Translation and Validation of the Korean Version of the Forgotten Joint Score

Abstract

배경: Forgotten Joint Score (FJS)는 인공관절 이후 환자의 주관적인 임상결과를 측정하는 patient reported outcome measure (PROM)으로 2012년 새롭게 개발된 설문도구이다. 이는 환자가 인공관절 치환술 이후 수술한 무릎을 자연스럽게 느껴서 마치 수술한 사실조차 잊고 사는 상태가 인공관절의 궁극적인 목표라는 점에 착안하여 만들어졌다. FJS는 WOMAC score에 비해 천장효과가 낮은 민감한 측정도구로 알려져 널리 사용되고 있다. 최근 세계 각국에서 여러 언어로 번역이 및 타당성에 대한 연구가 발표되었지만 국내에서는 아직 이에 대한 연구가 이루어진 바가 없다.

방법: 먼저 Cross-cultural adaptation을 위해 스위스의 개발자와 함께 guideline에 맞추어 5단계에 걸쳐 번역을 시행하였다. 이후 슬관절 인공관절 치환술을 받은 150명의 환자를 대상으로 한국어판 FJS와 함께 visual analogue scale (VAS), WOMAC, SF-36 설문을 작성하였다. Test-retest reliability를 평가하기 위해서 추가로 100명의 환자를 대상으로 전화 설문을 통하여 간격을 두고 한국어판 FJS를 2회 반복 작성하였다. Responsiveness는 50명의 환자를 대상으로 수술 후 3개월째와 1년째를 비교하여 후향적으로 평가하였다.

결과: 한국어판 FJS는 좋은 reliability(신뢰도)를 보여주었다. [Cronbach's α = 0.967, Intraclass correlation coefficient = 0.958, 95% CI: 0.930-0.974]. WOMAC score에 비해서 낮은 천장효과(Ceiling effect)를 보였으며(8.7%) 바닥효과(Floor effect)는 관찰되지 않았다. WOMAC, SF-36 score와의 상관계수는 각각 0.708, 0.682로 훌륭한 construct validity(구성타당도)를 보였다. 한국어판 FJS의 standardized response mean (SRM)값은 0.67로 이는 WOMAC score의 SRM(1.03)에 비해 낮았다.

결론: 한국어판 FJS는 좋은 reliability와 construct validity를 가지고 있으며 천장효과가 낮은 민감한 측정도구이다. 따라서 인공관절 수술 후 임상결과를 측정하기에 적합한 설문도구이다.

Background: Forgotten Joint Score (FJS) is a newly developed patient reported outcome measure (PROM) designed to evaluate clinical outcome after total knee arthroplasty (TKA). FJS is known as a sensitive test with low ceiling effect. It has been recently translated into many languages. However, no study has reported the validity or reliability of the Korean Version of FJS. Thus, the purpose of this study was to address this issue.

Method: According to guidelines for cross-cultural adaptation, translation of the English version of the FJS was performed. After obtaining license from the original developer, 150 patients who had undergone total knee arthroplasty at more than one year ago to less than five years completed the Korean version of FJS (K-FJS), visual analogue scale (VAS), Western Ontario McMaster Universities Osteoarthritis index (WOMAC), and the 36-Item Short Form Health Survey (SF-36). To measure test-retest reliability, K-FJS was completed twice by telephone survey for an additional 100 patients. Responsiveness was retrospectively calculated based on a survey of 50 patients at three months and one year after surgery.

Results: The Korean version FJS exhibited an excellent reliability [Cronbach's α = 0.967, Intraclass correlation coefficient = 0.958, 95% CI: 0.930-0.974]. The ceiling effect of K-FJS was 8.7% (N = 13). There was no floor effect. This was lower than that of WOMAC's ceiling effect (10%). Its correlation coefficients with WOMAC and SF-36 (Physical Function) were 0.708 and 0.682, respectively, indicating good construct validity. However, its correlation with mental health subscale of SF-36 was low (r = 0.143). At 3 to 12 months after TKA, standardized response mean (SRM) was 0.67, which was lower than the SRM of WOMAC (1.03) obtained in the same period. The Korean version of Forgotten Joint Score demonstrated strong measurement properties in terms of good construct validity and reliability.

Conclusions: This study suggests that the Korean version of Forgotten Joint Score is an excellent instrument that can be used to monitor clinical outcomes after total knee arthroplasty. Using this standardized version of K-FJS, it would be possible for institutions to share clinical results more accurately.