ARTHRITIS & RHEUMATOLOGY Vol. 66, No. 6, June 2014, pp 1432–1439 DOI 10.1002/art.38384 © 2014, American College of Rheumatology
US Trends in Rates of Arthroplasty for Inflammatory Arthritis Including Rheumatoid Arthritis, Juvenile Idiopathic Arthritis, and Spondyloarthritis Christina Mertelsmann-Voss, Stephen Lyman, Ting Jung Pan, Susan M. Goodman, Mark P. Figgie, and Lisa A. Mandl per 100,000 versus 0.31 per 100,000). Age at the time of arthroplasty increased for patients with RA (mean ⴞ SD 63.4 ⴞ 12.7 years versus 64.9 ⴞ 12.8 years), JIA (30.9 ⴞ 12.2 years versus 36.7 ⴞ 14.9 years), and SpA (54.3 ⴞ 16.1 years versus 60.4 ⴞ 13.9 years). However, the mean age at the time of arthroplasty among non-IA cases decreased (71.5 ⴞ 11.8 years versus 69.0 ⴞ 12.0 years). Conclusion. This population-based study is the first to show that arthroplasty rates have decreased significantly among patients with JIA and minimally among patients with RA, and have increased among patients with SpA. The increased age at the time of arthroplasty among patients with JIA and SpA suggests that these patients are increasingly able to defer surgical interventions. Further research is needed to assess the ongoing effect of biologic agents on the need for arthroplasties in patients with IA.
Objective. Although rates of arthroplasty have increased dramatically, rates among patients with rheumatoid arthritis (RA) are reported to be decreasing. It is not known if this is also the case among patients with other inflammatory arthritides. This study was undertaken to evaluate rates of arthroplasty due to RA, juvenile idiopathic arthritis (JIA), spondyloarthritis (SpA), and a composite group of patients with inflammatory arthritides (IA), compared to arthroplasty rates among patients without inflammatory or autoimmune conditions. Methods. Administrative discharge databases (State Inpatient Databases of the Healthcare Cost and Utilization Project, New York Department of Health Statewide Planning and Research Cooperative System, California Statewide Health Planning and Development) were used to compare rates of knee, hip, and shoulder arthroplasty occurring from 1991 to 2005. Results. Of 2,839,325 arthroplasties in 1991–2005, 2.7% were performed in patients with IA. The rate of arthroplasty for noninflammatory conditions doubled (124.5 per 100,000 persons in 1991 versus 247.5 per 100,000 persons in 2005), while the rate for IA remained stable at 5.1 per 100,000. Rates of arthroplasty for RA decreased slightly (4.6 per 100,000 versus 4.5 per 100,000) and those for JIA decreased by nearly 50% (0.22 per 100,000 versus 0.13 per 100,000), but the rate of arthroplasty for SpA increased by nearly 50% (0.22
In patients with inflammatory joint disease, arthroplasty is considered to represent a lack of success of medical management. In the past, arthroplasty was an accepted outcome for many patients with rheumatoid arthritis (RA). Wolfe and Zwillich reported that, among a cohort of RA patients assembled in 1974–1997, 25% underwent joint replacement surgery within 22 years of disease onset (1). However, the rate of joint replacements among patients with RA appears to have leveled off or decreased, in conjunction with increasing use of disease-modifying antirheumatic drug (DMARD) therapy (2–6). This decrease in arthroplasty utilization contrasts with the increase in arthroplasty rates in the general population (6,7). It is not known if the frequency of arthroplasty due to RA is continuing to trend downward, and if such a decreasing trend is occurring in other inflammatory arthritides. The aim of this study was to
Christina Mertelsmann-Voss, MD, MSc, Stephen Lyman, PhD, Ting Jung Pan, MPH, Susan M. Goodman, MD, Mark P. Figgie, MD, Lisa A. Mandl, MD, MPH: Hospital for Special Surgery, New York, New York. Address correspondence to Christina Mertelsmann-Voss, MD, Department of Pediatric Rheumatology, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021. E-mail: [email protected]. Submitted for publication June 27, 2013; accepted in revised form January 23, 2014. 1432
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evaluate trends in rates of knee, hip, and shoulder arthroplasty due to RA, juvenile idiopathic arthritis (JIA), and spondylarthritis (SpA), as well as a composite group of all inflammatory arthritides (IA), from 1991 to 2005, and to compare these rates with those among patients with no inflammatory or autoimmune conditions. METHODS Sources of data. Discharge data for the years 1991– 2005 were collected from 3 different sources. The State Inpatient Databases (SID) of the Healthcare Cost and Utilization Project (HCUP) provided data from Arizona, Colorado, Florida, Massachusetts, New Jersey, Washington, Iowa, and Wisconsin. Data from New York and California were obtained from the New York Department of Health Statewide Planning and Research Cooperative System and California Statewide Health Planning and Development, respectively. These databases encompass ⬃90% of all community hospital admissions, which include academic teaching hospitals, within these states and contain discharge diagnoses and indications. HCUP SID data rather than HCUP National Inpatient Sample (NIS) data were used as the NIS relies on sampling, which can be unreliable when evaluating rare conditions or events. Data on inpatients within a given state who were not residents of that state were excluded from this analysis. Primary total knee arthroplasty (TKA), primary total and partial hip arthroplasty (THA and PHA), and primary total and partial shoulder arthroplasty (TSA and PSA) were identified using procedure codes 81.54, 81.52, 81.51, 81.80, and 81.81, respectively, from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). Patients with a discharge diagnosis of malignant neoplasm (ICD9-CM 140.0–209.9, or V-code V10.0–10.9, V71.1) except for nonmelanoma skin cancer (ICD-9-CM 173) were excluded. ICD-9 codes were used to identify RA (714.0–714.1), JIA (714.30–714.33) as well as cases of Still’s disease and RA in individuals ⬍20 years of age (714.2 and 714.0, respectively), and SpA (720.0, 720.2, 720.8, 720.9, 696.0). A composite IA group included all RA, JIA, and SpA cases as well as total joint replacement (TJR) cases coded for Still’s disease (714.2), postrheumatic arthropathy (714.4), or unspecified inflammatory polyarthropathy (714.9 and 714.89). Cases with a dual diagnosis of RA/systemic lupus erythematosus (SLE), JIA/ SLE, and SpA/SLE were excluded, to ensure a homogeneous group of patients with inflammatory arthritis. The comparator group of arthroplasties among patients with noninflammatory conditions included arthroplasty cases without ICD-9-CM codes for any inflammatory or autoimmune condition. Inflammatory and autoimmune conditions excluded from the comparator group of arthroplasties among patients with noninflammatory conditions are listed in Table 1. Data on indications for surgery were derived from discharge diagnosis codes available in the same database. HCUP includes race and ethnicity in one data element, i.e., race. Therefore, race in this study was modified to be consistent across HCUP states and non-HCUP states such as California and New York. This study
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Table 1. Inflammatory and autoimmune conditions excluded from the study* Condition Sarcoidosis Sarcoid with arthropathy Behc¸et’s syndrome Arthropathy at site of Behc¸et’s syndrome Systemic lupus erythematosus Systemic sclerosis, Sjögren’s syndrome, dermatomyositis, polymyositis Other specified diffuse diseases of connective tissue Reactive arthritis Other inflammatory arthropathy associated with GI disorder Palindromic rheumatism Allergic arthritis Polymyalgia rheumatica Vasculitis Polyarteritis nodosa Kawasaki disease Hypersensitivity angiitis Goodpasture’s syndrome Granulomatosis with polyangiitis (Wegener’s) Takayasu arteritis Henoch-Schönlein purpura Regional enteritis–unspecified, ulcerative colitis Autoimmune disease, NEC
ICD-9-CM code 135 713.7 136.1 711.2 710.0 710.1–710.4 710.8–710.9 711.1 713.3 719.3 716.2 725 447.6 446.0 446.1 446.2 446.21 446–446.9 446.7 287.0 556 279.4–279.8
* ICD-9-CM ⫽ International Classification of Diseases, Ninth Revision, Clinical Modification; GI ⫽ gastrointestinal; NEC ⫽ not elsewhere classified.
