Supplements Current Treatment Options for Osteoarthritis
The Economic Burden of Osteoarthritis
Factors Influencing Costs
Disease Progression and Patient Status
To better understand how costs manifest in the OA population, it is useful to examine how factors such as disease severity and patient age impact expenditures. Gupta et al20 looked at a Canadian cohort of 2411 patients aged 55 years or older with hip and knee OA and found that greater disability was associated with higher costs in a linear fashion, based on Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores.21 Patients with WOMAC scores >55 had nearly 3.5 times the reported costs of those with a WOMAC score less than 15 (P <.0001). Losina et al recently reported data showing that annual direct costs for "end-stage" OA-that is, prior to hip or knee replacement-average $3800 per person but range considerably, from $2000 to $10,500.22 These are nearly double the additional costs described in the studies previously discussed.
A 2009 Spanish study compared costs based on radiographic severity-using the Kellgren/Lawrence scale, which grades severity from 1 to 4-in 1071 OA patients and found that Grade 4 patients had direct annual costs that were approximately 45% higher than Grade 1 patients, although no difference was seen between Grades 1 through 3.23 Total costs were 74% higher in Grade 4 compared with Grade 1 patients.
Impact of Medical Treatments
The above discussion of cost of treatment for OA has focused on average costs across patient populations. However, specific therapies (eg, NSAIDs, cyclooxygenase [COX]-2 inhibitors, opioid analgesics, topical agents, injectable products) differ in cost, although most studies addressing such expenditures deal with relative cost-effectiveness rather than the impact that individual agents have on total treatment costs.
Costs Associated With the Treatment of Pain. Data from a large claims database of a private insurer from 2003 to 2004 found that 15% of annual drug costs went to pain and pain-related medications.13 Taking into account the fact that many of the 24,457 patients in the study took more than 1 medication, it is interesting to note that more than half (54%) took a COX-2 inhibitor, 46% used nonselective NSAIDs, 34% were prescribed antidepressants, while 9% took tramadol.13 With regard to nonselective NSAID use, it is worth pointing out that 35% of the patient population was prescribed a proton pump inhibitor.
Costs Associated With Use of Viscosupplementation. Intraarticular hyaluronate (IAH) (also called viscosupplementation) for OA involves injections of hyaluronic acid into the affected joints. IAH, of which there are currently 5 available agents, is recommended in the clinical guidelines produced by the American College of Rheumatology (ACR) and Osteoarthritis Research Society International (OARSI).24,25 The ACR recommends its use in patients who have failed nonpharmacologic therapy or "simple" analgesic therapy, and in patients for whom NSAIDs and COX-2 inhibitors are contraindicated. Little data are available regarding the effect of IAH on total OA costs, although the actual cost of IAH treatment for a period of 6 months has been estimated as varying from $852 to $1840 (in 2006 dollars, including injections, arthrocentesis, and office visits) depending on the specific regimen.26 The remaining pharmacoeconomic data on IAH deal with its demonstrated efficacy in delaying joint replacement surgery.27
Epidemiology of Joint Replacement Surgery. The number of hip and knee replacement surgeries performed has been increasing and is projected to do so at a rapid rate. It has been estimated that hip arthroplasty will increase by 174% from 2005 to 2030, with 572,000 operations expected by the latter year.28 Knee arthroplasty is expected to increase to an even greater extent, 673% by 2030, resulting in nearly 3.5 million such operations (Figure 2). The enormous growth in hip arthroplasty may be justified by the fact that, despite its high cost, total hip replacement (THR) is an extremely cost-effective treatment intervention.29 Total knee replacement (TKR), although less well studied, appears to also represent a significantly cost-effective intervention.
The average age of a THR recipient in the United States is just under 68 years of age.30 The likelihood of having the procedure increases with age up to the age range of 75 to 79 years.31 At ages 75 to 79 years, 0.3% of US women have a THR compared with 0.25% of US men. In contrast, 0.64% of women have TKR between 75 and 79 years of age, whereas the peak age range for TKR in men is 80 to 84 years during which time 0.61% have the operation.
There is a paucity of US data that clarify the contribution of OA to the prevalence of TKR and THR. However, a recent Taiwanese study examined the diagnoses of recipients of THR and TKR from 1996 to 2004. The authors found that approximately 40% of all THRs occurred in patients with OA, while OA patients made up approximately 94% of all TKR subjects.32
Costs Associated With Use of Joint Replacement. The combined annual costs of knee and hip arthroplasty in 2007 are estimated to have been approximately $15.6 billion based on data compiled by the Healthcare Costs and Utilization Project (HCUP).33,34 To better understand the cost of knee and hip arthroplasty, it should be noted that as more THRs and TKRs are undertaken, more revision procedures also take place. The cost of these secondary surgeries was examined in a study of Medicare expenditures from 1997 to 2003, which found that revision hip arthroplasty constituted 18.8% of all Medicare expenditures for hip replacement, while revision knee arthroplasty expenditures were 8.2% of all Medicare costs for knee replacement.35 In 2007, Medicare paid for approximately 250,000 total and partial hip replacement surgeries, constituting nearly 62% of all such surgeries.36 In the same year, Medicare paid for slightly less than 340,000 knee arthroplasties, which was 55% of the total nationwide.37 The inpatient costs for primary THR are estimated to be between $30,000 and $38,000 for revision hip replacement.29 Primary TKR costs have been estimated at approximately $21,000, while TKR revisions are nearer $25,000.22
The data described in this review define OA as a significant economic burden based on very substantial direct and indirect costs. Although not normally as clinically severe a disease as rheumatoid arthritis (to which it is often studied in parallel), because of its higher prevalence, OA greatly surpasses rheumatoid arthritis in overall economic impact. That said, this review underscores the many gaps in OA economic data. For example, data on OA costs need to be more consistently gathered both to understand patterns of expenditure and simply to have available up-to-date information. At the same time, such data must be more detailed to be fully useful. To be fully practical OA costs need to be stratified by demography (eg, age, sex, location), disease severity, as well as payer/benefit type. In addition, greater clarification of OA costs by treatment type-whether pharmacotherapy, TKR/THR, etc-is needed to get a fuller picture of OA costs. More rigorous data such as these would be of enormous benefit to managed care providers as well as clinicians themselves, allowing for a deeper understanding of the comparative effectiveness of OA treatments, which could then help to improve clinical, humanistic, and economic outcomes.
Author Affiliation: From Health Plan of Nevada, Inc, Las Vegas, NV.
Funding Source: Financial support for this work was provided by Endo Pharmaceuticals.
Author Disclosure: The author (RB) reports no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.
Authorship Information: Concept and design (RB); analysis and interpretation of data (RB); critical revision of the manuscript for important intellectual content (RB).
Address correspondence to: Ryan Bitton, PharmD, MBA, Health Plan of Nevada, Inc, 2716 N Tenaya Way, Las Vegas, NV 88011. E-mail: firstname.lastname@example.org.
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