Foot Function Index Captures Well the Impact of Foot Impairments in Patients With CMT1A, Study Suggests

The foot function index may be a promising tool to capture the impact of foot impairments in patients with Charcot-Marie-Tooth disease type 1A (CMT1A), a study says.

The findings of the study, “Foot Function Index: a promising questionnaire for patients with Charcot-Marie-Tooth disease type 1A,” were published in Archives of Physical Medicine and Rehabilitation.

Charcot-Marie-Tooth (CMT) is the most common heritable disease that affects the peripheral nervous system — the network of nerves responsible for controlling movement and sensation in the limbs. The disease can be caused by different genetic mutations and manifest at various ages, depending on its particular type and subtype.

CMT1A, the most common subtype of the disease, is characterized by foot deformities, which are estimated to affect up to 71% of all patients.

“The severity of deformations is positively linked to the severity of the disease, and the impact on the gait pattern and therefore quality of life is major,” the researchers wrote.

In this study, researchers from the Université Clermont Auvergne (France) and their collaborators set out to assess the performance of the foot function index (FFI) questionnaire — one of the most common self-assessment surveys used to evaluate the impact of foot deformities on the quality of life of patients with other disorders (e.g. rheumatic diseases) — in a group of patients with CMT1A.

The single-center, exploratory, cross-sectional study (NCT01750710) involved a total of 26 patients with a confirmed diagnosis of CMT1A, who were asked to complete the FFI questionnaire and the Medical Outcomes Study Short Form 36 (SF-36).

In addition, all participants underwent gait tests to evaluate several walking parameters (velocity, cadence, and stride length), as well as peak torque tests to measure the speed of movement of their hamstrings and quadriceps.

The FFI questionnaire includes 23 questions divided into three main categories: pain, disability, and activity restriction. On each question, the respondent must answer with a number between zero and 10, where zero corresponds to “no pain/not difficult” and 10 to “extremely painful/very difficult without help.”

The SF-36 is a measure of health-related quality of life with 36 questions divided into mental and physical composite scores.

Analyses indicated patients’ degree of acceptability to complete the FFI questionnaire was satisfactory, with 1.5% of missing data.

All sub-scores in the different categories of the questionnaire were highly consistent with each other and reproducible.

The investigators also found that the scores strongly correlated with the SF-36 physical composite score, as well as with the patients’ cadence (the number of steps taken per minute).

Conversely, no significant correlations were found between the FFI scores and the SF-36 mental composite score, nor the peak torque values.

“We highlighted that the FFI is a promising scale for assessing foot-related disability in patients with CMT1A, with good global metrological [measurement] properties, especially because no questionnaires are currently validated in neurologic diseases. However, complementary studies are still needed to confirm our preliminary results,” the researchers wrote.