was approved by the Institutional Review Board at the Hospital for Special Surgery. Statistical analysis. This analysis was procedure-based, as unique patient identifiers were not regularly available for all states and years. Annual population data for each state were acquired from the US Census Bureau (8,9). Annual joint replacement rates per 100,000 persons were calculated as the ratio of the number of cases per period (numerator) to the number of persons living in each state during the same period (denominator). Poisson regression analysis was performed to investigate trends over time. Linear regression models were also used to compare trends over time between different groups. The data were analyzed SAS version 9 (SAS Institute). P values less than or equal to 0.05 (2-tailed) were considered significant.
RESULTS Arthroplasty. A total of 2,988,943 primary hip, knee, and shoulder arthroplasties were performed in the 10 states from 1991 through 2005. Following exclusion of 52,064 subjects with a concurrent diagnosis of malignancy, 96,916 non–state residents, and 638 subjects with a concomitant diagnosis of SLE along with RA, JIA, or SpA, 2,839,325 primary joint arthroplasties were identified for analysis. Of these, 76,665 (2.7%) were catego-
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Table 2.
MERTELSMANN-VOSS ET AL
Characteristics of the patients with IA and the patients with no inflammatory or autoimmune conditions who underwent arthroplasty*
No. of arthroplasties (% of total) Age at arthroplasty, mean ⫾ SD years† Female, % Race, % White Black Hispanic Other Missing data Length of stay, median no. of days Arthroplasty type, % Total hip Partial hip Total knee Total shoulder Partial shoulder Hospital type, % Rural Urban nonteaching Urban teaching Missing data
RA
JIA
SpA
IA
Noninflammatory
P for trend
68,349 (2.41) 64.2 ⫾ 13.0 79.8
2,441 (0.09) 33.9 ⫾ 13.5 76.9
3,825 (0.13) 56.9 ⫾ 15.1 40.3
76,665 (2.7) 62.8 ⫾ 14.3 77.7
2,762,660 (97.3) 70.5 ⫾ 12.1 63.5
⬍0.001 ⬍0.001 ⬍0.001
63.6 5.5 8.4 5.6 16.8 5
55.7 4.9 11.1 6.9 17.2 5
67.7 2.4 6.9 6.2 12.6 5
63.6 5.4 8.4 5.8 13.3 5
72.5 3.6 4.2 3.6 16.1 4
Referent ⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001
29.7 7.7 56.7 3.5 2.4
52.9 0.8 38.5 4.5 3.2
56.6 3.8 36.6 2.0 1.0
32.1 7.2 54.9 3.4 2.3
31.1 18.5 47.4 1.3 1.7
Referent ⬍0.001 ⬍0.001 0.002 0.55
6.5 62.6 19.5 11.4
2.3 48.1 37.7 12
5.5 55.9 24.5 14
6.3 61.7 20.5 11.5
8 70.5 13.5 8
Referent ⬍0.001 ⬍0.001 ⬍0.001
* Percentages may not add up to 100 due to rounding. IA ⫽ inflammatory arthritides (rheumatoid arthritis [RA], juvenile idiopathic arthritis [JIA], spondyloarthritis [SpA], and other [see Methods]). † For the 15-year study period overall.
rized as having been performed in patients with IA and 2,762,660 (97.3%) in patients with noninflammatory arthritis. We identified 68,349 RA cases (2.41%), 2,441 JIA cases (0.09%), and 3,825 SpA cases (0.13%); patient characteristics across these 3 groups and the composite IA group (which also included cases of Still’s disease, postrheumatic arthropathy, and unspecified inflammatory polyarthropathy) versus patients who underwent arthroplasty for noninflammatory/nonautoimmune conditions are summarized in Table 2. IA cases were younger than noninflammatory disease cases (mean ⫾ SD 62.8 ⫾ 14.3 years and 70.5 ⫾ 12.1 years, respectively; P ⬍ 0.001). All groups were predominantly female except the SpA group, in which 59.7% were male. All IA cases had a longer median length of hospital stay (5 days, versus 4 days in the noninflammatory disease group; P ⬍ 0.001). In the noninflammatory/nonautoimmune disease group, the most frequent indications for arthroplasty were osteoarthritis (71.7%) and avascular necrosis (20.6%); the remainder consisted of fractures (5.2%), avascular necrosis with fractures (0.2%), and other indications. Arthroplasties in both the noninflammatory/ nonautoimmune condition group and the IA group were most commonly performed at urban nonteaching institutions. However, compared with the noninflammatory/ nonautoimmune condition group, a higher proportion of
IA cases had arthroplasty performed at urban teaching institutions; this was especially true for JIA. Arthroplasty trends among patients with noninflammatory/nonautoimmune conditions versus patients with IA. Among patients with noninflammatory/nonautoimmune conditions, there was a significant increase in arthroplasty rates over the 15-year period (P ⬍ 0.001), with the overall rates doubling from the beginning to the end of the study period (average yearly increase 4.6%; P ⬍ 0.001). In contrast, among the IA group, the change in the arthroplasty rate was minimal (average yearly decrease 0.01%; P ⬍ 0.001) (Figure 1). The annual proportion of arthroplasties attributable to IA decreased by almost half from 1991 to 2005 (4.0% in 1991 versus 2.1% in 2005) (Figure 2). The increase in rates of arthroplasty among patients with noninflammatory conditions was evident across all arthroplasty types. TKA rates in this group more than doubled from 1991 to 2005 (Table 3). Rates of THA, TSA, and PSA in 2005 were also close to double what they were in 1991. Among patients with IA, in contrast, TKA, THA, and TSA rates decreased across the study period. However, rates of both PHA and PSA showed a modest increase in this group (average yearly increase 2.5% and 3.6%, respectively; both P ⬍ 0.001) (Table 3). In the group of patients with noninflammatory conditions, the mean age at arthroplasty decreased over
ARTHROPLASTY RATES IN RA, JIA, AND SpA
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Figure 1. Annual rates of arthroplasty per 100,000 persons in the group with noninflammatory/nonautoimmune conditions (A) and the group with inflammatory arthritides (B).
Figure 2. Annual proportion of arthroplasties attributable to inflammatory arthritides.
