OSTEOLOGY 



lodgement of the interosseous talocalcaneal ligament. In front and to the medial 

 side of this groove is an elongated facet, concave from behind forward, and with its 

 long axis directed forward and lateralward. This facet is frequently divided into 

 two by a notch : of the two, the posterior, and larger is termed the middle articular 

 surface; it is supported on a projecting process of bone, the sustentaculum tali, 

 and articulates with the middle calcaneal facet on the under surface of the talus; 

 the anterior articular surface is placed on the anterior part of' the body, and articu- 

 lates with the anterior calcaneal facet on the talus. The upper surface, anterior 

 and lateral to the facets, is rough for the attachment of ligaments and for the origin 

 of the Extensor digitorum brevis. 



The inferior or plantar surface is uneven, wider behind than in front, and convex 

 from side to side; it is bounded posteriorly by a transverse elevation, the calcaneal 

 tuberosity, which is depressed in the middle and prolonged at either end into a 

 process; the lateral process, small, prominent, and rounded, gives origin to part 

 of the Abductor digiti quinti; the medial process, broader and larger, gives attach- 

 ment, by its prominent medial margin, to the Abductor hallucis, and in front 

 to the Flexor digitorum brevis and the plantar aponeurosis ; the depression between 

 the processes gives origin to the Abductor digiti quinti. The rough surface in 

 front of the processes gives attachment to the long plantar ligament, and to the 

 lateral head of the Quadratus plantse; while to a prominent tubercle nearer the 

 anterior part of this surface, as well as to a transverse groove in front of the tubercle, 

 is attached the plantar calcaneocuboid ligament. 



The lateral surface is broad behind and narrow in front, flat and almost sub- 

 cutaneous; near its center is a tubercle, for the attachment of the calcaneofibular 

 ligament. At its upper and anterior part, this surface gives attachment to the 

 lateral talocalcaneal ligament; and in front of the tubercle it presents a narrow 

 surface marked by two oblique grooves. The grooves are separated by an elevated 

 ridge, or tubercle, the trochlear process (peroneal tubercle}, which varies much in 

 size in different bones. The superior groove transmits the tendon of the Perona'us 

 brevis; the inferior groove, that of the Peronaeus longus. 



The medial surface is deeply concave; it is directed obliquely downward and 

 forward, and serves for the transmission of the plantar vessels and nerves into the 

 sole of the foot; it affords origin to part of the Quadratus plants. At its upper 

 and forepart is a horizontal eminence, the sustentaculum tali, which gives attach- 

 ment to a slip of the tendon of the Tibialis posterior. This eminence is concave 

 above, and articulates with the middle calcaneal articular surface of the talus; 

 below, it is grooved for the tendon of the Flexor hallucis longus; its anterior margin 

 gives attachment to the plantar calcaneonavicular ligament, and its medial, 

 to a part of the deltoid ligament of the ankle-joint. 



The anterior or cuboid articular surface is of a somewhat triangular form. It is 

 concave from above downward and lateralward, and convex in a direction at right 

 angles to this. Its medial border gives attachment to the plantar calcaneonavicular 

 ligament. 



The posterior surface is prominent, convex, wider below than above, and divisible 

 into three areas. The lowest of these is rough, and covered by the fatty and fibrous 

 tissue of the heel; the middle, also rough, gives insertion to the tendo calcaneus 

 and Plantaris; while the highest is smooth, and is covered by a bursa which inter- 

 venes between it and the tendo calcaneus. 



Articulations. The calcaneus articulates with two bones: the talus and cuboid. 



The Talus (astragalus; ankle bone) (Figs. 270 to 273). The talus is the second 

 largest of the tarsal bones. It occupies the middle and upper part of the tarsus, 

 supporting the tibia above, resting upon the calcaneus below, articulating on 

 either side with the malleoli, and in front with the navicular. It consists of a 

 body, a neck, and a head 



