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Researchers identify risk factors for revision of unicompartmental knee arthroplasties
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SAN FRANCISCO — Investigators using the Kaiser-Permanente Total Joint Replacement Registry found high revision rates of cemented unicompartmental knee arthroplasties among younger patients and those with an American Society of Anesthesiologists score of 3 or less.
“The causes of unicompartmental knee failure are multiple,” Stefano A. Bini, MD, said during his presentation at the American Academy of Orthopaedic Surgeons 2012 Annual Meeting. “Selecting patients younger than 55 [years] can increase your risk of revision four-fold. Patients with an [American Society of Anesthesiologists] ASA score of less than 3 are also associated with an increased risk of revision. Additionally, selecting an implant with a poor track record increases the risk of revision independent of surgeon and patient factors, and a surgeon who performs at least one [unicompartmental knee arthroplasty] a month on average can halve their risk of revision.”
For their study, Bini and colleagues questioned whether clinicians and researchers put too much emphasis on the type of device used when assessing partial knee replacement outcomes asking, “Are we considering the effect of surgeons, their skills, and their volume and also the question of patient-specific factors?”
The investigators identified 1,784 cemented, primary unicompartmental knee arthroplasties (UKAs) performed between 2001 and 2009, and calculated the relative revision of risk for variables such as patient age, gender, weight, body mass index (BMI) and ASA score. Implant design, surgeon and hospital volume, surgeon experience and fellowship training were also investigated.
“We reported on implants with at least 100 cases with a minimum 2-year follow-up, and our endpoint was aseptic revision defined as the removal or exchange of at least one component. We excluded infection,” Bini said.
They noted 20% of patients were younger than 55 years, one in six had BMIs greater than 25, and 87 patients had aseptic revisions.
Bini and colleagues found a 19% revision rate among patients younger than 55 years — the highest in the study — with the next highest revision rate among patients with an ASA score of 3 or less. They did not find BMI, weight or gender to be associated with higher revision rates.
When looking at covariates, the surgeons found that hospitals with lower yearly volumes and surgeons with lower volumes and less experience had higher revision rates. After multivariate analysis, hospital and surgeon volume and cumulative surgical cases were no longer significant.
Bini and colleagues also found that an implant with an all polyethylene tibial component (DePuy Preservation) had a 10 times higher failure rate than the other devices studied. Bini noted the importance of selecting devices with a good track record. “This is particularly true today, as manufacturers constantly bring new products to market,” Bini told Orthopedics Today.
He also noted that high volume surgeons using UKA devices with good track records in patients older than 55 years have outcomes comparable to those of total knee arthroplasty (TKA).
“There is a lot of discussion these days about whether UKA is better than TKA, and people point to registry studies showing poor outcomes with UKA. Our point is that, at least in the short- to mid-term, UKAs can be as reliable as TKAs when performed in well selected patients by surgeons who do a reasonable volume using an implant with a good track record,” he told Orthopedics Today. – by Susan Rapp and Renee Blisard Buddle
Reference:
- Bini SA, Khatod M, Chen Y, Paxton L. The effect of patient specific factors on revision rates for unicompartmental knee arthroplasty. Paper #406. Presented at the American Academy of Orthopaedic Surgeons 2012 Annual Meeting. Feb. 7-11. San Francisco.
For more information:
- Stefano A. Bini, MD, can be reached at 1st Floor Station A, 280 W. Macarthur Blvd, Oakland, CA 94611; email: stefano.bini@kp.org.
- Disclosures: Bini has no relevant financial disclosures.