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Table 3. Trends in rates of arthroplasty (per 100,000 persons per year) by arthroplasty site, in the group with no inflammatory or autoimmune conditions and the group with inflammatory arthritides
Arthroplasty type in patients with noninflammatory conditions Total knee Total hip Partial hip Total shoulder Partial shoulder Arthroplasty type in patients with inflammatory arthritides Total knee Total hip Partial hip Total shoulder Partial shoulder
1991
2005
Average annual change, % (P)*
49.05 42.53 29.62 1.52 1.80
134.42 73.12 31.37 4.25 4.31
6.6 (⬍0.001) 3.9 (⬍0.001) 0.02 (⬍0.001) 6.9 (⬍0.001) 6.7 (⬍0.001)
2.74 1.84 0.24 0.21 0.06
2.88 1.52 0.39 0.17 0.14
⫺0.06 (⬍0.001) ⫺1.6 (⬍0.001) 2.5 (⬍0.001) ⫺3.5 (⬍0.001) 3.6 (⬍0.001)
* P values were derived from coefficients in Poisson regression analysis.
time (71.5 ⫾ 11.8 years to 69.0 ⫾ 12.0 years; P ⬍ 0.001). This contrasted with the findings with regard to mean age at arthroplasty among patients in the IA group (see below). Arthroplasty trends among RA, JIA, and SpA patients. Overall, rates of arthroplasty attributable to RA and to JIA decreased over the 15-year period. In RA the rate declined from 4.6 per 100,000 persons in 1991 to 4.5 per 100,000 persons in 2005 (average yearly decrease 0.01%; P ⬍ 0.001). The decrease was much more pronounced in JIA, with the rate declining by almost half (from 0.22 per 100,000 in 1991 to 0.13 per 100,000 in 2005) (average yearly decrease 3.6%; P ⬍ 0.001). In contrast, rates of arthroplasty due to SpA increased
(from 0.22 per 100,000 persons in 1991 to 0.31 per 100,000 persons in 2005) (average yearly increase 1.8%; P ⬍ 0.001) (Figure 3). Stratification of the RA patients by age (ⱕ44 years, 45–65 years, or ⬎65 years) showed that the decrease in arthroplasty rate was most prominent in the youngest age group (average yearly decrease 3.2%, versus 0.6% and 0.8% in the intermediate and oldest groups, respectively); however these differences between age groups were not statistically significant. Overall, the age at arthroplasty in the RA group increased from a mean ⫾ SD of 63.4 ⫾ 12.7 years in 1991 to 64.9 ⫾ 12.8 years in 2005 (P ⬍ 0.001), with no significant difference between male and female subgroups. When rates of arthroplasty among patients with RA were stratified by both age and sex, each subgroup showed a statistically significant decrease in rate (all P ⬍ 0.005). In the intermediate and oldest age groups, men and women with RA were equally likely to have a decreased rate of arthroplasty, whereas among RA cases age ⱕ44 years, the decrease was greater among women than among men (P ⬍ 0.001). When the JIA patients were stratified by age (ⱕ20 years, 21–35 years, or ⬎35 years), a statistically significant decrease in arthroplasty rates among the younger age groups was observed (average yearly decreases of 6.4% and 5.2% among patients age ⱕ20 years and patients age 21–35 years, respectively; both P ⬍ 0.001). However the rate of TJR among JIA patients age ⬎35 years did not decrease significantly (average yearly decrease 0.5%; P ⫽ 0.51). The mean age at the time of joint replacement increased by 6 years (30.9 ⫾ 12.2 years
Figure 3. Annual rates of arthroplasty per 100,000 persons among patients with rheumatoid arthritis (RA), spondyloarthritis (SpA), and juvenile idiopathic arthritis (JIA).
ARTHROPLASTY RATES IN RA, JIA, AND SpA
in 1991 versus 36.7 ⫾ 14.9 years in 2005; P ⬍ 0.001), with no difference between male and female subgroups. When the JIA patients were stratified by both age and sex, the rate of arthroplasty in both the ⱕ20-year-old group and the 21–35-year-old group was found to have decreased more in male patients than in female patients (average yearly decrease 8.7% and 5.6%, respectively, among male and female patients age ⱕ20 years, and 5.4% and 5.2%, respectively, among male and female patients age 21–35 years; P for trend ⬍ 0.001 in all 4 subgroups, P ⬍ 0.05 male versus female patients). Analysis of SpA patients stratified by age (ⱕ44 years, 45–65 years, or ⬎65 years) showed that the rate of arthroplasty decreased among patients ⬍45 years of age (average yearly decrease 2.9%; P ⬍ 0.001), but the rate among patients in the other 2 age groups increased (average yearly increase 3.7% among 45–65-year-old SpA patients and 2.7% among ⬎65-year-old patients; both P ⬍ 0.001). The mean age at the time of arthroplasty among patients with SpA increased by 6 years (54.3 ⫾ 16.1 years in 1991 and 60.4 ⫾ 13.9 years in 2005; P ⬍ 0.001), with no difference between male and female patients. There was also no difference in rates of arthroplasty due to SpA between men and women in any of the age subgroups. DISCUSSION To our knowledge, the present investigation is the largest, in terms of study population size, to evaluate arthroplasty in a composite group of patients with inflammatory arthritides, and the first to examine trends in rates of arthroplasty among patients with JIA and SpA. Other investigators have utilized the NIS to evaluate rates of arthroplasty for RA in the US (2). The NIS is a stratified sample of US hospitals, which can be weighted to produce national incidence rate estimates. However, the more rare a condition, the more unstable the estimates will be when using the NIS. In contrast, our study used actual discharge data from 10 states, providing a more robust representative sample from which to make rate estimates for rare events such as TJR in RA, SpA, and JIA. Overall, the rate of joint replacements due to IA showed only a minimal decrease over the 15-year study period. This is surprising given the widespread use of the DMARD methotrexate in the 1990s, and the introduction of biologic agents beginning in 1998. During this same time period the rate of arthroplasty among patients with RA—by far the largest group within the IA cohort—demonstrated only a slight downward trend (4.6
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per 100,000 in 1991 versus 4.5 per 100,000 in 2005), consistent with previous reports of a flattening out of the rates of RA-related arthroplasty (3–5). Age at the time of arthroplasty among patients with RA increased over the study period (from a mean ⫾ SD of 63.4 ⫾ 12.7 years in 1991 to 64.9 ⫾ 12.8 years in 2005), approaching the mean age at arthroplasty among patients with noninflammatory/nonautoimmune conditions. Both in RA patients and in patients with noninflammatory conditions, TKA was the most common arthroplasty type, whereas in patients with JIA or SpA, THA was the most common. The fact that demographic trends in arthroplasty among patients with RA are converging with trends among patients with noninflammatory conditions suggests that increasingly, patients with RA may be undergoing joint replacement for secondary osteoarthritis rather than inflammatory arthritis. This theory is also supported by the fact that in the RA group, the rate of arthroplasty was decreasing substantially more quickly among patients ⱕ44 years of age than among patients in the older age groups, suggesting that DMARDS and biologic agents are effectively reducing inflammatory damage in patients with active RA. Rates of arthroplasty among patients with JIA showed trends similar to those seen among young RA patients, with the rate declining by nearly half between 1991 and 2005 (Figure 3) and an increase in the mean age at the time of arthroplasty (30.9 ⫾ 12.2 years in 1991 versus 36.7 ⫾ 14.9 years in 2005). These findings are consistent with the increased use of immunomodulatory agents among children in recent decades (10), which appears to have successfully prevented end-stage joint damage and the need for arthroplasty. Within the JIA group, the rate of arthroplasty was decreasing faster in male patients than in female patients; interestingly, female sex has been reported to be a predictor of poor response to therapy in JIA (11). In contrast to RA and JIA, the rate of arthroplasty among patients with SpA increased by nearly 50% (0.22 per 100,000 persons in 1991 versus 0.31 per 100,000 persons in 2005) (Figure 3). Part of this increase could be explained by an increasing awareness of psoriatic arthritis. However the increase was driven primarily by SpA patients age ⱖ45 years. Similar to RA and JIA, the rate of arthroplasty in SpA patients ⱕ44 years of age was decreasing, with the mean ⫾ SD age at the time of arthroplasty increasing from 54.3 ⫾ 16.1 years in 1991 to 60.4 ⫾ 13.9 years in 2005. A possible explanation for these data could be that among younger patients, SpA responds partially to DMARDs/biologic agents, postponing the need for arthroplasty. DMARD therapy is
