Incidence of hip replacement among national health insurance enrollees in Taiwan
© Lai et al; licensee BioMed Central Ltd. 2008
Received: 03 March 2008
Accepted: 15 September 2008
Published: 15 September 2008
There is no national joint replacement registry in the country of Asia and reports of national outcomes of joint replacement in Asia as yet. Therefore, this study was then to report a national data of the number of hip replacements, incidence rate, demographic characteristics of hip replacement patients, and short-time survival rate after hip replacement of Han Chinese in Taiwan.
We analyzed 105,688 cases of hip replacements (including primary partial hip replacement, primary total hip replacement and revision of hip replacement) from National Health Insurance research database between 1996 and 2004. The survival rate of primary hip replacement was estimated for each disease by the Kaplan-Meier method.
Average annual number of primary partial hip replacement and primary total hip replacement were 4,257 and 6,206 cases, respectively. The most two common diagnosis of primary partial hip replacement were femoral neck fractures (73.6%, 34% men, mean age 76 years) and avascular necrosis (18.0%, 84% men, mean age 48 years). In primary total hip replacements, the most two common diagnosis were avascular necrosis (46.9%, 79% men, mean age 50 years) and osteoarthrosis (41.6%, 43% men, mean age 60 years). Both the number of primary partial hip replacements and primary total hip replacements increased steadily between 1996 and 2004. The cumulative survival of primary partial hip replacements and primary total hip replacements in all patients were 93.97% and 79.47% in 9 years follow-up, respectively.
Avascular necrosis is the main disease in total hip replacement in Taiwan. The epidemiology of hip diseases was different between Han Chinese (in Taiwan) and Caucasian and the number of hip replacements increased substantially in Taiwan between 1996 and 2004.
National joint replacement registry is a good solution to record and publish the information for the orthopaedic community on the outcome of joint replacement surgery. Norway (in 1987)  and Sweden (in 1979)  established national total hip replacement (THR) registry and collected data of arthroplasty from hospitals in the whole country. The main purpose of the registry was to discover inferior results as early as possible in order to avoid inferior implants from being used in large numbers of patients. The statistical analyses reports of registry provided epidemiology, outcomes assessment, and risk factors for revision, etc. However, there is no national joint replacement registry in the country of Asia and reports of national outcomes of joint replacement in Asia as yet. In Taiwan, there is also no official report related to joint replacement like the distribution of diseases between men and women, and survival rate, etc. Therefore, we always rely on the reference of foreign and adopted the medical concept from the Western country. But in clinics, a lot of surgeons realize the patterns of the epidemiology of joint replacement in Taiwan are quite different from the Western. No one could fully understand the distribution of diseases between men and women, and survival rate in whole Taiwan.
Since the implementation of the National Health Insurance (NHI) in Taiwan in 1995, we have accumulated a huge database of clinical cases greater than 96% of the total population in Taiwan. People have received medical health care coverage from this universal national health care system. There were greater than 95% of all the hospitals contained in the NHI databases in Taiwan . Information on all medical treatment undertaken at all medical institutions that contracted with NHI has been recorded in the database since 1996. Therefore, the NHI established a national health insurance research database to respond to current and emerging health issues effectively. The database makes possible the epidemiologic analysis of hip joint disease, because almost all patients who need hip operation treatment are hospitalized to receive hip surgery. Some studies also used data from the NHI in Taiwan [4, 5]. The detail information about the NHI program in Taiwan was described in the literature .
The purpose of this study was then to report a data of the number of hip replacements, incidence rate, demographic characteristics of hip replacement patients, and short-time survival rate after primary hip replacement in Taiwan.
The National Health Insurance program has implemented since March 1995, and the development of the Taiwan's health economy has really taken off. It provides several measures to protect the unemployed, the poor, and the victims of natural and manmade disasters. Moreover, by safeguarding the right of the weak to have access to medical care, the program maintains social order and provides security during this time of economic recession. Until June 2006, there were 22.3 million individuals enrolled in the NHI with a coverage rate of 99% populations (22.7 million) and 18,289 healthcare providers contracted with NHI, representing 91.45% of all providers in Taiwan.
In order to survey the results of hip replacement surgery, we analyzed 105,688 cases of registry for contracted medical facilities and inpatient expenditures by admissions from NHI research database between 1996 and 2004, on the basis of the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) code for THR (81.51), partial hip replacement (PHR) (81.52) and revision of hip replacement (including PHR and THR) (81.53) listed as the major operation. These cases included 38,349 cases of primary THR, 55,884 cases of primary PHR and 11,455 cases of revision of hip replacement. We excluded 51 cases (26 cases of primary THR and 25 cases of primary PHR) which aged less than 16 years old. The insurance data was registered by physicians before operation. The data of inpatient expenditures contained six categories including personal information, date of inpatient, diagnosis, operation, expenditures, and hospital information. The items including patient identity, date of operation, birthday, gender, diagnosis, and treatment were used in this study. We compared the patient identity between primary operation (PHR and THR) and revision of hip replacement, and found there were 1,201 and 1,905 cases of revision from the failure of primary PHR and THR originally enrolled in the database, respectively. Survival of primary hip replacement was estimated for each disease by the Kaplan-Meier method . The start date of follow-up was defined as the date of operation. The end-point of survival was defined as the date of revision. For the statistical analyses, we used the software SPSS 10.0 (SPSS Inc. Chicago, Illinois).
