Bilateral reversed palmaris longus muscle: a case report and systematic literature review

Abstract

Purpose We present a case of a bilateral reversed palmaris longus muscle and a systematic review of the literature on this anatomical variation. Methods Routine dissection of a 90-year-old male cadaver revealed a rare bilateral reversed palmaris longus. This was documented photographically, and length and relation to anatomical landmarks were recorded. This finding stimulated a systematic review of the literature on the reversed palmaris longus variation, from which measurements were collated and statistical analysis performed to determine the prevalence, average length, relationship to side and sex, and to discuss its clinical and evolutionary implications. Results The average length of the muscle belly and tendon of reversed palmaris longus was 135 mm and 126 mm, respectively. Statistical analysis revealed no disparity in presentation due to sex and side; however, bilateral reversed palmaris longus has only been reported in males. A high proportion (70.8%) of reversed palmaris longus were discovered in the right upper limb compared to the left. Conclusion Variations in palmaris longus are purported to be as a result of phylogenetic regression. Clinically, patients with this variant may present with pain or swelling of the distal forearm, often as a result of intense physical exertion related to occupation or sport. Clinicians should be aware of this muscle variant as its presence could lead to confusion during tendon allograft harvesting procedures in reconstructive and tendon grafting surgery.

Morphometric study and occurrence of the palmaris longus muscle in human fetuses

“…Variations of the PLM anatomy are generally believed to be asymptomatic; however, several authors have described that the PLM inversion could cause symptomatic compression of the median nerve. [27][28][29][30] Knowing this variation, we could avoid unsuccessful surgical explorations in the diagnosis of conditions such as carpal tunnel syndrome 3 and Dupuytren's disease, which is a pathological condition with fibrous degeneration in the longitudinal superficial layer of the palmar aponeurosis. 31 In addition, the PLM tendon is used as a landmark to locate the underlying median nerve for surgical procedures, 4 as well as being used as a graft in a large number of surgical procedures, such as chronic flexor tendon injuries, ligament reconstruction, pulley reconstruction, eye defects, blepharopitosis and other surgical reconstructions.…”

Clinical Significance of a Duplicated Palmaris Longus Muscle with One Reversed Muscle: A Case Report

“…Despite having a PL variation, the vasculature and innervation of the muscles were normal, consisting of branches of the ulnar artery and the median nerve, respectively [12].…”

A Cadaveric Study of Palmaris Longus Muscle

“…Palmaris longus is described as a slender superficial flexor muscle of the forearm. [1] The muscle belly is fusiform in shape which takes origin from the anterior surface of medical epicondyle of humerus in common with the other superficial flexor muscles of forearm, just medial to flexor carpi radialis muscle. [2] It converges to form a long tendon, which passes superficial to flexor retinaculum and then the tendon broadens out to form a flat sheet which gets attached to the apex of palmar aponeurosis.…”