THE STRUCTURE OF HUMAN ACHILLES TENDON AND ITS BIOMECHANICAL SIGNIFICANCE

Abstract

The morphological characteristics, particularly the rotation structure, of human Achilles tendon were investigated on 21 I lower limb specimens 101 Achilles tendons of male adult specimens were measured The structure, function and biomechanical properties of the tendon, as well as inter-individual differences in tendon rotation and morphological indicators of tendon injury have been discussed The tendon fibers of two muscle groups (gastrocnemius and soleus) intersect each other in a rotating manner. This rotation is from medial to lateral The rotation starts at 12-15 cm above the calcaneum but becomes most obvious at approximately 5 cm above h e calcaneum. The degrees of rotation vary in every body and were divided into 3 types: light, medium and heavy. The percentage of h e 3 types of rotation are 58.29f 3.39, 3270f 3.23,9.01f 1.86, respectively. No significant deferences were found between two distinct sexes, sides, age-groups or races. The tendon length, upper-width,lower-widthand lower-thickness of adult Chinese males are 19.77f 0.246.58f 0.18, I.5Of Q04,0.68f 0.01 cm, respectively. The tendon rotation structure has some biomechanical implications for he tendon's adaptation lo the tremendous tractive forces developed during special situations Along with common factors known to result in tendon injury, we believe structural weakness to be one of the most important factors resulting in tendon injury. Common weaknesses in morphological structure are: the most avascular part of the tendon (approx. 44 cm above insertion), which is the most obvious position of rotation; the presence of a large number of Type 111 collagen in the tendon; he light rotation pattern of this tendon among the great majority of human beings; and the damage caused by Le saw-like action between h e two parts of tendon fibers In addition, owing to the two-joint (knee and ankle) spanning of the gastrocnemius, a stretched tendon will develop even greater tension and easily tear when the quadriceps muscle group contracts strongly during knee extension.