Reliability of foot posture index (FPI-6) for evaluating foot posture in patients with knee osteoarthritis

Yi Wang; Zehua Chen; Zugui Wu; Junyi Li; Congcong Li; Jiaman Yang; Weijian Chen; Zixuan Ye; Xinxin Shen; Tao Jiang; Wengang Liu; Xuemeng Xu

doi:10.3389/fbioe.2023.1103644

Reliability of foot posture index (FPI-6) for evaluating foot posture in patients with knee osteoarthritis

Front Bioeng Biotechnol. 2023 Jan 18:11:1103644. doi: 10.3389/fbioe.2023.1103644. eCollection 2023.

Authors

Yi Wang¹, Zehua Chen², Zugui Wu¹, Junyi Li¹, Congcong Li¹, Jiaman Yang¹, Weijian Chen¹, Zixuan Ye¹, Xinxin Shen¹, Tao Jiang³, Wengang Liu³, Xuemeng Xu^{1

3}

Affiliations

¹ The Fifth Clinical College of Guangzhou University of Chinese Medicine, Guangzhou, China.
² The Orthopedics Hospital of Traditional Chinese Medicine Zhuzhou city, Zhuzhou, China.
³ Guangdong Provincial Second Hospital of Traditional Chinese Medicine, Guangzhou, China.

Abstract

Objective: To determine the reliability of FPI-6 in the assessment of foot posture in patients with knee osteoarthritis (KOA). Methods: Thirty volunteers with KOA (23 females, 7 males) were included in this study, assessed by two raters and at three different moments. Inter-rater and test-retest reliability were assessed with Cohen's Weighted Kappa (Kw) and Intraclass Correlation Coefficient (ICC). Bland-Altman plots and respective 95% limits of agreement (LOA) were used to assess both inter-rater and test-retest agreement and identify systematic bias. Moreover, the internal consistency of FPI-6 was assessed by Spearman's correlation coefficient. Results: FPI-6 total score showed a substantial inter-rater (Kw = .66) and test-retest reliability (Kw = .72). The six items of FPI-6 demonstrated inter-rater and test-retest reliability varying from fair to substantial (Kw = .33 to .76 and Kw = .40 to .78, respectively). Bland-Altman plots and respective 95% LOA indicated that there appeared no systematic bias and the acceptable agreement of FPI-6 total score for inter-rater and test-retest was excellent. There was a statistically significant positive correlation between each item and the total score of FPI-6, which indicated that FPI-6 had good internal consistency. Conclusion: In conclusion, the reliability of FPI-6 total score and the six items of FPI-6 were fair to substantial. The results can provide a reliable way for clinicians and researchers to implement the assessment of foot posture in patients with KOA.

Keywords: FPI-6; biomechanics; foot posture; knee osteoarthritis; reliability.

Grants and funding

This work was supported by Guangzhou Science and Technology Plan Project (202206010048), Guangdong Provincial Science and Technology Innovation Strategy Special Fund (2021B1111610007), and Natural Science Foundation of Guangdong Province (No. 2021A1515011545).