What Is the Real Cost of a New Knee?

Cost starts low, increases substantially with the expansion of eligibility criteria for TKA

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• by Pauline Anderson 
  Contributing Writer, MedPage Today

Action Points

Assuming current eligibility criteria for total knee arthroplasty (TKA), the per patient lifetime cost attributable to symptomatic knee OA is $12,400, which represents about 10% of total direct medical costs in patients with OA, a new study estimates.

But this relatively low cost substantially increases as eligibility criteria for TKA expand and more patients receive this treatment earlier, according to projections by Elena Losina, PhD of Harvard Medical School, Brigham and Women's Hospital and Boston University School of Public Health, and colleagues.

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This, they said, highlights the importance of alternative non-operative therapies.

The study, the first to report lifetime costs of knee OA, was published in Arthritis Care and Research.

Symptomatic knee OA is a chronic, painful condition affecting about 9.3 million adult Americans. More and more patients are opting for TKA surgery, the only long-term effective treatment for debilitating knee OA. Population growth and the obesity epidemic don't entirely explain this increased demand; according to the authors, it's partly due to a greater willingness among patients to undergo surgery and to expanding eligibility criteria.

Current criteria for TKA eligibility include pain unrelieved by nonsurgical regimens andKellgren/Lawrence (K/L) grades 3 and 4.

Various expert groups have published clinical guidelines for managing knee OA, but these guidelines don't consider costs of TKA.

Researchers aimed to get a better handle on the economic impact of expanding use of TKA by estimating lifetime resource use by knee OA patients. They applied the validated Osteoarthritis Policy (OAPol) Model, a computer simulation model of the natural history and management of symptomatic knee OA, defined as K/L grades 2-4, and pain on most days. They also accessed published data on costs, utilization, efficacy, and toxicity of OA treatments, and prevalence and incidence of comorbidities.

The researchers estimated lifetime direct medical costs (costs due to OA as well as all other conditions), knee OA-related costs, and time costs due to lost productivity, in patients with symptomatic OA, and compared these costs with those for individuals with similar demographic and clinical characteristics but without knee OA.

They considered two treatment strategies: care limited to occasional analgesics (modeled as acetaminophen, or one of three opioids: codeine, hydrocodone, or oxycodone) and care recommended by professional association guidelines. The guideline-concordant care strategy was modeled as four sequential and increasingly intense regimens, each offered upon failure of the previous one:

1. Nonsurgical regimen 1: Physical therapy, knee braces, acetaminophen, office visits and nonsteroidal anti-inflammatory drugs (NSAIDS)
2. Nonsurgical regimen 2: Office visits and corticosteroid injections
3. Surgical regimen 3: TKA in patients whose pain was not relieved by nonsurgical treatment and who had structural changes due to OA on radiographs
4. Surgical regimen 4: Those who failed primary TKA who received revision TKA

According to the model, patients spent several years on each nonsurgical regimen before waiting a mean of 13.3 years to receive TKA. Under current eligibility criteria, primary TKA is utilized by 54% of patients with symptomatic knee OA.

The model estimated that when followed from a mean age at knee OA diagnosis of 54 years, the matched control group (with zero prevalence of symptomatic knee OA) had average per person discounted (3% per year) lifetime medical costs (total for all conditions) of $117,500 (in 2013 U.S. dollars). Under treatment strategy 1 (occasional analgesics only), those with symptomatic knee OA incurred average lifetime direct medical costs of $119,300 per person.

Under treatment strategy 2 (guideline-concordant care), the estimate for direct medical costs was $129,600 per person, with about 10% ($12,400) attributable to knee OA. This, said the authors, "represents a low but nontrivial cost burden" for knee OA patients.

As eligibility criteria for TKA expanded, OA-related costs increased. Lifetime direct medical costs for each patient with a lesser degree of structural damage (K/L 2 or greater) were $16,000.

These results highlight the need for more effective non-operative therapies, said the authors. Preventive measures to reduce obesity and knee injury, for example, exercise and weight loss programs, could delay onset of knee OA and reduce the likelihood of eventual TKA. Developing disease-modifying OA drugs (DMOADs) might also help, but since such therapies may be expensive, it might be more cost effective to offer TKA earlier in OA progression.

"Additional research is needed to fully explain the costs and/or benefits of earlier surgery," wrote the authors.

A limitation of the study was that it assumed that patients underwent treatments sequentially, failing prior treatments before undergoing new ones. As well, lifetime estimates didn't account for the costs of nursing home care or the benefits of drugs and surgeries now under development.