Ultrasound histogram metrics for subscapularis tendon: Toward standardized musculoskeletal image interpretation

Rotator cuff tears are a prevalent pathology that is present in orthopedic clinics, with subscapularis tears being recognized in 50% of rotator cuff repairs. Changing of the echogenicity of the tendon in ultrasound is an important factor for diagnosis. However, the echogenicity is mostly determined based on subjective assessment. Therefore, the aim of the study is to quantify the normal gray-level value of the subscapularis tendon measured by ultrasonography. Fifty participants with a mean age of 21.08 ± 0.70 years underwent bilateral shoulder ultrasonography; ImageJ calculated the mean echogenicity of the histogram. The gray-level value of each participant was identified and compared between the dominant and nondominant shoulder and between male and female participants. The mean gray-level value of healthy subscapularis tendon was 85.45 ± 3.61 and 85.35 ± 3.31 for male and female participants, respectively. There were no statistically significant differences between participants' dominant and nondominant shoulders between neither males nor females (P-value > .05). The gray-level histogram method is a valuable tool for quantifying the echogenicity of the tendon in ultrasound images. This research establishes baseline gray-level histogram readings for normal subscapularis tendons to support better distinction between healthy and diseased tendon conditions. The baseline data serve as a foundation for upcoming studies to establish diagnostic thresholds for symptomatic patient populations.