Reliability and Limits of Agreement of the Supraspinatus Muscle Anatomical Cross-Sectional Area Assessment by Ultrasonography

Reliability of Ultrasound Measurement of Muscle Thickness in Patients with Supraspinatus Tendon Pathology

Objectives of the study were to observe supraspinatus muscle thickness in patients with supraspinatus tendon pathology using ultrasound (US) and examining inter- and intra-rater reliability, and to compare muscle thickness with cross-sectional area (CSA) and occupation ratio measured by both US and magnetic resonance imaging (MRI). The investigation was designed as a prospective cohort study. Two groups of patients were included in the study: 43 patients with tendon rupture and 44 patients without tendon rupture as a control group. A written consent was obtained from all patients. In both groups, muscle thickness, CSA and occupation ratio were measured with US, and CSA and occupation ratio with MRI. Study results showed statistically significant between-group differences. The mean supraspinatus muscle thickness measured by US was 14.01 mm and 19.83 mm in patients with and without tendon rupture, respectively. CSA and occupation ratio measured by US and MRI also showed statistically significant between-group differences. Pearson correlation coefficient between supraspinatus thickness and occupation ratio and CSA measured by US and MRI showed strong to moderate correlation. US measurements showed moderate to strong intra- and inter-rater reliability. In conclusion, supraspinatus muscle thickness measurement by US is a reliable method for muscle atrophy evaluation and strongly correlates with other acknowledged methods.

Quantitative Measurement of Muscle Atrophy and Fat Infiltration of the Supraspinatus Muscle Using Ultrasonography After Arthroscopic Rotator Cuff Repair

Objective

To investigate the utility of ultrasonography to objectively examine morphological changes (i.e., muscle atrophy and fatty infiltration) of the supraspinatus muscle.

Methods

Thirty-four patients were prospectively enrolled in this study. The degrees of muscle atrophy and fat infiltration were measured using ultrasonography 3–4 months after arthroscopic supraspinatus tendon repair. Shoulder function (i.e., shoulder active range of motion, visual analogue scale, and constant score) was examined. Using the symmetricity of the muscles in the human body, the degrees of morphological changes of the supraspinatus muscle were quantitatively measured. The associations between the morphological changes of the supraspinatus muscle and shoulder function were identified.

Results

There were statistically significant differences in the cross-sectional area (CSA) and echogenicity between the surgery and non-surgery sides (p<0.001). The CSA ratio, which represents the degree of muscle atrophy, was associated with shoulder forward flexion, external rotation, and constant score; however, the echogenicity ratio, which represents the degree of fat infiltration, was not associated with shoulder function after surgery.

Conclusion

This study demonstrated that shoulder function could be predicted by evaluating the morphological changes of the supraspinatus muscle using ultrasonography and that objective evaluation is possible through quantitative measurement using the symmetricity of the human body.