242 



SPECIAL ANATOMY OF THE SKELETON 



(Jades articularis anterior) supports the head of the astragalus. The more pos- 

 teriorly situated facet (fades articularis calcanea media) articulates with the middle 

 facet on the under surface of the astragalus. The anterior articular surface is 

 supported on a projecting process of bone, called the lesser process of the cal- 

 caneus (sustentaculum tali); it is oblong, concave longitudinally, and sometimes 

 subdivided into two parts, which differ in size and shape. More anteriorly is 



seen the upper surface of the greater 

 process of the calcaneus, marked by a 

 rough depression for the attachment 

 of numerous ligaments, and a tubercle 

 for the origin of the Extensor brevis 

 digitorum muscle. 



The inferior surface is narrow, 

 rough, uneven, wider behind than in 

 front, and convex from side to side; 

 it is bounded posteriorly by two 

 tubercles separated by a rough de- 

 pression; the external tubercle (pro- 

 cessus lateralis tuberis calcanei), small, 

 prominent, and rounded, gives attach- 

 ment to part of the Abductor minimi 

 digiti; the internal tubercle (processes 

 medialis tuberis calcatiei), broader and 

 larger, for the support of the heel, 

 gives origin, by its prominent inner 

 margin, to the Abductor hallucis, and 

 in front to the Flexor brevis digitorum 

 muscle and plantar fascia; the de- 

 pression between the tubercles gives 

 origin to the Abductor minimi digiti. 

 The rough surface in front of the 

 tubercles gives attachment to the long 

 plantar ligament and origin to the 

 outer head of the Flexor accessorius 

 muscle; while to a prominent tubercle 

 nearer the anterior part of this sur- 

 face, as well as to a transverse groove 

 in front of it, is attached the short 

 plantar ligament. 



The external surface is broad, flat, and almost subcutaneous; it presents near 

 its centre a tubercle, for the attachment of the middle fasciculus of the exter- 

 nal lateral ligament. At its upper and anterior part this surface gives attach- 

 ment to the external calcaneo-astragaloid ligament; and in front of the tubercle 

 it presents a narrow surface marked by two oblique grooves; separated by an 

 elevated ridge which varies much in size in different bones, it is named the peroneal 

 spine (processus trochlearis), and gives attachment to a fibrous process from the 

 external annular ligament. The superior groove transmits the tendon of the 

 Peroneus brevis; the inferior groove the tendon of the Peroneus longus. 



The internal 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 Flexor accessorius muscle. At 

 its upper and fore part it presents an eminence of bone, the sustentaculum tali, 

 which projects horizontally inward, and to it a slip of the tendon of the Tibialis 

 posticus is attached. This process is concave above, and supports the anterior 



FIG. 193. Schematic representation of the articula- 

 tions of the tarsus. Occasional articulations shown by 

 x x x x. 



