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Infection, periprosthetic fractures the major factors for TKA reoperation

Decreased long-term implant survivorship linked with age at surgery, failed high tibial osteotomy.

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CHICAGO — As designs for cemented total knee implants have improved, infection and periprosthetic fractures have emerged as the greatest threats for component replacement, revision and reoperation.

Researchers studying 1000 cemented condylar total knee arthroplasties (TKA) recently found implant survivorship rates of 94% to 97% at 15 years postop. In the 65 knees that underwent reoperation, investigators discovered that mechanical implant failure accounted for just one third of these cases. Another third of revisions resulted from infection and one third from other causes, mainly periprosthetic fractures and instability.

“We’ve done a good job at improving implant durability and we're not saying that reduced risk of mechanical failures is not important, especially in our younger patients,� said Michael B. Vessely, MD, an orthopedist with the Portland Clinic, in Portland, Ore., during his presentation at the American Academy of Orthopaedic Surgeons 73rd Annual Meeting. “However, based on the results of our study, we feel that greater efforts should be directed toward the prevention and treatment of infection and periprosthetic fractures. These two complications represent more than half of the reoperations in the first 15 years after knee arthroplasty.�

In the Chitranjan Ranawat award-winning study, Vessely and his colleagues reviewed 1000 consecutive primary TKAs performed at the Mayo Clinic in Rochester, Minn., between 1987 and 1989. The study consisted of 745 patients with an average age of 70 years. All patients received the same cemented, cruciate-retaining implant. Researchers followed the cohort for a mean of 15.7 years. During this time, 578 arthroplasties were in patients who died with their components in situ and 46 arthroplasties were lost to follow-up.

Of the remaining 376 knees, researchers discovered that 331 retained implants without revision or removal. “Excellent survivorship at more than 15 years for cemented, condylar, cruciate-retaining total knee arthroplasty was obtained in this cohort of mostly older patients,� Vessely said.

The researchers found 15-year survivorship rates of 93.7% and 95.9% for overall component removal and revision, respectively. Revision due to mechanical implant failure carried a 97% survivorship rate, while revision for aseptic loosening was 98.9%, they wrote in their abstract. “Factors associated with decreased survivorship were an age less than 60 at the time of the arthroplasty or a diagnosis of failed prior high tibial osteotomy,� Vessely said.

Reoperations

Investigators found 65 cases of open reoperation. Surgeons removed or revised implants in 45 cases and left the original components in 20 knees. Vessely cited the following as the most common causes for reoperation with component removal or revision: infection (16 knees), aseptic loosening (nine) and polyethylene wear (seven). He also pointed to superficial infection and periprosthetic fracture as reasons for reoperation with intact components.

Overall, infection led to a third of reoperated cases. “Over half of the reoperations performed in the first five years postoperatively were due to infection,� Vessely said. Similarly, periprosthetic fractures resulted in 22% of all reoperations. Most patellar periprosthetic fractures occurred within the first five years postop, and most femoral periprosthetic fractures occurred 10 or more years postoperatively, he noted.

For more information:

• Vessely MB, Whaley AL, Harmsen, WS, et al. Long term survivorship and failure modes of 1000 cemented condylar total knee arthroplasties. Presented at the American Association of Hip and Knee Surgeons Specialty Day Meeting. March 25, 2006. Chicago.