NS, LPC, JDL, MB, PG, AJM, M. Pickford, M. Porter, KT, and JHvdM contributed to the design of the study. NS, LPC, JDL, M. Pickford, and JHvdM analysed the data. NS and JHvdM wrote the first draft of the paper. NS, LPC, JDL, MB, PG, AJM, M. Pickford, M. Porter, KT, and JHvdM contributed to the writing of the paper.
MB: Chair of ABHI Orthopaedics Special Interest Section; currently employed by DePuy International Ltd, manufacturer of orthopaedic prostheses. PG: Consultant orthopaedic surgeon, South Tees Hospitals NHS Trust. Unit receives research/audit funding from DePuy International Ltd, Stryker UK, and Smith & Nephew plc. Orthopaedic advisor for Capio Healthcare. AJM: Professor of chronic disease epidemiology, University of East Anglia. Consultant rheumatologist, Norfolk and Norwich University Hospital NHS Trust. M Pickford: Managing director of Accentus Medical and consultant to Northgate Informations Systems, the current contractor for the NJR. Does not receive any direct payment from any orthopaedic manufacturer or other third party. M Porter: Consultant orthopaedic surgeon, Wrightington, Wigan and Leigh NHS Trust. Works at a unit that has received financial support from DePuy International for clinical and RSA studies for Elite Plus femoral stem and C-stem. Has acted as consultant to DePuy International for development of a hip femoral stem (C-stem AMT). KT: Consultant orthopaedic surgeon, Norfolk and Norwich University Hospital NHS Trust. Various sources of financial support for research undertaken by orthopaedic department. Paid royalties by Johnson and Johnson Orthopaedic more than 5 y ago for contribution to design of hip prostheses. All royalties paid to orthopaedic charity. NS, LPC, JDL, and JHvdM declare that they have no competing interests.
Hip and knee replacement are some of the most frequently performed surgical procedures in the world. Resurfacing of the hip and unicondylar knee replacement are increasingly being used. There is relatively little evidence on their performance. To study performance of joint replacement in England, we investigated revision rates in the first 3 y after hip or knee replacement according to prosthesis type.
We linked records of the National Joint Registry for England and Wales and the Hospital Episode Statistics for patients with a primary hip or knee replacement in the National Health Service in England between April 2003 and September 2006. Hospital Episode Statistics records of succeeding admissions were used to identify revisions for any reason. 76,576 patients with a primary hip replacement and 80,697 with a primary knee replacement were included (51% of all primary hip and knee replacements done in the English National Health Service). In hip patients, 3-y revision rates were 0.9% (95% confidence interval [CI] 0.8%–1.1%) with cemented, 2.0% (1.7%–2.3%) with cementless, 1.5% (1.1%–2.0% CI) with “hybrid” prostheses, and 2.6% (2.1%–3.1%) with hip resurfacing (
Overall, about one in 75 patients needed a revision of their prosthesis within 3 y. On the basis of our data, consideration should be given to using hip resurfacing only in male patients and unicondylar knee replacement only in elderly patients.
Jan van der Meulen and colleagues show that about one in 75 patients with a primary hip or knee replacement needed a revision of their prosthesis within 3 years.
Though records show attempts to replace a hip date back to 1891, it was not till the 1960s before total hip replacements were successfully performed, and the 1970s before total knee replacements were carried out. These procedures are some of the most frequently performed surgical operations, with a total of 160,00 total hip and knee replacement procedures carried out in England and Wales and about half a million in the US in 2006. Hip and knee replacements are most commonly used as a treatment for severe arthritis once other approaches, such as pain relief medications, have failed. A total hip replacement involves replacing the head of the femur (the thigh bone) with an artificial component, typically metal; the socket into which the new femur head will insert is also replaced with artificial components. In an alternative procedure, resurfacing, rather than replacing the entire joint, the diseased surfaces are replaced with metal components. This procedure may be better suited to patients with less severe disease, and is also thought to result in quicker recovery. The techniques for hip and knee replacement can also be divided into those where a cement is used to position the metal implant into the bone (cemented) versus those where cement is not used (cementless).
