Anatomy of the Achilles tendon-Apictorial review.

Abstract

The Achilles tendon (AT) is the strongest tendon of the human body. The knowledge of AT anatomy is abasic prerequisite for the successful treatment of acute and chronic lesions. The structure of the AT results from acomplicated fusion of three parts: the tendons of the medial and lateral gastrocnemius and the soleus muscles. From proximal to distal, the tendon fibers twist in along spiral into aroughly 90° internal rotation. The tendon is narrowest approximately 5-7 cm above its calcaneal insertion and from there it expands again. The topography of the footprints of the individual AT components reflects the tendon origins. The anterior (deep) AT fibers insert into the middle third of the posterior aspect of the calcaneal tuberosity, the posterior (superficial) fibers pass over the calcaneal tuberosity and fuse with the plantar aponeurosis. Adeep calcaneal bursa is interposed between the calcaneal tuberosity and the AT anterior surface. The AT has no synovial sheath but is covered along its entire length with asliding connective tissue, the paratenon which is, however, absent on its anterior surface. The AT is supplied by the posterior tibial artery (PTA) and the peroneal artery (PA). Motor innervation of the triceps surae muscle is provided by fibers of the tibial nerve which also gives off sensitive fibers for the AT. Sensitive innervation is also provided via the sural nerve. The sural nerve crosses the AT approximately 11 cm proximal to the calcaneal tuberosity. The forces acting on the AT during exercise may be up to 12 times the body weight. Physiological stretching of AT collagen fibers ranges between 2% and 4% of its length. Stretching of the tendon over 4% results in microscopic failure and stretching beyond 8% in macroscopic failure.