A Systematic Temporal Assessment of Changes in Tendon Stiffness Following Rotator Cuff Repair.

Abstract

How the material properties of the human supraspinatus tendon change following arthroscopic rotator cuff repair is undetermined. Shear wave elastography ultrasound is a relatively new, noninvasive measure of tissue stiffness. We aimed to evaluate any temporal changes in stiffness and/or thickness of supraspinatus tendons in humans following primary arthroscopic rotator cuff repair. Shear wave elastography was performed at three predetermined regions by a single sonographer at 1-, 6-, 12-, 24-, and 52weeks postoperatively in 50 consecutive single-row invertedmattress primary arthroscopic rotator cuff repairs. One-way ANOVA with Tukey's correction and Spearman's correlation tests was performed. Of 50 patients, two retore by 1-week and were excluded. Two patients retore at 6weeks, two at 12weeks, and one at 24weeks. The mean tendonstiffness in 48 patients at the tendon footprint increased by 21% (1.32 m/s) at 6months (P < .001), with the lateral tendon stiffening before the medial tendon. Tendonthickness decreased by 11% (0.6 mm) at 6weeks (P=.008), then stabilized to 24weeks. Tendons that were less elastographicallystiff at 1 week were more likely to be thinner at 6-weeks (r=.38, P=.010). The data supports the hypothesis that rotatorcuff tendons repaired using the single-row inverted-mattress technique take 6weeks to heal to bone. Unlike inother tendons, there was no hypertrophic healing response. Prior to 6weeks, the tendon may stretch/thin-out, particularly if its material properties, as assessed by shear wave elastography, are inferior. The material properties of the tendon improved at the tendon insertion site first, then medially out to 12months post-repair.