The relationship of gender, age, and percentage of patients to hip disease, in the NHI research database 1996–2004.
All primary operations including partial and total hip replacement (94,182)
Age < 60 years (%)
Mean age in years
Femoral neck fractures
Malunion and nonunion of fracture
Congenital anteversion of femur
Partial hip replacements
The relationship of gender, age, and percentage of patients to hip disease of primary partial hip replacement, in the NHI research database 1996–2004.
All primary partial hip replacement/Revision (55,859/1,201)
Age < 60 years (%)
Mean age in years (range)
Revision Rate %
Femoral neck fractures
Total hip replacements
The relationship of gender, age, and percentage of patients to hip disease of primary total hip replacement, in the NHI research database 1996–2004.
All primary total hip replacement/Revision (38,323/1,905)
Age < 60 years (%)
Mean age in years (range)
Revision Rate %
Femoral neck fractures
The relationship of gender, and percentage of patients to revision reason of primary partial and total hip replacement, in the NHI research database 1996–2004.
Revision of PHR(1,201)
Revision of THR (1,905)
Revision Reason (ICD-9 Code)
Mechanical complication (996.4, 996.5)
Other complications (996.7)
The major limitation of this study is that the information of the replacement side, implant type and size, surgical approach and cement brand are not recorded in the national health insurance research database. The survival of hip prosthesis was not available. It is the important factor that influences the survival rate of hip replacement. Another limitation is that some cases were failed from severe infection and did not receive revision of hip replacement. Therefore, our results of survival rate would be higher than the true condition.
Our results indicated that the number of primary PHR and THR increased substantially in Taiwan between 1996 and 2004. The trend was pronounced in primary PHR as compared with primary THR (Figure 1). There is a strong relationship between ageing society and the risk of FNF. The age structures indicated that 10.2% of the populations are 65 years old or older in Taiwan at present. The distribution of diagnosis in all primary PHR and THR by age showed that most of the patients (95.4%) with FNF were above 60 years old (Table 1). Aging coincided with a loss of muscle strength, flexibility and balance. Fall down may be the factor caused the FNF in elder patients . In this study, there were 98.5% of FNF patients (39,557) who underwent primary PHR and only 1.5% performed primary THR. This is because that the hemiarthroplasty is recommended for the old patient, who may be occasionally active outside of household . Therefore, for lower expenditure, the law of NHIB provided that FNF should be undergone by PHR of Moore hip prosthesis for patients whose age greater than 80 years old. The NHI also provides the pay of hip arthroplasty for the patients who implant with Moore hip prosthesis. Those policies also explained our results that the annual proportion of patients who aged 65 years old (retired on merit) and received primary PHR were highly and increased year by year as compared with the patients who received primary THR (Figure 4).
In the two groups of primary THR and PHR, we found that the cumulative survival of primary PHR (93.97%) in all patients was higher than primary THR (79.47%). Compared the cumulative survival of primary PHR with Australian (54.6% at 5-years, primary bipolar) , our results showed an extra high cumulative survival at 9 years. This may be due to the reason that the patients died before receiving revision replacement because of the old age in Taiwan. The highest incidence of primary PHR and THR were occurred in the age during 70–79 and 60–69 years, respectively (Figure 3a and 3b). The possible reason for lower survival rate in primary THR was that the young patients had more high activity than elder, and it increased the risk of revision. However, the lower survival for younger patients could be due to different implant types, some specific hospitals or regions, some specific diagnosis, or other confounders.
Although the FNF was the main indication for primary PHR in Taiwan (70.8%), the proportion of FNF in primary PHR was low as compared with Australian (94.7%) . Because there were 36% of AVN patients who underwent primary PHR, and the proportion of young patients was higher (76.7%) in AVN group in this study. In the 90's, literatures  showed that the hemiarthroplasty was be considered a better way to retained more bone stock for the AVN young patients who had healthy acetabulum. That could be the reason why 36% of AVN patients who underwent primary PHR in this study. However, recent studies showed that hemiarthroplasty is not a good choice for AVN patients and that the acetabulum needs to be done .
The relationship of gender, age, and percentage of patients to hip disease of primary THR, in Taiwan, Norwegian and Swedish.
Mean age (range) (yrs)
It is worth to be taken notice of the difference that the mean age of OA patients in Taiwan (60 years) were younger than Norwegian and Swedish (70 years) as shown in Table 5. Literatures [22, 23] reported the much lower incidence of OA among non-whites than among whites but did not point out the difference of age. The cumulative survival of primary THR with OA at 7 to 8 years was similar in Norwegian (90%) , Swedish (91%)  and Taiwan (89%). Unlike the decrease of cumulative survival steadily in Norwegian and Swedish, it was diving to 76% after 8 years in Taiwan. We could not confirm the reason that it was due to the younger OA patients with a high activity level in Taiwan, because the information of prosthesis is not recorded in the database.
This study reported statistical data of primary PHR and THR in Taiwan and showed the difference in epidemiology of hip diseases between Han Chinese and Caucasian. AVN is the main disease in primary THR in Taiwan and it is very different form Caucasian in age and gender. Moreover, mechanical complication of hip prosthesis is the main reason for revision. We should be careful with the generalizing results from western countries to other ethnic groups.
The authors thank the bureau of National Health Insurance, Taiwan for data support.
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