Summary
Objective
To estimate and compare the lifetime risk of total knee replacement surgery (TKR) for osteoarthritis (OA) between countries, and over time.
Method
Data on primary TKR procedures performed for OA in 2003 and 2013 were extracted from national arthroplasty registries in Australia, Denmark, Finland, Norway and Sweden. Life tables and population data were also obtained for each country. Lifetime risk of TKR was calculated for 2003 and 2013 using registry, life table and population data.
Results
Marked international variation in lifetime risk of TKR was evident, with females consistently demonstrating the greatest risk. In 2013, Finland had the highest lifetime risk for females (22.8%, 95%CI 22.5–23.1%) and Australia had the highest risk for males (15.4%, 95%CI 15.1–15.6%). Norway had the lowest lifetime risk for females (9.7%, 95%CI 9.5–9.9%) and males (5.8%, 95%CI 5.6–5.9%) in 2013. All countries showed a significant rise in lifetime risk of TKR for both sexes over the 10-year study period, with the largest increases observed in Australia (females: from 13.6% to 21.1%; males: from 9.8% to 15.4%).
Conclusions
Using population-based data, this study identified significant increases in the lifetime risk of TKR in all five countries from 2003 to 2013. Lifetime risk of TKR was as high as 1 in 5 women in Finland, and 1 in 7 males in Australia. These risk estimates quantify the healthcare resource burden of knee OA at the population level, providing an important resource for public health policy development and healthcare planning.
Introduction
Knee osteoarthritis (OA) represents a significant public health challenge internationally. The increasing burden of knee OA worldwide is evident from the results of the Global Burden of Disease Study
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The global burden of hip and knee osteoarthritis: estimates from the Global Burden of Disease 2010 study.
. This landmark study highlighted a major shift in the global burden of disease over the past 20 years from infectious diseases to non-communicable diseases including musculoskeletal conditions that are associated with significant disability
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. This is supported by data from a range of developed countries that show steady growth in the rate of knee replacement surgeries performed predominantly for severe knee OA over the past two decades
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. Total knee replacements (TKRs) represent the majority of procedures performed, with only a small proportion of patients receiving unicompartmental knee replacement (UKR)
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. While joint replacement surgery is cost-effective
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, planning for future healthcare demand is critical and requires robust population-level data on disease burden and healthcare utilisation.
Estimating the lifetime risk of joint replacement surgery is an evolving area within musculoskeletal epidemiology. This statistical approach is commonly used in the cardiovascular and cancer fields
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. The lifetime risk of TKR refers to the probability of having this surgical procedure over an individual's lifetime. Lifetime risk estimates provide a complementary approach to quantifying population-level disease burden and related use of healthcare services, and can be easily interpreted by health policymakers, clinicians and patients (as they are expressed as percentages). A key advantage of the lifetime risk statistic is that it provides a cumulative measure of risk that incorporates population life expectancy and all-cause mortality.
Data on the lifetime risk of TKR surgery are limited. Research from the United Kingdom found that the lifetime risk of TKR had increased markedly over a 15-year period from 1991 to 2006, particularly for women
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used national health survey data to estimate the cumulative lifetime risk of TKR, although changes in risk over time were not evaluated. Most recently, Bohensky and colleagues used hospital administrative data to estimate the lifetime risk of TKR in the state of Victoria, Australia
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. A clear increase in the lifetime risk of TKR was evident over a nine-year period (1999–2008), most notably for females. Previous studies investigating the lifetime risk of TKR have all obtained data on joint replacement utilisation from observational studies or health system administrative datasets, which have known limitations around generalisability, completeness and accuracy. The use of population-based procedure data from national arthroplasty registries with almost complete coverage would enable more precise estimates of the lifetime risk of TKR.
While a number of earlier studies have compared TKR incidence rates or utilisation rates between countries
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Utilization rates of knee-arthroplasty in OECD countries.
, an international comparison of the lifetime risk of TKR has not been undertaken. The present study aimed to:
- •
estimate and compare the lifetime risk of primary TKR for OA in five countries;
- •
describe change in lifetime risk over a ten-year period (2003–2013); and
- •
examine changes in utilisation rates of primary TKR and UKR performed for OA over time.
Discussion
This study is the first to use population-based arthroplasty registry data to estimate the lifetime risk of TKR at the national level, and to compare lifetime risk between countries and over time. We used data from five well-validated registries to obtain the most accurate information on TKR utilisation. We found a marked increase in the lifetime risk of primary TKR for OA in all countries over the ten-year study period, and substantial variation between countries in the utilisation of TKR. These lifetime risk estimates advance our understanding of population-level knee OA disease burden and healthcare utilisation, beyond data from the Global Burden of Disease Study that were modelled using systematic reviews of OA prevalence and incidence
1- Cross M.
