A problematic variation of the palmaris profundus muscle

During the routine dissection of a 77-year-old male, researchers identified a variation of the palmaris profundus muscle (PP), an atypical accessory muscle of the forearm as recently described by McClelland (2012) [1]. In this cadaver, the PP was identified bilaterally in the absence of palmaris longus. Proximally the PP had two tendinous slips that attached on the interosseus ridge of the radius with the radial head of the flexor digitorum superficialis (FDS) muscle. Additionally, PP had a broad aponeurotic proximal attachment to the deep surface of the radial head of pronator teres (PT). Distally the PP muscle travelled with the median nerve beneath the transverse carpal ligament before investing in the deep palmar aponeurosis. To our knowledge this is the only case report of palmaris profundus with a dual tendinous proximal attachment with FDS and PT involvement. In this variation of PP there is potential for compression of the median and/or anterior interosseus nerves proximally as well as the median nerve distally. As a result, this variation of PP should be of interest to clinicians and surgeons.