260 



OSTEOLOGY. 



POST. 



MID. 



SULCUS 

 CALCANEI 



TROCHLEAR PROCESS 



LATERAL PROCESS 



spring the fibres of origin of the abductor digiti quinti muscle. On the anterior part 

 of the plantar surface there is an elevated elongated tubercle, which terminates 

 somewhat abruptly just behind the anterior border of this aspect of the bone, giving 

 rise at times to a notch. From the tubercle spring the fibres of the long plantar 

 ligament, whilst the notch serves for the attachment of the deeper fibres of the 

 plantar calcaneo-cuboid ligament. The two heads of origin of the quadratus plantse 

 muscle arise from the bone on either side of the long plantar ligament.- 



The medial surface of the calcaneus is crossed obliquely, from above downwards 

 and forwards, by a broad groove of considerable depth ; along this pass many of 

 the structures which enter the sole of the foot from the back of the leg. The 



groove is overhung in front and 



FACETS FOR TALUS above by a projecting bracket- 



like process, called the sustenta- 

 culum tali. The plantar surface 

 of the sustentaculum is chan- 

 nelled by a groove in which is 

 lodged the tendon of the flexor 

 hallucis longus muscle; whilst 

 its medial border, to which is 

 attached a' part of the deltoid 

 ligament (tibio-calcanean fibres) 

 of the ankle, is overlain by the 

 tendon of the flexor digitorum 

 longus. To the anterior border 

 of the sustentaculum isattached 

 the plantar calcaneo-navicular 

 ligament, and placed on its 

 dorsal surface is the articular 

 facet already referred to (facies 

 articularis media). Posteriorly 

 the medial surface of the bone 

 is limited inferiorly by the pro- 

 jection of the medial process of 

 the tuber calcanei, and above 

 by the medial lipped edge of 

 the tuber osity. 



The lateral surface, broad 

 behind and narrower in front, 

 is of flattened form. Springing 

 from it, just below the lateral 

 end of the sinus tarsi, is the 

 trochlear process, often in- 

 distinctly marked. To this 

 the fibres of the inferior retina- 

 culum of the peroneal tendons 

 are attached ; whilst in grooves, 

 above and below it, pass the 



tendons of the peronaeus brevis and longus muscles respectively. To the upper 

 and posterior part of this surface are attached the fibres of the calcaneo-fibular 

 ligament of the ankle. 



The anterior extremity is furnished with a saddle-shaped surface on its anterior 

 aspect for articulation with the cuboid. This facet is concave from above down- 

 wards, and slightly convex from side to side ; its edges are sharply defined, except 

 medially, and serve for the attachment of ligaments. 



The posterior extremity, called- the tuber calcanei (tuberosity), forms the 

 projection of the heel. Of oval form and rounded surface, it rests upon the two 

 processes or tubercles inferiorly and is divisible into three areas. Of these the highest 

 is smooth and crescentic, and is covered by a bursa ; the intermediate is also fairly 

 smooth, and is defined inferiorly by an irregular line, sometimes a definite ridge, 



ANT. 



FACETS FOR TALUS 

 MID. 



POST. 



SUSTENTACULUM 



TALI 



LATERAL PROCESS 

 D 



MEDIAL PROCESS 



FIG. 260. THE RIGHT CALCANEUS. C. Seen from the lateral 

 side ; D. Seen from the medial side. 



