The Lower Extremity and Pelvis 179 



thick inner border, and the inferior calcaneo-navicular ligament further forward : these 

 two ligaments are continuous in front of and internal to the sustentaculum, where 

 they form part of the capsule for the head of astragalus. The groove below the 

 process is a continuation of the postero-internal groove on the astragalus : it is 

 lined by a synovial sheath surrounding the tendon of Flexor longus hallucis, shown 

 in Fig. 147. 



The inner surface of the body is practically covered by the origin of the inner head 

 of Flexor accessorius, whose limits can as a rule be easily made out on the bone. 



This limiting line is made by the thin aponeurosis covering it, which is described 

 as part of the internal annular ligament, and thus the ligament is brought to the inner 

 side of the calcanean tuberosity. 



It would probably be more accurate to confine the description of annular ligament to the 

 strong band covering the tendons and vessels, thus making its lower attachment on the line that 

 runs along the outer border of the groove below the sustentaculum. 



The outer surface presents a tuberculated point for the middle fasciculus of the 

 external lateral ligament. The peroneal tendons turn forward superficial to this band 

 and diverge to their insertions, so that the area in front of the ligamentous tubercle 

 is covered by these tendons, whereas the back part of the surface is only covered by 

 the nbro-fatty subcutaneous tissue at the side of the heel. The peroneal area may 

 show a groove for the long tendon running to the lower corner of the surface, and above 

 this there is frequently a ridge or tubercle that separates this tendon from that of 

 Peroneus brevis. 



The hinder aspect of the bone shows two surfaces, upper and lower, facing in different 

 directions. The lower is vertically striated and ends above in an irregular ridge, 

 affording attachment to the tendo Achillis : above this there is an area for the tendon, 

 and above this again the bone is smooth and covered by a bursa deep to the tendon. 

 The bursa extends a little way on to the upper surface as a rule. 



Lower surface has a concave depression at its front end and internally for fibres 

 of the short plantar ligament : behind this the broad keel of the bone is covered by, 

 and gives attachment to, fibres of the long plantar ligament, almost as far back as the 

 tuberosity. The pointed outer head of Flexor accessorius arises from the outer margin 

 of this region, fused with the ligamentous fibres. 



The tuberosity has a prominent lip which marks the attachment of the plantar 

 fascia. The short muscles of the superficial layer of the sole are immediately deep to 

 this, and their attachments to the bone are fused with the fascia on the ridge and also 

 on the bone in front of this : they overlap one another from within outwards as seen 

 in the figure. 



Abductor hallucis, from the inner tubercle, extends its origin from this on to the 

 fascia covering the inner head of Flexor accessorius, and thus gets an extensive origin 

 from the annular ligament and covers the structures entering the sole here. This 

 origin may extend as far as the tuberosity of the scaphoid, from which the muscle 

 may even obtain a small origin. 



In addition to the ligaments mentioned in connection with the bone, the markings 

 for others can be found on the various surfaces as indicated in the figures. Attention 

 may be called particularly to the calcaneo-cubo-navicular and the internal talo-cal- 

 canean band (Fig. 147). 



The bone rests solely on its tuberosity, with its front portion raised from the 

 ground. Its concavo-convex facet for the cuboid has its upper lip overhanging and 

 thus resting on the cuboid : this keeps the bone from sliding up on the calcaneum, so 



