Despite the continual introduction of new technologies and improvements in surgical technique, total hip replacement (THR) in young and active adults still remains a challenge for the longevity of prosthetic reconstruction.1,2 A hip replacement performed in patients aged 55 years or younger projects a period in service of the implant up to between 40 and 50 years, which in turn imposes on the implants about one hundred million loading cycles. More vigorous physical activities are characteristic of this particular population, which leads to even greater mechanical demands on the prosthetic components.3 Furthermore, the nature of the arthritic process in the young differs considerably from the most common conditions affecting the elderly1 and is frequently associated with more demanding reconstructive procedures and variable degrees of bone stock impairment.4
For these reasons, revision surgery is regarded as an inevitable procedure during the life span of a young adult submitted to THR, approaching 20% within the first 10 years of follow-up.2
Although recent studies report a general trend for increased percentage of THR in the young,5 even in demographically stable populations6 there is great variation in the incidence of prosthetic reconstruction among different countries,7 different regions of the same country8,9 and among different institutions in the same community. It is believed that this disparity could be somewhat influenced by racial/ethnic, socioeconomic, and demographic determinants, as well as by factors specifically related to the patient and the surgeon.9-13
The following discussion will focus on the epidemiology of THR, the demographics of South America, and information related to the growth trend in the 20 – 55-year-old age group, the current and expected incidence of THR performed annually and the most frequently used implants and bearing surfaces in comparison with American and Europe.
Epidemiology of THR
Time trends of THR globally.
The annual demand for THR has grown substantially on a global level during the last two to three decades.6 According to a survey based on administrative data provided by national health authorities of 30 countries, in 1998 the rate of primary THR was eight procedures per 100 000 people in Singapore, ranged between 53 and 93 per 100 000 in Australia, the US, England, Finland and Denmark, and between 118 and 135 per 100 000 in Sweden, Norway, and France.14 In 2006, considering the differences and opportunities of THR in the US, Asia and Europe, the figures varied from 30 to 40 per 100 000 in Korea and Japan; 140 to 170 per 100 000 in the US, Scandinavia, the UK, and France; and between 210 and 220 per 100 000 in Austria and Germany.15 More recently, an international survey compared THR utilisation in nine countries (US, Canada, Portugal, Spain, France, Italy, Germany, Netherlands and Switzerland) with the published registry data from six countries with operating arthroplasty registers (Romania, Denmark, England and Wales, Sweden, Norway and Australia).7 An average rate of 131 procedures per 100 000 was detected with an annual growth of 3.2% (ranging from 0.6% in France to 10% in Romania).
Because the classical indication of THR was formerly more restricted to elderly and less active patients, a higher utilisation rate in patients 75 years or older is expected. This fact, coupled with the progressive aging of the world population, corroborates the widespread use of THR in this particular age group. However it has been noted that the increased demand for THR is associated not only with the absolute increase in population and longer life expectancy, but also with factors intrinsically linked to the expansion of indications in younger patients, the increasing number of surgeons, and greater willingness of the patient to undergo a joint replacement.7-13 In Sweden, which has a more demographically stable population, there was a 41% increase in the incidence of THR between 2000 and 2010.16 In the same period the population increased 5.9%, from 8.8 million to 9.3 million inhabitants, while the Swedish arthroplasty register reported an increased percentage from 4.4% to 5.4% in patients aged 50 years or younger, and from 48.3% to 54.4% in patients in the 60 –79-year-old age group.16
The Finnish register also detected a substantial increase in the use of primary THR for the 30 – 59-year-old age group, from 9.5 per 100 000 in 1980 to 61 per 100 000 in 2007.6
Furthermore, an extrapolation of the data collected by Kurtz et al5 which evaluates the future demand for primary and revision joint replacement in young patients, revealed an incidence of 21.1% THR in patients aged 55 years or younger in 2006. However, when considering an expanded concept of young patient as the group aged 65 years old or younger, the authors projected the incidence of THR to exceed 50% by the year 2011.
Time trends of THR in South America.
