National Arthroplasty Registries Research Articles

Impact of Implant Developers on Published Outcome and Reproducibility of Cohort-Based Clinical Studies in Arthroplasty

The reproducibility of the results of cohort-based clinical studies of arthroplasty procedures by the average orthopaedic surgeon is a major issue involving the quality of the scientific literature. We compared the results of a comprehensive literature analysis with data from national arthroplasty registries to examine the influence of arthroplasty implant inventors on the outcomes published in peer-reviewed journals. A structured review of the literature published in MEDLINE-listed journals was performed. A comparison of the average revision rates in the identified studies (adjusted for the number of arthroplasty cases and the duration of follow-up) with the registry data was then conducted. Seventeen of the analyzed arthroplasty implants were developed in the United States. Studies by the developers of these implants often had a substantial influence on the published outcome. For approximately 50% of the implant systems analyzed, the average revision rate derived by combining all published studies showed a statistically significant and clinically relevant deviation from the revision rate derived from the arthroplasty registry data, which reflected the outcome in the average patient. For the majority of implants for which the revision rate calculated from the published clinical studies was very low compared with the rate calculated from the registry data, the developing institution accounted for 39% to 100% of the published outcome data for the implant. In contrast, the published results were usually reproducible in clinical practice if <25% of the published data were reported by the developers. Three of the nine arthroplasty implants developed in Europe showed a significant and clinically relevant difference between the revision rate derived from only the studies published by the developers and the rate calculated from the registry data. However, because of the considerably greater amount of data from independent studies that was typically available for the European implants than for the American implants, studies by the developer that deviated significantly from the registry data could usually also be identified as outliers by a meta-analysis of all published studies. A high proportion of the published data involving three of the European implants was reported by the inventors, but comparison with the registry data revealed that the average published revision rates for two of these three implants were reproducible in clinical practice. The published results of the clinical studies involving many of the arthroplasty implants, especially implants developed in the United States, were highly influenced by reports from the center that developed the implant. This often had a substantial effect on the reproducibility of the outcome data. There appeared to be relevant differences between the medical research systems in Europe and the United States that also affected the reproducibility and applicability of the results for the average surgeon. Registry data can contribute substantial added value to an informed discussion of arthroplasty outcomes.

Total hip arthroplasty: to cement or not to cement the acetabular socket? A critical review of the literature

The optimal method for acetabular socket fixation remains controversial. We present a critical analysis of the current evidence from a systemic literature review of comparative studies, long-term case series, prior literature reviews, meta-analysis, and national arthroplasty registry data for cemented and uncemented acetabular components to determine the respective survivorship rates, overall risk of re-operation, dislocation rates, and wear-related complications. Using contemporary techniques, both cemented and uncemented sockets can yield good long-term results, but our evaluation suggests that the overall/all cause re-operation risk is lower for cemented fixation. Until and unless crosslinked polyethylene (PE) liners or alternative bearings can prove to yield superior outcome in the future, the cemented PE cup remains the gold standard, in all age groups, by which every acetabular component should be compared.

Revision Rates after Total Ankle Arthroplasty in Sample-Based Clinical Studies and National Registries

The aim of this study was to evaluate the outcome of specific implants in total ankle arthroplasty as reported in clinical studies and determined by national registries. A structured literature review was conducted regarding sample-based clinical studies and national registry data. To allow for comparative analyses, registry data had to be available for the implants included. These were STAR Ankle, Büchel-Pappas, Hintegra, Mobility, Agility, and Ramses Total Ankle Arthroplasty. The revision rate was used as the main outcome parameter. On average, the revision rates published in sample-based clinical studies were about half the value found in registries. Implant developers represent a share of almost 50% of the published content and are therefore over-represented in scientific publications. The inventors of STAR Ankle and BP total ankle implants published data which was statistically significantly superior to the outcome achieved in average patients as documented in registries. Irrespective of the implant, the average revision rate to be expected according to the registry data available is 21.8% after 5 years, and 43.5% after 10 years. The average revision rate published in peer-reviewed scientific articles was significantly lower than the outcome achieved according to national arthroplasty registry data, which reflect actual average patient care in the respective countries. Publications by some research groups, particularly by implant inventors, show a deviation from the outcome published by other users and those shown in registry data.

