A report on the accessory head of Flexor Pollicis Longus and Variations of Forearm Musculature

Abstract

Introduction: Gantzer's muscle has drawn attention from several authors owing to the possibility of interosseous nerve compression. This is a report of an accessory head of flexor pollicis longus (FPL, a variant of Gantzer's muscle) and a review of the variations of all muscles of the forearm. Materials and Methods: An accessory head of FPL was discovered in both the right and left antebrachial regions during a cadaver dissection. The muscle was dissected and photographed. Results: The anatomical variation I report is a slender conical muscle joining the FPL. Its origin merged with fibers of the flexor digitorum superficialis. It inserted into the upper part of the middle third of the forearm by joining the medial tendinous part of the FPL; this join was by means of a short cylindrical tendon. The reported muscle was innervated by the anterior interosseous nerve, which was seen to be present posterolateral to the muscle in both forearms. Conclusion: The described muscle might cause pressure problems to the underlying structures especially the anterior interosseous nerve. Variations must be considered during surgical intervention to avoid unintentional damage to healthy tendons. In addition, accessory tendons can potentially be useful in the repair or replacement of damaged tendons through surgical transfer or transplantation. Variations of muscles, especially accessory muscles, may mimic the behavior of soft tissue tumors and can result in nerve compressions. This collection of variations of the forearm musculature will be useful to surgeons in practice as well as students in dissection labs.

A Morphological Study of a Rare Variant of Gantzer’s Muscle

“…An incomplete AIN syndrome occurs where only the medial branch of the AIN to the FDP (which passes underneath the belly) is compressed, or the lateral branch to the FPL (which runs alongside the belly) is compressed. This results in the loss of function of only the FDP or the FPL [17]. However, in present study, FDPah, showed no direct contact with the median or anterior…”

A unique bilateral accessory forearm flexor muscle

“…Abundant literature also exists documenting different types of variant lumbricals, especially the lateral two [12,14,15,24]. Rarer variations, such as those associated with flexor carpi ulnaris (FCU) [4,18] and flexor pollicis longus (FPL) [8] have also been reported.…”