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Observational Study
. 2017 Mar 30;48(1):25-31.

Variability between Clarke's angle and Chippaux-Smirak index for the diagnosis of flat feet

Cristina Gonzalez-Martin  1 , Salvador Pita-Fernandez  2 , Teresa Seoane-Pillado  2 , Beatriz Lopez-Calviño  2 , Sonia Pertega-Diaz  2 , Vicente Gil-Guillen  3
Affiliations
Observational Study

Variability between Clarke's angle and Chippaux-Smirak index for the diagnosis of flat feet

Cristina Gonzalez-Martin et al. Colomb Med (Cali). .

Abstract
in English, Spanish

Background: The measurements used in diagnosing biomechanical pathologies vary greatly. The aim of this study was to determine the concordance between Clarke's angle and Chippaux-Smirak index, and to determine the validity of Clarke's angle using the Chippaux-Smirak index as a reference.

Methods: Observational study in a random population sample (n= 1,002) in A Coruña (Spain). After informed patient consent and ethical review approval, a study was conducted of anthropometric variables, Charlson comorbidity score, and podiatric examination (Clarke's angle and Chippaux-Smirak index). Descriptive analysis and multivariate logistic regression were performed.

Results: The prevalence of flat feet, using a podoscope, was 19.0% for the left foot and 18.9% for the right foot, increasing with age. The prevalence of flat feet according to the Chippaux-Smirak index or Clarke's angle increases significantly, reaching 62.0% and 29.7% respectively. The concordance (kappa I) between the indices according to age groups varied between 0.25-0.33 (left foot) and 0.21-0.30 (right foot). The intraclass correlation coefficient (ICC) between the Chippaux-Smirak index and Clarke's angle was -0.445 (left foot) and -0.424 (right foot). After adjusting for age, body mass index (BMI), comorbidity score and gender, the only variable with an independent effect to predict discordance was the BMI (OR= 0.969; 95% CI: 0.940-0.998).

Conclusion: There is little concordance between the indices studied for the purpose of diagnosing foot arch pathologies. In turn, Clarke's angle has a limited sensitivity in diagnosing flat feet, using the Chippaux-Smirak index as a reference. This discordance decreases with higher BMI values.

Introducción: Existe una gran variabilidad en las mediciones para el diagnóstico de la patología biomecánica. El objetivo de este estudio fue determinar la concordancia entre el ángulo de Clarke y el índice de Chippaux-Smirak, para determinar la validez del ángulo de Clarke utilizando como referencia el índice de Chippaux-Smirak.

Métodos: Se realizó un estudio observacional en una muestra aleatoriamente seleccionada (n=1,002) en A Coruña (España). Tras el consentimiento informado del paciente y la aprobación del comité de ética, se estudiaron variables, antropométricas, índice de comorbilidad de Charlson y un examen podológico (ángulo de Clarke, índice de Chippaux-Smirak). Se realizó un estudio descriptivo y un análisis multivariado de regresión logística.

Resultados: La prevalencia de pie plano utilizando el podoscopio fue de 19.0% (pie izquierdo) y 18.9% (pie derecho), incrementándose con la edad.La prevalencia de pie plano según el índice Chippaux-Smirak o el ángulo de Clarke se incrementan considerablemente llegando a 62.0% y 29.7%.La concordancia (kappa I) entre los índices según grupos de edad oscila entre 0.25-0.33 (pie izquierdo) y 0.21-0.30 (pie derecho). El coeficiente de correlación intraclase (CCI) entre el índice de Chippaux-Smirak y el ángulo de Clarke es -0.445 (pie izquierdo) y 0.424 (pie derecho). Tras ajustar por edad, índice de masa corporal (IMC), score de comorbilidad y sexo la única variable con un efecto independiente para predecir discordancia es el IMC (OR= 0.969; IC 95%: 0.940-0.998).

Conclusiones: La concordancia entre los índices estudiados para el diagnóstico de la patología del arco plantar es reducida. Existe a su vez una reducida sensibilidad del ángulo de Clarke para el diagnóstico de pie plano, utilizando como referencia el índice de Chippaux-Smirak. Esta discordancia disminuye con valores más altos de IMC.

Keywords: Anthropometry; Chippaux-Smirak index; Clarke's angle; Flatfoot; Foot; Footprint; Pedigraph; Podiatry; Sensitivity and Specificity.

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Conflict of interest statement

Conflicts of interests: The authors declare that they have no competing interests

Figures

Figure 1
Figure 1. Positive and negative likelihood ratio for the diagnosis of flat feet by foot
See this image and copyright information in PMC

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