Pathoanatomic findings in radiohumeral epicondylopathy. A combined anatomic and electromyographic study.

Several authors believe that a compression syndrome of the radial nerve or its muscle branches is responsible for the clinical picture of radiohumeral epicondylopathy. Various structural and functional stenoses have been discussed as possible causes. We performed systematic electromyographies (EMGs) on the extensors subdividing from the radial epicondyle and found significant changes (P < 0.05) in 27/51 patients regarding latency, velocity of nerve conduction and rate of polyphasic potentials. Especially affected were the extensor carpi radialis brevis and the extensor digitorum muscle. In order to clarify causal anatomic correlations, we performed a longitudinal and cross-sectional study on a total of 40 arms from cadavers. We found constant variations from the topographic anatomy published in the standard literature which corresponded to the EMG results in the area between the epicondyle and place of entry into the supinator muscle. In addition, we observed a regularly occurring ulnar deviation from the distal part of the extensor carpi radials brevis origin which protrudes over the plane of insertion of the joint extensor tendon aponeurosis and forms in most cases the arcade of Frohse. Because the deep radial branch and its parallel muscular branches cross this part at an obtuse angle, we think that dynamic pressure on a nerve without structural influences is the pathoanatomic result of this heterogeneously interpreted clinical picture.