Shoulder surgery is a source of intense postoperative pain that justifies the use of opioids. In this context, analgesia provided by locoregional anesthesia (ALR) improves the rehabilitation of patients by reducing the length of hospital stay and morphine consumption. Thus anesthesia of the brachial plexus interscalene (interscalene block or BIS) is considered as the reference technique for the management of post-operative pain after shoulder surgery. It is however provider of hemi-diaphragmatic paralysis (PhD) in nearly 100% of cases. Thus, this technique is usually avoided in patients with respiratory insufficiency. In arthroscopic shoulder surgery, the development of a suprascapular and axillary nerve (SSAX) conjugate block appears to be an effective analgesic alternative in this context.

Two ultrasound-guided approaches of the suprascapular nerve (anterior and posterior approaches) have been described in the literature. From an anatomical point of view, the anterior approach could expose patients to the risk of ipsilateral PhD by phrenic nerve block secondary to diffusion of the local anesthetic into the supraclavicular region.

By measuring the diaphragm excursion during a sniff test, ultrasound allows reliable and reproducible analysis of the diaphragm function.

No study has evaluated the incidence of PhD after ultrasound block of the suprascapular nerve. Knowing the influence of the approach on this complication could be of major interest in this context.

Inclusion Criteria:

• to benefit from scheduled arthroscopic surgery of the shoulder under general anesthesia
• Affiliate or beneficiary of a social security scheme
• Having signed the informed consent

Exclusion Criteria:

• the existence of contralateral diaphragmatic paralysis
• pre-existing respiratory insufficiency
• impossibility of performing diaphragmatic ultrasound
• the patient's refusal
• the existence of major spontaneous or acquired haemostatic disorders
• an infection at the point of puncture
• allergy to local anesthetics
• Pregnant or likely to be pregnant
• Patients under protection of the adults (guardianship, curators or safeguard of justice)
• Patients whose cognitive state does not allow assessment by the scales used