Knee Replacements on the Rise for People in their Fifties

The incidence of total knee arthroplasty rose from 0.5 per 100,000 in 1980 to 65 per 100,000 in 2006, for an incidence rate ratio (IRR) of 1.19 (95% CI 1.19 to 1.20, P<0.001), according to Jarkko Leskinen, MD, of Helsinki University Central Hospital, and colleagues.

And among those ages 50 to 59, the incidence increased from 1.5 to 160 per 100,000, with an IRR of 16.8 (95% CI 12.2 to 23.2, P0.001), the researchers reported online in Arthritis & Rheumatism. According to the research, women were more likely to underg Knee arthroplasty (knee replacement surgeries) than men, reaching a 1.6 to 2.4-fold higher incidence during the last ten years.

Most long-term data are for patients who were 60 and older at the time of the surgery, but younger patients increasingly have been undergoing total or partial knee replacements.

Knee Arthroplasty

Knee arthroplasty is a common and effective treatment for patients with severe osteoarthritis who are not responsive to medical therapy. 

Knee replacement is surgery for people with severe knee damage. Knee replacement can relieve pain and allow you to be more active. Your doctor may recommend  Knee replacement if you have knee pain and medicine and other treatments are not helping you anymore.

Partial Knee Replacement vs. Total Knee Replacement

In a partial knee replacement, the surgeon only replaces one part of your knee joint. When you have a total knee replacement, the surgeon removes damaged cartilage and bone from the surface of your knee joint and replaces them with a man-made surface of metal and plastic.

Knee Arthroplasty Study

To explore trends in incidence over time among younger patients, Leskinen and colleagues analyzed data from the national Finnish arthroplasty register, which now includes 98% of patients with these implants.

Among the 95,577 primary knee arthroplasties done in the country between 1980 and 2006, 8,961 were for osteoarthritis in individuals younger than 60.

A total of 65% of these were in women, and mean age at implantation was 55.

The most rapid increase overall for total knee replacement was between 2001 and 2006, when the rate rose from 18 to 65 per 100,000.

The incidence of partial, or unicondylar, arthroplasty also rose, though less than for the total knee procedure, increasing from 0.2 to 10 per 100,000 (IRR 1.19, 95% CI 1.19 to 1.20, P<0.001).

Throughout the study period, women were the recipients more often than men, reaching a 1.6 to 2.4-fold higher incidence during the last ten years.

When the researchers looked at the data according to age groups, they found only minor increases for both total and partial arthroplasties in patients ages 30 to 39 and those 40 to 49.

As with total knee arthroplasty, the incidence of partial knee replacement rose most rapidly among patients ages 50 to 59, with an IRR of 147.2 (95% CI 66 to 328.5, P0.001) when that group was compared with those ages 30 to 39, according to Leskinen and coleagues.

The researchers also looked at trends in incidence according to the volume of procedures by hospital, and found that low- and intermediate-volume centers had the greatest increases.

The IRR between intermediate- and high-volume centers was 1.23 (95% CI 1.16 to 1.31, P<0.001) and 1.23 (95% CI 1.13 to 1.34, P0.001) for low- versus high-volume centers.

Despite the significant increases in knee replacement surgeries since 1980, the researchers noted that the incidence of osteoarthritis has actually fallen in Finland in that time.

"Possible explanations for this phenomenon include the high functional and quality of life demands of younger patients," the researchers observed.

Greater awareness of osteoarthritis treatment options among Baby Boomers and ongoing refinements of surgical technique also are likely to have contributed.

Knee Arthroplasty Demand Rising in the US

In the U.S., demand for Knee arthroplasty is expected to increase by almost 675% by the year 2030.

Long Term Knee Arthroplasty Risks Need to be Studied

Leskinen and colleagues cautioned that long-term data are needed on the use of knee arthroplasty among younger patients, because their outcomes and risks may be different than older patients.

"Since younger patients are likely to have more strenuous physical demands and to make treatment choices that support an active lifestyle, the longevity or 'survival' of knee implants in this group may be lower than in older patients," Elena Losina, PhD, and Jeffrey N. Katz, MD, of Harvard University in Boston. wrote in a accompanying editorial.

"In fact, as data on this issue emerge, it appears that rates of knee replacement failure leading to revision in younger patients are two-fold higher than in older patients," they observed.

Losina and Katz called for further "intensive study" before even wider adoption of knee arthroplasty for younger patients.

"We would be wise to heed the time-honored investment advice that past performance may not guarantee future success," they warned.

The authors had no financial disclosures, while the editorialists were supported by the National Institutes of Health.

References:

• Leskinen J, et al. "The incidence of knee arthroplasty for primary osteoarthritis grows rapidly among baby boomers -- A population based study" Arthritis Rheum 2012; DOI: 10.1002/art.33367.
• Losina E, Katz J. "Total knee arthroplasty on the rise in younger patients: Are we sure that past performance will guarantee future success?" Arthritis Rheum 2012; DOI: 10.1002/art.33371.