Deficits of Strength of the Rotator Muscles of the Shoulder in Children

The purpose of this retrospective work is to study the consequences of obstetrical brachial plexus paralysis on the rotator muscles of the shoulder. First of all, the investigators want to study the reproducibility of the isometric contraction forces of the rotator muscles of the shoulder thanks to an isokinetic dynamometer. The investigatorsthen want to compare the measurements obtained from the paralyzed side compared to the healthy side. The preoperative MRI performed will be studied in search of amyotrophy. These data will be compared with those of the isokinetic assessment to identify children requiring muscle transfer of reinforcement of the external rotator muscles.