Despite the relevant implications of the increased trend for THR utilisation in the young throughout the world, little is known about its epidemiology in South America. Because there is no active national registry, no epidemiological registry-based data are available; in addition, we are not aware of relevant population-based studies. In Chile, the Ministry of Health has detected, in 2006, a total of 1412 THR performed in a population of about 1.4 million people above 65 years of age.17 In 2011, the National Fund resources of Uruguay detected 2713 THR, which corresponds to an utilisation rate of 82/100 000.18 In Brazil a pilot project was initiated in 2007, which includes the data from all THR performed in three cities of different regions.19 In Argentina a national registry is still in development and a pilot phase is expected to start in 2012.20
With the aim of providing some additional information for this article, we performed a survey of various orthopaedic and hip national associations, as well as among hospitals in different countries and regions in South America.19 Because the utilisation of THR could not be determined due to the lack of community-based data (except for Brazil) we focused our queries on the rate of THR in patients aged 55 or younger, diagnosis, and most frequent implants utilised.
In Brazil, the pilot project of the national arthroplasty register is based on data collected from a population close to 2.5 million. Our extrapolation of the data from September 2007 to August 2008 pointed to a THR utilisation rate of 28 per 100 000.19 In this period the relative use of THR in patients aged 55 years or younger was 18.8%, with higher incidence in males (56.2%). Ages ranged from 17 to 55 years, (46.5). The most common diagnoses in males were osteonecrosis (41.5%), sequelae of childhood diseases (28.3%), idiopathic osteoarthritis (20.8%), sequelae of traumatic disorders (7.5%), and rheumatic diseases (1.9%). In females, the most frequent diagnoses were idiopathic osteoarthritis (27.5%), osteonecrosis (25.5%), sequelae of childhood diseases (21.6%), rheumatic diseases (17.6%), and sequelae of traumatic disorders (7.8%). Despite the small difference in incidence of sequelae of childhood diseases among males and females, the primary etiology differed considerably. In males the most frequent causes were Legg-Calvé-Perthes disease (13.3%), slipped capital femoral epiphysis (7.5%) and developmental dysplasia of the hip (7.5%), whereas in females the figures were respectively 2.0%, 5.9%, and 13.7%. Similarly, in our institution we detected a trend for increased utilisation of THR in patients aged 55 years or younger and in male patients. In the five year periods from 1996 to 2010 (1996 to 2000, 2001 to 2005, and 2006 to 2010), the percentages of THR in patients aged 55 years or younger were, respectively 12.5%, 14.4%, and 22.5%, while the incidence in males was 33.3%, 42.9%, and 51.3%. Furthermore, the use of diagnostic criteria more appropriate to the knowledge of each study period showed a progressive decrease in the incidence of idiopathic osteoarthritis with percentages of 39.2%, 22.5%, and 12.6% respectively.
A survey of nine hospitals from different regions of Argentinaconducted for the purposes of this article, showed a total of 3350 primary THR performed in the time period between 2007 and 2011. A total of 654 THR (18.4%) involved patients aged 55 years or younger. However, the incidence of hip replacements in this age group varied from 4.0% to 24.4%. In one high-volume hospital, 2286 THR were performed between 2007 and 2011, with 481 procedures (21.0%) involving patients under 55 years. The most frequent diagnoses were idiopathic osteoarthritis (average 47.6%) sequelae of childhood diseases (19.1%), osteonecrosis (15%), diseases secondary to traumatic disorders (7.5%), rheumatic diseases (2.9%), and other less frequent conditions (8%). In addition to the data from Brazil and Argentina and the figures for Venezuela the incidence of THR in patients aged 55 or younger approaches 20%.
When reporting global figures for THR utilisation rates, we must also consider the strong evidence for disparity and inequity in access, mostly linked to demographic, racial/ethnic and socio-economic status, and to specific factors directly related to the surgeon and the patient. These characteristics are shared, in different intensities and modalities, by the majority of the countries throughout the world, independently of financial resources and health policies.8-15 We discuss below some common demographic features of South America that may influence the utilisation rates and equity in access to THR.
Demographics of South America
Although the expected population growth in South America points to an overall increase in the age group above 20 years, the greatest relative increase will occur at the age of 65 years or older, which will nearly double between 2000 and 2030 (Table 1).
On average this age group will grow from 6.3% to 12% between 2000 and 2030 which, in absolute numbers, represents an increase from 23 million to 55 million people. Since this same age group houses about 70% to 80% of all primary THR, a substantial increase in the utilisation of prosthetic hip reconstructions in South America is to be expected. Particularly in Brazil and Colombia, which are the most populous countries, with respectively 49.8% and 11.8% of the current total population, this figure will nearly triple in the same period.
Although the age group between 20 and 54 years is expected to present a relative growth increase of only 3.7% between 2000 and 2030, this figure represents an absolute increase of 68 842 million people. In this particular age group, growth rates will be higher in Colombia (8.6%), Paraguay (7.2%), and Bolivia (6.6%), while Chile will have a negative growth (-2.5%).
