Majority of Knee, Hip Replacements Last 25 Years

Nicola M. Parry, DVM

February 15, 2019

The majority of knee and hip replacements can be expected to last 25 years, according to two new studies.

Jonathan T. Evans, MRCS, Bristol Medical School, Southmead Hospital, United Kingdom, and colleagues conducted both studies. Their findings were published online February 14 in the Lancet.

Overall, approximately 82% of primary total knee replacements (TKRs) last 25 years, as do 70% of unicondylar knee replacements (UKRs) and approximately 58% of hip replacements.

Although knee and hip replacements are effective procedures for many patients, the replacements can fail for a variety of reasons, including loosening and infection.

Thus, physicians need to know how long these replacements are likely to last, not only to help them advise patients and benchmark different implants but also for purposes of medicolegal assessment.

For each study, Evans and colleagues conducted a systematic review and meta-analysis, evaluating data from multiple sources, including national joint replacement registries and published reports. They provided simple and generalizable estimates of survival for knee and hip replacements.

In the knee replacement study, Evans and colleagues included articles reporting at least 15-year survival rates of TKRs, UKRs, and patellofemoral replacements in patients with osteoarthritis.

Their analysis included 33 case series that reported all-cause survival for 6490 TKRs and 742 UKRs. None of the case series provided long enough follow-up for TKRs; data from one case series suggested a 72.0% 25-year survival rate for UKRs (95% confidence interval [CI], 58.0 – 95.0).

A registry search identified 47 series reporting 299,291 TKRs and 7714 UKRs. On the basis of these data, the estimated 25-year survival of TKRs (14 registries) was 82.3% (95% CI, 81.3 – 83.2); for UKRs (four registries), it was 69.8% (95% CI, 67.6 – 72.1).

Their search produced no case series on patellofemoral replacements that met the study's inclusion criteria.

Similarly, in the hip replacement study, the researchers included articles reporting at least 15-year survival of primary, conventional total hip replacement constructs for patients with osteoarthritis.

Their analysis included 44 case series reporting 13,212 total hip replacements. The registry search identified 92 series reporting 215,676 total hip replacements.

On the basis of these case series, the estimated 25-year survival of hip replacements was 77.6% (95% CI, 76.0 – 79.2). On the basis of registry data, it was 57.9% (95% CI, 57.1 – 58.7).

In an accompanying editorial regarding the hip replacement study, Nipun Sodhi, MD, and Michael A. Mont, MD, both from the Department of Orthopaedic Surgery, Lenox Hill Hospital, Northwell Health, New York City, praise Evans and colleagues for their robust analysis and note that the data will help address a common question asked by patients.

Orthopedic surgeons can use the study's findings to counsel patients, assess postoperative benchmarks, and plan potential revision surgeries, Sodhi and Mont conclude.

"The study is essential reading for orthopaedic surgeons performing, and patients considering, total hip replacement," they write.

Sources of individual funding of the authors and editorialists are listed in the original articles.

Lancet. Published online February 14, 2019. Hip replacement study, Full text; knee replacement study, Abstract; Editorial

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