DORSUM OF THE FOOT AND THE KNEE JOINT

1. Make the following incisions:

(a)a vertical incision in the midline of the front of the leg down to the ankle;

(b) extend incision

(a)along the middle of the dorsum of the foot to the nail bed of the middle toe;

(c) a transverse incision across the front of the ankle connecting the two malleoli;

(d) a transverse incision across the roots of the toes; and

(e) midline incisions along the dorsum of the other toes. Reflect the skin flaps and clean away the superficial fascia.

2. Note the dorsal venous arch situated opposite the distal ends of the metatarsal bones and note its formation. Trace:

(a)the great saphenous vein commencing from the medial side of the venous arch and passing in front of the medial malleolus; and

(b) the small saphenous vein arising from the lateral side of the arch and running behind the lateral malleolus. There are communications between the great saphenous vein and the deep veins in the region of the ankle, knee and adductor canal. Similar communications exist between the small saphenous vein and the deep veins at the level of the ankle. These communicating veins are called perforating veins.

3. As you clean away the superficial fascia note the following nerves:

(a)superficial fibular nerve from the common fibular nerve piercing the deep fascia about the junction of upper two-thirds with the lower third of the anterior aspect of the leg. Trace this nerve into the foot where it divides into medial and intermediate cutaneous branches which supply all the toes except the first interdigital cleft and the lateral side of the little toe;

(b) saphenous nerve along with the great saphenous vein passing in front of the medial malleolus to the medial side of the foot; and

(c) terminal part of the deep fibular nerve, a branch of the common fibular nerve, piercing the deep fascia in the first intermetatarsal space to supply the first interdigital cleft.

4. Clean the deep fascia and note the retinacular bands below which are thickenings in the deep fascia:

(a)the superior extensor retinaculum which is a transverse band of fascia that extends between the lower ends of the tibia and fibula; and

(b) the Y-shaped inferior extensor retinaculum lying across the ankle joint.

5. Similarly, identify the superior and inferior fibular retinacula. Define:

(a)the superior retinaculum passing between the back of the lateral malleolus and the lateral surface of the calcaneus; and

(b) the inferior retinaculum stretching between the anterior part of the upper surface of the calcaneus and its lateral surface.

6. Remove the deep fascia over the anterior and lateral aspects of the leg, and note the anterior and posterior intermuscular septa attached to the anterior and posterior borders of the fibula. Observe how these septa together with the overlying deep fascia form the anterior (extensor) and lateral (fibular) compartments.

7. Clean the fibularis longus and fibularis brevis muscles taking origin from the lateral surface of the fibula, the longus being superficial to the brevis. Note that their tendons pass behind the lateral malleolus with the fibularis longus tendon lying posterior to that of the brevis. Trace these tendons into the foot and observe the insertion of the fibularis brevis into the base of the fifth metatarsal bone. The insertion of the longus will be dissected later.

8. Trace the common fibular nerve round the lateral side of the neck of the fibula into the fibular compartment. Follow the nerve by cutting through the fibularis longus muscle and secure its terminal branches, i.e. the deep and superficial fibular nerves. Trace the superficial fibular nerve distally. It supplies the fibularis longus and brevis. Trace the deep fibular nerve into the extensor compartment.

9. Now clean the muscles of the extensor compartment and trace their tendons which pass beneath the superior extensor retinaculum. From medial to lateral these muscles are:

(a)tibialis anterior;

(b) extensor hallucis longus;

(c) extensor digitorum longus; and

(d) fibularis tertius. Tibialis anterior arises from the lateral surface of the tibia and extensor hallucis longus, extensor digitorum longus and fibularis tertius originate from the medial surface of the fibula. Tibialis anterior is inserted into the medial cuneiform and base for the first metatarsal. Extensor hallucis longus is attached to the terminal phalanx of the first toe. Extensor digitorum longus divides into four slips, which insert into the bases of the intermediate and distal phalanges of the lateral four toes. And fibularis tertius is attached to the dorsum of the fifth metatarsal bone. These four muscles are supplied by the deep fibular nerve.

10. Divide the superior extensor retinaculum and identify the anterior tibial artery, and the deep fibular nerve lying between the extensor hallucis longus and extensor digitorum longus tendons. Follow the artery and nerve upwards into the leg and note that they lie between the tibialis anterior and extensor digitorum longus in the upper part of the leg and are crossed by the extensor hallucis longus tendon near the ankle. Now trace the artery downwards towards the dorsum of the foot where it continues as the dorsalis pedis artery to reach the first intermetatarsal space. The continuation of this artery through the first intermetatarsal space into the sole of the foot will be seen later. Similarly trace the course of the deep fibular nerve, whose medial branch accompanies the dorsalis pedis artery.

1. Note that the lateral branch of the deep fibular nerve enters the deep aspect of the extensor digitorum brevis muscle. This muscle arises from the dorsal aspect of the calcaneus. Clean the four tendons issuing from this muscle and passing to the medial four toes. Note that the tendon to the first toe is inserted into its proximal phalanx while the other three tendons join the extensor digitorum longus tendons to form the extensor expansions over the second, third and fourth toes. Cut and reflect the long extensor tendons at the level of the ankle joint. Follow the extensor expansions and note that their slips insert into the middle and distal phalanges of the lateral four toes.

2. Reflect the extensor digitorum brevis from its origin and find the arcuate artery, a lateral branch of the dorsalis pedis artery lying deep to the tendons. Note that the arcuate artery gives off the dorsal metatarsal arteries which become the dorsal digital arteries.

3. Trace the tendon of the fibularis tertius muscle to its insertion on to the dorsum of the fifth metatarsal bone.