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