- Smith E.
- Hoy D.
- Nolte S.
- Ackerman I.
- Fransen M.
- et al.
The global burden of hip and knee osteoarthritis: estimates from the Global Burden of Disease 2010 study.
, and beyond published TKR incidence or utilisation rates that do not consider life expectancy, age-specific mortality, or whether individuals have multiple surgical procedures
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International survey of primary and revision total knee replacement.
, 15- Pabinger C.
- Lothaller H.
- Geissler A.
Utilization rates of knee-arthroplasty in OECD countries.
.
The observed international variation in lifetime risk is unlikely to be explained purely by differences in knee OA prevalence, given the overlap in prevalence data for the five included countries
20- National Public Health Institute
Musculoskeletal Disorders and Diseases in Finland: Results of the Health 2000 Survey.
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Prevalence and burden of osteoarthritis: results from a population survey in Norway.
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Obesity and increased burden of hip and knee joint disease in Australia: results from a national survey.
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. It is possible that differences in OA severity distributions may have contributed to our findings, although country-level severity data are not available to confirm this hypothesis. Variation in obesity rates between countries
15- Pabinger C.
- Lothaller H.
- Geissler A.
Utilization rates of knee-arthroplasty in OECD countries.
, and changes over time may also influence the knee OA burden in individual countries. According to national health survey data collated by the Organisation for Economic Co-operation and Development (OECD)
, the prevalence of self-reported obesity in Finland increased from 12.8% in 2003 to 15.7% in 2013, and from 9.8% in Sweden in 2003 to 11.7% in 2013. Only single year obesity prevalence estimates are available for Denmark and Norway during the period 2003–2013 (14.2% in Denmark in 2013, and 10.0% in Norway in 2012). For Australia, the national prevalence of obesity increased from 24.6% in 2007 to 28.3% in 2011 but these estimates are based on measured height and weight data rather than self-reported data (the latter tend to under-report obesity). As high-income countries, life expectancy in Australia and the Nordic countries was similar and unlikely to have contributed to the international variation in lifetime risk. Longer life expectancy for females is likely, however, to have contributed to the higher lifetime risk of TKR seen for females in all countries.
The most plausible explanation for the between-country differences in lifetime risk of TKR is international variation in health system factors. These include (but are not limited to) differences in local indications for surgery, access to surgery, healthcare funding and health workforce issues. Earlier research has shown significant international variation in the pre-operative status of people undergoing joint replacement for OA
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, suggesting differing clinical thresholds for performing surgery. The higher lifetime risk in Australia could also relate to increased access to surgery within the private healthcare system. In contrast, orthopaedic surgeons in the Nordic countries might be more likely to consider non-surgical management, given the availability of region-based OA prevention and management programs that actively encourage people to trial physiotherapy, disease education and exercise prior to considering surgery. These include the ‘Better management of patients with OsteoArthritis’ (BOA) program in Sweden
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, the ‘Good Life with osteoArthritis in Denmark’ (GLA:D) program in Denmark
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, and ‘AktivA’ in Norway
. However, while conservative management programs might improve OA symptoms and delay the need for TKR surgery
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, whether they can ultimately reduce an individual's lifetime risk is not known. Personal factors could also play a role in promoting the uptake of TKR in individual countries and increasing lifetime risk; for example, greater acceptance of joint replacement surgery in the community, cultural factors, more exposure to successful outcomes among peers, and access to paid leave or injury compensation schemes. The high lifetime risk in Finland might relate to local patient preferences for surgery, with registry research suggesting that Finnish baby-boomers elect to undergo TKR when their OA symptoms are relatively mild
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. It is not clear why Norway had the lowest lifetime risk of TKR for both sexes in 2013 but this could relate to their relatively high utilisation of UKR and the comparatively good patient-reported outcomes for UKR in that country
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Pain and function in patients after primary unicompartmental and total knee arthroplasty.
, although a recent systematic review reported higher revision rates than for TKR
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.
The significant increases in lifetime risk over time for each country are also unlikely to relate simply to growth in OA prevalence. In contrast, Global Burden of Disease data showed that worldwide, the age-standardised prevalence of knee OA did not change significantly from 1990 to 2010
1- Cross M.
- Smith E.
- Hoy D.
- Nolte S.
- Ackerman I.
- Fransen M.
- et al.
The global burden of hip and knee osteoarthritis: estimates from the Global Burden of Disease 2010 study.
while in Finland, national health surveys have shown that the prevalence of knee OA among women has actually decreased over a 20-year period
20- National Public Health Institute
Musculoskeletal Disorders and Diseases in Finland: Results of the Health 2000 Survey.