Validity of published outcome data concerning Anatomic Graduated Component total knee arthroplasty: a structured literature review including arthroplasty register data

Total knee arthroplasty (TKA) as a treatment for end-stage osteoarthritis of the knee shows good results in terms of patient satisfaction. For the assessment of outcome and revision rate after total joint arthroplasty, there are two major data sources: clinical studies and national arthroplasty registers. The purpose of this study was to analyse the outcome of Anatomic Graduated Component (AGC) TKA reported in clinical studies and to perform a comparison with the outcome reported by national arthroplasty registers. A systematic literature review was performed using standardised methodology in order to determine the outcome and revision rate of AGC TKA. In a comprehensive meta-analysis of clinical studies and worldwide register results we examined the quality of the basic data and the occurrence and influence of potential bias factors. Confidence intervals were calculated to determine the statistical significance of differences. We found significant differences as regards the revision rate measured in revisions per 100 observed component years. Compared to worldwide register data it turned out to be significantly lower in clinical studies published by the implant development team. Actually, they reported a revision rate of 0.18 revisions per 100 observed component years, whereas annual reports of national arthroplasty registers report 0.74 revisions per 100 observed component years. A comparison of the results from national arthroplasty registers of different countries revealed a significantly higher revision rate for Denmark in relation to worldwide register data. A conventional meta-analysis of clinical studies is affected by the influence of the development team and therefore subject to bias. For the assessment of outcome arthroplasty register data should be rated as superior and, being used as reference data for the detection of potential bias factors in the clinical literature, could make an essential contribution to the quality of scientific meta-analysis.

Outcome of the cementless Taperloc stem: a comprehensive literature review including arthroplasty register data

Background and purpose The validity of various data sources for the assessment of the outcome quality of medical devices was investigated by comparative analysis of the published data sources available for a sample of implants. It was the aim of the study to determine the performance of this implant and to identify potential bias factors inherent to the various datasets.Methods A comprehensive literature search was carried out from English-language, peer-reviewed journals and worldwide reports from national arthroplasty registers. Publications from Medline-listed journals were included. The main parameter was revision rate, calculated as “revisions per 100 observed component years” to allow adjusted direct comparison of different datasets.Results Of 16 clinical studies that met the inclusion criteria, 9 originated from the implant developer's hospital. In the clinical studies category, publications from the developer's hospital suggested considerably lower revision rates than the other datasets. In fact, the values quoted were 5.5 times below the average of all other studies, and 9.51 times lower than in the Australian arthroplasty register. These differences are statistically significant.Interpretation The cementless Taperloc stem is an implant that shows good performance regarding revision rates in registry data and in clinical studies. However, the excellent results published by the developer's clinic are generally not reproducible by other surgeons. In terms of reference data, registry data are able to make an important contribution to the assessment of clinical sample-based studies, particularly regarding evaluation of the extent to which published results are reproducible in daily routine.

Scientific production and impact of national registers: the example of orthopaedic national registers

National arthroplasty registers are often cited as examples of a non-randomized design that have made an essential contribution to advances in assessing arthroplasty procedures. We aimed to compare national registers to randomized controlled trials (RCTs) and meta-analyses in the field of arthroplasty in terms of scientific production and impact. We systematically searched Medline via PubMed and the registers' websites to select all articles from national registers, RCTs and meta-analyses assessing hip and knee arthroplasty. The scientific production and impact were evaluated by number of publications, number of citations (total and the 3-year citation counts), and information on the 2008 journal impact factor (IF), for each design and identified articles. We also contacted representatives of all the selected registers to determine the availability of the data for external research projects. We retrieved information on 13 active national hip or knee arthroplasty registers; for 9, data were available for research projects under specific conditions. Overall, 190 publications in peer-reviewed journals resulted from national arthroplasty registers, 476 from RCTs, and 40 from meta-analyses. We found 4,112 citations for national register reports, 7,328 for RCT reports and 552 for meta-analysis reports. The median [interquartile [IQR] range] number of citations for register, RCT and meta-analysis reports in the 3-year period after publication was 3.5 [1.0-6.0], 2.0 [1.0-6.0], and 2.5 [0.5-7.5], respectively. Publications from national registers may have the highest impact among the 3 designs in terms of median citation counts, but data from RCTs remain the most productive evidence in the arthroplasty field. Because of the number of patients recruited by registers, the quality of data collected, and the potential availability of data, scientific production and impact from national registers should be improved.

