BONES OF THE FOOT. 



343 



with a synovial membrane, which is only a 

 prolongation from that of the joint between 

 the astragalus and scaphoid. 



The chief bond of union between the as- 

 tragalus and os calcis is by means of the 

 interusseous ligament (apparatus ligamentosus 

 cuvitatis sinuoste, Weitbr.): this ligament oc- 

 cupies the hollow which is manifest on the 

 outside between the os calcis and the neck 

 of the astragalus. It consists of a series 

 of strong ligamentous fibres, which arise all 

 along the inner part of the depression on the 

 astragalus in a curved course, and descend 

 vertically, or nearly so, to be inserted into 

 the corresponding depression between the two 

 articular surfaces on the os calcis. A con- 

 siderable quantity of fat occupies this space, 

 and covers this ligament, and is intermixed 

 with its fibres. 



The bones forming the second row of the 

 tarsus are articulated as follows : 



The scaphoid or navicular bone is articulated 

 with the three cuneiform, by means of the 

 triple surface already described on the former 

 bone ; to each division of which one cuneiform 

 is adapted (cuneo-scaphoid articulation). A 

 common synovial membrane lines the surface on 

 the scaphoid, the surfaces of the cuneiform bones, 

 and passes in between them to line the lateral 

 articular facets on the latter bones. The three 

 cuneiform bones are connected to the navicular 

 by means of six ligaments, which pass from 

 the former to the latter; three on the dorsal 

 surface and three on the plantar. The dorsal 

 ligament of the internal cuneiform extends 

 directly from behind forwards, those of the 

 others proceed obliquely forwards and out- 

 wards. The internal cuneiform has likewise 

 an internal ligament, which proceeds from its 

 internal part directly backwards to the navi- 

 cular; it lies above" the tendon of the tibialis 

 posticus. As to the plantar ligaments, that 

 of the internal cuneiform is the strongest : it 

 is extended between the tubercle on the na- 

 vicular bone and that on the cuneiform, and 

 is in part confounded with the tendon of the 

 tibialis posticus, which sends a process out- 

 wards to the other cuneiform bones, and 

 strengthens the ligamentous fibres which belong 

 to them. 



The cuneiform bones are articulated to each 

 other by means of the lateral facets, which 

 are lined by synovial membrane prolonged 

 from that of the cuneo-scaphoid articulation. 

 Each joint is strengthened by a dorsal, a 

 plantar, and an interosseous ligament. The two 

 former are extended transversely from one 

 cuneiform bone to the other, the dorsal being 

 considerably the stronger. The principal bond 

 of union, however, is by the interosseous liga- 

 ment, which is extended between the non- 

 articular parts of the lateral surfaces of each 

 cuneiform bone. 



The cuboid bone is articulated with the 

 external cuneiform (cuboido-cuneen articula- 

 tion) in a manner so similar to that by which 

 the cuneiform bones are articulated with each 

 other as to render a separate description super- 

 fluous. Its synovial membrane is continuous 



with that of the cuneo-scaphoid, and its liga- 

 ments are precisely similar to those of the 

 cuneiform articulations. 



The cuboid bone is united to the scaphoid 

 by means of ligaments. The outer extremity 

 of the latter bone is in contact with a small 

 portion of the inner surface of the former, near 

 its posterior superior angle, and sometimes a 

 small articular facet indicates the point of each 

 bone where contact is established. The liga- 

 ments which pass between these bones under 

 all circumstances are & dorsal ligament, directed 

 obliquely from without inwards, a plantar 

 ligament, transverse and very thick, and an in- 

 terosseous ligament extended between the cor- 

 responding surfaces of the two bones, excepting 

 where the facets are found, when they exist. 



Articulation of the two rows of tarsal bones 

 to each other. This is effected by means of the 

 astragalus and os calcis behind, and the scaphoid 

 and cuboid in front. 



Astragalo-scaphoid articulation. The head 

 of the astragalus is received into a cavity which 

 is in greatest part formed by the glenoid cavity 

 of the scaphoid bone, and is completed infe- 

 riorly and internally by a ligament (the inferior 

 calcaneo-scaphoid), which extends from the 

 sustentaculum of the os calcis to the inner part 

 of the inferior surface of the scaphoid. On 

 the outer side and inferiorly the head of the 

 astragalus is supported by a short ligament 

 (the external calcaneo-scaphoid) which is at- 

 tached posteriorly to the inner part of the os 

 calcis, and in front to the external extremity of 

 the scaphoid. The extension of the recipient 

 cavity for the head of the astragalus by means 

 of the ligaments just named was rendered 

 necessary by the considerable excess in the size 

 of the head of the astragalus over the glenoid 

 cavity of the scaphoid. By means of these 

 ligaments, too, the os calcis is connected with 

 the scaphoid, although there is no articulation 

 between them. 



The astragalo-scaphoid articulation is strength- 

 ened by but one proper ligament, and that is 

 situated in the dorsal aspect; it is the superior 

 astragalo-scaphoid ligament, and is attached 

 posteriorly to the neck of the astragalus, and in 

 front to the margin of the glenoid cavity; the 

 transverse extent of this ligament is equal to 

 that of the scaphoid bone on its dorsal surface; 

 the direction of its fibres is forwards and out- 

 wards. It is a thin fibrous expansion, covered 

 superiorly by the extensor brevis digitorum 

 muscle, and on its inferior surface lined by the 

 synovial membrane of the joint. 



Calcaneo-cuboid articulation. The articular 

 surface on the os calcis is slightly concave in 

 the direction from above downwards; that on 

 the cuboid is convex in the same direction. 

 The two surfaces are closely adapted to each 

 other, and their union maintained by the fol- 

 lowing ligaments : 1 . The superior or dorsal 

 Cfilcaneo-cuboid ligament, which consists of but 

 a few fibres extending from the superior and 

 anterior part of the os calcis to the cuboid. 

 2. The internal calcaneo-cuboid ligament, a 

 short, strong, quadrilateral ligament from three 

 to four lines in breadth, placed m great part 