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thought to be less effective in SpA than in RA and JIA (12–14), which may explain why joint replacement is deferred to a later age among SpA patients but the need for the procedure is not ultimately decreased. This speculation should be explored in further long-term studies. The finding that population-based rates of arthroplasty are decreasing predominantly in the younger age groups was consistent across RA, JIA, and SpA. This suggests that DMARDs and biologic agents may be effective in preventing end-stage joint destruction if initiated soon after disease onset. Strengths of the present study include use of a large, longitudinal population-based sample representing different geographic areas of the US. Procedure and diagnosis codes are audited at the state level prior to data release. Data sources include all payers rather than Medicare only (the lack of younger patients being a limitation of many similar studies). In addition, the most common arthroplasty sites—hip, knee, and shoulder— were evaluated. Limitations of the study include those common to administrative ICD-9-CM coding–based analyses. Diagnoses were not validated with chart review, and there is the possibility of miscoding and, therefore, misclassification bias. While the coding of major surgical procedures has been demonstrated to be reliable in similar studies (3), inflammatory arthritis diagnoses may have been underascertained, as they might not have been included in the hospital discharge diagnosis codes (15). However, this should not create a bias unless the trends in coding for these conditions were shifting over time. In addition, patient-level data regarding current or past medication use were not included in the database. This was a procedure-based analysis, and we could not determine whether the same patient underwent multiple arthroplasties. Because state-by-state data on annual population rates of IA and its analyzed subtypes were not available, annual rates of arthroplasty were based on population census data rather than on the population at risk (i.e., patients with IA), which would provide diseasebased rates (16,17). However, this would affect the relative rates only if the incidence of the various IAs were changing over time. From 1991 through 2005, the need for joint replacement among patients with IA persisted despite improvements in medical care, although rates among JIA patients and younger RA and SpA patients were decreasing. Among patients with noninflammatory conditions, our data demonstrate the same dramatic increase in arthroplasty rates as has been shown in other
MERTELSMANN-VOSS ET AL
cohorts (6,7).The opposing trends in IA and non-IA arthroplasties has resulted in IA accounting for an increasingly smaller proportion of overall arthroplasties. Nevertheless, given that TJR appears to remain an important intervention among patients with IA, it will be important that surgical trainees have exposure to these complex medical conditions during training. In conclusion, this large population-based study of arthroplasty among patients with inflammatory arthritides, including JIA and SpA in addition to RA, demonstrates that between 1991 and 2005, rates of arthroplasty have decreased significantly among patients with JIA, decreased minimally among patients with RA, and increased among patients with SpA. Ongoing prospective studies are needed in order to determine whether these trends continue with increasing use of biologic therapies. ACKNOWLEDGMENT We are grateful to Sean Wilson for assistance with the formatting of figures. AUTHOR CONTRIBUTIONS All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. Dr. Mertelsmann-Voss had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study conception and design. Mertelsmann-Voss, Lyman, Pan, Figgie, Mandl. Acquisition of data. Lyman. Analysis and interpretation of data. Mertelsmann-Voss, Lyman, Pan, Goodman, Figgie, Mandl.
REFERENCES 1. Wolfe F, Zwillich SH. The long-term outcomes of rheumatoid arthritis: a 23-year prospective, longitudinal study of total joint replacement and its predictors in 1,600 patients with rheumatoid arthritis. Arthritis Rheum 1998;41:1072–82. 2. Jain A, Stein BE, Skolasky RL, Jones LC, Hungerford MW. Total joint arthroplasty in patients with rheumatoid arthritis: a United States experience from 1992 through 2005. J Arthroplasty 2012; 27:881–8. 3. Ward MM. Decreases in rates of hospitalizations for manifestations of severe rheumatoid arthritis, 1983–2001. Arthritis Rheum 2004;50:1122–31. 4. Fevang BT, Lie SA, Havelin LI, Engesaeter LB, Furnes O. Reduction in orthopedic surgery among patients with chronic inflammatory joint disease in Norway, 1994–2004. Arthritis Rheum 2007;57:529–32. 5. Kobelt G, Eberhardt K, Geborek P. TNF inhibitors in the treatment of rheumatoid arthritis in clinical practice: costs and outcomes in a follow up study of patients with RA treated with etanercept or infliximab in southern Sweden. Ann Rheum Dis 2004;63:4–10. 6. Dixon T, Shaw M, Ebrahim S, Dieppe P. Trends in hip and knee
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7. 8. 9. 10.
11. 12. 13.
joint replacement: socioeconomic inequalities and projections of need. Ann Rheum Dis 2004;63:825–30. Kurtz SM, Ong KL, Lau E, Widmer M, Maravic M, GomezBarrena E, et al. International survey of primary and revision total knee replacement. Int Orthop 2011;35:1783–9. US Census Bureau. Population estimates: 1990s. URL: http:// www.census.gov/popest/archives/1990s US Census Bureau. Population estimates: 2000s. URL: http:// www.census.gov/popest/archives/2000s Beukelman T, Ringold S, Davis TE, DeWitt EM, Pelajo CF, Weiss PF, et al. Disease-modifying antirheumatic drug use in the treatment of juvenile idiopathic arthritis: a cross-sectional analysis of the CARRA Registry. J Rheumatol 2012;39:1867–74. Otten MH, Prince FH, Armbrust W, ten Cate R, Hoppenreijs EP, Twilt M, et al. Factors associated with treatment response to etanercept in juvenile idiopathic arthritis. JAMA 2011;306:2340–7. Chen J, Veras MM, Liu C, Lin J. Methotrexate for ankylosing spondylitis. Cochrane Database Syst Rev 2013;2:CD004524. Van der Heijde D, Salonen D, Weissman BN, Landewe R,
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14.
15. 16.
17.
Maksymowych WP, Kupper H, et al. Assessment of radiographic progression in the spines of patients with ankylosing spondylitis treated with adalimumab for up to 2 years. Arthritis Res Ther 2009;11:R127. Van der Heijde D, Landewe R, Einstein S, Ory P, Vosse D, Ni L, et al. Radiographic progression of ankylosing spondylitis after up to two years of treatment with etanercept. Arthritis Rheum 2008;58:1324–31. Losina E, Barrett J, Baron JA, Katz JN. Accuracy of Medicare claims data for rheumatologic diagnoses in total hip replacement recipients. J Clin Epidemiol 2003;56:515–9. Myasoedova E, Crowson CS, Maradit Kremers H, Therneau TM, Gabriel SE. Is the incidence of rheumatoid arthritis rising? Results from Olmsted County, Minnesota, 1955–2007. Arthritis Rheum 2010;62:1576–82. Helmick CG, Felson DT, Lawrence RC, Gabriel S, Hirsch R, Kwoh CK, et al. Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part I. Arthritis Rheum 2008;58:15–25.
