Anatomic study of the extensor carpi radialis brevis in its relation with the motor branch of the radial nerve

IntroductionThe cause of the tunnel syndrome is the entrapment of the posterior interosseous nerve, and can occur due to different anatomic structures, the arcade of Frohse being the main one of them.PurposeTo describe the anatomic relation between the extensor carpi radialis brevis (ECRB) muscle and the motor branch of the radial nerve at its entrance under the arcade of Frohse.Materials and methodsAn anatomic dissection of 21 elbows of fresh human cadavers was conducted, describing the deep aponeurosis and the superomedial tendinous arch of ECRB and its relation with the motor branch of the radial nerve.ResultsIn 100% of the specimens, there was evidence of an aponeurosis in the undersurface of ECRB. A tendinous arch at the superomedial margin of ECRB was found in 20 cases (95.2%). In 71.5%, this arch surpassed proximally the arcade of Frohse on an average of 4.5 mm (2–10 mm); it passes in direct contact with the motor branch of the radial nerve.ConclusionsThe extensor carpi radialis brevis muscle courses in a close relation to the motor branch of the radial nerve at its entrance under the arcade of Frohse, and it demonstrates an aponeurosis at its undersurface and a tendinous arch at its medial edge that could play an important role in the development of the radial tunnel syndrome.Level of evidenceLevel IV. Anatomic research study.