Nonabsorbable Suture Knot on the Tendon Affects Rotator Cuff Healing: A Comparative Study of the Knots on Tendon and Bone in a Rat Model of Rotator Cuff Tear

Background: Nonabsorbable suture knots are usually used to link the tendon and bone during rotator cuff repair surgery. There are many variations in the arthroscopic knot-tying technique; however, the location of suture knot placement for rotator cuff healing has rarely been studied.

Hypothesis: The authors compared the rotator cuff healing between knots tied on tendon and bone in a rotator cuff tear rat model. It has been hypothesized that knots can cause chronic inflammation and create the weakest link between tendon and bone, thus affecting rotator cuff healing.

Study design: Controlled laboratory study.

Methods: Bilateral supraspinatus tenotomy and rotator cuff repair at the greater tuberosity were performed on 24 Wistar rats. Nonabsorbable surgical suture knots were made on the right supraspinatus tendon tissue and left humerus inferior to the greater tuberosity, respectively. Twelve rats each were sacrificed at 3 and 9 weeks. Six of the 12 rats were used for biomechanical testing and the remaining 6 for histologic evaluation.

Results: The surgical knots placed on the bursal side of the tendon migrated to the articular side, as noted on gross observation in 22 of 24 samples. The knots on the tendon group showed significantly inferior tendon-bone integration and significantly inferior biomechanical results in terms of maximum load to failure and stiffness. An obvious chronic foreign body inflammatory reaction was found in the knots on the tendon group at 3 and 9 weeks. Furthermore, inferior bone-tendon interface regeneration and weakest link formation were obtained in the knots on the tendon group compared with those on the bone group.

Conclusion: Nonabsorbable suture knots placed on the tendon migrate to the articular side, causing chronic inflammation and weakening tendon-bone healing, which may explain some retears after rotator cuff repair.

Clinical relevance: The present animal study suggests that it is not recommended in clinical practice to make several bulky nonabsorbable suture knots on the rotator cuff tendon during rotator cuff repair surgery. It may be better to tie the knots at the bone side or do knotless repair.