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Background In addition to muscle morphology, ultrasound imaging (US) could be a potential tool to determine muscle quality assessing the echo-intensity and using offline software to quantify the percentage of intramuscular fatty infiltration. Objective To investigate intra- and inter-rater image measurement reliability of morphological (i.e., cross-sectional area, perimeter) and echo intensity features (i.e., mean muscular echo intensity, fat echo intensity cut-offs, fatty infiltrates percentage estimation) of deep neck extensors in asymptomatic subjects. Methods Brightness-mode images of the cervical spine at C4/C5 were acquired in 25 asymptomatic subjects (40%women, age: 24 years) by an experienced examiner. Cross-sectional area, perimeter and echo-intensity measures of cervical multifidus and short rotators were measured on two separate days (one-week apart) in a randomized order by two assessors. Intra-class correlation coefficients (ICC), standard error of measurement, minimal detectable change, and mean, absolute and percent errors were calculated. Results Intra- (ICC3,1 0.800–0.989) and inter- (ICC3,2 0.841–0.948) examiner reliability of echo-intensity measures ranged from good to excellent. Women exhibited higher echo-intensity features than men. Intra-examiner reliability of morphological measures was excellent (ICC3,1 0.917–0.974) for multifidus and good-excellent (ICC3,1 0.868–0.987) for short rotators. Inter-examiner reliability of morphological measures also ranged from good to excellent (ICC3,2 0.765–0.965). Men exhibited higher CSA and perimeter than women. No side-to-side differences were observed in any ultrasound measure. Conclusion This study found that intra- and inter-rater image analysis reliability of muscle morphology, mean echo intensity, and fatty infiltration quantification of cervical multifidus and short rotators at C4/C5 level was good-to-excellent in healthy subjects.

Studies analyzing morphometry of neck extensor musculature have mostly used Magnetic Resonance Imaging (MRI). Panoramic Ultrasound View could be used for obtaining high-quality 2D cross-sectional images with a wide field of view more cost-effectively imaging acquisition by creating an automatic construction of 2D cross-sectional images.To measure neck extensors cross-sectional area (CSA) using panoramic ultrasound view in healthy subjects.Cross-sectional study.Panoramic B-mode ultrasound images of the neck extensor muscles at C4/C5 level were acquired in 25 healthy subjects (40% women, mean age: 24 ± 5 years) by an experienced assessor. The CSA of the upper trapezius, splenius (layer), semispinalis (layer), multifidi, short rotators, and levator scapulae were calculated. The relative percentage in the total neck extensor muscle volume of each CSA was also determined. Sex and side-to-side comparisons were conducted.Men showed larger CSAs than women in all muscles (all, P 0.01). No side-to-side differences were found in either men or women (all, P 0.05). Significant positive associations between CSA with weight (r: 0.654 to 0.375, P 0.01), height (r: 0.386 to 0.581, P 0.05), and BMI (r: 0.369 to 0.563, P 0.05) were found. Men showed greater percentage of upper trapezius and semispinalis muscle layers than women (P 0.01), whereas women had a greater percentage of levator scapulae muscle than men (P 0.01) from the total volume of the neck extensors. No side-to-side differences were found either.The current study describes CSA, as assessed with panoramic ultrasound view, of the neck extensors in healthy people. Men exhibited greater CSA than women with no side-to-side differences.