US Trends in Rates of Arthroplasty for Inflammatory Arthritis Including Rheumatoid Arthritis, Juvenile Idiopathic Arthritis, and Spondyloarthritis Christina Mertelsmann-Voss, Stephen Lyman, Ting Jung Pan, Susan M. Goodman, Mark P. Figgie, and Lisa A. Mandl per 100,000 versus 0.31 per 100,000). Age at the time of arthroplasty increased for patients with RA (mean ⴞ SD 63.4 ⴞ 12.7 years versus 64.9 ⴞ 12.8 years), JIA (30.9 ⴞ 12.2 years versus 36.7 ⴞ 14.9 years), and SpA (54.3 ⴞ 16.1 years versus 60.4 ⴞ 13.9 years). However, the mean age at the time of arthroplasty among non-IA cases decreased (71.5 ⴞ 11.8 years versus 69.0 ⴞ 12.0 years). Conclusion. This population-based study is the first to show that arthroplasty rates have decreased significantly among patients with JIA and minimally among patients with RA, and have increased among patients with SpA. The increased age at the time of arthroplasty among patients with JIA and SpA suggests that these patients are increasingly able to defer surgical interventions. Further research is needed to assess the ongoing effect of biologic agents on the need for arthroplasties in patients with IA.
Objective. Although rates of arthroplasty have increased dramatically, rates among patients with rheumatoid arthritis (RA) are reported to be decreasing. It is not known if this is also the case among patients with other inflammatory arthritides. This study was undertaken to evaluate rates of arthroplasty due to RA, juvenile idiopathic arthritis (JIA), spondyloarthritis (SpA), and a composite group of patients with inflammatory arthritides (IA), compared to arthroplasty rates among patients without inflammatory or autoimmune conditions. Methods. Administrative discharge databases (State Inpatient Databases of the Healthcare Cost and Utilization Project, New York Department of Health Statewide Planning and Research Cooperative System, California Statewide Health Planning and Development) were used to compare rates of knee, hip, and shoulder arthroplasty occurring from 1991 to 2005. Results. Of 2,839,325 arthroplasties in 1991–2005, 2.7% were performed in patients with IA. The rate of arthroplasty for noninflammatory conditions doubled (124.5 per 100,000 persons in 1991 versus 247.5 per 100,000 persons in 2005), while the rate for IA remained stable at 5.1 per 100,000. Rates of arthroplasty for RA decreased slightly (4.6 per 100,000 versus 4.5 per 100,000) and those for JIA decreased by nearly 50% (0.22 per 100,000 versus 0.13 per 100,000), but the rate of arthroplasty for SpA increased by nearly 50% (0.22
In patients with inflammatory joint disease, arthroplasty is considered to represent a lack of success of medical management. In the past, arthroplasty was an accepted outcome for many patients with rheumatoid arthritis (RA). Wolfe and Zwillich reported that, among a cohort of RA patients assembled in 1974–1997, 25% underwent joint replacement surgery within 22 years of disease onset (1). However, the rate of joint replacements among patients with RA appears to have leveled off or decreased, in conjunction with increasing use of disease-modifying antirheumatic drug (DMARD) therapy (2–6). This decrease in arthroplasty utilization contrasts with the increase in arthroplasty rates in the general population (6,7). It is not known if the frequency of arthroplasty due to RA is continuing to trend downward, and if such a decreasing trend is occurring in other inflammatory arthritides. The aim of this study was to
Christina Mertelsmann-Voss, MD, MSc, Stephen Lyman, PhD, Ting Jung Pan, MPH, Susan M. Goodman, MD, Mark P. Figgie, MD, Lisa A. Mandl, MD, MPH: Hospital for Special Surgery, New York, New York. Address correspondence to Christina Mertelsmann-Voss, MD, Department of Pediatric Rheumatology, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021. E-mail: [email protected]. Submitted for publication June 27, 2013; accepted in revised form January 23, 2014. 1432
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evaluate trends in rates of knee, hip, and shoulder arthroplasty due to RA, juvenile idiopathic arthritis (JIA), and spondylarthritis (SpA), as well as a composite group of all inflammatory arthritides (IA), from 1991 to 2005, and to compare these rates with those among patients with no inflammatory or autoimmune conditions. METHODS Sources of data. Discharge data for the years 1991– 2005 were collected from 3 different sources. The State Inpatient Databases (SID) of the Healthcare Cost and Utilization Project (HCUP) provided data from Arizona, Colorado, Florida, Massachusetts, New Jersey, Washington, Iowa, and Wisconsin. Data from New York and California were obtained from the New York Department of Health Statewide Planning and Research Cooperative System and California Statewide Health Planning and Development, respectively. These databases encompass ⬃90% of all community hospital admissions, which include academic teaching hospitals, within these states and contain discharge diagnoses and indications. HCUP SID data rather than HCUP National Inpatient Sample (NIS) data were used as the NIS relies on sampling, which can be unreliable when evaluating rare conditions or events. Data on inpatients within a given state who were not residents of that state were excluded from this analysis. Primary total knee arthroplasty (TKA), primary total and partial hip arthroplasty (THA and PHA), and primary total and partial shoulder arthroplasty (TSA and PSA) were identified using procedure codes 81.54, 81.52, 81.51, 81.80, and 81.81, respectively, from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). Patients with a discharge diagnosis of malignant neoplasm (ICD9-CM 140.0–209.9, or V-code V10.0–10.9, V71.1) except for nonmelanoma skin cancer (ICD-9-CM 173) were excluded. ICD-9 codes were used to identify RA (714.0–714.1), JIA (714.30–714.33) as well as cases of Still’s disease and RA in individuals ⬍20 years of age (714.2 and 714.0, respectively), and SpA (720.0, 720.2, 720.8, 720.9, 696.0). A composite IA group included all RA, JIA, and SpA cases as well as total joint replacement (TJR) cases coded for Still’s disease (714.2), postrheumatic arthropathy (714.4), or unspecified inflammatory polyarthropathy (714.9 and 714.89). Cases with a dual diagnosis of RA/systemic lupus erythematosus (SLE), JIA/ SLE, and SpA/SLE were excluded, to ensure a homogeneous group of patients with inflammatory arthritis. The comparator group of arthroplasties among patients with noninflammatory conditions included arthroplasty cases without ICD-9-CM codes for any inflammatory or autoimmune condition. Inflammatory and autoimmune conditions excluded from the comparator group of arthroplasties among patients with noninflammatory conditions are listed in Table 1. Data on indications for surgery were derived from discharge diagnosis codes available in the same database. HCUP includes race and ethnicity in one data element, i.e., race. Therefore, race in this study was modified to be consistent across HCUP states and non-HCUP states such as California and New York. This study
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Table 1. Inflammatory and autoimmune conditions excluded from the study* Condition Sarcoidosis Sarcoid with arthropathy Behc¸et’s syndrome Arthropathy at site of Behc¸et’s syndrome Systemic lupus erythematosus Systemic sclerosis, Sjögren’s syndrome, dermatomyositis, polymyositis Other specified diffuse diseases of connective tissue Reactive arthritis Other inflammatory arthropathy associated with GI disorder Palindromic rheumatism Allergic arthritis Polymyalgia rheumatica Vasculitis Polyarteritis nodosa Kawasaki disease Hypersensitivity angiitis Goodpasture’s syndrome Granulomatosis with polyangiitis (Wegener’s) Takayasu arteritis Henoch-Schönlein purpura Regional enteritis–unspecified, ulcerative colitis Autoimmune disease, NEC
ICD-9-CM code 135 713.7 136.1 711.2 710.0 710.1–710.4 710.8–710.9 711.1 713.3 719.3 716.2 725 447.6 446.0 446.1 446.2 446.21 446–446.9 446.7 287.0 556 279.4–279.8
* ICD-9-CM ⫽ International Classification of Diseases, Ninth Revision, Clinical Modification; GI ⫽ gastrointestinal; NEC ⫽ not elsewhere classified.
