An unusual variation of an additional plantaris originating from the soleus

Introduction The plantaris muscle belongs to the posterior superficial crural muscles in the anatomy of human’s body, which are subdivided into two groups as superficial and deep. It is placed between the gastrocnemius and soleus. Its origin is from the inferior part of the lateral supracondylar line of the femur at a position a little superior to the origin of the lateral head of gastrocnemius [1]. In some cases the plantaris may arise from the oblique popliteal ligament. It is composed of a small fusiform belly and a long thin tendon. The tendon runs along the leg in lower medial direction alongside the medial border of the tendo calcaneus and inserts into the posterior part of the calcaneus. Occasionally the tendon of the plantaris inserts into the tendo calcaneus. Very rarely its tendon is lost in the fascia of the leg. The functions of the plantaris are to support plantar flexion in the ankle joint and flexion in the knee joint. Plantaris has minimal motor function and its long tendon can readily be harvested for reconstruction elsewhere in the human body [1]. Due to our observation in the left lower limb from a cadaver that the additional muscle belly of the plantaris merged with the tendon of the main belly and inserted into the tendo calcaneus, the aim of this paper is to analyze and describe this rare and interesting finding. Case Report The cadaveric material was taken during a routine autopsy at the Department of Anatomy and Morphology, in accordant to the ethical principles applying by the Sofia’s Medical University. The anatomical variation was photographed using a Nikon Coolpix 995 camera, analyzed and described. The plantaris muscle is one of the posterior superficial muscles of the calf. The muscle arose from the posterosuperior aspect of the lateral femoral condyle a little more high to the origin of lateral head of gastrocnemius (Figure 1). The plantaris muscle was composed of a small fusiform belly and a long thin tendon. Posterior to the knee joint, muscle immediately run obliquely from the lateral one to the medial side. Then in the calf, the long thin tendon of the muscle lied in between the medial head of the gastrocnemius and soleus. Finally, the tendon inserted into the posterior part of the calcaneus medially of the tendo Achilles. Sometimes the tendon of the plantaris merges with the tendo Achilles. In our case we observed a very interesting variation of the additional plantaris originating from the soleus. This additional part of the plantaris muscle (actually a tendon) merged with the tendon of the main belly and inserted into the calcaneal tendon (Figures 2, 3). Manol Anastasov KALNIEV [1] Nikolay Stoyanov KRASTEV [1] Dimo Stoyanov KRASTEV [2] Milka Milcheva MILEVA [2, 3] Department of Anatomy and Histology, Medical University, Sofia [1], Department of Anatomy and Histology, College of Medicine “Jordanka Filaretova”, Medical University, Sofia [2], Department of Virology, The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences [3], Sofia, BULGARIA. Dr. Milka Milcheva Mileva Department of Virology The Stephan Angeloff Institute of Microbiology Bulgarian Academy of Sciences 26 Acad. G. Bonchev Str. 1113 Sofia, BULGARIA. +359 899 151 159 [email protected] Received July 31st, 2013; accepted April 7th, 2014 Abstract