PURPOSE: To investigate the alteration of passive stiffness in the supraspinatus 
muscle after double-row (DR) and knotless transosseous-equivalent (KL-TOE) 
repair techniques, using shear wave elastography (SWE) in cadavers with rotator 
cuff tears. We also aimed to compare altered muscular stiffness after these 
repairs to that obtained from shoulders with intact rotator cuff tendon.
METHODS: Twelve fresh-frozen cadaveric shoulders with rotator cuff tear (tear 
size: small [6], medium-large [6]) were used. Passive stiffness of 4 anatomic 
regions in the supraspinatus muscle was measured based on an established SWE 
method. Each specimen underwent DR and KL-TOE footprint repairs at 30° 
glenohumeral abduction. SWE values, obtained at 0°, 10°, 20°, 30°, 60°, and 90° 
abduction, were assessed in 3 different conditions: preoperative (torn) and 
postoperative conditions with the 2 techniques. The increased ratio of SWE 
values after repair was compared among the 4 regions to assess stiffness 
distribution. In addition, SWE values were obtained on 12 shoulders with intact 
rotator cuff tendons as control.
RESULTS: In shoulders with medium-large-sized tears, supraspinatus muscles 
showed an increased passive stiffness after rotator cuff repairs, and this was 
significantly observed at adducted positions. KL-TOE repair showed uniform 
stiffness changes among the 4 regions of the supraspinatus muscle (mean, 189% to 
218% increase after repair), whereas DR repair caused a significantly 
heterogeneous stiffness distribution within the muscle (mean, 187% to 319% after 
repair, P = .002). Although a repair-induced increase in muscle stiffness was 
observed also in small-sized tears, there were no significant differences in 
repaired stiffness changes between DR and KL-TOE (mean, 127% to 138% and 127% to 
130% after repairs, respectively). Shoulders with intact rotator cuff tendon 
showed uniform SWE values among the 4 regions of the supraspinatus muscle (mean, 
38.2 to 43.0 kPa).
CONCLUSIONS: Passive stiffness of the supraspinatus muscle increases after 
rotator cuff repairs for medium-large-sized tears. KL-TOE technique for the 
medium-large-sized tear provided a more uniform stiffness distribution across 
the repaired supraspinatus muscles compared with the DR technique.
CLINICAL RELEVANCE: Based on this insight, investigating rotator cuff muscle 
stiffness changes, further studies using SWE may determine the optimal repair 
technique for various sizes of rotator cuff tears.