Clinical outcomes and tendon lengthening after arthroscopic rotator cuff repair.

Background: There is a phenomenon in which the tendon appears to increase the length after rotator cuff repair. However, it is unclear in which cases tendon lengthening occurs and how the degree of lengthening affects the surgical outcome. This study aimed to evaluate preoperative and postoperative musculotendinous junction (MTJ) and tendon length on magnetic resonance imaging and assess the postoperative tendon lengthening and its impact on postoperative outcomes.

Methods: We reviewed 109 patients with good repair integrity after arthroscopic rotator cuff repair. Patients whose supraspinatus tendons were simply pulled out laterally without any additional procedures were included. They underwent serial magnetic resonance imaging before surgery and at 3, 6, and 24 months after surgery. The location of the MTJ in relation to the line of the glenoid fossa and the supraspinatus tendon length were measured. Clinical evaluation was conducted 2 years after surgery, including the range of shoulder motion, shoulder strength index (affected/unaffected strength), Constant score, University of California, Los Angeles score, and pain numeric rating scale. The characteristics of the preoperative tendon, change in tendon length over time, amount of the lateral shift of MTJ location and tendon length, and impact of tendon lengthening on postoperative clinical outcomes were analyzed.

Results: The preoperative tendon retraction significantly correlated with the MTJ location (r = -0.75; P < .0001) and preoperative tendon length (r = -0.46; P < .0001). The tendon length at 3, 6, and 24 months after surgery was significantly longer than those before surgery (26.7 ± 5.8 mm, 27.9 ± 6.6 mm, 28.5 ± 5.6 mm, and 21.5 ± 5.1 mm, respectively). From before surgery to 24 months after surgery, the MTJ location moved 8.4 ± 8.6 mm laterally and the tendon length increased 7.0 ± 6.1 mm. A significant and weak negative correlation was found between tendon lengthening and the abduction strength index (r = -0.22; P = .03); however, no significant correlation with pain, range of shoulder motion, external rotation strength index, Constant score, and University of California, Los Angeles score was found. Multiple linear regression analysis also showed that tendon lengthening was only associated with the abduction strength index (standardized coefficient = -0.20, P = .03).

Conclusions: Tendon lengthening and lateral shift of MTJ location were observed after arthroscopic rotator cuff repair, and they correlated with preoperative tendon retraction. Although the amount of tendon lengthening had negative weak correlation with abduction strength index, it did not affect other postoperative outcomes.