The Effect of Medial Knots on Footprint Contact and Self-Reinforcement in TOE Rotator Cuff Repair

Abstract

Transosseous-equivalent (TOE) rotator cuff repair has been shown to demonstrate a self-reinforcing effect, providing a protective mechanism in the face of potentially destructive forces. A variant, which uses tape-type sutures, has been performed clinically with and without medial row mattress knots. This study assessed the effect of medial row knots at the tendon-footprint interface. In 8 fresh frozen human shoulders, TOE supraspinatus repairs using tape-type sutures with (knotted) and without (knotless) two medial row mattress knots were performed in each specimen. A Tekscan pressure sensor was fixed at the tendon-footprint interface prior to all repairs. Parameters included footprint contact force, area, pressure and peak pressure. The supraspinatus tendon was loaded with 0, 15, 30, 45, and 60 N at 0° and 30° abduction, with 0° humeral rotation. Medial row knots did not significantly change footprint contact force, area, pressure, or peak pressure under all conditions. The knotted repair had increases in footprint contact pressure with increasing load at both abduction angles. The knotless repair demonstrated the same relationships for footprint contact pressure with increasing load. This relationship was also seen for footprint contact force for both repairs. With increasing load, the knotless repair had a significantly higher progression (slope) of footprint force and pressure (P < 0.05). There is no measurable change in tendon-footprint contact force, area, pressure, or peak pressure with the addition of medial row knots at both abduction angles. In addition, the lower progression (slope) of footprint force and pressure seen with the addition of medial row knots demonstrates that they can inhibit the self-reinforcing effect of the TOE repair. Knotless TOE repair using tape-type sutures may provide superior tendon-footprint interface characteristics and improve healing potential under post-operative conditions, while avoiding the risk of medial over-tensioning, strangulation, and catastrophic failure at the medial tendon.