. Our data showed that Australia experienced the greatest absolute change in lifetime risk over time (for both sexes), and this probably reflects ‘catch up’ of previous unmet need following the introduction of government financial incentives in 1999–2000 to promote the uptake of private health insurance cover. Finland also experienced considerable unmet need for TKR prior to 2005, with patients experiencing long delays in accessing surgery. New Finnish legislation introduced in 2005 specified maximum waiting times for orthopaedic consultation and TKR, and hospitals received additional resources to meet these requirements. Although this cannot be quantified, these macro-level initiatives would undoubtedly have contributed to the rise in lifetime risk of TKR in both Australia and Finland. While detailed information on policy changes in each country was not available, it is possible that changes to government healthcare policies in the other countries over the study period may have contributed to the growth observed.
Our calculated utilisation rates showed the greatest burden of TKR was borne by the 70–79 age group in 2003 and 2013. Younger patients (those aged 40–59 years) demonstrated only a small absolute increase in utilisation rates over the ten-year period, and perhaps this reflects awareness of the relatively high TKR revision rates for younger individuals
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Younger age increases the risk of early prosthesis failure following primary total knee replacement for osteoarthritis. A follow-up study of 32,019 total knee replacements in the Finnish Arthroplasty Register.
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. These utilisation rates cannot be directly compared to other studies examining TKR incidence or utilisation rates between countries, predominantly due to differences in data sources and methods. The study by Kurtz
et al.13- Kurtz S.M.
- Ong K.L.
- Lau E.
- Widmer M.
- Maravic M.
- Gomez-Barrena E.
- et al.
International survey of primary and revision total knee replacement.
used a combination of inpatient hospital administrative data and arthroplasty registry data. Their reported incidence rates were not stratified by age or sex and were calculated at different time points (2007–2010) than those used for our study. The authors also acknowledged hospital coding limitations, where it was not possible to consistently determine primary TKR from revision TKR, or TKR from UKR. Most recently, Pabinger
et al.15- Pabinger C.
- Lothaller H.
- Geissler A.
Utilization rates of knee-arthroplasty in OECD countries.
compared TKR utilisation rates in OECD countries but separate analyses for males and females were not reported.
Our research design has uniquely generated burden of knee OA estimates using national data from five countries. Combined, the five countries had a population of almost 49 million people and performed over 74,000 primary TKRs in 2013. A major strength of this study is our use of robust arthroplasty registry data to ensure accurate estimations of lifetime risk and enable fair international comparisons. The Nordic countries have led the world with regard to implementing and maintaining high-quality national arthroplasty registries and the five included registries have near-complete TKR capture at the population level. We counted all TKR procedures when calculating utilisation rates but were careful to avoid erroneously inflating our lifetime risk estimates by only counting bilateral TKR procedures at the patient-level for these analyses. Given that provision of TKR is highly age-related, the standardised lifetime risk approach was important for dealing with changes to a country's age structure over time (for example, growth in older age groups due to population ageing). In this way, standardised lifetime risk calculations are likely to be more accurate for monitoring changes in lifetime risk and undertaking between-country comparisons than non-standardised methods. We also acknowledge the limitations of this research. We included all patients who received a primary TKR for OA in 2003 or 2013 (regardless of whether they had previously received a contralateral primary TKR), as from a clinical perspective these patients are still ‘at risk’ of having surgery in the years of interest. This method also accounts for the different establishment years for each registry, and reflects the challenges of estimating lifetime risk for conditions that can have multiple occurrences over time
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- Shelton J.
- Ormiston-Smith N.
- Thomson C.S.
- Silcocks P.B.
What is the lifetime risk of developing cancer?: the effect of adjusting for multiple primaries.
or conditions that can affect more than one joint, in the case of knee OA. Annual lifetime risk was not calculated as annual life tables were not consistently available for all countries, and it is possible that fluctuations may have occurred over the ten-year study period. Finally, we acknowledge that there may be some variation in the coding of diagnoses and classification of knee replacement procedures between the national registries that cannot be accounted for in our analyses.
In conclusion, this study has identified significant increases in the lifetime risk of primary TKR performed for OA in Australia, Denmark, Finland, Norway and Sweden over a ten-year period. There was substantial variation in lifetime risk across all countries, with females consistently demonstrating the highest risk. These data augment our understanding of the population burden of knee OA, and can be used by individual countries to inform public health policy and resource planning.
Article info
Publication history
Published online: November 14, 2016
Accepted:
November 7,
2016
Received:
August 2,
2016
Copyright
© 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd.