medwireNews: Two meta-analyses published in The Lancet provide estimates for how long hip and knee replacements are likely to last in patients with osteoarthritis (OA).
This is “a simple question that is posed to us by our patients, multiple times per day,” say Jonathan Evans (University of Bristol, UK) and colleagues, who conducted both analyses.
In the first study, Evans et al analyzed data from 44 published case series including 13,212 total hip replacements, and 92 series from Australian and Finnish national joint replacement registries with 215,676 total hip replacements.
Based on the published case series data, pooled survival of hip replacements was 85.7% at 15 years, 78.8% at 20 years, and 77.6% at 25 years.
And pooled data from the registries showed that hip replacements lasted for 15 years in 89.4% of patients, for 20 years in 70.2% of patients, and for 25 years in 57.9% of patients.
The researchers say that concordance in survival rates between published case series and registry data at 15 years “is encouraging, but the differences at 20 and 25 years suggest that the two types of data probably have different sources of bias.”
They point out that case series are particularly prone to selection and publication bias, and “the more conservative and generalisable estimates provided by the registry annual reports are likely to be more reliable.”
Therefore, “patients and surgeons can expect a hip replacement to last 25 years in around 58% of patients,” the team concludes.
Writing in an accompanying commentary, Nipun Sodhi and Michael Mont, both from Lenox Hill Hospital in New York, USA, say that “these results are particularly important because of the growing number of younger, more active patients receiving hip replacements, as well as increasing population ageing and life expectancy.”
They note, however, that 20- and 25-year follow-up data were only available in the Finnish registry, limiting the generalizability of the findings.
“[S]imilar studies to this one should be done using registries from other countries,” they recommend.
The second study, which employed a comparable approach to the first, estimated the longevity of knee replacements based on 6490 total knee replacements (TKRs) and 742 unicondylar knee replacements (UKRs) from 33 published case series, along with 299,291 TKRs and 7714 UKRs from Australian and Finnish registries.
Analysis of the published case series demonstrated 15- and 20-year TKR survival rates of 96.3% and 94.8%, respectively, but none of the studies reported 25-year rates for TKRs. The 15-, 20-, and 25-year survival rates for UKRs were a respective 85.5%, 81.9%, and 72.0%.
Using the registry data, Evans and colleagues found that 93.0% of TKRs lasted for 15 years, 90.1% for 20 years, and 82.3% for 25 years. The corresponding UKR survival rates were 76.5%, 71.6%, and 69.8%.
Although they caution that “[n]ot enough information is yet available to tell us exactly how long a TKR or UKR lasts,” the researchers conclude that, based on the registry data, around 82% of TKRs and 70% of UKRs can be expected to last for 25 years.
These findings should be “of use to patients, people providing and commissioning health-care services, and those needing an estimate of knee replacement survival for medicolegal purposes,” they say.
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