Resurfacing registers concern

We review the history and literature of hip resurfacing arthroplasty. Resurfacing and the science behind it continues to evolve. Recent results, particularly from the national arthroplasty registers, have spread disquiet among both surgeons and patients. A hip resurfacing arthroplasty is not a total hip replacement, but should perhaps be seen as a means of delaying it. The time when hip resurfacing is offered to a patient may be different from that for a total hip replacement. The same logic can apply to the timing of revision surgery. Consequently, the comparison of resurfacing with total hip replacement may be a false one. Nevertheless, the need for innovative solutions for young arthroplasty patients is clear. Total hip replacement can be usefully delayed in many of these patients by the use of hip resurfacing arthroplasty.

Organisation, data evaluation, interpretation and effect of arthroplasty register data on the outcome in terms of revision rate in total hip arthroplasty

Originally developed in Scandinavia, national arthroplasty registers have spread worldwide during the last decade. The value of registers for quality improvement in arthroplasty has frequently been documented. However, for the development of a successful register a few key points should be taken into account. Uncontrolled loss of patients from the registry area should be avoided. Registers should form an integral part of a country's medical system. To realise the potential for improvement, it is crucial that physicians deal with the results in detail. Thus it is absolutely essential to involve the specialty societies in the interpretation and dissemination of results. With respect to revision rates, register data are usually more valid than meta-analyses of clinical studies. For every physician the most valuable data are those coming from a register in his own country; the development of national arthroplasty registers should therefore be continued.

In Brief: Classifications in Brief: Vancouver Classification of Postoperative Periprosthetic Femur Fractures

With a growing elderly population, the rates of primary and revision THAs also have increased. Paralleling the increased number of hip reconstructive procedures performed is the incidence of periprosthetic femur fractures [14]. Each periprosthetic fracture poses a unique challenge to the treating orthopaedic surgeon because of the many variables that must be considered with each fracture pattern. These variables include the relationship of the fracture to the implant, the specifics of the implant including wear, and the functional demands of the patient. A couple studies outline the impact of periprosthetic femur fractures on mortality. Lindahl et al. investigated outcomes in patients from the Swedish national hip arthroplasty register and described higher mortality rates after surgery for patients with periprosthetic femoral fractures compared with patients who had total hip replacements [16]. Bhattacharyya et al. similarly found an increased mortality rate of 11% at 1 year (21% cumulative mortality rate) in patients treated operatively for periprosthetic femur fractures compared with a rate of 2.9% in patients who underwent primary joint arthroplasties [3]. They recorded mortality rates approaching those documented after hip fracture (16.5%), and also noted a nearly threefold increase in mortality in patients who sustained a fracture at the level of the prosthesis and were treated with open reduction and internal fixation versus patients treated with revision arthroplasty [3]. The Vancouver classification developed by Duncan and Masri [10] and Masri et al. [17] is the most widely accepted classification scheme to group fractures with similar characteristics from which a treatment algorithm is derived. Previous classification schemes and treatment algorithms for periprosthetic femur fractures focused primarily on location, fracture pattern, implant stability, and/or potential for loosening [2, 7, 13, 18, 21]. The Vancouver classification assimilates three key factors: location, stability of the implant, and the surrounding bone stock (Table 1). The classification has since been modified by Masri et al. to include intraoperative in addition to postoperative periprosthetic femur fractures [17]. The remainder of this discussion will focus on the Vancouver classification of postoperative periprosthetic femur fractures.

