In vivo strain analysis of the intact supraspinatus tendon by ultrasound speckles tracking imaging.

Limited data exist regarding why delaminated tears occur within the rotator cuff tendon, and no general agreement exists on how to handle this complicated tear. To analyze in vivo intratendinous strain of the supraspinatus tendon, the superficial, middle, and deep regions were marked with speckles using 2D speckle tracking echocardiography (2D STE) of 15 shoulders. The displacement and the strain of each speckle during isotonic and isometric shoulder motion were evaluated. Significantly different displacement and strains in the tendon were found between isometric and isotonic shoulder motions. In isometric motion, the average longitudinal displacement of the speckle at the superficial region (1.66 mm) was larger than at the deep region (0.61 mm), and the average peak strain at the superficial region (17.03%) was also higher than that at the deep region (3.42%). Conversely, in isotonic motion, the average longitudinal displacement of the speckle at the superficial region (0.70 mm) was less than that at the deep region (1.61 mm), and the average peak strain at the superficial region (4.73%) was also lower than that at the deep region (15.69%). A different strain was found between the superficial and deep regions within the intact live supraspinatus tendon. The strain and displacement patterns vary according to isometric versus isotonic shoulder motions. On the basis of our observations, we suggest that the delaminated tear of the rotator cuff tendon must be repaired separately layer by layer to resist the inhomogeneous strain after the repair.