To date, little evidence has been available to compare patient outcomes following hip or knee replacement with the many different types of techniques and prostheses available. National registries have been established in a number of countries to try to collect data in order to build the evidence base for evaluating different types of prosthesis. Specifically, it is important to find out if there are any important differences in revision rates (how often the hip replacement has to be re-done) following surgery using the different techniques. In England and Wales, the National Joint Registry (NJR) has collected data on patient characteristics, types of prostheses implanted, and the type of surgical procedures used, since its initiation in April 2003.
The researchers linked the records of the NJR and the Hospital Episode Statistics (HES) for patients treated by the NHS in England who had undergone a primary hip and knee replacement between April 2003 and September 2006. The HES database contains records of all admissions to NHS hospitals in England, and allowed the researchers to more accurately identify revisions of procedures that were done on patients in the NJR database.
They identified 327,557 primary hip or knee replacement procedures performed during that time period, but only 167,076 could be linked between the two databases.
76,576 patients in the linked database had undergone a primary hip replacement. The overall revision rate was 1.4% (95% confidence interval [CI] 1.2%–1.5%) at 3 years, with the lowest revision rates experienced by patients who had cemented prostheses. Women were found to have higher revision rates after hip resurfacing, and the revision rate was about twice as high in patients who had had a hip replacement for other indications than osteoarthritis. A patient's age did not appear to affect revision rates after hip surgery.
80,697 patients in the linked database had undergone a primary knee replacement. The overall revision rate was 1.4% (95% CI 1.3%–1.6%) at three years, again with the lowest rates of replacement experienced by patients who had cemented prostheses. Revision rates after knee replacement strongly decreased with age.
Overall, about one in 75 patients required a revision of their joint replacement, which is considered low, and cemented hip or knee prosthesis had the lowest revision rates. Post hip replacement, the highest revision rate was in patients who had undergone hip resurfacing, especially women. Following knee replacement, the highest revision rate was in patients who had undergone unicondylar prosthesis. However, in this study patients were only followed up for three years after the initial knee replacement, and it's possible that different patterns regarding the success of these differing techniques may emerge after longer follow-up. Importantly, this study was entirely observational, and data were collected from patients who had been managed according to routine clinical practice (rather than being randomly assigned to different procedures). Substantial differences in the age and clinical characteristics of patients receiving the different procedures were seen. As a result, it's not possible to directly draw conclusions on the relative benefits or harms of the different procedures, but this study provides important benchmark data with which to evaluate future performance of different procedures and types of implant.
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Information is available from the US National Institutes of Health (Medline)
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Total hip replacement was first successfully performed in 1962 in the United Kingdom and approved for use in the United States in 1969 [
A large number of different designs of hip and knee prostheses have been developed and introduced on the market. For example in England and Wales in 2006, at least 155 different brands of acetabular cups and 176 different brands of femoral stems were used for hip replacement and 86 different prosthesis brands for knee replacement [
Metal-on-metal resurfacing of the hip has been developed as an alternative procedure that conserves femoral bone and only replaces the surface of the joint [
The unicondylar knee replacement was originally introduced in the mid-1980s as a procedure for patients with joint damage that is limited to either the medial or lateral compartment of the knee [
There is relatively little high-quality evidence on the performance of the different prosthesis types available for hip and knee replacement and even less on the performance of individual brands. In a number of countries, national registries were established to fill this gap and to identify poorly performing prostheses as early as possible after their introduction on the market [
The National Joint Registry (NJR) for England and Wales was established in April 2003 to provide patients, healthcare professionals, regulators, and suppliers with timely evidence on the performance of prosthesis brands [
The NJR covers a population that is considerably larger than any of the existing national joint registries (53.7 million in 2006), which puts it in a unique position to provide information on large numbers of patients who have recently undergone a joint replacement. The emphasis on replacements that took place in recent years is important because of the observed decline in revision rates. The NJR can furthermore achieve near complete follow-up through linkage with the Hospital Episode Statistics database (HES) that contains records of all admissions to National Health Service (NHS) hospitals in England [
We considered revision rates for any reason in the first 3 y after primary hip and knee replacement as a measure of performance. We investigated how these rates differed according to prosthesis type and we gave special attention to revision rates after hip resurfacing and unicondylar knee replacement.
