Testing the Reliability of a Procedure Using Shear-Wave Elastography for Measuring Longus Colli Muscle Stiffness.

BACKGROUND: Objective, reproducible assessment of deep cervical muscle mechanics is clinically relevant, yet the reliability of shear-wave elastography (SWE) for the longus colli (LC) has not been established. Therefore, the aim of this study was to determine intra- and inter-examiner reliability of LC stiffness measured by SWE under a tightly standardized protocol in patients with mechanical neck pain. METHODS: A longitudinal reliability study was conducted. Adults suffering from neck pain for ≥6 months were recruited. Two examiners (with different levels of experience) acquired bilateral LC images using fixed presets. The SWE region of interest covered the full muscle thickness (excluding fascia) to measure the LC shear-wave speed and Young's modulus. Intraclass correlation coefficients (ICCs), standard error of measurement and minimal detectable changes were computed. RESULTS: Nineteen participants with neck pain completed imaging (left and right sides analyzed). Inter-examiner agreement was good to excellent for single measurements (ICC3,2 > 0.818) and improved when averaging two acquisitions (ICC3,2 > 0.866). Intra-examiner repeatability was good to excellent for the novel examiner (ICC3,1 > 0.891) and excellent for the experienced examiner (ICC3,1 > 0.973). No meaningful stiffness differences by sex or side were observed in this sample (p > 0.05). CONCLUSIONS: A standardized SWE workflow yields reproducible LC stiffness measurements in mechanical neck pain. For longitudinal use, keep a single operator when feasible; in multi-examiner settings, average at least two acquisitions per side to enhance sensitivity to true change.