SAN FRANCISCO – March 6, 2008 – When it is time to replace a knee, a hybrid implant appears to have better longevity than conventional, totally cemented versions, according to a report at the American Academy of Orthopaedic Surgeons (AAOS) 75th Annual Meeting.
“Reducing revision rate is a key goal as we go to younger, more active patients [who need knee replacement],” said Mark Zawadsky, MD, Chief of Arthroplasty Service, Kaiser Permanente, Oakland, California, but “cementless knee implants have a lower cumulative survival rate,” according to new data presented here March 5.
Yet the hybrid implants that use cement for the tibia appear to be equivalent to totally cemented joints, he said, “which is an important finding.”
Cemented implants sometimes can shed cement debris, he said, and it has been postulated that the porous, cementless implants that depend on the bone to grow into them might provide a more durable, biological fixation of the device. Studies of the comparative longevity of the various implants have given mixed results so far and have suffered from poor design, Dr. Zawadsky said.
Dr. Zawadsky and colleagues began collecting data prospectively into a joint registry in April 2001, and he presented the results of their analysis of these data from 19,966 primary total knee arthroplasties (TKA).
Cementless TKA has a statistically lower survival rate at 5 years compared with cemented knee implants. Survival rates of cemented and cementless TKAs (17,934 and 2,032, respectively) were 99% compared with 95% (P = .001). Revision rates for cementless implants were 2.85%, compared with less than 1% for cemented implants.
Cementless implants were more often given to younger (13% in those aged <55 years vs 8% in those aged >55 years), male (44% in men vs 35% in women) patients (P < .001 for both comparisons).
The faster failure rate with cementless TKA persisted when the data were statistically corrected for age, gender, body mass, and osteoarthritis, according to the researchers.
[Presentation title: Lower Cementless Total Knee Arthroplasty (TKA) Survival Rate Among 19,966 Primary TKAs. Abstract 104]