The NJR aims to collect data on all hip and knee replacements in England and Wales. Candidates for inclusion are patients who undergo a cemented, cementless, or “hybrid” total hip replacement or hip resurfacing, those who undergo a total knee replacement, unicondylar replacement, or patello-femoral replacement, and those who had a revision of any of these procedures. Hybrid hip prostheses have one cemented and one cementless component. Further information can be found in the NJR 4th Annual Report [
A revision for any reason was used as outcome. Revisions were identified through linkage with the HES database. We did not use the NJR database to identify revisions, because incomplete case ascertainment and missing patient identifiers in the NJR would have led to considerable underestimation. The HES database contains routinely collected records on admissions of patients treated in England in NHS hospitals, in NHS treatment centres, as well as of those treated in independent hospitals and independent sector treatment centres with NHS funding [
Admissions for primary knee replacement were identified if the first procedure field contained the codes W401 (primary total prosthetic replacement of knee joint using cement), W411 (primary total prosthetic replacement of knee joint not using cement), W421 (primary total prosthetic replacement of knee joint not elsewhere classified), W581 (primary resurfacing arthroplasty) in combination with Z846 (knee joint), and W521 (primary prosthetic replacement of articulation of bone using cement not elsewhere classified). The HES database contained 160,035 records of primary hip procedures and 167,522 primary knee procedures (
Linkage of NJR records and HES records was carried out according to five hierarchical linkage criteria: (1) local hospital number and NHS Trust code; (2) NHS number and NHS Trust code; (3) NHS number only; (4) patient date of birth, sex, and NHS Trust code; and (5) patient date of birth and NHS Trust code. Linkage was considered to be successful if both the NJR and the HES record described a primary hip replacement or a primary knee replacement and if the date of the joint replacement according to the NJR was within the start and end dates of the episode (i.e., the period that an admitted patient is under the care of a consultant) according to HES. A number of patients had undergone bilateral primary hip or primary knee procedures on different dates. In such cases, only the earliest primary procedure was retained in the linked database to avoid including the same patient twice.
For each patient with a linked primary procedure, all hospital admissions recorded in HES succeeding the primary procedure were identified on the basis of a unique patient identifier available in HES (HESID), which is based on the patients' sex, date of birth, and NHS number or in case NHS number was unavailable on sex, date of birth, postcode, and local hospital number. From these succeeding admissions, the first revision that occurred on the same side as the primary was selected. Where the side of the primary or the revision was not recorded, the first revision that occurred after the primary procedure was assumed to be a revision of that primary procedure.
Hip revision procedures were identified using the OPCS-4 procedure codes W373 (revision of total prosthetic replacement of hip joint using cement), W383 (revision of total prosthetic replacement of hip joint not using cement), W393 (revision of total prosthetic replacement of hip joint not elsewhere classified), W372 (conversion to total prosthetic replacement of hip joint using cement), W382 (conversion to total prosthetic replacement of hip joint not using cement), W392 (conversion to total prosthetic replacement of hip joint not elsewhere classified), W394 (attention to total prosthetic replacement of hip joint not elsewhere classified) in combination with Y032 (renewal of prosthesis in organ not otherwise classified), and W582 (revision of resurfacing arthroplasty of joint) in combination with Z843 (hip joint) [
Knee revision procedures were identified using the codes W403 (revision of total prosthetic replacement of knee joint using cement), W413 (revision of total prosthetic replacement of knee joint not using cement), W423 (revision of total prosthetic replacement of knee joint not elsewhere classified), W402 (conversion to total prosthetic replacement of knee joint using cement), W412 (conversion to total prosthetic replacement of knee joint not using cement), W422 (conversion to total prosthetic replacement of knee joint not elsewhere classified), W424 (attention to total prosthetic replacement of knee joint) in combination with Y032 (renewal of prosthesis in organ not otherwise classified), and W582 (revision of resurfacing arthroplasty of joint) in combination with Z846 (knee joint) [
Using the revisions identified in HES as described above, revision rates were then estimated for the different prosthesis types. Revision rates were estimated using the Kaplan-Meier survival analysis method with time of death or September 30, 2006 as the end of follow-up. The nonparametric Peto-Peto-Prentice test, a modification of the log-rank test that gives greater weight to observations made early in the course of follow-up, was used to test whether revision rates over time were equal among the different prosthesis types.
