Original ContributionDiagnostic Performance of Axial-Strain Sonoelastography in Confirming Clinically Diagnosed Achilles Tendinopathy: Comparison with B-Mode Ultrasound and Color Doppler Imaging
Introduction
Achilles tendinopathy causes substantial morbidity and performance deficits among athletes as well as the general population (Maffulli et al. 2003). Magnetic resonance imaging (MRI) and ultrasound (US) are the most commonly used diagnostic imaging modalities for assessment of tendon pathologies. US is inexpensive, easily accessible and fast and has the advantage of dynamic capability compared with MRI, whereas MRI is preferable for global assessment and differential diagnosis of joint, cartilage and bone. US is the first-line imaging modality for tendon injury. Previous studies investigating the association between US abnormalities and the clinical severity of Achilles tendinopathy have reported conflicting results (Boesen et al., 2012, Emerson et al., 2010, Fredberg and Bolvig, 2002, Gibbon et al., 2000, Khan et al., 2003, Yang et al., 2010). Gibbon et al. (2000) reported that US is helpful in diagnosing clinical Achilles tendinopathy, whereas another observational study of elite gymnasts reported that US overestimates the prevalence of Achilles tendinopathy, with only one-third (35%) of the US abnormalities associated with clinical symptoms (Emerson et al. 2010). Axial-strain sonoelastography (ASE) is a non-invasive US-based technique that evaluates the mechanical properties of tissues. ASE is based on the principle that tissue displacement in response to external compression produces “strain” within the tissue and the strain is lower in harder tissue than in softer tissue (Klauser et al. 2010). This strain information can be presented either as a visual map (gray scale or color coded, depending on the user's preference) or semiquantitative strain ratio (measurements of strain differences between two user-defined areas). To date, several clinical studies applying strain ratios in differentiating malignant from benign lesions of the breast, thyroid, prostate and pancreas have reported promising results (Chang et al., 2013, Itokawa et al., 2011, Ning et al., 2012, Zhang et al., 2012). To our knowledge, there are no published data on the clinical feasibility of the strain ratio in the evaluation of Achilles tendinopathy. The aims of this study were to evaluate the diagnostic performance and reliability of ASE, B-mode US and color Doppler US in confirming clinically symptomatic Achilles tendinopathy. The secondary objective was to establish the relationship between the strain ratio measurements and clinical VISA-A (Victorian Institute of Sport Assessment—Achilles) scores.
Section snippets
Study population
This study was conducted with the approval of our institutional ethical review board. Written informed consent was obtained from all participants. Between December 2012 and August 2013, 142 consecutive patients who presented with swelling and pain localized to the Achilles tendon (duration of symptoms >3 mo) were invited for conventional US as well as ASE evaluation of the Achilles tendon. Patients with a history of Achilles tendon rupture or previous surgery were excluded. Only the affected
Results
One hundred twenty participants (30 women, 90 men) formed the patient group, yielding a total of 360 tendon sections (3 tendon sections in each patient). Table 1 summarizes the demographic data and US and ASE findings (continuous data) for the 240 participants in the patient and control groups. The mean duration of symptoms was 13.9 ± 12.1 mo (range: 3–72 mo). For the 16 patients who presented with bilateral symptoms, the more severely affected side was included for analysis. Patients with
Discussion
The present study indicates that ASE has excellent sensitivity (97.5%) and specificity (94.5%) in the diagnosis of clinically confirmed Achilles tendinopathy and good to excellent agreement with conventional B-mode US (κ = 0.81) and clinical results (κ = 0.91). Given its excellent diagnostic accuracy (97.8%) in confirming clinically symptomatic Achilles tendinopathy, ASE may be a valuable adjunct to conventional B-mode US similar to the use of color or power Doppler in routine clinical
Conclusions
Axial strain sonoelastography is a reliable and accurate clinical tool in the evaluation of Achilles tendinopathy, with results superior to those of B-mode US and excellent correlation with clinical findings. The strain ratio index may offer promise as a supplementary tool for the objective evaluation of Achilles tendon properties. However, additional work is needed to establish the usefulness of this diagnostic algorithm in the clinical context.
Acknowledgments
The authors value the support of Philips Healthcare for provision of elastography software. We thank Greg Lammers and Donna Goulsbra for their invaluable assistance in this study.
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