I 7 8 



Anatomy of Skeleton 



The anterior annular ligament is usually described as consisting of two bands, of which the 

 upper is a simple transverse thickening of the deep fascia in front of the lower part of the leg, while 

 the lower part, situated on the foot, is Y-shaped and on a deeper plane than the deep fascia. This 

 lower band is not simple : the single limb of the Y is really a strong loop that passes round the 

 extensor tendons of the digits and holds them from the outer side so that they do not slip inwards 

 when the foot is inverted, and the diverging limbs act simply as riding lines for the loop, holding 

 it in position as the tendons move, but not concerned in preventing any displacement of the tendons 

 (Fig. 146). 



From this description it follows that the loop must be strongly fastened externally, whereas the 



f.ltng 



FIG. 146.- Diagrams to illustrate the structure of the anterior 

 annular ligament. On the right the upper band is seen as a 

 simple strap, a., across the tendons, but the lower portion is a 

 strong loop, b., which holds most of the tendons so that they 

 cannot move out of position when the foot is turned in ; thus 

 this loop must be fastened on the outer side of the foot, and the 

 two " stays," c., which keep it from riding up and down, do not 

 require to be strong. A scheme of the arrangement as seen on 

 section is on the left ; observe that the loop is strongly fixed 

 to the os calcis and astragalus in the sinus tarsi, forming an 

 attachment continuous with the interosseous ligament. From 

 this region the loop passes over the astragalus to surround the 

 tendons, with the exception of the Tibialis anticus ; the vessels 

 and nerve lie deep to it. 



diverging bands need not be strong, and may go over or under the Tibialis anticus tendon ; frequently 

 one is superficial and the other deep to the tendon. The attachment of the loop, as seen in the 

 scheme, is to the os calcis and astragalus, and on the os calcis it is continuous with the origin of the 

 short extensor : the two structures appear to be developed from the same continuous mass of cells 

 in the embryo. The loop may surround the long extensor of the great toe as well as the common 

 extensor, with a septum between them, or this may be modified in degree so that the main loop 

 takes the common extensor and Peroneus tertius, and a secondary loop takes the extensor of the 

 hallux : there is no essential difference in the arrangement. All the tendons running through 

 the loop are in synovial sheaths ; the Tibialis anticus tendon is the only one that may have a 

 sheath as it passes under the upper or leg band, because it is the only one that may be purely 

 tendinous. 



The sustentaculum tali has the internal lateral ligament of ankle fastened to its 



