To investigate the elastic properties of the supraspinatus (SSP) muscle in patients with rotator cuff tear (RCT) by using shear wave sonoelastography (SWS) and comparing the stiffness of SSP muscle according to severity of RCT.

Seventy-six patients (43 males, 33 females; mean age 64.4±9.2 year) with one hundred and fifty two shoulders (85 symptomatic, 67 asymptomatic) were recruited. Severity of RCT, fatty infiltration and echogenicity of SSP muscle, and SSP muscle atrophy were assessed on B-mode ultrasound (US). Shear wave velocity (SWV) was measured twice in proximal and distal upper trapezius and SSP muscles at suprascapular fossa on longitudinal SWS using acoustic radiation force impulse imaging.

In the 85 symptomatic/67 asymptomatic shoulders, US revealed 1/37 shoulders with normal supraspinatus tendon (group 1), 16/16 shoulders with tendinopathy (group 2), 41/2 shoulders with partial-thickness tear (group 3), and 27/12 shoulders with full thickness tear [4/4 small and 8/2 medium (group 4), 4/3 large and 11/3 massive (group 5)]. The SWV of SSP muscle in groups 1, 2, 3, 4, and 5 were 2.88±0.25m/s, 2.79±0.27m/s, 2.64±0.21m/s, 2.34±0.14m/s, and 2.12±0.17m/s, respectively. SWV in SSP muscle was negatively correlated with the severity of RCT (r=−0.809), fatty infiltration grade of SSP muscle (r=−0.677), echogenicity grade of SSP muscle (r=−0.637), Warner grade (r=−0.671), and Goutallier stage (r=−0.672, P<0.05).

The SWS demonstrated a difference of elastic properties of SSP muscle according to the severity of RCT and was correlated with fatty infiltration, echogenicity, and atrophy of SSP muscle, and the severity of RCT. Therefore, SWS can be used as an imaging method to provide insight into the biomechanics and pathophysiology of supraspinatus muscles in patients with RCT.