 2008.
Over the 10-year period, US institutions published 908 articles involving THA and/or TKA, while 135 articles came from the
United Kingdom, 107 from Japan, 87 from Canada, and 73 from Korea. Thirty-three other countries published <50 articles during
this time period (). The percentage of publications from US institutions steadily declined from 65.8% in 1999 to 46.9% in 2008 (Figure ). In contrast, the annual percentage of publications from non-US institutions increased from 34.2% in 1999 to 53.1% in 2008.
The annual absolute number of US publications has remained relatively constant during the past decade, with an average of
91 per year, while the non-US countries effectively doubled their annual number of publications from 50 in 1999 to 103 in
2008 (Figure ).
Table. Number of Publications Per Country of Origin From January 1999 to December 2008
Figure 1:. The percentage of annual publications from the United States and non-US institutions (excluding American Association of Hip
and Knee Surgeons, Hip Society, and Knee Society meeting proceedings) demonstrating the decreasing trend in percentage of
publications from the United States and the conversely increasing percentage of publications from non-US institutions (A).
The absolute number of annual publications from US and non-US institutions (excluding American Association of Hip and Knee
Surgeons, Hip Society, and Knee Society meeting proceedings) demonstrating the relatively constant number of publications
from the United States and the conversely increasing number of publications from non-US institutions (B). The percentage of
annual publications from US and non-US institutions, including the American Association of Hip and Knee Surgeons, Hip Society,
and Knee Society meeting proceeding publications. The decreasing trend in percentage of publications from the United States
is demonstrated (C).
When including the annual meeting proceeding publications from the American Association of Hip and Knee Surgeons, Hip Society,
and Knee Society, the same trends are evident with regard to the steady decline in the percentage of US publications. Because
these meeting proceedings are predominantly US institution-based, including these publications in the analysis increases the
overall annual number of US publications; however, the trend of a decreasing percentage remains relative to other countries.
The percentage of publications from US institutions steadily declined from 72.8% in 1999 to 52.8% in 2008 (Figure ). The annual absolute number of US publications has again remained relatively constant during the past decade, with 142 publications
in 1999, 133 publications in 2008, and a mean 140.9 publications over that 10-year period. This relatively constant rate of
annual publications from the United States remains evident even when the American Association of Hip and Knee Surgeons, Hip
Society, and Knee Society meeting proceedings’ publications are included in the analysis.
Of the 1724 published articles, the largest number were classified as Level IV evidence, with 568 studies (33%), whereas 131
were classified as Level I (8%), 184 Level II (10%), and 344 Level III (20%). There were 494 basic science publications (29%).
The percentage of high-quality Level I and II evidence studies from the United States increased from 9.7% in 1999 to 23.3%
in 2008, which parallels the increase seen from all countries from 7.8% to 24.8% during the same decade (Figure ).
Figure 2:. The percentage of level of evidence classification for publications from all countries, including the United States, annually
in all 3 journals. The linear regression line is shown for each level of evidence classification to more clearly see the trends
(A). The percentage of level of evidence classification for the publications from US institutions annually in all 3 journals.
The linear regression line is shown for each level of evidence classification to more clearly see the trends (B).
The results of this study reveal a relative decrease in joint arthroplasty publications from US institutions relative to other
countries in the world, with the percentage of publications from US institutions steadily declining from 65.8% in 1999 to
46.9% in 2008. In addition, despite the total annual number of overall THA and TKA publications in the 3 journals queried
increasing from 146 articles in 1999 to 194 articles in 2008, the annual number of US publications has remained relatively
constant during the past decade, with an average of 91 per year. Alternatively, non-US countries have effectively doubled
their annual number of publications, from 50 in 1999 to 103 in 2008 (Figure ).
A potential explanation for the relative decline in the THA and TKA publication rate in these journals by US institutions
may be a difference in the scientific quality of the research performed. In JBJS-AM, there has been a documented improvement
in the level of evidence of the research studies published over the past 30 years.
However, the results of this study demonstrate the percentage of high-quality Level I and II evidence studies from the United
States increased from 9.7% in 1999 to 23.3% in 2008, which parallels the increase seen in all countries, from 7.8% to 24.8%,
during the same decade (Figure ). Therefore, the level of evidence as an indicator of a study’s scientific quality does not appear to be a factor in the
difference between US and non-US institution publication rates over the past decade in THA and TKA.
