ANATOMICAL ANALYSIS OF GANTZER'S MUSCLE AND ITS POTENTIAL NEUROPATHIC CONSEQUENCES: A CASE REPORT

Context: The flexor compartment of the forearm is prone to anatomical variations, including Gantzer's muscle (GM) — an accessory head of the flexor pollicis longus (AHFPL). GM is an inconstant muscle innervated by the anterior interosseous nerve (AIN), exhibiting a widely varying prevalence (0.5-89%). It frequently originates from the medial epicondyle of the humerus or the coronoid process of the ulna, often inserting into the flexor pollicis longus tendon. Detailed knowledge of GM is vital due to its potential for nerve compression, which can lead to AIN neuropathy or Kiloh-Nevin Syndrome, clinically manifested by the inability to form the "Spinner's Sign." Objective: This study aimed to report the occurrence of a Gantzer's muscle (AHFPL), describing its morphology and morphometry in a specific case. Case Report: During a routine dissection of the left forearm of a 65-year-old male cadaver, a GM was identified originating from the medial epicondyle of the humerus and the lateral aspect of the flexor digitorum superficialis fibers. It presented with an initial triangular portion and a fusiform muscle belly (63.57 mm in length, 10.61 mm in width), inserting into the flexor pollicis longus tendon via a rectangular tendinous slip (29.80 mm in length, 3.47 mm in width). Its dimensions, especially the width of the belly and the length of the distal tendon, were greater than the average values reported in the literature. Conclusion: In-depth knowledge of GM morphometry, morphology, and topographic relationships is crucial for clinical and surgical practice. Such understanding allows for anticipating complications, optimizing procedures (such as fasciotomies), and improving the differential diagnosis of nonspecific hand pain and neuromuscular dysfunctions, thereby ensuring a safer and more precise diagnostic and therapeutic approach.