In clinical practice, local anesthetic injection pressure monitoring is performed manually or by a pressure transducer according to the availability of the equipment or preferences of clinicians. To date, no comparative study has measured the advantages of this measure during PNB.

The aim of this study is to evaluate injection pressure monitoring in order to reduce the risk of intraneural injection during peripheral nerve blocks

Current recommendations for peripheral nerve block (PNB) procedure advocate combining ultrasound guidance and nerve stimulation.

Despite these different means of identification, nerves contacts and intraneural injection are frequent. Even rare, nerve damage may occur.

The nerve damage may be related to direct trauma with the needle or inadvertent intra-neural injection. High injection pressure of local anesthetic (AL) is an indicator that further characterize the location of the needle in terms of tissue density. In clinical practice, local anesthetic injection pressure monitoring is performed manually or by a pressure transducer according to the availability of the equipment or preferences of clinicians. To date, no comparative study has measured the advantages of this measure during PNB.

The aim of this study is to evaluate injection pressure monitoring in order to reduce the risk of intraneural injection.

Group 1: ultrasound-guided technique PNB "in plane" needle approach, nerve stimulator set to sentinel mode. Manual injection pressure control Group 2: ultrasound-guided PNB, "in plane" approach, Nerve stimulator set to detection mode. Electronic Injection Pressure controlled with low flow local anesthetic during procedure

Inclusion Criteria:

• Adult patient
• Orthopedic surgery

Exclusion Criteria:

• Allergy to local anesthetics
• ASA score >III
• Severe neuropathy
• puncture site disease
• parturient or breastfeeding