Sonoelastography of Plantar Fascia: Reproducibility and Pattern Description in Healthy Subjects and Symptomatic Subjects

Abstract

The purpose of the work reported here was to describe the sonoelastographic appearance of the plantar fascia of healthy volunteers and patients with fasciitis. Twenty-three healthy subjects and 21 patients with plantar fasciitis were examined using B-mode and real-time sonoelastography (RTSR) scanning. B-Mode examination included fascia thickness and echotexture. Echogenicity and echovariation of the color histogram were analyzed. Fasciae were classified into type 1, blue (more elastic); type 2, blue/green (intermediate); or type 3, green (less elastic). RTSE revealed 72.7% of fasciae as type 2, with no significant association with fasciitis (χ² = 3.6, df = 2, p = 0.17). Quantitative analysis of the color histogram revealed a significantly greater intensity of green (mean = 77.8, 95% confidence interval [CI] = 71.9–83.6) and blue (mean = 74.2, 95% CI = 69.7–78.8) in healthy subjects. Echovariation of the color red was 33.4% higher in the fasciitis group than in the healthy group (95% CI = 16.7–50.1). Sonoelastography with quantitative analysis of echovariation can be a useful tool for evaluation of plantar fascia pathology.

Introduction

Plantar fasciitis is a degenerative syndrome of the plantar fascia and is reported to be the most common cause of inferior heel pain in adults (Rompe, 2009, Wearing et al., 2006). Ultrasonography is a useful tool for the assessment of fascia pathology because it allows clinical diagnosis and confirms the exact location of the fasciopathy (Ieong et al., 2013, McMillan et al., 2009).

Real-time sonoelastography (RTSE) is a new ultrasound-based imaging technique that provides information on tissue elasticity and stiffness (Turan et al. 2013). The principle underlying elastography is that tissue compression produces a strain (displacement) within the tissue, providing a color-coded image superimposed over the B-mode image. The color indicates the relative elasticity of tissues within the region of interest (ROI) (Wu et al. 2011).

Real-time sonoelastography has been applied to the musculoskeletal system to evaluate lateral epicondylitis (De Zordo et al. 2009b), to describe the elasticity pattern of normal (De Zordo et al., 2009a, Drakonaki et al., 2009) and damaged (Sconfienza et al., 2010, Tan et al., 2012, Turan et al., 2013) Achilles tendon, and a number of articles on RTSE of plantar fascia have also been published. Wu et al., 2011, Wu et al., 2012 reported plantar fascia softening in subjects with the characteristic symptoms of plantar fasciitis and propose a quantitative measurement of the color histogram. This quantitative method allows a more objective interpretation than color visual grading, although postexamination analysis is required (Sconfienza et al. 2011). The loss of elasticity of affected plantar fascia has been reported to precede morphologic changes visible on B-mode imaging using semiquantitative methods (Lee et al., 2014, Sconfienza et al., 2013).

The disadvantages of RTSE include operator dependency and reproducibility (Havre et al 2008). Previous studies have assessed inter-observer agreement on visual inspection of elastograms (Lee et al., 2014, Sconfienza et al., 2013, Wu et al., 2011). However, to the best of our knowledge, the reliability of RTSE image acquisition has not been addressed to date.

The purpose of this study was to describe the sonoelastographic appearance of the plantar fascia of healthy volunteers and patients with symptomatic plantar fasciae and to evaluate RTSE reproducibility in image acquisition. We also performed correlation analyses of RTSE findings with subjective heel pain, perceptions of health status and ultrasound findings.