Discriminative and convergent validity of strain elastography for detecting tendinopathy within the supraspinatus tendon: a cross-sectional study

BACKGROUND: We aimed to explore the discriminative validity of ultrasound strain elastography (SEL) between patients with painful supraspinatus tendinopathy and healthy control shoulders, as well as the associations between SEL and magnetic resonance imaging (MRI), conventional ultrasound (tendon thickness), and the Disabilities of the Arm, Shoulder and Hand questionnaire (DASH). METHODS: Thirty patients with shoulder pain and MRI-verified supraspinatus tendinopathy and 30 healthy control shoulders (no pain) were examined using SEL, MRI, and conventional ultrasound of the supraspinatus tendon. SEL variables included raw data, ratios between the deltoid muscle and supraspinatus tendon (deltoid ratio), color rating, and presence of red/yellow lesions (middle, worst part, and total tendon). RESULTS: Statistically significant increases in odds ratios for being symptomatic (increased softening) were seen for all raw data variables, corresponding to 3.978 (95% confidence interval [CI], 1.414-11.197) for middle, 4.602 (95% CI, 1.536-13.788) for worst, and 4.865 (95% CI, 1.406-16.836) for total tendon, and 1.260 (95% CI, 1.027-1.545) for the deltoid ratio (worst), adjusted for sex and body mass index (BMI). Tendon thickness was not associated with SEL; however, significantly positive associations were found between raw data variables and MRI (β ≥ 0.58, P < .01), and positive associations were found between raw data variables and the DASH score (β = 0.01, P ≤ .04), adjusted for sex and BMI. CONCLUSIONS: Raw data variables and the deltoid ratio (worst) discriminated between patients with painful supraspinatus tendinopathy and healthy control shoulders when adjusted for sex and BMI. Associations were statistically significant for raw data variables and MRI or DASH score when adjusted for sex and BMI. Further studies are needed to understand SEL and the role of sex and BMI, including the responsiveness of SEL.