Foot Function Index (FFI)
Original Editors - Xiomara Hernandez
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Objective[edit | edit source]
A Foot Function Index (FFI) was developed in 1991 to measure the impact of foot pathology on function in terms of pain, disability and activity restriction. [1] It is a self-administered index consisting of 23 items divided into 3 sub-scales. Both total and sub-scale scores are produced.
Intended Population[edit | edit source]
The FFI has been shown to be a reasonable tool for use with low functioning individuals with foot disorders[2] ,patients with rheumatoid arthritis[1] and non-traumatic foot or ankle problems.[3] It can be used in both clinical and research settings.
However, it may not be appropriate for individuals who function at or above the level of independence in activities of daily living. [2]
Method of Use[edit | edit source]
The FFI (questionnaire) consists of 23 self-reported items divided into 3 subcategories on the basis of patient values: pain, disability and activity limitation.[4] The patient has to score each question on a scale from 0 (no pain or difficulty) to 10 (worst pain imaginable or so difficult it requires help), that best describes their foot over the past week.
The pain subcategory consists of 9 items and measures foot pain in different situations, such as walking barefoot versus walking with shoes.
The disability subcategory consists of 9 items and measures difficulty performing various functional activities because of foot problems, such as difficulty climbing stairs.[4]
The activity limitation subcategory consists of 5 items and measures limitations in activities because of foot problems, such as staying in bed all day. Recorded on a visual analogue scale (VAS), scores range from 0 to 100 mm, with higher scores indicating worse pain. Both total and subcategory scores are calculated. [1]
| Scale | Questions | Scoring |
|---|---|---|
| Pain Scale |
|
0/90 |
| Disability Scale |
|
0/90 |
| Activity Limitation |
|
0/50 |
Evidence[edit | edit source]
Reliability[edit | edit source]
The FFI was examined for test-retest reliability and internal consistency. Test-retest reliability of the FFI total and subscale scores ranged from 0.87 to 0.69. Internal consistency ranged from 0.96 to 0.73.[1]
It is reported that the FFI is a reliable instrument for patients with rheumatoid arthritis[1] and it has also been recommended as a reliable measurement scale for use in other foot orthopaedic intervention trials. [5]
For the purposes of orthopaedic studies in which one foot serves as an internal control, a study assessed the side-to-side reliability of the seven-question Foot Function Index pain subscale. Internal reliability of the scale was high, with Cronbach's alphas ranging from 0.94 to 0.96, suggesting good left versus right discriminatory abilities. Intraclass correlation coefficients were examined for test-retest reliability (separated by side) and for side-to-side reliability (separated by the day of test). The resultant intraclass correlation coefficients were nearly equivalent, ranging from 0.79 to 0.89. Generalisability analysis yielded similar results. Intraclass correlation coefficients and generalisability analysis demonstrate that the majority of variation is best explained by the differences within subjects or between subjects rather than by test-retest or side-to-side differences. [5]
Validity[edit | edit source]
The FFI has been validated and determined to be a reliable instrument for patients with rheumatoid arthritis [1]and non-traumatic foot or ankle problems.[3] In the study to examine the construct validity of the FFI there were a total of 87 patients, with rheumatoid arthritis were used. With the exception of two items, factor analysis supported the construct validity of the total index and the sub-scales. Strong correlation between the FFI total and sub-scale scores and clinical measures of foot pathology supported the criterion validity of the index. [1]
Responsiveness[edit | edit source]
FFI is an instrument that was rated positively (level 3) for responsiveness. [6]
Miscellaneous[edit | edit source]
FFI-5pt versus original FFI
The clinimetric value of the Dutch version of the Foot Function Index (FFI) was assessed by Kuyvenhoven et al. in comparison with the original FFI using verbal rating scales (FFI-5pt) rather than visual analogue scales (VAS). The FFI-5pt is a suitable generic measure. Its clinimetric properties are comparable with those of the original FFI. Its administration and data entry are less time-consuming. However, responsiveness has to be more exactly assessed in an intervention study. [7]
Revision of the FFI[edit | edit source]
In 2006, the FFI was revised (the FFI-R) on the basis of criticisms from researchers and clinicians; items were added, including a scale to measure psychosocial activities and quality of life related to foot health [11]. A literature review was conducted to develop a theoretical model of foot functioning [12], based on the World Health Organization International Classification of Functioning (ICF) model. The FFI-R items were developed from the original 23 FFI items, and more items were added as a result of the literature review. As a result of clinicians and patients’ input, the final draft of the FFI-R, which consisted of 4 subscales and 68 items, was completed. The results were the FFI-R long form (FFI-R L; 4 subscales and 68 items) and the FFI-R short form (FFI-R S; 34 items) as total foot function assessment instruments. Both the 68-item and 34-item measures demonstrated good psychometric properties. The FFI-R in its current form is one of the most comprehensive instruments available. However, in a review article [13], questions were raised about the unidimensionality and independence of FFI-R subscales, and we did not include such reports in our previous article about the FFI-R [11]. We carefully reviewed the comments about the FFI-R and assessed the unidimensionality of the subscales by use of the Rasch model. On the basis of these critiques, the FFI-R required a periodic revision of its metrics to ensure it represented patient-centered health values and state-of-the-art methodology
Resources[edit | edit source]
References[edit | edit source]
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Budiman-Mak E, Conrad KJ, Roach KE. The Foot Function Index: a measure of foot pain and disability. J Clin Epidemiol. 1991;44:561–570. (level of evidence B)
- ↑ 2.0 2.1 Agel J, Beskin JL, Brage M, Guyton GP, Kadel NJ, Saltzman CL, Sands AK, Sangeorzan BJ, SooHoo NF, Stroud CC, Thordarson DB: Reliability of the foot function index: a report of the AOFAS outcomes committee. Foot Ankle Int 2005, 26:962-967. (level of evidence C)
- ↑ 3.0 3.1 Martin RL, Irrgang JJ. A survey of selfreported outcome instruments for the foot and ankle. J Orthop Sports Phys Ther.2007;37:72–84. (level of evidence A)
- ↑ 4.0 4.1 Kornelia Kulig, Stephen F Reisch I. Nonsurgical Management of Posterior Tibial Tendon Dysfunction With Orthoses and Resistive Exercise: A Randomized Controlled Trial. Physical Therapy, 2009 Jan; 89 (1): 26-37. (Level of evidence 1B)
- ↑ 5.0 5.1 Saag KG, Saltzman CL, Brown CK, Budiman-Mak E: The Foot Function Index for measuring rheumatoid arthritis pain: evaluating side-to-side reliability. Foot Ankle Int 1996, 17:506-510. (level of evidence C)
- ↑ Marike Van Der Leeden, Martijn P.M. Steultjens, Caroline B. Terwee, Dieter Rosenbaum, Debbie Turner, Jim Woodburn and Joost Dekkera. Systematic review of instruments measuring foot function, foot pain, and foot-related disability in patients with rheumatoid arthritis. Arthritis & Rheumatism (Arthritis Care & Research) Vol. 59, No. 9, September 15, 2008, pp 1257–1269. (level of evidence 1A)
- ↑ Kuyvenhoven MM, Gorter KJ, Zuithoff P, Budiman-Mak E, Conrad KJ, Post MW. The foot function index with verbal rating scales (FFI-5pt): A clinimetric evaluation and comparison with the original FFI. J Rheumatol. 2002 May;29(5):1023-8. (level of evidence C)
