This study investigates one of the mechanism factors of neck pain. Cervical lordotic angle alterations affect the tension of serratus anterior muscle. Expected result that the long thoracic nerve can be affected in this situation, and could be observed the functional changes of the nerve with serratus anterior electromyographic findings.

Different methods exist in order to evaluate muscle function. For the neck pain, the most commonly used method by researchers and clinicians are spot radiography and surface electromyography (sEMG). Radiographs can be used for the kyphotic angle or cervical lordotic angle measurements. Parameters that can be studied by EMG are amplitude, timing, conduction velocity, fatigability and characteristic frequencies/patterns.

The long thoracic nerve innervates the serratus anterior muscle. This nerve arises from the anterior rami of three spinal nerve roots: the fifth, sixth, and seventh cervical nerves (C5-C7) The nerve descends through the cervicoaxillary canal behind (posterior to) the brachial plexus and the axillary artery and vein, resting on the outer surface of the serratus anterior. The Serratus anterior electromyography, the needle can be inserted into the muscle superficially to the fourth to sixth rib in the medial or posterior axillary line. The usual nerve latency time is between 2.6-4 ms.

In this study, the results of serratus anterior muscle EMG activity and postural cervical angle alterations (lateral radiography) in patients with chronic mechanical neck pain will be compared with healthy volunteers without neck pain.

Inclusion Criteria:

• Patient whose age is > to 18 years and <40 yo
• Patient presenting a chronic neck pain (symptoms over 3 months)
• No neurological deficit
• Asymptomatic volunteers (for control group)
• Obtaining the enlightened consent of the patient

Exclusion Criteria:

• Patient having refused to sign his consent
• Patients whose age is < to 18 years or >40 yo.
• Patients with neurologic deficits
• Patients presenting history of allergy
• History of cervical spine surgery
• Patient presenting an anticoagulant or salicylated treatment which can not be interrupted.
• Pregnant woman.
• Patient with acute head and neck trauma
• Patient with a contra-indication to radiography.
• Patient with a psychiatric pathology preventing a clinical evaluation.
• Patient with contra-indication (cutaneous or different) to needle electromyography.
• Surgery contra-indication (cardiac failure, respiratory…)
• Patient without health coverage.