Carpal tunnel syndrome and compression of the ulnar nerve at the elbow are common pathologies, which are treated surgically.

Diagnosis is usually based on an electromyogram (EMG), as well as symptomatology, etiology of typical symptoms and an evocative clinical examination. Provocative tests performed in consultation include the Tinel and Phalen sign for the carpal tunnel, and the Tinel and prolonged flexion sign for the ulnar nerve at the elbow.

The Scratch Collapse Test (SCT) has recently emerged as a new provocation test to help diagnose nerve compression in the upper limb.

This non-invasive, pain-free test looks for a reduction in the force of external rotation of the shoulder by applying resistance (the doctor's arm), before and then after a sensory stimulus by "scratching" the area of compression. Nevertheless, this test remains controversial and not based on objective measurements.

Our aim is therefore to assess shoulder external rotation force, and thus TBS, objectively with a dynamometer, before and after stimulation in cases of median nerve compression syndrome at the carpal tunnel and ulnar nerve compression syndrome at the elbow, when these are clinically and electromyographically proven.

This test has already been studied in the literature, but the results in terms of sensitivity and specificity are highly disparate. One study has already published negative results on the subject, with the limitation that the trial was monocentric.

Through this multicenter study, principal investigator wish to highlight the very probable subjectivity of the SCT when it is performed. As the resistance is applied by the physician's arm, the investigator cannot determine the force applied against the patient, unlike with a measurement object. The principal investigator expects this study to refute the notion that external shoulder rotation force decreases after trigger zone stimulation in cases of proven nerve compression syndrome.

The results of this study will thus make it possible to discontinue the use of this technique if it does not help in the diagnosis of compression.

The literature shows a lack of prospective, objective studies involving a large number of patients.

Inclusion Criteria:

• Patient affiliated or entitled to a social security plan
• Patient who has received informed information about the study
• Patient of legal age
• Patient with ulnar nerve or carpal tunnel compression confirmed by EMG during preoperative consultation

Exclusion Criteria:

• Recurrence of nerve compression
• Any history that may affect arm sensitivity
• Infra-electromyographic nerve compression syndrome (pure ulnar nerve instability)