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Low reliability of Knee Society Score suggests need for alternative assessment methods
Objective inertia-based motion tests and patient-reported outcome measures should be used in clinical outcomes assessment of primary knee arthroplasty.
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BERLIN — Significant variance seen in Knee Society Scores for primary total knee arthroplasty has called into question the score’s utility for effectively measuring function in patients postoperatively, according to a study presented at the 13th EFORT Congress 2012, here.
“Huge variability in Knee Society knee and function score exists between studies on comparable groups of primary total knee arthroplasty (TKA) patients at preoperative and various follow-up times,” Rachel Senden, PhD, of the Department of Orthopaedic Surgery and Traumatology at Atrium Medical Center in Heerlen, Netherlands, told Orthopaedics Today Europe.
The disparity range (the difference between maximum and minimum average scores reported over 71 study groups, including 4,170 patients, across 37 studies) in the Knee Society Score (KSS) reported in the analysis that Senden presented was 42 points and 44 points, respectively, for KSS knee and KSS function. This was too large to only be attributed to treatment differences or patient indications.
Rachel Senden
Alternative scores, results
“This variability shows that the reliability of KSS scoring is poor, which challenges the concurrent validity of the KSS,” Senden said. She suggested using additional knee scores, such as patient-reported outcome measures (PROMs) like the Knee Injury and Osteoarthritis Outcome Score, and the recently developed new Knee Society Score. However, further studies are needed to see whether the reliability is improved with these patient-reported outcomes, she noted.
According to the study abstract, KSS scoring differs between hospitals, countries and cultures and even between individual doctors. The average KSS knee score over all study groups ranged from 23 points to 65 points, showing a difference of 40 points, which covers nearly half of the 100-point KSS scale.
Other discrepancies noted
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In addition, investigators noted in two studies that the preoperative knee function was so high that it would be considered a fair outcome and not a low preoperative score indicating for TKA.
Except for KSS function scores at the 1-year follow-up, the postoperative disparity range was either similar or smaller than that of the preoperative scores, which was noted in the abstract.
In addition to PROMs, another possible alternative, Senden said, was to perform objective inertia-based motion analysis tests, which could analyze function without requiring patient input.
“I think this will become increasingly necessary for outcome assessment in clinical studies,” Senden said. – by Jeff Craven
Reference:
- Senden R, Heyligers I, Grimm B. Poor reproducibility of the Knee Society Scores challenges its value for clinical follow-up and comparative studies. Paper #12-2831. Presented at the 13th EFORT Congress 2012. May 23-25. Berlin.
For more information:
- Rachel Senden, PhD, can be reached at Henri Dunantstraat 5, Heerlen, Netherlands; email: rachel.senden@bw.unimaas.nl.
- Disclosure: Senden has no relevant financial disclosures. Heyligers and Grimm are consultants to and receive grant/research support from Biomet and Stryker.