Quantification of sonographic echogenicity by the gray-level histogram in patients with supraspinatus tendinopathy

Purpose: The aim of this study was to compare the gray-level value of the supraspinatus tendon of a painful shoulder with that of a normal shoulder measured by ultrasonography, and to investigate whether a low mean gray-level value of the supraspinatus tendon could indicate a partial-thickness or incomplete full-thickness tear. Methods: Two hundred and ten patients had significant unilateral shoulder pain with the clinical suspicion of rotator cuff tendinopathy. They underwent bilateral shoulder ultrasonography, and the mean echogenicity of the histogram was calculated on the screen. The mean gray-level value of each patient's contralateral asymptomatic shoulder was compared with that of the painful shoulder. Results: Based on the scan of transverse and longitudinal planes, a significant difference existed between the symptomatic shoulder and contralateral asymptomatic shoulder (p < 0.0001). The mean gray-level values of symptomatic shoulders showed no statistically significant difference between the patients who underwent surgery and the patients who underwent conservative treatment. Conclusions: We demonstrated that the ultrasound gray-level histogram is a promising tool for detecting the hypoechogenic appearance of supraspinatus tendinopathy. A decrease in the mean gray-level value on the symptomatic shoulder may be used as an alternative sonographic indicator of rotator cuff partial-thickness tear or tendinopathy. Level of evidence: Diagnostic level III.