Short-Form New Knee Society Score: What Is Its Responsiveness and Convergent Validity with Other Scores?

Abstract

The short-form version of New Knee Society Score (SF-NKSS) was designed with a purpose to reduce respondent burden. Literature review revealed only one report by Scuderi et al on responsiveness of derived SF-NKSS, but it was evaluated in two separate patient cohorts pre- and postsurgery. Our study had evaluated responsiveness and convergent validity of derived SF-NKSS in a single, large patient cohort followed longitudinally from preoperative status to over 1 year. Our database of 148 knee arthroplasty patients operated by the same surgeon, whose NKSS, Western Ontario and McMaster Universities Arthritis Index (WOMAC), and 12-item Short-Form Survey (SF-12) scores were prospectively collected preoperatively and postoperatively at 3 and 12 months for a study published earlier, was analyzed for derived SF-NKSS. Responsiveness was evaluated by determining the effect size, standardized response mean (SRM), and ceiling and floor effects. For convergent validity, Pearson's correlation coefficient was used. SF-NKSS was found to be most responsive with the largest effect size and SRM at 3 months (3.02 and 2.50, respectively) and at 12 months (3.58 and 2.92, respectively) with no ceiling or floor effect. SF-NKSS was followed in responsiveness by original NKSS, WOMAC, and SF-12 in a descending order. Convergent validity showed a strong correlation (r = 0.8–1.0; p < 0.001) of SF-NKSS with NKSS and a moderate to strong correlation (r = 0.5–0.6; p < 0.001) with WOMAC and SF-12. We concluded that SF-NKSS is a reliable, highly responsive tool for post-total knee replacement evaluation. It also has the ability to register improvement in the patient's recovery, which can continue even after 1 year. We found that the SF-NKSS can be used interchangeably with the original NKSS.

Keywords

knee - arthroplasty - patient-reported outcome measure - New Knee Society Score - short form

Note

This work was primarily performed at the Department of Orthopaedics, Lilavati Hospital and Research Centre, Mumbai, India as well as Breach Candy Hospital, Mumbai, India. The manuscript has been read and approved by all the authors and requirement for authorship of this document has been met. Each author believes that the manuscript represents honest work. A written informed consent was obtained from all patients authorizing radiological examination, photographic documentation, and surgery. They were also informed that the data concerning the case would be submitted for publication and they consented.

Publikationsverlauf

Eingereicht: 07. Januar 2019

Angenommen: 07. Januar 2020

Artikel online veröffentlicht:
17. März 2020

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