was approved by the Institutional Review Board at the Hospital for Special Surgery. Statistical analysis. This analysis was procedure-based, as unique patient identifiers were not regularly available for all states and years. Annual population data for each state were acquired from the US Census Bureau (8,9). Annual joint replacement rates per 100,000 persons were calculated as the ratio of the number of cases per period (numerator) to the number of persons living in each state during the same period (denominator). Poisson regression analysis was performed to investigate trends over time. Linear regression models were also used to compare trends over time between different groups. The data were analyzed SAS version 9 (SAS Institute). P values less than or equal to 0.05 (2-tailed) were considered significant.
RESULTS Arthroplasty. A total of 2,988,943 primary hip, knee, and shoulder arthroplasties were performed in the 10 states from 1991 through 2005. Following exclusion of 52,064 subjects with a concurrent diagnosis of malignancy, 96,916 non–state residents, and 638 subjects with a concomitant diagnosis of SLE along with RA, JIA, or SpA, 2,839,325 primary joint arthroplasties were identified for analysis. Of these, 76,665 (2.7%) were catego-
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Table 2.
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Characteristics of the patients with IA and the patients with no inflammatory or autoimmune conditions who underwent arthroplasty*
No. of arthroplasties (% of total) Age at arthroplasty, mean ⫾ SD years† Female, % Race, % White Black Hispanic Other Missing data Length of stay, median no. of days Arthroplasty type, % Total hip Partial hip Total knee Total shoulder Partial shoulder Hospital type, % Rural Urban nonteaching Urban teaching Missing data
RA
JIA
SpA
IA
Noninflammatory
P for trend
68,349 (2.41) 64.2 ⫾ 13.0 79.8
2,441 (0.09) 33.9 ⫾ 13.5 76.9
3,825 (0.13) 56.9 ⫾ 15.1 40.3
76,665 (2.7) 62.8 ⫾ 14.3 77.7
2,762,660 (97.3) 70.5 ⫾ 12.1 63.5
⬍0.001 ⬍0.001 ⬍0.001
63.6 5.5 8.4 5.6 16.8 5
55.7 4.9 11.1 6.9 17.2 5
67.7 2.4 6.9 6.2 12.6 5
63.6 5.4 8.4 5.8 13.3 5
72.5 3.6 4.2 3.6 16.1 4
Referent ⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001
29.7 7.7 56.7 3.5 2.4
52.9 0.8 38.5 4.5 3.2
56.6 3.8 36.6 2.0 1.0
32.1 7.2 54.9 3.4 2.3
31.1 18.5 47.4 1.3 1.7
Referent ⬍0.001 ⬍0.001 0.002 0.55
6.5 62.6 19.5 11.4
2.3 48.1 37.7 12
5.5 55.9 24.5 14
6.3 61.7 20.5 11.5
8 70.5 13.5 8
Referent ⬍0.001 ⬍0.001 ⬍0.001
* Percentages may not add up to 100 due to rounding. IA ⫽ inflammatory arthritides (rheumatoid arthritis [RA], juvenile idiopathic arthritis [JIA], spondyloarthritis [SpA], and other [see Methods]). † For the 15-year study period overall.
rized as having been performed in patients with IA and 2,762,660 (97.3%) in patients with noninflammatory arthritis. We identified 68,349 RA cases (2.41%), 2,441 JIA cases (0.09%), and 3,825 SpA cases (0.13%); patient characteristics across these 3 groups and the composite IA group (which also included cases of Still’s disease, postrheumatic arthropathy, and unspecified inflammatory polyarthropathy) versus patients who underwent arthroplasty for noninflammatory/nonautoimmune conditions are summarized in Table 2. IA cases were younger than noninflammatory disease cases (mean ⫾ SD 62.8 ⫾ 14.3 years and 70.5 ⫾ 12.1 years, respectively; P ⬍ 0.001). All groups were predominantly female except the SpA group, in which 59.7% were male. All IA cases had a longer median length of hospital stay (5 days, versus 4 days in the noninflammatory disease group; P ⬍ 0.001). In the noninflammatory/nonautoimmune disease group, the most frequent indications for arthroplasty were osteoarthritis (71.7%) and avascular necrosis (20.6%); the remainder consisted of fractures (5.2%), avascular necrosis with fractures (0.2%), and other indications. Arthroplasties in both the noninflammatory/ nonautoimmune condition group and the IA group were most commonly performed at urban nonteaching institutions. However, compared with the noninflammatory/ nonautoimmune condition group, a higher proportion of
IA cases had arthroplasty performed at urban teaching institutions; this was especially true for JIA. Arthroplasty trends among patients with noninflammatory/nonautoimmune conditions versus patients with IA. Among patients with noninflammatory/nonautoimmune conditions, there was a significant increase in arthroplasty rates over the 15-year period (P ⬍ 0.001), with the overall rates doubling from the beginning to the end of the study period (average yearly increase 4.6%; P ⬍ 0.001). In contrast, among the IA group, the change in the arthroplasty rate was minimal (average yearly decrease 0.01%; P ⬍ 0.001) (Figure 1). The annual proportion of arthroplasties attributable to IA decreased by almost half from 1991 to 2005 (4.0% in 1991 versus 2.1% in 2005) (Figure 2). The increase in rates of arthroplasty among patients with noninflammatory conditions was evident across all arthroplasty types. TKA rates in this group more than doubled from 1991 to 2005 (Table 3). Rates of THA, TSA, and PSA in 2005 were also close to double what they were in 1991. Among patients with IA, in contrast, TKA, THA, and TSA rates decreased across the study period. However, rates of both PHA and PSA showed a modest increase in this group (average yearly increase 2.5% and 3.6%, respectively; both P ⬍ 0.001) (Table 3). In the group of patients with noninflammatory conditions, the mean age at arthroplasty decreased over
ARTHROPLASTY RATES IN RA, JIA, AND SpA
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Figure 1. Annual rates of arthroplasty per 100,000 persons in the group with noninflammatory/nonautoimmune conditions (A) and the group with inflammatory arthritides (B).
Figure 2. Annual proportion of arthroplasties attributable to inflammatory arthritides.
