Elsevier

The Foot

Volume 25, Issue 1, March 2015, Pages 12-18
The Foot

17-Italian Foot Function Index with numerical rating scale: Development, reliability, and validity of a modified version of the original Foot Function Index

https://doi.org/10.1016/j.foot.2014.09.004Get rights and content

Highlights

  • The painful foot and ankle conditions limit the activities of daily living and are the leading cause of immobility and disability.

  • FFI is one of the most frequently used self-reported questionnaires that is used across national and international clinical and research communities.

  • The adapted 17 Italian Foot Function index is a reliable and valid outcome measure that showed more specific and sensitive properties than a generic questionnaire such as the LEFS.

Abstract

Background

Clinical research quantifies symptoms and signs of pain.

Objective

To develop a brief outcome measure to assess foot and ankle conditions, the psychometric properties of a modified version of the original Foot Function Index (FFI) were examined.

Methods

Eighty-six subjects with musculoskeletal foot and ankle disorders were enrolled. The internal consistency and test–retest reliability were evaluated by using Cronbach's α and intraclass correlation coefficient (ICC). Criterion validity was tested by Pearson's correlation coefficient between 17 items of the Italian FFI (17-IFFI) and the Lower Extremity Functional Scale (LEFS). The responsiveness was calculated using the receiver operating characteristic curve (ROC).

Results

Cronbach's Alpha was 0.95 (95% CI: 0.92, 0.99). The intra-interviewer and inter-interviewer ICC values were, respectively, 0.92 (95% CI: 0.88–10 0.96) and 0.90 (95% CI: 0.89–0.94). Correlations between the 17-IFFI scores and the LEFS scores were −0.564 and −0.456 at the initial and at the end of the treatment, respectively. The ROC analysis revealed an area under the curve of 0.732 (95% CI: 0.61–0.82) for the 17-IFFI and 0.633 (95% CI: 0.52–0.71) for the LEFS score.

Conclusions

The 17-IFFI is a reliable and valid scale and we recommend its application to evaluate the effectiveness of a treatment in patients with musculoskeletal foot and ankle disorders.

Introduction

The painful foot and ankle conditions limit the activities of daily living and are the leading cause of immobility and disability [1], [2], [3]. They are secondary to traumatic and non-traumatic problems such as metatarsalgia, hallux valgus, abnormal position of toes, ankle sprain and arthritis, and they may also be attributed to improper footwear and/or abnormal biomechanics [4], [5], [6], [7]. Foot pain prevalence is 24% for women and 20% for men aged 18–80 years [8].

Many outcome measures have been used to detect changes in a patient's health status in response to an intervention [7]. In Italy several generic measures have been applied to a variety of patients with lower-extremity musculoskeletal conditions, including the 36-Item Short-Form Health Survey (SF-36) [9], the Western Ontario and McMaster Universities (WOMAC) [10], Arthritis Impact Measurement Scales (AIMS2) [11] and Lower Extremity Functional Scale (LEFS) [12].

Foot Function Index [13] is a specific outcome measure of the impact of pathologies on foot and ankle function. At first it was used for patients with rheumatoid arthritis [14] but its reliability and validity were examined in several populations and the results were satisfactory [15], [16]. It consists of 23 items divided into three subscales: pain (9 items), disability (9 items), and activity limitation (5 items). The items are rated on a Visual Analogue Scale (VAS) consisting of horizontal line (10 cm). The poles are labeled “no pain” and “worst pain imaginable” (pain), “no difficulty” and “so difficult unable” (disability), and “none of the time” and “all of the time” (limitations). The patient is asked to mark the horizontal line at the spot that best corresponds to the effect of the foot complaints. Scores are added and divided by the maximum total possible (90 for both pain and disability subscale and 50 for activity limitation subscale). If a subject indicates as not applicable an item score, it is excluded from the total score. Decimal points were eliminated by multiplying the score by 100 (Fig. 1).

This scale has been translated and validated into several different languages [17], [18], and most recently in Italian too [19]. Although the Italian version of the FFI showed satisfactory psychometric properties in patients with foot and ankle diseases, we adapted the original version of FFI as the basis for the creation of a new 17 Italian FFI, since the Italian FFI has not yet been widely used in clinical outcome research.

