[The relation of the short radial extensor muscle of the wrist with the deep branch division of the radial nerve. Its significance in the physiopathology of elbow pain].

Since Roles and Maudsley's publication, in 1972, it has been admitted that the entrapment of the posterior interosseous nerve (PION) is a possible cause of lateral elbow pain. In the radial tunnel, at least 4 or 5 compressive structures have been described. The arcade of Frohse is a well known compressive cause while the medial edge of the extensor radialis brevis (ECRB) muscle is less frequently incriminated. An anatomic study of 45 supper limbs from 40 cadavers was performed to analyse the relations between the medial edge of the ECRB and the PION. The medial edge of the ECRB was a real fibrous arch in 43 cases (95%). It crossed over the PION in 42 cases, 9 mm more proximally than the arcade of Frohse. So the relationships between the ECRB and PION are very close in 93% of cases. The proximal edge of the supinator muscle was fibrous in 40% of cases but always supple. These findings suggest that the ECRB is a possible cause of PION entrapment. Its role is underestimated in pathology. The frequent association between lateral epicondylitis and PION compression can be explained by the presence of this fibrous structure. Lateral elbow pain must be considered as a regional pathology. The treatment has to deal with every pathological aspect.