BackgroundThe most common complication of arthroscopic rotator cuff repair is retear, which is more common in larger tears and older patients. We hypothesized that the quality of the torn tendon is important in protecting against retear. Surgeons have traditionally assessed the quality of repaired tendons with a four-point Likert scale. Shear Wave Elastography Ultrasound (SWEUS) is a recent technological advancement that can quantify soft-tissue stiffness. This study aimed to determine how closely a surgeon’s intraoperative ranking of tissue quality during rotator cuff repair correlated to postoperative supraspinatus tendon stiffness measured by SWEUS.MethodsThis was a prospective case series on 50 patients undergoing arthroscopic rotator cuff repair, involving SWEUS measurements of each patient’s supraspinatus tendon at 8 days, 6 weeks, 12 weeks, 6 months, and 12 months. The intraoperative surgeon score of tissue quality for each patient was ranked on a four-point Likert scale. Each patient’s scores were compared to postoperative SWEUS velocity measurements of the supraspinatus tendon postrepair.ResultsThe SWEUS determined stiffness of supraspinatus tendons at their repaired insertion site postrepair increased by 22% from 6.3 ± 0.2 m/s to 7.7 ± 0.3 m/s over 12 months as the tendons healed (P= .0001). Supraspinatus tendon stiffness was greater in patients with smaller tears (r= −0.50,P= .001) and of younger age (r= −0.58,P= .00001). Surgeons also consistently rated younger patients (rs= −0.49,P= .0001) and smaller tears (rs= −0.56,P= .00001) as having superior intraoperative tendon quality. The correlations between SWEUS velocity and surgeon tissue quality rankings were modest at best and strongest at 12 weeks (rs= 0.27,P= .04). There were modest associations between SWEUS tendon stiffness and surgeon tendon mobility rankings at 6 weeks (rs= 0.26,P= .04) and repair quality rankings at 12 months (rs= 0.36,P= .02).ConclusionsThese data support the finding that machines (SWEUS) are better at assessing torn rotator cuff tendon quality and whether that tendon will heal after repair than the ‘person’ performing the surgery. Supraspinatus tendons lose stiffness as they get older and when the tear is larger, likely explaining why retear post-cuff repair is more common with advanced age and larger tears.