Prevalence and clinical implications of the Gantzer's muscle

The Gantzer's muscle is considered to be the accessory head of the flexor pollicis longus. The prevalence of the Gantzer's muscle and its anatomical relations vary in the literature. So, we aimed to study its prevalence and anatomical relations on a broad population on magnetic resonance (MRI) and ultrasound (US) images.

We investigated a total of 473 upper extremities of 378 people (171 women, 207 men), aged between 18 and 73 years, by MRI and US. We investigated the prevalence and length of the Gantzer's muscle and its anatomical relationship with the median (MN) and anterior interosseous nerves (AIN).

Of the 473 extremities, 96 had Gantzer's muscle (20.3%). Overall prevalence of the Gantzer's muscle was 21.9% (51 in 232) in women and 18.7% (45 in 241) in men. In the population we performed US, Gantzer's muscle was located 40.0% in only the right limb, 37.1% in only the left limb and 22.9% bilaterally. All the Gantzer's muscles originated from the coronoid process. Of the 43 Gantzer's muscles seen in US, thirty-four (79.1%) were attached to flexor pollicis longus and nine (20.9%) were attached to flexor digitorum superficialis. The mean length of the Gantzer's muscle was 29.7 (range 17.2-44.5) mm. MN was anterior to the Gantzer's muscle in all extremities except ten. In all extremities, AIN was located posterior to the Gantzer's muscle.

Although it is seen at a rare rate of 20.3%, Gantzer's muscle should be considered in MN and AIN compressions due to its close proximity to these nerves.