Capsular attachment of the brachialis muscle (Portal’s muscle): an anatomical and functional study

There is a paucity of information regarding the detailed anatomy of the capsular part of the brachialis muscle in the extant literature. Our current study seeks to further elucidate the presence, morphology, and potential function of this muscle. Thirty-six cadaveric upper extremities underwent dissection of their anterior elbow joint capsule with special attention to any fibers attaching onto it from the brachialis muscle. We found that the majority of fibers of the brachialis simply passed superficial to the anterior elbow joint capsule. The highest concentration of fibers was noted to be onto the anteromedial joint capsule via connective tissue and not direct muscle attachment. No specimen was found to have a distinct muscle belly associated with these connections to the joint capsule. On all sides, such fibers were simply deeper attachments of the brachialis muscle. Following tension on these deeper fibers, retraction of the joint capsule was not noted. We would speculate, based on our study, that these fibers of the brachialis do not represent a separate muscle per se and do not retract the anterior elbow joint capsule with flexion of the forearm as has been theorized. These data may be of use to surgeons who operate this region so that attention to preservation of such fibers may be of less importance.