In addition it should be noted that the number of THRs in young patients is increasing in absolute and relative numbers, regardless of population growth in the corresponding age group. This trend is observed even in populations with decreasing growth rates, as in Finland, the UK, and the US.5,6,9,11 It is striking that despite the lower overall rate of THR utilisation in South America, the incidence of this procedure in patients aged 55 years or younger approaches the figures reported for the US (20%).5
These population growth figures point to a substantial increase in the THR utilisation rate in South America over the next decades. Indeed, in an international survey, Kurtz et al7 found the only clear correlation to be between the national population and the annual number of THR performed per country.
Continuous increase in THR utilisation does not necessarily imply fairness in access to hip replacement procedures. Racial and ethnic characteristics have been reported to be an important determinant of disparities in the use of joint replacements on a global level. In fact, recent studies reported that racial disparity in arthroplasty procedures is not only persistent but potentially widening.10,11,13,14
The ethnic background of Brazil is European (48%; predominately Portuguese but also from Italy and Germany), African (7.6%), Asian (1.1%; primarily Japanese), and multiracial Ameridian (0.4%). Brazil’s population is 43% multiracial; mestizos (European and native background) or mulattos (European and African background). The ethnic makeup of the rest of South America is primarily of Spanish descent. Uruguay, Argentina and Chile have a great predominance of white European descent, while in Peru and Bolivia the indigenous population is the majority. In Colombia, Ecuador, Paraguay and Venezuela mestizos make up the majority of the population.
We are not aware of any population-based studies addressing the incidence of THR within different ethnic populations in South America. However, several studies in Europe, Canada, the US, Australia and other countries have consistently demonstrated evidence of inequalities in the provision of THR among different races and ethnic groups. In a cohort observational study21 among Medicare beneficiaries who underwent THR between 1991 and 2008, the procedures provided for Caucasian people varied from 91.6% to 93.2%; for African-American from 3.7% to 4.6% and from 1.4% to 1.9% for other ethnic groups (Hispanic, Asian, and North American Native). However, the need for THR among ethnic groups does not vary in similar proportions.
Recent studies, which seek to detect different factors associated with disparities in the use of THR, have shown an overlap of racial/ethnic factors and lower socioeconomic status. Confronting racial and ethnic disparities in health care, Nelson22 found that socioeconomic status accounted for more than 30% of the difference. In fact, inequity in joint replacement has been associated with income and assets, education, cultural competency, health care model, and payer type.
In South America most of the population is assisted by universal systems of health policies, which largely depend on public investments. However, the disparity in the socioeconomic status and the public investments in health between South America and the US, the UK and Sweden are enormous (Table 2).
Furthermore, the universal health policy system frequently imposes a fixed reimbursement or tariff which may lead to financial constraints, adding institutional reasons for disparities in the use of THR. In Brazil, among patients who use the public health system, the relative annual increase in the number of THR has shown unexpected values of 7.2% between 2008 and 2009, 4.6% between 2009 and 2010, and 1.5% between 2010 and 2011,23 which increase the impact of payer type on resource utilisation and may induce patient out-of-pocket expenses through a private health system.
The patient’s willingness to consider THR and the surgeon’s to offer it have contributed to the increased utilisation of total joint replacements. From the standpoint of the patient, use of THR is clearly dependent on age and cultural, educational, racial and socioeconomic characteristics. Younger patients tend to exhibit greater preference for joint replacement. In South America, although there are lower overall rates of THR utilisation, the relative use in patients aged 55 years or younger approaches 21%,19 which is quite similar to the 21.1% rate observed in the US.5
South America does not share the North American concern which predicts a supply side crisis in the number of joint specialists, which may threaten patient access to THR.12 Overall, the number of specialists in South America has increased considerably. As an example, the Brazilian Hip Society (SBQ; Sociedade Brasileira de Quadril) database currently reports a total of 643 members aged 49.1 years in average. Each year, on average, 65 new applications for the entrance examination are held, of which about 28 candidates (43%) are approved, accumulating annually about 37 specialists who were trained in hip surgery but have not yet been accepted by SBQ. Considering the functional retirement for surgeons aged 65 years or older, these figures project about 45% increase in hip specialists by 2020 (Table 3).
This numerical projection differs markedly from the projected growth of only 1.6% in the number of hip and knee specialists between 2008 and 2016, reported by Fehring et al.12 If we consider a 50% increase (from 70 000 to 105 000) in the number of primary and revision THR between 2010 and 2020 and that hip specialists perform about 80% of such procedures, each hip surgeon on average will support a workload of nearly 4.6 THRs per month.