To address the need for a brief outcome measure to assess foot and ankle musculoskeletal conditions, the psychometric properties of the modified version of the original Foot Function Index were examined.

Section snippets

Methods

Translation and cross-cultural adaptation of the FFI was performed according to international guidelines [20], [21]. The original English version of the FFI [13] was independently translated into Italian by two bilingual translators, one of whom was a native English speaker and the second one was a physician whose native language was Italian. The two translations were analyzed by a health care committee (three physiatrists, one orthopedist, and one rheumatologist), which first ensured that the

Subjects

Patients were randomly selected from a population of 195 subjects who had reported musculoskeletal lower limbs disorders. Eighty-six patients (42 women and 44 men) with foot and ankle complaints lasting longer than 6 weeks were enrolled in our study. The data were collected from March 2011 to May 2012. Subjects ranged in age from 35 to 78 years, with a mean ± SD age of 58 ± 10.2 years (Table 1). Informed consent was obtained from all patients prior to their participation in the study.

Procedures

The diagnosis of foot disorders was established in all patients on the basis of clinical examinations and imaging (e.g. X-ray, ultrasound, computed tomography, or magnetic resonance imaging). The 17-IFFI was administered independently by two physicians–interviewers, physician 1 and physician 2 to estimate inter-interviewer reproducibility. Two days later, the scale was again administered by physician–interviewer 1 to examine intra-interviewer (test–retest) reproducibility. Patients did not

Statistical analysis

Statistical tests were conducted using SPSS Release 18 for Windows. We used the Kolmogorov–Smirnov test to verify the normal distribution of variables. Therefore, we could apply parametric tests. The change in values in 17-IFFI and LEFS at the end of the treatment in comparison with the baseline was assessed using a paired t-test.

One-way ANOVA was used to evaluate the education level (elementary, secondary, and university) as the between-subject factor, followed by a Tukey post hoc comparison

Results

Eighty-six patients underwent rehabilitation therapy with a mean duration of 4 weeks. They completed the 17-IFFI and LEFS. No individual scored the worst or best possible score (no floor/ceiling effects) for both scales. No differences were found between the 17-IFFI scores of subjects with different education levels (F = 0.07, p = 0.993).

Discussion

The scope of clinical research is to quantify symptoms and signs of pain. Rehabilitation is that field of medicine that requires specific instruments to measure pain, activity limitations, and functions to evaluate the effectiveness of treatments. However, the creation of satisfactory instruments is complex and time-consuming, and requires extended research effort and specialized knowledge.

FFI [13] is one of the most frequently used self-reported questionnaires that is used across national and

Conclusions

The adapted 17 Italian Foot Function index is a reliable and valid outcome measure that showed more specific and sensitive properties than a generic questionnaire such as the LEFS. However, the cross cultural data have to be confirmed in future investigations. Two major changes have been adopted with respect to the original version of the scale. First of all, we shortened it permitting to reduce the time necessary for the questionnaire compilation. Moreover, we introduced the numerical rating

Conflict of interest

None declared.

References (36)

  • R.A. Deyo et al.

    Assessing the responsiveness of functional scales to clinical change: an analogy to diagnostic test performance

    J Chronic Dis

    (1986)
  • H.B. Menz et al.

    Foot pain impairs balance and functional ability in community-dwelling older people

    J Am Podiatr Med Assoc

    (2001)
  • F. Benvenuti et al.

    Foot pain and disability in older persons: an epidemiologic survey

    J Am Geriatr Soc

    (1995)
  • M.E. Tinetti et al.

    Risk factors for falls among elderly persons living in the community

    N Engl J Med

    (1988)
  • G. Spahn et al.

    The prevalence of pain and deformities in the feet of adolescents: results of a cross-sectional study

    Zeitschrift fur Orthopadie und ihre Grenzgebiete

    (2004)
  • T.M. van Wyngarden

    The painful foot: Part I. Common forefoot deformities

    Am Fam Phys

    (1997)
  • S. Lardenoye et al.

    The effect of taping versus semi-rigid bracing on patient outcome and satisfaction in ankle sprains: a prospective, randomized controlled trial

    BMC Musculoskelet Disord

    (2012)
  • C. Frey

    Foot health and shoewear for women

    Clin Orthop Relat Res

    (2000)
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