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Table 3. Trends in rates of arthroplasty (per 100,000 persons per year) by arthroplasty site, in the group with no inflammatory or autoimmune conditions and the group with inflammatory arthritides
Arthroplasty type in patients with noninflammatory conditions Total knee Total hip Partial hip Total shoulder Partial shoulder Arthroplasty type in patients with inflammatory arthritides Total knee Total hip Partial hip Total shoulder Partial shoulder
1991
2005
Average annual change, % (P)*
49.05 42.53 29.62 1.52 1.80
134.42 73.12 31.37 4.25 4.31
6.6 (⬍0.001) 3.9 (⬍0.001) 0.02 (⬍0.001) 6.9 (⬍0.001) 6.7 (⬍0.001)
2.74 1.84 0.24 0.21 0.06
2.88 1.52 0.39 0.17 0.14
⫺0.06 (⬍0.001) ⫺1.6 (⬍0.001) 2.5 (⬍0.001) ⫺3.5 (⬍0.001) 3.6 (⬍0.001)
* P values were derived from coefficients in Poisson regression analysis.
time (71.5 ⫾ 11.8 years to 69.0 ⫾ 12.0 years; P ⬍ 0.001). This contrasted with the findings with regard to mean age at arthroplasty among patients in the IA group (see below). Arthroplasty trends among RA, JIA, and SpA patients. Overall, rates of arthroplasty attributable to RA and to JIA decreased over the 15-year period. In RA the rate declined from 4.6 per 100,000 persons in 1991 to 4.5 per 100,000 persons in 2005 (average yearly decrease 0.01%; P ⬍ 0.001). The decrease was much more pronounced in JIA, with the rate declining by almost half (from 0.22 per 100,000 in 1991 to 0.13 per 100,000 in 2005) (average yearly decrease 3.6%; P ⬍ 0.001). In contrast, rates of arthroplasty due to SpA increased
(from 0.22 per 100,000 persons in 1991 to 0.31 per 100,000 persons in 2005) (average yearly increase 1.8%; P ⬍ 0.001) (Figure 3). Stratification of the RA patients by age (ⱕ44 years, 45–65 years, or ⬎65 years) showed that the decrease in arthroplasty rate was most prominent in the youngest age group (average yearly decrease 3.2%, versus 0.6% and 0.8% in the intermediate and oldest groups, respectively); however these differences between age groups were not statistically significant. Overall, the age at arthroplasty in the RA group increased from a mean ⫾ SD of 63.4 ⫾ 12.7 years in 1991 to 64.9 ⫾ 12.8 years in 2005 (P ⬍ 0.001), with no significant difference between male and female subgroups. When rates of arthroplasty among patients with RA were stratified by both age and sex, each subgroup showed a statistically significant decrease in rate (all P ⬍ 0.005). In the intermediate and oldest age groups, men and women with RA were equally likely to have a decreased rate of arthroplasty, whereas among RA cases age ⱕ44 years, the decrease was greater among women than among men (P ⬍ 0.001). When the JIA patients were stratified by age (ⱕ20 years, 21–35 years, or ⬎35 years), a statistically significant decrease in arthroplasty rates among the younger age groups was observed (average yearly decreases of 6.4% and 5.2% among patients age ⱕ20 years and patients age 21–35 years, respectively; both P ⬍ 0.001). However the rate of TJR among JIA patients age ⬎35 years did not decrease significantly (average yearly decrease 0.5%; P ⫽ 0.51). The mean age at the time of joint replacement increased by 6 years (30.9 ⫾ 12.2 years
Figure 3. Annual rates of arthroplasty per 100,000 persons among patients with rheumatoid arthritis (RA), spondyloarthritis (SpA), and juvenile idiopathic arthritis (JIA).
ARTHROPLASTY RATES IN RA, JIA, AND SpA
in 1991 versus 36.7 ⫾ 14.9 years in 2005; P ⬍ 0.001), with no difference between male and female subgroups. When the JIA patients were stratified by both age and sex, the rate of arthroplasty in both the ⱕ20-year-old group and the 21–35-year-old group was found to have decreased more in male patients than in female patients (average yearly decrease 8.7% and 5.6%, respectively, among male and female patients age ⱕ20 years, and 5.4% and 5.2%, respectively, among male and female patients age 21–35 years; P for trend ⬍ 0.001 in all 4 subgroups, P ⬍ 0.05 male versus female patients). Analysis of SpA patients stratified by age (ⱕ44 years, 45–65 years, or ⬎65 years) showed that the rate of arthroplasty decreased among patients ⬍45 years of age (average yearly decrease 2.9%; P ⬍ 0.001), but the rate among patients in the other 2 age groups increased (average yearly increase 3.7% among 45–65-year-old SpA patients and 2.7% among ⬎65-year-old patients; both P ⬍ 0.001). The mean age at the time of arthroplasty among patients with SpA increased by 6 years (54.3 ⫾ 16.1 years in 1991 and 60.4 ⫾ 13.9 years in 2005; P ⬍ 0.001), with no difference between male and female patients. There was also no difference in rates of arthroplasty due to SpA between men and women in any of the age subgroups. DISCUSSION To our knowledge, the present investigation is the largest, in terms of study population size, to evaluate arthroplasty in a composite group of patients with inflammatory arthritides, and the first to examine trends in rates of arthroplasty among patients with JIA and SpA. Other investigators have utilized the NIS to evaluate rates of arthroplasty for RA in the US (2). The NIS is a stratified sample of US hospitals, which can be weighted to produce national incidence rate estimates. However, the more rare a condition, the more unstable the estimates will be when using the NIS. In contrast, our study used actual discharge data from 10 states, providing a more robust representative sample from which to make rate estimates for rare events such as TJR in RA, SpA, and JIA. Overall, the rate of joint replacements due to IA showed only a minimal decrease over the 15-year study period. This is surprising given the widespread use of the DMARD methotrexate in the 1990s, and the introduction of biologic agents beginning in 1998. During this same time period the rate of arthroplasty among patients with RA—by far the largest group within the IA cohort—demonstrated only a slight downward trend (4.6
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per 100,000 in 1991 versus 4.5 per 100,000 in 2005), consistent with previous reports of a flattening out of the rates of RA-related arthroplasty (3–5). Age at the time of arthroplasty among patients with RA increased over the study period (from a mean ⫾ SD of 63.4 ⫾ 12.7 years in 1991 to 64.9 ⫾ 12.8 years in 2005), approaching the mean age at arthroplasty among patients with noninflammatory/nonautoimmune conditions. Both in RA patients and in patients with noninflammatory conditions, TKA was the most common arthroplasty type, whereas in patients with JIA or SpA, THA was the most common. The fact that demographic trends in arthroplasty among patients with RA are converging with trends among patients with noninflammatory conditions suggests that increasingly, patients with RA may be undergoing joint replacement for secondary osteoarthritis rather than inflammatory arthritis. This theory is also supported by the fact that in the RA group, the rate of arthroplasty was decreasing substantially more quickly among patients ⱕ44 years of age than among patients in the older age groups, suggesting that DMARDS and biologic agents are effectively reducing inflammatory damage in patients with active RA. Rates of arthroplasty among patients with JIA showed trends similar to those seen among young RA patients, with the rate declining by nearly half between 1991 and 2005 (Figure 3) and an increase in the mean age at the time of arthroplasty (30.9 ⫾ 12.2 years in 1991 versus 36.7 ⫾ 14.9 years in 2005). These findings are consistent with the increased use of immunomodulatory agents among children in recent decades (10), which appears to have successfully prevented end-stage joint damage and the need for arthroplasty. Within the JIA group, the rate of arthroplasty was decreasing faster in male patients than in female patients; interestingly, female sex has been reported to be a predictor of poor response to therapy in JIA (11). In contrast to RA and JIA, the rate of arthroplasty among patients with SpA increased by nearly 50% (0.22 per 100,000 persons in 1991 versus 0.31 per 100,000 persons in 2005) (Figure 3). Part of this increase could be explained by an increasing awareness of psoriatic arthritis. However the increase was driven primarily by SpA patients age ⱖ45 years. Similar to RA and JIA, the rate of arthroplasty in SpA patients ⱕ44 years of age was decreasing, with the mean ⫾ SD age at the time of arthroplasty increasing from 54.3 ⫾ 16.1 years in 1991 to 60.4 ⫾ 13.9 years in 2005. A possible explanation for these data could be that among younger patients, SpA responds partially to DMARDs/biologic agents, postponing the need for arthroplasty. DMARD therapy is