Multivariable Cox regression was used to estimate hazard ratios for prosthesis type, age group, sex, and indication for surgery as risk factors for revision [
The proportional hazard assumption was assessed by testing the interaction of log time from operation with prosthesis type. We found
Of the 327,557 primary hip or knee replacement procedures carried out between April 1, 2003 and September 30, 2006 in the NHS in England according to the HES database, 167,076 (51%) could be linked to an NJR record (
Characteristics of Patients Who Had a Primary Hip Replacement
Characteristics of Patients Who Had a Primary Knee Replacement
76,576 patients in the linked database had undergone a primary hip replacement. Of these patients, 41,232 (54%) had received a cemented prosthesis, 19,022 (25%) had received a cementless prosthesis, 10,120 (13%) had received a hybrid prosthesis, and 6,202 (8%) had undergone resurfacing (
The overall revision rate following primary hip replacement was 0.7% (95% confidence interval [CI] 0.6%–0.7%) at 1 y and 1.4% (95% CI 1.2%–1.5%) at 3 y. Revision rates varied according to the type of prosthesis used (
The pattern of revision rates according to hip prosthesis type was related to the patients' sex (
Primary Hip Replacement: Revision Rates (%) and Multivariable Hazard Ratios (95% CIs) According to Prosthesis Type and Patient Characteristics
We also found that the revision rate was about twice as high in patients who had had a hip replacement for other indications than osteoarthritis. There was no evidence that the revision rates varied according to the patients' age.
80,697 patients had undergone a primary knee replacement. Of these patients, 68,904 (85%) had received a cemented prosthesis, 5,905 (7%) a cementless prosthesis, 1,178 (1%) a hybrid, 4,110 (5%) a unicondylar prosthesis, and 600 (0.7%) a patello-femoral replacement (
The overall revision rate following primary knee replacement was 0.4% (95% CI 0.3%–0.4%) at 1 y and 1.4% (95% CI 1.3%–1.6%) at 3 y. Considering cemented, cementless, and unicondylar prostheses only, we found that revision rates varied according to the prosthesis type used (
There was no evidence that the pattern of revision rates according to the type of knee prosthesis type was related to sex (
Primary Knee Replacement: Revision Rates (%) and Multivariable Hazard Ratios (95% Confidence Intervals) According to Prosthesis Type and Patient Characteristics
Revision rates in the first 3 y after hip and knee replacements carried out in the NHS in England since April 2003 were low. Overall, we found that about one in 75 patients needed a revision of their joint replacement. Patients who had a cemented hip or cemented knee prosthesis had the lowest revision rates. The highest rates after hip replacement were seen in patients who had undergone hip resurfacing and the highest rates after knee replacement in patients who had a unicondylar prosthesis. Revision rates after hip resurfacing were especially high in women. It is essential to continue following up these patients to assess whether these differences remain beyond the first 3 y, because it has been shown that risk factors for revision as well as reasons for revision change with time after the joint replacement [
The identification of revisions of primary hip and knee replacement within the HES database may have been incomplete. The completeness of this identification process depends on the following two conditions. First, the revision procedure must have been carried out in the NHS and not in the independent sector. Further explorations within the NJR database only indicated that more than 98% of the revisions were carried out in the NHS. Second, the revisions must be captured by the OPCS-4 codes in the HES database. Given that deficiencies in these codes cannot be excluded, we need to accept that the reported revision rates may be underestimates.