Knee arthroplasty in Denmark, Norway and Sweden

Background and purpose The number of national arthroplasty registries is increasing. However, the methods of registration, classification, and analysis often differ.Methods We combined data from 3 Nordic knee arthroplasty registers, comparing demographics, methods, and overall results. Primary arthroplasties during the period 1997–2007 were included. Each register produced a dataset of predefined variables, after which the data were combined and descriptive and survival statistics produced.Results The incidence of knee arthroplasty increased in all 3 countries, but most in Denmark. Norway had the lowest number of procedures per hospital—less than half that of Sweden and Denmark. The preference for implant brands varied and only 3 total brands and 1 unicompartmental brand were common in all 3 countries. Use of patellar button for total knee arthroplasty was popular in Denmark (76%) but not in Norway (11%) or Sweden (14%). Uncemented or hybrid fixation of components was also more frequent in Denmark (22%) than in Norway (14%) and Sweden (2%).After total knee arthroplasty for osteoarthritis, the cumulative revision rate (CRR) was lowest in Sweden, with Denmark and Norway having a relative risk (RR) of 1.4 (95% CI: 1.3–1.6) and 1.6 (CI: 1.4–1.7) times higher. The result was similar when only including brands used in more than 200 cases in all 3 countries (AGC, Duracon, and NexGen). After unicompartmental arthroplasty for osteoarthritis, the CRR for all models was also lowest in Sweden, with Denmark and Norway having RRs of 1.7 (CI: 1.4–2.0) and 1.5 (CI: 1.3–1.8), respectively. When only the Oxford implant was analyzed, however, the CRRs were similar and the RRs were 1.2 (CI: 0.9–1.7) and 1.3 (CI: 1.0–1.7).Interpretation We found considerable differences between the 3 countries, with Sweden having a lower revision rate than Denmark and Norway. Further classification and standardization work is needed to permit more elaborate studies.

Cemented Femoral Fixation: The North Atlantic Divide

European nations, especially Scandinavian countries, have used cemented fixation since the introduction of total hip arthroplasty. In Sweden, with arguably the best national-level data on prostheses survivorship, >90% of all stems are fixated with cement. In sharp contrast, it is estimated that in the United States, >88% of all femoral stems use cementless technology. This represents a diametrically opposed difference in philosophical approach: the so-called North Atlantic Divide. The departure in North America from cemented femoral stems can be traced to the coinage of the phrase "cement disease," which implicated cement as a leading cause of osteolysis. This led to prolific innovation of uncemented technologies in North America, while European countries favored standardization enabled by the national arthroplasty registries. The term "cement disease" has been proven to be a misnomer, as supported by excellent outcomes from the Scandinavian registries, as well as excellent long-term outcomes for cemented stems in United States series, even in patients younger than 50 years. Like uncemented stems, there is variability in survivorship between femoral stems, and this appears to be related to specific design features. Despite the excellent long-term results, the use of cemented femoral components in Europe and Canada is decreasing in favor of uncemented stems. The reasons for this are not immediately obvious.

Das European Arthroplasty Register (EAR), die Entwicklung und Sinnhaftigkeit übernationaler Zusammenarbeit von Endoprothesenregistern

In Scandinavia national arthroplasty registers are accepted instruments in the assessment of joint implants. They have contributed essentially to the rapid detection of inferior products and, by encouraging a continuous process of quality improvement through feedback, have helped to avoid revision operations. However, national registers have a limited significance with regard to other countries and rarely used implants. In recent years, a great number of registers have been founded. The European Arthroplasty Register (EAR), an EFORT project, aims at supporting these projects, enhancing cooperation within a network, realising further benefit through registers, and fostering scientific activities. The registers have been conceived according to the successful Scandinavian model. It is, however, necessary to adapt the concept to the individual national circumstances. In order to increase the value of register publications for other countries, it makes sense to achieve a minimum of stardardisation in datasets, definitions, product designations, as well as in evaluation and publication methods. Since the datasets of national registers implicitly reflect the prevailing national circumstances, they are always more valuable for use in the respective country than evaluations from aggregated, supranational and therefore larger datasets. Supranational evaluations may yield additional findings, but they cannot replace a national register. Therefore, EAR has been conceived as a network of independent national registers considering itself as a supplement and by no means as a competitor of the established national registers.

