What causes internal stitches of a rotator cuff to come out?

Tendon quality: Poor tendon quality or degeneration accounts for the majority or suture pull- out. Some can also be attributed to surgical technique. Failure to mobilize the tendon before repair, too much tension on the repair, or an insufficient number or pattern of suturing can lead to repair failure.

Poor tissue quality: Rotator cuff repairs can fail in many ways. More commonly this is due to poor tissue quality in the tendon itself. Repair using sutures is dependent on the tendon tissue being strong enough to hold the sutures. The tendon can simply put out of the sutures. In similar fashion the suture anchor or suture can pull through the bone because the bone is not strong enough.