Another limitation is that we could only include 51% of the primary procedures carried out in the NHS. This percentage was low because the NJR only started in 2003 and case ascertainment and the collection of patient identifiers (needed to link the NJR records with HES records) are gradually improving. However, the differences in age, sex, and indications for surgery between the linked and nonlinked procedures were marginal (unpublished data). Furthermore, and even more importantly, the overall revision rates following the primary hip and knee replacements in the NHS that could not be included was 1.5%, and the corresponding figure following a primary knee replacement was 1.6%. These revision rates are very similar to those observed in patients who were included, which supports our conclusion that the observed results are representative at a national level.
The clinical characteristics of the patients and their joint problem will partly determine the choice of prosthesis type. For example, cemented prostheses are generally implanted in older and less active patients whereas cementless prostheses are used in the youngest and most active ones. Therefore, we took differences in patient characteristics into account when comparing revision rates according to prosthesis type by carrying out multivariable regression analyses. However, there was little overlap between the distribution of patients' age and sex of some of the prosthesis types. As a consequence, we have to accept that some of the adjusted differences in revision rates according to prosthesis type are due to differences in the age and sex distribution as well as to clinical characteristics that were not included in the multivariable model.
It has been suggested that the results of hip resurfacing and unicondylar knee replacement strongly depend on the surgeons' experience with this technique [
A number of national registries have published quantitative figures on revision rates in patients who had a hip and knee replacement since 2000 (
Hip and Knee Revision Rates (95% CIs) in Other National Registries
The National Institute for Health and Clinical Excellence (NICE) recommended in 2002 that hip resurfacing should be considered as an option for patients with advanced hip disease who are likely to live longer than the expected lifespan of a conventional joint prosthesis [
A recent systematic review found no differences in the revision rates after unicondylar knee replacement and total knee replacement, but this review was limited by the quality and quantity of the available evidence [
Unicondylar knee replacement is often recommended because it is thought to be linked to shorter hospital and recovery periods, and to produce superior functional outcomes [
A recent meta-analysis compared revision rates after cemented and cementless total hip replacement [
The most up-to-date revision rates reported by the NJR and other national registries should be used as benchmarks against which the performance of new prosthesis designs and brands can be compared. This would also imply that the benchmark revision rate set by National Institute for Health and Clinical Excellence (NICE) for hip prostheses, now set at 10% or less at 10 y [
Furthermore, our results demonstrate that linking clinical and administrative databases has the potential to improve the quality and completeness as well as the efficiency of national data collection. Record linkage might also provide additional data on physical activity levels, smoking, and alcohol use, which would allow a study of the impact of lifestyle factors on revision rates.
High-quality national registries allow immediate evaluation of the outcome of the ongoing technological innovations of orthopaedic practice [
We thank the staff of all the hospitals in England and Wales who contributed data to the NJR. We also thank the staff of the NJR Centre for the collection of the data and for their support of the data linkage and analysis. The NJR has been managed by Momenta (AEA Technology) before April 1, 2006 and by Northgate Information Solutions (UK) Ltd thereafter, under contracts with the Department of Health (England).
Members of the Steering Committee of the NJR for England and Wales: William Darling, Chair; Paul Gregg, Vice Chair (consultant orthopaedic surgeon); Martyn Porter (consultant orthopaedic surgeon); Keith Tucker (consultant orthopaedic surgeon); Patricia Durkin (patient representative); Michael Borroff (orthopaedic device industry); Anthony Lowther (orthopaedic device industry); Carolyn Naisby (practitioner with special interest in orthopaedics); Mary Cowern (patient representative); Alex MacGregor (public health and epidemiology); Andrew Woodhead (NHS Trust management); Patricia Cassidy (independent healthcare sector). In attendance of the Steering Committee of the NJR for England and Wales: Andy Smallwood (NHS Supply Chain); Andy Crosbie (Medicines and Healthcare Products Regulatory Agency); Ramila Mistry (Department of Health); Kate Wortham (Department of Health); Christine Miles (Welsh Assembly Government).
confidence interval
Hospital Episode Statistics
National Health Service
National Joint Registry