Femoral impaction bone grafting with the Exeter stem - the Swedish experience

We identified 1305 femoral impaction bone grafting revisions using the Exeter stem performed between 1989 and 2002 in 30 hospitals throughout Sweden. There were 1188 patients with a mean age of 71 years (29 to 94) followed up for between five and 18 years. The participating departments reported 70 further revisions in total, of which 57 could also be identified on the Swedish National Arthroplasty Registry. Kaplan-Meier survivorship for all causes of failure was 94.0% (95% confidence interval (CI) 92 to 96) for women and 94.7% (95% CI, 92 to 96) for men at 15 years. Survivorship at 15 years for aseptic loosening was 99.1% (95% CI 98.4 to 99.5), for infection 98.6% (95% CI 97.6 to 99.2), for subsidence 99.0% (95% CI 98.2 to 99.4) and for fracture 98.7% (95% CI 97.9 to 99.2) Statistically significant predictors of failure were the year in which revision was conducted (p < 0.001). The number of previous revisions was slightly above the level of significance (p = 0.056). Age, gender, the length of the stem and previous septic loosening were not predictors of failure (p = 0.213, p = 0.399, p = 0.337, p = 0.687, respectively). The difference in survivorship between high- and low-volume departments was only 3% at ten years. We conclude that impaction bone grafting with the Exeter stem has an excellent long-term survivorship following revision arthroplasty. The technique of impaction grafting appears to be reliable, can be learned rapidly and produces a predictably low incidence of aseptic loosening.

Comparison of the information in arthroplasty registers from different countries

This article considers some of the problems of the interpretation of information from other national arthroplasty registers when setting up a new register. In order for the most useful information to be available from registers much international co-operation is required between all those responsible for the design of registers as well as those who gather, assess and publish the data.

Clinical Issues Summary

Clinical Issues Summary

The Norwegian Hip Fracture Register: Experiences after the first 2 years and 15,576 reported operations

Background and purpose The Norwegian Hip Fracture Register was established in January 2005 to collect nationwide information as a basis for improved management of patients with hip fractures. We now report our experience after the first 2 years.Methods After both primary operations and reoperations, the surgeons fill in a standardized 1-page form with information about the patient, the fracture, and the operation. Fractures treated with a total hip arthroplasty are reported to the national arthroplasty register, but are added to the hip fracture register before analyses are performed. 4, 12, and 36 months postoperatively, a standardized questionnaire including health-related quality of life (EQ-5D), visual analog scales concerning pain and patient satisfaction, and Charnley class for functional assessment is sent directly from the register to the patients. To evaluate the completeness of registration, our data were compared with data from the Norwegian Patient Registry (NPR).Results During the first year of registration, all 55 hospitals treating hip fractures in Norway started to report their hip fracture operations. During 2005, the monthly reporting increased and it stabilized in 2006. 13,251 primary-operated hips (mean age of patients: 80 years; 72% females) and 2,325 reoperations were reported during 2005 and 2006. Compared to the NPR, the completeness of registration was 64% in 2005 and 79% in 2006. 58% of the patients who were alive answered the 4-month questionnaire. The non-responders were older, were more often cognitively impaired, and had a higher degree of comorbidity than the responders. Undisplaced femoral neck fractures (19% of all fractures) were almost exclusively operated with screw osteosynthesis (95%). Dislocated femoral neck fractures (38% of all fractures) were operated with a hemiarthroplasty in 52% of the cases. Osteosynthesis with a hip compression screw was the predominant operation method for trochanteric fractures (81%).Interpretation After only 2 years, our nationwide system for surveillance of demographics, treatment, and outcome of hip fractures is functioning well. As expected, the response rate for the 4-month questionnaires was relatively low due to the old population with high comorbidity and cognitive impairment. The different treatment methods used for patients in the same groups of fracture types show that there is still no consensus in Norway regarding the treatment of hip fractures.

