1 68 Anatomy of Skeleton 



The peroneal artery comes into relation with the fibula as it runs down on the 

 aponeurotic covering of Tibialis posticus. There is frequently an indication of the 

 course of this artery in the form of a slight groove in the bone (Fig. 137). 



The artery follows the aponeurosis, and thus ultimately arms on to the inter- 

 osseous membrane, where it divides into its anterior and posterior divisions : therefore 

 the height at which the anterior artery appears on the front of the leg depends largely 

 on the size of the Tibialis posticus. The posterior branch runs down deep to the long 

 flexor to emerge from under its outer border to pass behind the malleolus : it must 

 therefore pierce the attachment of the deep transverse fascia here, and when the line 

 of this fascia is definite there is usually a depression in it that marks the passage of 

 the vessels (Fig. 137, i). 



The lower end has tuberculated prominences in front and behind, at the level of 

 the top border of its articular surface, for the anterior and posterior tibio-fibular 

 ligaments (Fig. 136). Below the anterior mass is another marking, on the malleolus, 

 for the anterior band of the external lateral ligament ; the other bands are attached 

 to the margin of the digital fossa, the concavity of which is filled by a fibre-fatty pad 

 and a synovial prolongation from the joint (see Fig. 137). 



The groove on the back of the malleolus is lined by a synovial sheath for the 

 peroneal tendons. 



Notice that the articular surface has its long axis almost vertically placed, thus 

 differing from the corresponding surface on the tibial malleolus : it is also longer than 

 the inner malleolus, a development probably associated with the upright position. 

 The epiphysial line of the lower end lies above the articular surface. 

 This bone has the " growing end " at its upper extremity, and it is an exception 

 to the rule that the centres for the growing end appear first, for the centre for the lower 

 end comes as a rule some little time before that for the upper end : the latter, however, 

 unites last otherwise it would not be the " growing end." 



Now consider the bone as a whole. The shaft is very exceptionally straight : 

 it is nearly always bowed in a curve with the concavity forwards. It does not carry 

 weight, so does not require the great strength of the tibia. An examination of the bone 

 shows that there is a primary cylindrical bar running through it, covered in and largely 

 hidden by the moulding of the muscles, so that the various surfaces and ridges may 

 be mainly considered as secondary in nature. The primary bar is most evident 

 in the lower half of the peroneal surface, running down to the malleolus : in the 

 upper half of the bone it lies near its back part, and the secondary production 

 of the bone in front of it leads to the concavities found here on the inner and outer 

 surfaces. 



The shaft of the fibula, in its middle portion, is just behind the plane-level of the 

 posterior surface of the tibia. The head can be felt distinctly, as can also the prominent 

 lower malleolus, but the upper two-thirds or so of the shaft is only indirectly palpable 

 through the mass of the peroneal muscles. The end of the external popliteal nerve can 

 be felt, in the substance of the Peroneus longus, against the neck of the bone. The line 

 of the tibio-fibular articulation can sometimes be distinctly felt just above the ankle, 

 immediately internal to the lower end of the fibula and external to the common mass of 

 extensor and Peroneus tertius tendons. 



Ossification of Tibia and Fibula. 



Each bone is developed in cartilage and ossified from three centres, one for the 

 shaft and one for either end : the upper epiphysis is the " growing " one in both 

 bones. 



