Effects of age and pathology on shear wave speed of the human rotator cuff

Abstract

Rotator cuff tears are common and often repaired surgically, but post-operative repair tissue healing, and shoulder function can be unpredictable. Tear chronicity is believed to influence clinical outcomes, but conventional clinical approaches for assessing tear chronicity are subjective. Shear wave elastography (SWE) is a promising technique for assessing soft tissue via estimates of shear wave speed (SWS), but this technique has not been used extensively on the rotator cuff. Specifically, the effects of age and pathology on rotator cuff SWS are not well known. The objectives of this study were to assess the association between SWS and age in healthy, asymptomatic subjects, and to compare measures of SWS between patients with a rotator cuff tear and healthy, asymptomatic subjects. SWE images of the supraspinatus muscle and intramuscular tendon were acquired from 19 asymptomatic subjects and 11 patients with a rotator cuff tear. Images were acquired with the supraspinatus under passive and active (i.e., minimal activation) conditions. Mean SWS was positively associated with age in the supraspinatus muscle and tendon under passive and active conditions (p ≤ 0.049). Compared to asymptomatic subjects, patients had a lower mean SWS in their muscle and tendon under active conditions (p ≤ 0.024), but no differences were detected under passive conditions (p ≥ 0.783). These findings identify the influences of age and pathology on SWS in the rotator cuff. These preliminary findings are an important step toward evaluating the clinical utility of SWE for assessing rotator cuff pathology. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:282-288, 2018.

Keywords: muscle; pathology; rotator cuff; shear wave elastography; tendon.

Figure 1.

Photograph showing the scanning position for passive trials. The transducer was oriented parallel to the muscle fibers (as shown) or intramuscular tendon fibers. The shoulder was positioned in 30 degrees of scapular-plane abduction.

Figure 2.

To calculate mean shear wave speed, B-mode (A) and shear wave elastography (B) images were simultaneously acquired. The B-mode image was segmented based on echogenic thresholds to create a segmentation mask (C), and then this segmentation mask was applied to the shear wave elastography image to retain only the shear wave speed values of interest (D).

Figure 3.

In asymptomatic subjects, mean SWS of the supraspinatus muscle increased significantly with age under both active (●p = 0.049) and passive (●p = 0.039) testing conditions.

Figure 4.

In asymptomatic subjects, mean SWS of the supraspinatus intramuscular tendon increased significantly with age under both active (●p = 0.011) and passive (●p = 0.005) testing conditions.

Figure 5.

Compared to asymptomatic control subjects, patients with a rotator cuff tear had a significantly lower mean SWS in the supraspinatus muscle (p = 0.024) and intramuscular tendon (p = 0.012) when shear wave elastography images were acquired under active testing conditions.