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Study: Change scores indicate that UKA and TKA are equally successful
Outcome scores fail to show the whole picture in the unicompartmental vs total knee arthroplasty debate.
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A 30-year database analysis shows higher 5-year and 10-year survivorship with total knee arthroplasty compared to unicompartmental procedures and highlights the importance of analyzing change scores when evaluating the efficacy of procedures.
“If you look at clinical outcome scores, you can look at the absolute score — in which case, you would suggest [unicompartmental knee arthroplasties] UKAs do better [than total knee arthroplasties], given this cohort of patients — but if you look at the change score, there is actually no difference between the two,” Matt C. Lyons, MBBS, FRACS, said during his presentation at the American Academy of Orthopaedic Surgeons 2012 Annual Meeting. “When comparing outcomes between interventions, it is critical to evaluate change scores and not just the raw postoperative data.”
Similar change scores
Lyons and his colleagues studied 5,606 total knee arthroplasties (TKAs) and 279 UKAs with a 2-year minimum follow-up that were performed between 1978 and 2009. The investigators compared the groups using WOMAC scores, Knee Society Clinical Ratings (KS), SF-12 scores and survivorship data.
“When we look at the results … historically, people have looked at the absolute values. However, this ignores the severity of the disease preoperatively and the change from intervention,” Lyons said. “Recent studies have suggested that the change in the clinical outcome scores from preoperative to postoperative represents the effect of the intervention, and therefore allows for a valid comparison between groups.”
The investigators found the UKA group displayed higher preoperative scores than those found in the TKA group, as well as significantly higher postoperative SF-12, KS and WOMAC function scores. However, change scores for all WOMAC fields were similar between the UKA and TKA groups. KS change scores were also similar between the groups.
Lower survivorship for UKA
According to Lyons, UKA displayed a higher cumulative revision rate than TKA (12.9% vs. 6.4%). Kaplan-Meier survivorship at 5 years was 94.6% for the UKA group and 98.4% for the TKA group. At 10 years, the UKA group continued to show lower survivorship compared to the TKA cohort (90.4% vs. 94.9%)
Lyons concluded that the data indicate a need for researchers and clinicians to look beyond raw clinical outcome scores, as these scores fail to indicate that TKA and UKA are equally successful when the change score is taken into account. – by Robert Press
Reference:
- Lyons MC, MacDonald SJ, Somerville L, et al. 30-year database analysis of unicompartmental and total knee arthroplasty. Paper #15. Presented at the American Academy of Orthopaedic Surgeons 2012 Annual Meeting. Feb. 7-11. San Francisco.
For more information:
- Matthew C. Lyons, MBBS, FRACS, can be reached at Suite 2, Mater Clinic, 25 Rocklands Road, North Sydney, NSW 2060; email: mattylyons@hotmail.com
- Disclosure: Lyons has no relevant financial disclosures.