THE FOOT AND ANKLE. 1217 
interosseous membrane, while in its lower third it winds on to the front of the tibia, 
to terminate at a point opposite the ankle-joint, midway between the two malleoli. 
Ineisions to expose the vessel should strike the outer border of the tibialis anticus, 
which corresponds to a line drawn from a point midway between the external 
tuberosity of the tibia and the head of the fibula, to the termination of the vessel. 
When the muscles of the calf are thrown into action, a groove is seen between 
the two heads of the gastrocnemius, the fleshy fibres of which extend a little below 
the middle of the leg. The fleshy fibres of the soleus extend to the junction 
of the middle and lower thirds of the leg, and project beyond the margims of the 
gastrocnemius. The narrowest part of the tendo Achillis is situated opposite the 
bases of the malleoh, and it is here that the tendon is divided in the operation 
of tenotomy. The short saphenous vein, which hes a little to the outer side of 
the tendon, gradually reaches the middle of the calf, along which it ascends to the 
middle of the popliteal space. The internal saphenous vein and nerve lie along the 
inner border of the tibia. 
The course of the posterior tibial artery is mapped out by drawing a line from 
the lower angle of the popliteal space, at the level of the lower border of the 
tubercle of the tibia, to a pomt midway between the internal malleolus and the 
tendo Achillis. 7o ALO: the vessel in the upper half of the leg, an incision is 
made parallel to and } in. behind the inner border of the tibia; after retract- 
ing the inner border of the gastrocnemius and dividing the tibial origin of the 
soleus, the artery is found lying on the tibialis posticus, Im exposing the artery 
below the soleus, divide two layers of deep fascia and keep the knife directed 
towards the tibia. 
The peroneal artery is given off 3 in. below the head of the fibula; incisions 
to expose the vessel are made in the direction of a line extending from the 
posterior border of the head of the fibula to a point midway between the external 
malleolus and the tendo Achillis. 
THE FOOT AND ANKLE. 
The tip of the external malleolus is situated + in. lower and ? in. further 
back than that of the internal malleolus. Above the external malleolus is the 
Fibula 
Line of ankle-joint, 
Peroneus tertius 
Extensor brevis digitornm 
Tendon of flexor longus 
digitorum to fifth toe 
Second metatarso- 
phalangeal join 
Fifth metatarso-phalangeal join 3ase of fifth metatarsal ‘|| \ \ \ External malleolus 
Peroneus brevis Peroneal tubercle 
Greater process of os calecis  Peroneus longus 
Fic. 820.—OutTER ASPECT OF Foor AND ANKLE. 
triangular subcutaneous surface of~the fibula, the apex of which corresponds to 
the lower end of the extensor-peroneal intermuscular septum. 
The line of the ankle-joint can be felt on either side of the extensor tendons, and 
when the foot is extended the anterior part of the superior articular surface of the 
astragalus forms a visible prominence below the anterior border of the lower end of 
the tibia. The small posterior surface of the astragalus is felt below and behind 
lay der é 
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