Repair of massive tears of the rotator cuff can be problematic. In some cases they are considered irreparable. Studies have been done trying different surgical methods of treatment for this problem. So far there hasn’t been a single type of surgery that works best.
For the most part the best approach seems to be cleaning up the damaged tendons. This is called debridement. Then the bone across the top of the shoulder (acromion) is removed. This is called an acromioplasty. If just the underside of the acromion is shaved, it’s called a subacromial decompression.
When any part of the rotator cuff is torn and can’t be repaired, an imbalance occurs at the shoulder. That’s why the rest of the rotator cuff can get impinged. Reducing or removing the acromion leaves room for the remaining tendons of the rotator cuff to slide and glide without getting pinched.
Other surgeries used to reconstruct massive rotator cuff tears include tendon transfers, fusion, and tendon grafting. No one method seems to have better results than the others.