Copyright © 2007 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Cecil H. Rorabeck, MD, FRCSC*
University of Western Ontario, London, Ontario, Canada
Posted January 2007
Outcome studies have indicated that primary total hip
replacement is among the most cost-effective interventions of any surgical
procedure. The article by Röder et al. highlights this point and demonstrates
that postoperative functional outcome, including walking capacity and hip
flexion, are closely tied to preoperative function. Irrespective of
preoperative function, however, pain relief was universal and, as others have
found, was immediate and long lasting after primary total hip replacement.
While there are many indications for primary total hip
replacement, the principle ones are related to pain and loss of function. How
best to evaluate pain and loss of function over time is the question the
authors are attempting to answer. Their review of the literature would suggest
that other outcome measures, including the Western Ontario and McMaster
Universities Osteoarthritis Index (WOMAC) and the Short Form-36 (SF-36), are
variable in terms of their accuracy in reporting an association between low
postoperative scores and preoperative scores. This, however, has not been our
experience. I suspect, given the methodology available in 1967, that other
scores, such as the WOMAC and the SF-36, could not be collected at the time of
the initiation of the International Documentation and Evaluation System
European hip registry (IDES).
The importance of the information obtained from this paper,
and hence the conclusion, depends on the accuracy of data at the time of
collection. This study by Röder et al. addresses the timing of intervention and
demonstrates that, if surgery is put off until function has been severely
compromised, patients are generally less likely to be as satisfied with
functional recovery after total hip replacement.
If the notion is accepted that it is important to collect
information on outcome after primary total hip replacement, then, to reduce the
revision burden, the question must be asked—How best can we inform the
orthopaedic community at large of this information?
The current study, in effect, is a retrospective review of a
prospectively collected case series. Critical to the success of the IDES
Registry, or any registry, for that matter, is the quality control of the
collected information. The IDES Registry collects information by means of a
paper-based system and punch cards, with the data being entered by a data-entry
person in a central location. This method was implemented in 1967 because of
its simplicity. Whether or not this method is able to identify and accurately correct
errors is unknown. Data in any registry need to be validated, a step that is
even more important in a study such as this one, which had sixty-five
participating hospitals and clinics in eight different countries. Thus, there
needs to be an ability to match the data from each hospital, not only with the
patient (which the authors have done) but also with data collected by the
hospital or the clinic, as the case may be. One of the problems with
retrospective case series with prospectively collected data is that the centers
contributing the data are most likely specialized in joint replacement surgery,
and thus their results may not be generalizable to the orthopaedic community at
large. This is particularly important in the United States, where 52% of
primary total hip replacements and 77% of revision total hip replacements
performed in Medicare patients are being carried out by surgeons who do ten or
fewer of these procedures annually1. Thus, it is unrealistic to
expect that the results from low-volume surgeons would be likely to mirror the
results presented from this registry.
It is important for any registry to be able to disseminate
information to the orthopaedic community not only regarding successes, but also
regarding failures (revision rates). Perhaps the most important function of a
registry is that it allows surgeons to identify implants that seem to have a
higher short-term failure rate than others. One of the weaknesses of this paper
is that there is no information regarding the type of hip prosthesis used. There
are over 100 different hip implants available for use, with some requiring
cement fixation and others requiring either cementless fixation or a
combination of both (hybrid). The choice of prosthesis has not been explained
in this study, and no attempt has been made to identify surgeon error or
prosthetic-specific reasons for failure. In my view, this is the most important
value of a case-based series and, unfortunately, the authors have been unable
to offer any information in that regard. On the other hand, the information
which they do offer, namely, that poor preoperative mobility and function are
predictors of poorer postoperative recovery of function, is indeed important.
In the early days of total hip replacement, orthopaedic surgeons were more
interested in pain relief as the only important outcome when recommending total
hip replacement to patients with primary osteoarthritis. Today, as "baby-boomers"
are reaching the age at which hip replacement is offered and as hip replacement
is beginning to be offered at a younger and younger age, it will be even more
important to have information available to allow our policy makers and
clinicians, as well as the public and patients, to make evidence-based
decisions. While there is no doubt that the economic consequences of unrelieved
pain and suffering associated with osteoarthritis of the hip have been well
documented, it is nevertheless equally important to ensure a reproducible and
sustained functional outcome after total hip replacement. The data in this
paper give us considerable reassurance of sustained functional outcome.