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thought to be less effective in SpA than in RA and JIA (12–14), which may explain why joint replacement is deferred to a later age among SpA patients but the need for the procedure is not ultimately decreased. This speculation should be explored in further long-term studies. The finding that population-based rates of arthroplasty are decreasing predominantly in the younger age groups was consistent across RA, JIA, and SpA. This suggests that DMARDs and biologic agents may be effective in preventing end-stage joint destruction if initiated soon after disease onset. Strengths of the present study include use of a large, longitudinal population-based sample representing different geographic areas of the US. Procedure and diagnosis codes are audited at the state level prior to data release. Data sources include all payers rather than Medicare only (the lack of younger patients being a limitation of many similar studies). In addition, the most common arthroplasty sites—hip, knee, and shoulder— were evaluated. Limitations of the study include those common to administrative ICD-9-CM coding–based analyses. Diagnoses were not validated with chart review, and there is the possibility of miscoding and, therefore, misclassification bias. While the coding of major surgical procedures has been demonstrated to be reliable in similar studies (3), inflammatory arthritis diagnoses may have been underascertained, as they might not have been included in the hospital discharge diagnosis codes (15). However, this should not create a bias unless the trends in coding for these conditions were shifting over time. In addition, patient-level data regarding current or past medication use were not included in the database. This was a procedure-based analysis, and we could not determine whether the same patient underwent multiple arthroplasties. Because state-by-state data on annual population rates of IA and its analyzed subtypes were not available, annual rates of arthroplasty were based on population census data rather than on the population at risk (i.e., patients with IA), which would provide diseasebased rates (16,17). However, this would affect the relative rates only if the incidence of the various IAs were changing over time. From 1991 through 2005, the need for joint replacement among patients with IA persisted despite improvements in medical care, although rates among JIA patients and younger RA and SpA patients were decreasing. Among patients with noninflammatory conditions, our data demonstrate the same dramatic increase in arthroplasty rates as has been shown in other
MERTELSMANN-VOSS ET AL
cohorts (6,7).The opposing trends in IA and non-IA arthroplasties has resulted in IA accounting for an increasingly smaller proportion of overall arthroplasties. Nevertheless, given that TJR appears to remain an important intervention among patients with IA, it will be important that surgical trainees have exposure to these complex medical conditions during training. In conclusion, this large population-based study of arthroplasty among patients with inflammatory arthritides, including JIA and SpA in addition to RA, demonstrates that between 1991 and 2005, rates of arthroplasty have decreased significantly among patients with JIA, decreased minimally among patients with RA, and increased among patients with SpA. Ongoing prospective studies are needed in order to determine whether these trends continue with increasing use of biologic therapies. ACKNOWLEDGMENT We are grateful to Sean Wilson for assistance with the formatting of figures. AUTHOR CONTRIBUTIONS All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. Dr. Mertelsmann-Voss had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study conception and design. Mertelsmann-Voss, Lyman, Pan, Figgie, Mandl. Acquisition of data. Lyman. Analysis and interpretation of data. Mertelsmann-Voss, Lyman, Pan, Goodman, Figgie, Mandl.
REFERENCES 1. Wolfe F, Zwillich SH. The long-term outcomes of rheumatoid arthritis: a 23-year prospective, longitudinal study of total joint replacement and its predictors in 1,600 patients with rheumatoid arthritis. Arthritis Rheum 1998;41:1072–82. 2. Jain A, Stein BE, Skolasky RL, Jones LC, Hungerford MW. Total joint arthroplasty in patients with rheumatoid arthritis: a United States experience from 1992 through 2005. J Arthroplasty 2012; 27:881–8. 3. Ward MM. Decreases in rates of hospitalizations for manifestations of severe rheumatoid arthritis, 1983–2001. Arthritis Rheum 2004;50:1122–31. 4. Fevang BT, Lie SA, Havelin LI, Engesaeter LB, Furnes O. Reduction in orthopedic surgery among patients with chronic inflammatory joint disease in Norway, 1994–2004. Arthritis Rheum 2007;57:529–32. 5. Kobelt G, Eberhardt K, Geborek P. TNF inhibitors in the treatment of rheumatoid arthritis in clinical practice: costs and outcomes in a follow up study of patients with RA treated with etanercept or infliximab in southern Sweden. Ann Rheum Dis 2004;63:4–10. 6. Dixon T, Shaw M, Ebrahim S, Dieppe P. Trends in hip and knee
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7. 8. 9. 10.
11. 12. 13.
joint replacement: socioeconomic inequalities and projections of need. Ann Rheum Dis 2004;63:825–30. Kurtz SM, Ong KL, Lau E, Widmer M, Maravic M, GomezBarrena E, et al. International survey of primary and revision total knee replacement. Int Orthop 2011;35:1783–9. US Census Bureau. Population estimates: 1990s. URL: http:// www.census.gov/popest/archives/1990s US Census Bureau. Population estimates: 2000s. URL: http:// www.census.gov/popest/archives/2000s Beukelman T, Ringold S, Davis TE, DeWitt EM, Pelajo CF, Weiss PF, et al. Disease-modifying antirheumatic drug use in the treatment of juvenile idiopathic arthritis: a cross-sectional analysis of the CARRA Registry. J Rheumatol 2012;39:1867–74. Otten MH, Prince FH, Armbrust W, ten Cate R, Hoppenreijs EP, Twilt M, et al. Factors associated with treatment response to etanercept in juvenile idiopathic arthritis. JAMA 2011;306:2340–7. Chen J, Veras MM, Liu C, Lin J. Methotrexate for ankylosing spondylitis. Cochrane Database Syst Rev 2013;2:CD004524. Van der Heijde D, Salonen D, Weissman BN, Landewe R,
1439
14.
15. 16.
17.
Maksymowych WP, Kupper H, et al. Assessment of radiographic progression in the spines of patients with ankylosing spondylitis treated with adalimumab for up to 2 years. Arthritis Res Ther 2009;11:R127. Van der Heijde D, Landewe R, Einstein S, Ory P, Vosse D, Ni L, et al. Radiographic progression of ankylosing spondylitis after up to two years of treatment with etanercept. Arthritis Rheum 2008;58:1324–31. Losina E, Barrett J, Baron JA, Katz JN. Accuracy of Medicare claims data for rheumatologic diagnoses in total hip replacement recipients. J Clin Epidemiol 2003;56:515–9. Myasoedova E, Crowson CS, Maradit Kremers H, Therneau TM, Gabriel SE. Is the incidence of rheumatoid arthritis rising? Results from Olmsted County, Minnesota, 1955–2007. Arthritis Rheum 2010;62:1576–82. Helmick CG, Felson DT, Lawrence RC, Gabriel S, Hirsch R, Kwoh CK, et al. Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part I. Arthritis Rheum 2008;58:15–25.
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