Influence of Intraoperative Repair Tension on Postoperative Healing of Full-thickness Rotator Cuff Tears

Relevant problems of rotator cuff repair: * High retear rate after rotator cuff repair of 13%, despite regard of the criteria for \"reparability\" of a tear. * Long and exhausting rehabilitation after rotator cuff repair with an abduction splint for six weeks. Hypothesis: The investigators believe that high tension repair has a higher retear rate than low tension repair, regardless of the tear size. The investigators also believe that abduction of the arm can reduce relevant tension on the repair. But not each repair benefits equally from this. Relevance of this hypothesis: The ingenious advantage of this new parameter (intraoperative repair tension) is, that it can be influenced. In future, if this hypothesis would be true, the repair tension could be reduced intraoperative by release, side-to-side (margin convergence) repair or medialization of the footprint and thereby convert a high risk to a low risk tension repair. Moreover, it could be that patients with a low tension repair does not necessarily have to wear an abduction splint. And on the other hand, high tension repair patients should probably wear the abduction splint longer with gradually reduction. Approach: The present research plan focused on a new intraoperative (arthroscopic) determinable parameter (\"repair tension\" on footprint in 0° and 40° abduction) to determine the risk of recurrence after tendon repair in rotator cuff tears, which are pre- and intraoperative defined as \"reparable\". Therefore, the tension of the repaired tendon is measured intraoperative with a spring balance (newtonmeter) and correlated with the postoperative retear-rate. • Measure intraoperative repair tension with the arm in 0° and 40° of abduction