While it is tempting to be critical of case-based series, this
study demonstrates that very valuable information can ensue from this
methodology.
The alternatives to case-based studies such as this, of
course, include meta-analysis. In this type of study, a specific question to be
answered is identified and appropriate inclusion criteria are determined, and
then the results of several studies on that subject are reviewed. As a result,
meta-analysis is able to enlarge the sample size, and hence the validity, of
the conclusions. While meta-analysis works well in certain areas of surgery, it
has nonetheless been criticized because of its lack of a randomization process
as part of the inclusion criteria. This fact makes its usefulness somewhat
limited in total joint replacement2.
It is tempting to suggest that randomized clinical trials should
be the gold standard for the assessment of new technology in total hip
replacement. From a practical standpoint, however, it is difficult to
generalize the results from one particular implant to another by a randomized
clinical trial process because of the large number of different implants on the
market and because of ongoing redesigns of implants. Also, as a result of constantly
changing technology, randomized clinical trials are extremely expensive and are
thus of limited value in assessing outcome after total hip replacement1.
The IDES Registry has withstood the test of time. It has
demonstrated that it is possible to develop a voluntary registry within
different clinics and universities in several different countries. This has
been done by achieving effective cooperation of clinicians and hospitals as
well as hospital staff and, most importantly, patients. The IDES registry has proven
to be a powerful tool for use in analyzing and disseminating information such
as that regarding fixation method and implant type. In addition, it allows
comparison of the joint replacement practices of surgeons in different
countries around the world. Despite its shortcomings, it can be used to
identify the potential revision burden associated with different implants and
should facilitate comparisons with other registries. In addition to the use of IDES,
a number of countries, including Sweden, Finland, Norway, and Denmark as well
as Canada, Australia, and England, have established a National Joint
Replacement Registry, which, in my view, is the wave of the future3-7.
When registry data are incomplete, as seems to be the case
with IDES, the data are much more prone to selection bias. The authors address
that issue in their manuscript and unfortunately, there is very little they can
do to correct that problem. The information contained in the IDES database could
better inform the orthopaedic public if it were stratified (e.g., according to
the type of implant, method of fixation, age at the time of primary surgery, and
body mass index). However, it is important that outcome measures are carefully
documented preoperatively, and this study goes a long way toward making that
point.
*The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.
References
1. Katz JN, Losina E, Barrett J, Phillips CB, Mahomed NN, Lew RA, Guadagnoli E, Harris WH, Poss R, Baron JA. Association between hospital and surgeon procedure volume and outcomes of total hip replacement in the United States Medicare population. J Bone Joint Surg Am. 2001;83:1622-9.
2. Laupacis A, Bourne R, Rorabeck C, Feeny D, Tugwell P, Wong C. Comparison of total hip arthroplasty performed with and without cement: a randomized trial. J Bone Joint Surg Am. 2002;84:1823-8.
3. Graves SE, Davidson D, Ingerson L, Ryan P, Griffith EC, McDermott BF, McElroy HJ, Pratt NL. The Australian Orthopaedic Association National Joint Replacement Registry. Med J Aust. 2004:180:S31-4.
4. Malchau H, Herberts P, Eisler T. Garellick G, Soderman P. The Swedish Total Hip Replacement Register. J Bone Joint Surg Am. 2002;84:S2-20.
5. Utting MR, Lankester BJ, Smith LK, Spencer RF. Total hip replacement and NICE. BMJ. 2005;330:318-9.
6. Canadian Joint Replacement Registry (CJRR) 2006 report: total hip and total knee replacements in Canada. Toronto: Canadian Institute for Health Information; 2006. p 47-52.
7. Maloney WJ. National joint replacement registries: has the time come? J Bone Joint Surg Am. 2001;83:1582-5.
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