Variant plantaris muscle with degenerated accessory head: Gross and histological analysis

Brianne A. Futa, Łukasz Olewnik, Marko Konschake, Juan J. Cardona, Joe Iwanaga, Paloma Aragones, Jose Sanudo, R. Shane Tubbs

The variant plantaris muscle has itself been reported to have variable presentations. Here, we report an unusual finding of the plantaris muscle and report its gross and histological findings. A duplicated head of the plantaris muscle was identified in the right leg of an adult cadaver age and sex. The more anterior head of the muscle was in the typical location and originated from the superolateral condyle of the femur. However, the more posteriorly located head arose from the iliotibial band at the level of the distal thigh. The two heads united and continued as the typical distal tendon of the plantaris muscle to insert into the calcaneus tendon (Achilles). The normally positioned head of the plantaris muscle was found to be composed of typical skeletal muscle fibres. However, the accessory head of the plantaris muscle was found to be severely degenerated and infiltrated with adipose tissue. We report a duplicated head of the plantaris muscle. Histologically, the accessory head was degenerated and infiltrated with adipose tissue. To our knowledge, this is the first report of such a case. Further cases are now necessary to further elucidate this finding.