The suprascapular nerve innervates the musculi supra- and infraspinatus, which, as part of the rotator cuff, allow lifting and external rotation in the shoulder joint. Damage to this nerve can lead to pain and functional deficit. Causes of injury are compression by bony / ligamentous anomalies, fracture sequelae and traction damage. In the literature, a (often subclinical) traction damage is increasingly claimed by a muscle retraction after rupture of the supra- and / or infraspinatus tendon as a cause of pain and functional disturbances. The retraction of the ruptured tendon-muscular unit is said to lead to traction damage of the nerve, which can be demonstrated by pathological EMG derivations. By repositioning the tendon to its outbreak site, the nerve is occasionally overstretched, so that individual authors propagate a routine nerve decompression as prophylaxis. In individual cases, a previously pathologic EMG result could be improved after reconstitution of an rotator cuff rupture. However, prospective studies are not available.

It is not known how often a nerve damage is present before a rotator cuff operation and it is not known how often the tendon repair leads to nerve damage or recovery of damage. It is not known whether the surgical nerve decompression is associated with reduced postoperative pain and what a profit or what risks bring about a routine decompression of the nerve to the patient. To answer this question, this prospective randomized study is to be carried out.

On the basis of preoperative electromyography (EMG) and electroneurography (ENG), the investigators would like to determine the frequency of suprascapular neuropathy in ruptures of supra- and / or infraspinatus tendons and the risk factors for their presence.

In a ruptured rotator cuff, the muscle is partly retracted so much that the innervating nerve (suprascapular nerve) is stretched and has pathological neurological findings. The Investigators now want to analyze how the arthroscopic reconstruction of the nasal suprascapular nerve affects the pre-operative neuropathy. Does the pre-existing nerve recover by decompression (liberation) from surrounding / entangling tissue or does decompression have no influence on measurable neurology? Other patients with rotator cuff ruptures have normal neurological findings preoperatively despite severe retraction of the muscular / tendon unit. In these cases, the investigators are interested in whether the mobilization and reconstruction of the torn muscle / tendon unit leads to a neurologically measurable elongation of the nerve. This nerve stretching is a possible explanation for protracted postoperative pain. With the postoperative electrophysiological measurements we can quantify this nerve change.

The comparison between preoperative and postoperative neurology findings allows confirmation or refutation of our hypothesis.

Inclusion Criteria:

• Informed Consent
• MRI diagnosis of partial or full thickness rotator cuff tear

Exclusion Criteria:

• Previous surgery
• Fatty muscle infiltration Goutallier stages III and IV
• Diabetes mellitus
• pregnancy
• unwillingness or contraindications for Magnetic resonance imaging
• unwillingness or contraindications to electrophysiological assessment
• substance abuse