Another possibility for the increase in publications from other countries is that their interest and ability to perform and
publish high-quality research is increasing, while the United States remains relatively stagnant or is at its peak capacity
within the current health care environment. The changing economic climate in the practice of THA and TKA in the United States,
combined with the increased costs of doing research because of institutional review board requirements, may be making it more
difficult for surgeons in the United States to conduct high-quality clinical research.
A steady decline in physician reimbursement for THA and TKA has been observed over the past 10 to 15 years.
There has been a 20% to 23% decrease in primary and revision THA and TKA Medicare reimbursement from 1998 to 2007.
When adjusted for inflation with the consumer price index, there has been a dramatic decrease of >40% in Medicare reimbursement
for primary and revision THA and TKA since 1992.
This decrease in reimbursement has made it difficult for surgeons, as both practice and employee expenses continue to escalate.
Furthermore, in the same time interval of decreasing reimbursement, the surgical volume of THA and TKA in the United States
has increased steadily. The annual number of TKAs performed in the United States has steadily increased from 266,000 in 1998
to 542,000 in 2006.
Likewise, 160,000 THAs were performed in 1998 and increased to 231,000 in 2006.
Decreasing physician reimbursement, rising fixed business costs, and rising malpractice premiums have created an environment
where an arthroplasty surgeon must increase the volume of THAs and TKAs performed to maintain their given income level or
even allow practice survival.
To accommodate this volume, much emphasis has been placed on optimizing the efficiency of THA and TKA surgical care; however,
regardless of the degree of practice efficiency, one could surmise that the increased surgical volume with the accompanying
patient care and complication volumes expected may result in less time for the busy arthroplasty surgeon to devote to clinical
and/or basic science research. Furthermore, the burden of revision procedures, which are more time consuming and demanding,
is typically borne by fellowship-trained arthroplasty surgeons at institutions that might be more apt to perform research.
The rates of revision THA and TKA in the United States have risen over the past decade and are expected to continue rising
over the next 2 decades.
It has been reported that current and future orthopedic surgery residents are becoming less likely to choose adult hip and
knee reconstruction as a subspecialty.
Ten adult reconstructive fellowship programs have been discontinued over the past 5 years due to an inability to attract
applicants, and only 77% of the 119 fellowship positions were filled in the academic year 2006–2007.
This percentage decreased to only 62% of fellowship positions being filled in the following 2007–2008 academic year.
This decrease in the number of fellows reduces the number of individuals available to perform the procedures in the present
and future. Finally, over the past decade, meeting institutional review board requirements to perform clinical research has
become more stringent and more expensive. Therefore, the combination of increasing clinical workload, decreased revenue, and
increased costs associated with performing research may be contributing to this decline in arthroplasty productivity research
in the United States. Further studies will be necessary to confirm this hypothesis.
This study has limitations, which primarily involve the selection of the orthopedic journals reviewed. We limited our research
publication query to 3 journals that were deemed to be of the highest quality and yield for THA and TKA research by the 2
senior authors (R.M.M., J.R.L.). This may represent a bias, as research from United States and non-US institutions may preferentially
be submitted to other journals of high quality. However, the authors believe that other journals that frequently publish arthroplasty
articles, such as
Acta Orthopaedica Scandanavica and the
Journal of Bone and Joint Surgery, British Volume, likely publish a lower percentage of articles from US centers than the 3 journals evaluated in this study. In addition,
these 3 journals demonstrate an emphasis on clinical research rather than basic science research, as is emphasized by journals
such as the
Journal of Orthopaedic Research. Furthermore, we intentionally analyzed US-based specialty meeting proceedings separately, as we felt artificial bias may
be introduced into the conclusions based on the altered peer-review process that may occur with invited manuscripts, as opposed
to those that are submitted without specific invitation.
Whether this relative decline in US-based THA and TKA research is specifically related to decreased physician reimbursement,
decreased time available for research due to increased practice volume, or a decline in interest from orthopedic residents
in this subspecialty remains to be determined and requires further study. However, with health care reform a top national
priority, the role of the United States as a leader in THA and TKA research, development, and innovation must be concomitantly
addressed. Further study is warranted to elicit the etiology of the trends revealed in this study and to implement changes
and reform that enable and promote opportunities and incentives for the busy arthroplasty surgeon and clinician-scientist
to perform and publish high-quality research in THA and TKA.
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Number of Publications Per Country of Origin From January 1999 to December 2008