Extensor compartment of the leg (dave's notes)

Question 1

What is the nerve to the extensor compartment of the leg?

Answer 1

The deep peroneal

Question 2

Where is the extensor compartment found ie. what are its boundaries?

Answer 2

Between the deep fascia and the interosseous membrane

Question 3

What is medial to the extensor compartment of the leg? What is lateral?

Answer 3

The extensor surface of the tibia? Laterally the extensor surface of the fibula and the anterior intermuscular septum

Question 4

What are the muscles of the extensor compartment of the leg? What vessels and nerves are found here?

Answer 4

Tibialis anterior, EHL, EDL, Peroneus tertius

Deep peroneal nerve, anterior tibial vessels

Question 5

What forms the extensor retinaculum? Where? What perforates this?

Answer 5

Above the lateral malleolus the fascia is thickened to form the superior extensor retinaculum (TA tendon perforates it).

Question 6

What is the origin and insertion of tibialis anterior?

Answer 6

Origin: Upper half of the lateral shaft of tibia and interosseous membrane
Insertion: Inferomedial aspect of medial cuneiform and base of first MT

Question 7

What is the origin and insertion of extensor hallucis longus?

Answer 7

Origin: Middle half of anterior shaft of fibula
Insertion: Dorsal base of distal phalanx of the great toe

Question 8

What is the origin and insertion of extensor digitorum longus?

Answer 8

Origin: Upper 2/3rds of anterior shaft of fibula, IOM, and superior TF joint
Insertion: Extensor expansion of lateral four toes.

Question 9

What is the origin and insertion of peroneus tertius?

Answer 9

Origin: Lower 1/3rd of the fibula
Insertion: Dorsal shaft and base of 5th metatarsal

Question 10

What is the action and innervation of tibialis anterior?

Answer 10

Extends and inverts foot at the ankle. Holds up the medial longitudinal arch.
Deep peroneal nerve.

Question 11

What is the action and innervation of extensor hallucis longus?

Answer 11

Extends big toe and foot. Inverts foot and tightens subtler joint.
Deep peroneal nerve.

Question 12

What is the action and innervation of extensor digitorum longus?

Answer 12

Extends toes and extends foot at the ankle.

Deep peroneal nerve.

Question 13

What is the action and inneravtion of peroneus tertius?

Answer 13

Extends and everts the foot.

Deep peroneal nerve.

Question 14

Where does inversion of the foot occur?

Answer 14

At the subtler and mid tarsal joints.

Question 15

Where does the deep peroneal nerve arise? What is its course thereafter?

Answer 15

Within the PL?? per the neck of the fibula (bifurcation of the common peroneal nerve). It spirals around the fibula neck to reach the interosseous membrane. With them?? it likes between EDL and TA. Supplies the four muscles of this compartment.

Question 16

Where is the anterior tibial artery formed? What is its course thereafter?

Answer 16

Anterior tibial artery is formed at the bifurcation of the popliteal artery passing forwards above the upper border of the interosseous membrane to reach the extensor compartment with two companion veins (fibular may notch the bone). It runs vertically down on the IOM and crosses the lower end of ht tibia at the front of the ankle joint between the malleoli -> DPA.

Question 17

How are the muscles of the anterior compartment of the leg located relative to the anterior tibial artery?

Answer 17

Tibialis anterior lies to the medial side of the artery throughout. EDL and PT lie laterally throughout. EHL crosses it from fibular to tibial sides.

Question 18

When does the they fibula articulate with the femur? Why does this stop occurring? What passive articulation results?

Answer 18

In the embryo the fibula articulates with the femur but differential growth results in the fibula sinking below. Hence superior tibiofibular articulation (synovial joint with capsule (thickened A/P) and membrane movements are entirely passive.

Question 19

What joint may communicate with the bursa under popliteus? What is the significance of this?

Answer 19

The joint cavity of the superior tibiofibular joint may communicate with the bursa under popliteus and hence to the knee.

Question 20

What binds the distal tibia and fibula?

Answer 20

Ligamentous fibres. The IOM also strongly hods the bones together.

Question 21

In what direction do IOM fibres run?

Answer 21

Sloping steeply from tibia down to the fibula

Question 22

Describe the interior tibiofibular joint

Answer 22

Fibrous, with the two bones strongly held together by the interosseous tibiofibular ligament.