Key factors for a successful National Arthroplasty Register

Since the introduction of the first National Arthroplasty Register in Sweden in 1975, many other countries have tried to adopt the successful Scandinavian system. However, not all have overcome the political and practical difficulties of establishing a working register. We have surveyed the current registries to establish the key factors required for an effective database. We have received detailed information from 15 arthroplasty registers worldwide. The legal conditions under which they operate together with the methods of collection and handling of the data differ widely, but the fulfilment of certain criteria is necessary achieve a high degree of completeness of the data to ensure the provision of statistically relevant information.

Risk factors for periprosthetic femoral fracture

Periprosthetic femur fractures are associated with high patient morbidity and are difficult reconstructive challenges. Early identification and appropriate intervention are critical to prevent this complication. Studies varying from case reports to national arthroplasty registry databases have demonstrated that certain factors are associated with an increased risk of fracture. These include trauma, patient-specific problems, and technical issues related to the hip replacement itself. Recent evidence from large registries has shown that the key to prevention of periprosthetic femur fractures is routine follow-up with radiographic studies.

The excess mortality due to periprosthetic femur fracture. A study from the Swedish national hip arthroplasty register

A rare but serious adverse event of total hip replacement (THR) is periprosthetic femoral fracture. The aim of the present study was to assess whether there was an excess mortality due to such a fracture and to estimate the probability of death caused by the fracture. We studied primary total hip replacement in 27,652 men and 35,930 women with osteoarthritis from The Swedish National Hip Arthroplasty Register operated from 1979 to 2000. From the same register we also studied 392 men and 344 women with periprosthetic fracture from 1979 to 2000, all with osteoarthritis as the primary diagnosis. By the special method applied, it was possible to perform the estimation of death due to the fracture event though we could not determine in the individual case whether the fracture caused the death. Compared to the total population of patients operated with a primary THR there was a higher mortality rate immediately after the surgery for patients with periprosthetic fracture and in the longer run for patients below the age of 70 years. At the age of 70 years the estimated probability of death due to the fracture was 2.1% for men and 1.2% for women. At the age of 80 years at fracture the corresponding probabilities were 3.9% and 2.2% for men and women, respectively.

Revision Total Knee Arthroplasty

National and regional arthroplasty registries have been used to study the results of primary total knee arthroplasties. The purpose of this paper was to present the results of revision total knee replacements and describe predictors of survival of those replacements, with repeat revision as the end point.The nationwide Finnish Arthroplasty Registry included 2637 revision total knee arthroplasties from 1990 through 2002. Survivorship of the revision total knee arthroplasties was analyzed, with repeat revision as the end point. The survivorship analyses comprised evaluations of the proportional hazards assumption followed by calculations of univariate and multivariate statistics and model diagnostics as appropriate.The survival rate following the revision total knee arthroplasties was 95% (95% confidence interval, 94% to 96%) at two years (1874 knees), 89% (95% confidence interval, 88% to 90%) at five years (944 knees), and 79% (95% confidence interval, 78% to 81%) at ten years (141 knees). Multivariate regression analysis showed the most significant predictors of prosthetic survival to be the age of the patient and the life in service of the primary total knee replacement (that is, the time between the primary total knee replacement and the revision). Survivorship was also significantly predicted by the year of the first revision total knee arthroplasty and the reason for the revision.An age greater than seventy years, revision five years or more after the primary arthroplasty, and absence of patellar subluxation are positive indicators of survival of a revision total knee replacement. We believe that normal aging as well as the deconditioning effect of disease (osteoarthritis and rheumatoid arthritis) and its treatment (primary total knee replacement) may lead to a reduced activity level, which, together with a presumed reluctance to operate on elderly patients, protects against repeat revisions.Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.