THE TARSUS 



269 



downward and medialward, and transmitting the tendon of the Flexor hallucis 

 longus. Lateral to the groove is a prominent tubercle, the posterior process, to 

 which the posterior talofibular ligament is attached; this process is sometimes 

 separated from the rest of the talus, and is then known as the os trigonum. Medial 

 to the groove is a second smaller tubercle. 



The Neck (collum tali}. The neck is directed forward and medialward, and. 

 comprises the constricted portion of the bone between the body and the oval head. 

 Its upper and medial surfaces are rough, for the attachment of ligaments; its lateral 

 surface is concave and is continuous below with the deep groove for the inter- 

 osseous talocalcaneal ligament. 



The Head (caput tali). The head looks forward and medialward; its anterior 

 articular or navicular surface is large, oval, and convex. Its inferior surface has two 

 facets, which are best seen in the fresh condition. The medial, situated in front 

 of the middle calcaneal facet, is convex, triangular, or semi-oval in shape, and 

 rests on the plantar calcaneonavicular ligament; the lateral, named the anterior 

 calcaneal articular surface, is somewhat flattened, and articulates with the facet on 

 the upper surface of the anterior part of the calcaneus. 



Articulations. The talus articulates with four bones: tibia, fibula, calcaneus, and navicular. 



The Cuboid Bone (os cuboideum) (Figs. 274, 275). The cuboid bone is placed on 

 the lateral side of the foot, in front of the calcaneus, and behind the fourth and fifth 

 metatarsal bones. It is of a pyramidal shape, its base being directed medialward. 



For 3rd cuneiform For 4lh metatarsal 



Occasional facet 

 for navicular 



For 5th 

 metatarsal 



Peronceal Tuberosity For calcaneus 

 sulcus 



FIG. 274. The left cuboid. Antero-medial view. 



FIG. 275. The left cuboid. Postero-lateral view. 



Surfaces. The dorsal surface, directed upward and lateralward, is rough, for the 

 ittachment of ligaments. The plantar surface presents in front a deep groove, 

 tie peroneal sulcus, which runs obliquely forward and medialward; it lodges the 



indon of the Peronseus longus, and is bounded behind by a prominent ridge, 

 ;o which the long plantar ligament is attached. The ridge ends laterally in an 

 ?minence, the tuberosity, the surface of which presents an oval facet; on this facet 

 slides the sesamoid bone or cartilage frequently found in the tendon of the Pero- 

 ?us longus. The surface of bone behind the groove is rough, for the attachment 



f the plantar calcaneocuboid ligament, a few fibers of the Flexor hallucis brevis, 

 md a fasciculus from the tendon of the Tibialis posterior. The lateral surface 

 presents a deep notch formed by the commencement of the peroneal sulcus. The 

 posterior surface is smooth, triangular, and concavo-convex, for articulation with 

 the anterior surface of the calcaneus; its infero-medial angle projects backward 

 as a process which underlies and supports the anterior end of the calcaneus. The 

 anterior surface, of smaller size, but also irregularly triangular, is divided by a 

 vertical ridge into two facets: the medial, quadrilateral in form, articulates with 

 the fourth metatarsal; the lateral, larger and more triangular, articulates with the 

 fifth. The medial surface is broad, irregularly quadrilateral, and presents at 

 its middle and upper part a smooth oval facet, for articulation with the third 





