the investigators are interested in assessing the feasibility and value of brachial plexus block at the level of the humeral head in children. As a first step, the investigators propose to carry out a sono-anatomical study to describe the plexus at this level, the distribution of nerves in relation to the axillary artery, and the description of bone and muscle structures.

Brachial plexus blocks below the clavicle provide anesthesia and analgesia of the upper limb for elbow, forearm and hand surgery. Among the techniques described, axillary and costo-clavicular blocks are most frequently used.

In the axillary approach to the brachial plexus, the ulnar, median and radial nerves are in the direct vicinity of the axillary artery. However, there is considerable variability in the location of these nerves . What's more, the musculocutaneous nerve is most often distant from the other nerves of the plexus. These disadvantages are not encountered with the costo-clavicular technique, in which the nerves are brought together in the same diffusion space. On the other hand, this method does run the risk of pneumothorax and anesthesia of the phrenic nerve.

In this context, the investigators have described the brachial plexus block at the level of the humeral head in adults, which enables practicians to work on nerves gathered around the axillary artery without any risk of phrenic or pulmonary damage4.

In children, Small et al described a supra-clavicular approach, but Clayton et al, noting the high risk of pneumothorax, strongly advocated the axillary approach.

Inclusion Criteria:

• patient ASA 1-2
• aged 0 to 10 years
• scheduled surgery
• parental consent obtained

Exclusion Criteria:

• Parental refusal to participate
• suspicion of local skin infection
• inability to place the limb in the position required for sonographic examination
• Upper limb malformation
• ASA III, IV
• Major surgery (cardiac, neurosurgery...)
• emergencies

The study will be carried out in 100 children aged 0-10, divided into 5 groups of 20: 0-2 years, 2-4 years, 4-6 years, 6-8 years and 8-10 years. After obtaining informed consent from parents, patients will be included in the study according to inclusion and exclusion criteria. Sonographic observations and measurements will be performed during narcosis, if possible, without delaying or interfering with surgery. No puncture will be performed.