Fascicles of the adult human Achilles tendon - an anatomical study.

The Achilles or calcaneal tendon is the structural base for the biomechanical work of the ankle joint. The purpose of this study is to describe the internal structure of the human Achilles tendon. The anatomy of the Achilles tendon has been described in lower mammals in which it has three parts which can be dissected from its beginning to the insertion onto the calcaneus. The partial ruptures of each part suggest that the human Achilles tendon may also be composed of parts. The Achilles tendon is one of the most commonly torn tendons in the human body. Each segment of the Achilles tendon described by us can be ruptured separately, which can cause a partial dysfunction in flexion of the ankle joint as observed in clinical practice. We dissected 20 Achilles tendons previously fixed in 10% formaldehyde and 20 fresh-frozen Achilles tendons, paying particular attention to the relationship between the lateral and medial heads of the gastrocnemius and the soleus muscles. The layer-by-layer method and a microscope were used in our study. We found that the medial group of fibers from the medial head of the gastrocnemius muscle constitutes the posterior layer of the tendon. The lateral border of the tendon is composed of the fibers from the lateral part of the medial head of the gastrocnemius muscle. The fibers from the lateral head of the gastrocnemius muscle constitute the anterior layer of the Achilles tendon. The fibers from the soleus muscle are located in the anteromedial part of the Achilles tendon. Our findings are supported by clinical descriptions and observations of the partial rupture of the Achilles tendon.