In one study reported at the American Academy of Orthopaedic Surgeons' meeting here, only 31% of knee replacements implanted at least 20 years ago have required any type of reoperation.
Another study found that, among 128 patients with a total of 171 replacements implanted in 1989 or before, mean Knee Society scores were 78 and pain scores were 49 -- both considered good outcomes following such procedures.
Terence Gioe, MD, of the University of Minnesota in Minneapolis, who co-moderated the session at which the studies were presented, commented that such long-term data were both reassuring and sorely needed.
"We don't have enough 20-year studies in the literature, so anything [like these studies] is helpful," Gioe said.
In the failure-rate study, presented by Matthew D. Miller, MD, of Stanford University in California, surviving members of a 51-patient consecutive series receiving cruciate-retaining implants from 1984 to 1989 were evaluated clinically and radiographically.
Miller noted that the literature on long-term outcomes of knee replacements varies widely, with reported failure rates as low as 1.5% and as high as 50%