Accessory muscle in the forearm: a clinical and embryological approach

Abstract

Muscular variations of the flexor compartment of forearm are usual and can result in multiple clinical conditions limiting the functions of forearm and hand. The variations of the muscles, especially accessory muscles may simulate soft tissue tumors and can result in nerve compressions. During a routine dissection of the anterior region of the forearm and hand, an unusual muscle was observed on the left side of a 65-year-old male cadaver. The anomalous muscle belly arose from the medial epicondyle approxiamately 1 cm posterolateral to origin of normal flexor carpi ulnaris muscle (FCU), and from proximal part of the flexor digitorum superficialis muscle. It inserted to the triquetral, hamate bones and flexor retinaculum. Passive traction on the tendon of accessory muscle resulted in flexion of radiocarpal junction. The FCU which had one head, inserted to the pisiform bone hook of hamate and palmar aponeurosis. Its contiguous muscles displayed normal morphology. Knowledge of the existence of muscle anomalies as well as the location of compression is useful in determining the pathology and appropriate treatment for compressive neuropathies. In this study, a rare accessory muscle has been described.

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

“…A subsequent review of 5,000 cadaveric dissections of the forearm did not identify any such variations related to FCU (ANG, ROZEN, VALLY et al, 2010). Ciftçioğlu, Kopuz, Corumlu et al (2011) reported an unusual muscle on the left side of a 65-year-old male cadaver. The anomalous muscle belly arose from the medial epicondyle approximately 1 cm posterolateral to the origin of the normal FCU muscle, and from the proximal part of the FDS muscle.…”

Hypertrophic reversed palmaris longus muscle: a cadaveric finding

“…One of the main theories is that those masses begin to differentiate into the muscles through apoptotic mechanisms and growth factors, thus, giving shape and appearance of the muscles [5,18].…”

Notes on the Accessory Flexor Carpi Ulnaris Muscle: A Rare Supernumerary Variation

“…Furthermore, The aFCUM may simulate a ganglion or a soft tissue tumor. 2 The ulnar artery could also be a target to compression, as the presence of more muscle mass in the fascial compartment would cause more pressure on this vessel, thus, provoking a decreased local blood flow either during forearm flexion or even in stationary position. 15 The clinical diagnosis of an accessory muscle belly should be kept in mind when there is a soft and palpable mass at the wrist associated with flexion deformities, albeit not a constant symptom.…”

“…Hence the importance of reporting anatomical variations to provide knowledge and further expand the surgeon's awareness. 2,3 Furthermore, the FCUM has been used as local and free muscular flap in soft-tissue reconstruction surgery, as well as in tendon transfer procedures. 5 As the tip of the olecranon has a thin and movable skin, postoperative complications of total elbow arthroplasty are not uncommon.…”

“…The flexor carpi ulnaris muscle (FCUM) originates from two slips: one from the olecranon and another from the medial epicondyle of the humerus; these muscle bands fuse and forms a fleshy muscle with a strong tendon that inserts itself onto the pisiform bone. 1,2 The FCUM is innervated by the ulnar nerve (UN), which lies between these fasciculi before they fuse, and it is accompanied by the posterior ulnar recurrent artery. FCUM allows the hand to flex over the forearm and has a slight adductor function.…”