Implants for THR in the young: the unmet need?
Despite the long history of success associated with cemented THR, cementless implants were the first to challenge Charnley’s original indication of arthroplasty, which restricted its use to older and less active patients.
The controversy over implant fixation is well characterised by the philosophical concept known as ‘The North Atlantic Divide’. This concept refers to the almost exclusive use of cemented implants in some European nations, especially in the Nordic countries, while in the US and Canada cementless implants are used in about 90% of patients.
Currently, the reported outcomes for both cemented and cementless are outstanding with contemporary designs and techniques; however, the majority of the worldwide orthopaedic community is switching to uncemented fixation.
A trend towards more frequent use of cementless implants in the population aged 55 years or younger can also be seen in South America. In Argentina a survey including 469 THR in this particular age group, held in nine different hospitals from different regions of the country, showed an incidence of 81.2% for cementless, 17.0% for hybrid, and only 1.9% for cemented arthroplasties (personal communication).
Although the use of cementless THR in the public health system in Brazil is only allowed in some accredited hospitals, the data collected from the pilot project of the National Arthroplasty Register19 showed an incidence of 51.6% for cementless arthroplasties, 38.6% for cemented, and 9.8% for hybrid. However, there was a clear difference in the incidence rates of cemented arthroplasties between females (50.2%) and males (24.6%). This difference may be somewhat explained by the higher incidence of inflammatory arthroplasties in females (17.6%), compared with males (1.9%), a situation in which the cemented THR is preferred by most surgeons in Brazil.
A detailed discussion of the clinical and tribological aspects of the bearing surfaces in THR is beyond the scope of this article. However, this is a relevant issue for the young patient who undergoes THR. As already stated, the young patient submitted to THR accumulates additional drawbacks of greater period in service of the implant, greater mechanical demands to the prosthetic components, more demanding reconstructive procedures, and variable degrees of bone stock impairment.
To date, no bearing surface currently used presents clinical results to confirm its performance for at least 30 years, which is a common requirement in young patients. However, new technologies and biomaterials recently introduced in clinical practice have provided new perspectives for the longevity of the prosthetic joint reconstruction. The question is, are these new bearing surfaces cost-effective? This is a relevant issue considering the disparities in financial resource investments in public health throughout the world (Table 2).
In Brazil, the most widely used bearing surfaces, even for patients aged 55 years or younger are: metal-on-conventional polyethylene (52.5%), ceramic-on-ceramic (42.0%), ceramic-on-highly cross-linked polyethylene (5.0%), and metal-on-metal (0.5%).19 In Argentina the figures are respectively 10.2%, 51.6%, 17.0%, and 19.8%, with an additional 1.4% for ceramic-on-metal bearing surface. The higher usage of metal-on-conventional polyethylene in Brazil may be somewhat related to per-tariff payment applied by the public health system, which prevents the implantation of alternative bearings. As an example, the tariff paid by the government for a primary cementless THR, converted to US dollars, is as follows: surgeon $72.2, anaesthesiologist $44.4, hospital $526.1 and implant $1421.1.
The overall utilisation of THR in South America is expected to increase substantially during the next decades due to the absolute increase in population, longer life expectancy, expansion of indications to younger patients, the increasing number of surgeons and greater willingness of the patient to undergo a joint replacement.
The only population-based study performed in Brazil pointed to a lower utilisation rate of THR (28 per 100 000) compared with the range from 140 to 220 per 100 000 reported by the US and some European countries. However, this figure may reflect striking differences among countries in socioeconomic status, health care policies, and patient preferences. Also, the subset of the population evaluated may not represent the actual trend throughout the country because it does not account for health disparities, thus leading to underestimation of THR utilisation.
THR demand in the young and more active patient is continuously rising on a global level. In South America, the absolute and relative increase in the population between 20 and 55 years projects 226 648 million people in this particular age group by 2030. Considering that about 20% of all THR performed in South America are in patients aged 55 years or younger, the associated higher costs and revision rates should be taken into account by the health policies systems, so that disparities are decreased and access is not threatened. Population-based studies are recommended in order to examine the actual demand, trends, and disparities in THR utilisation.
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17. No authors listed. Ministry of Health: Chile Government. Guia Clínica: Endoprótesis Total de cadera en personas de 65 años y más con artrosis de cadera con limitación funcional severa, 2010 (in Spanish).
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