Anterior and Lateral Compartments of Leg

Question 1

What are the compartments of the leg and how are they formed?

Answer 1

Anterior, lateral and posterior

These are formed by the tibia, fibula, interosseous membrane and the ant/posterior intermuscular septae

Question 2

Which leg compartment is most at risk for compartment syndrome and why?

Answer 2

The anterior compartment, as there is little space, and it is bound rigidly by deep fascia, interosseous membrane and the tibia/fibula bones.

Question 3

What are the muscles of the anterior leg compartment

Answer 3

Tibialis Anterior
Extensor Digitorum Longus
Extensor Hallicus longus
Peroneus tertius

Question 4

What is the interosseous membrane?

Answer 4

Thick sheet of tissue, like deep fascia. Strongly binds tibia and fibula and divides leg into ant/post compartments.

Question 5

What is the function of the anterior compartment?

Answer 5

Dorsiflex (extensor)

Question 6

What is the origin and insertion of the Tibialis ant.?

Actions?

Answer 6

Origin: Superior lateral tibia and interosseous membrane
Insertion: Medial cuneiform and base of the 1st metatarsal

Dorsiflexion and inversion at subtalar joint

Question 7

What is the origin and insertion of the extensor digitorum Longus? Actions?

Answer 7

Origin: Superior fibula and interosseous membrane
Insertion: Lateral four digits

Dorsiflexion and extension of digits

Question 8

What is the origin and insertion of the extensor hallicus longus? Action?

Answer 8

Origin: middle ant fibula and interosseous membrane
Insertion: Great toe

Question 9

What is the peroneus tertius

Answer 9

Random little muscle that originates on the inferior fibula and inserts onto the base of the 5th metatarsal. As it crosses the ankle joint it dorsiflexes and also slightly everts foot.

Question 10

What muscles are within the lateral compartment?

Answer 10

Peroneus Longus

Peroneus Brevis

Question 11

Where does the peroneus Longus originate and insert? And what does this mean for movement?

Answer 11

Origin: Superior lateral fibula
Insertion: Medial cuneiform and base of 1st metatarsal

This muscle inserts in the same area as tibialis anterior, and therefore does the opposing action to EVERT the foot, as well as weakly plantaflex

Question 12

Where does the peroneus brevis originate and insert?

Answer 12

Origin: inferior fibula
Insertion: Base of 5th metatarsal

Weak dorsiflexor and slightly everts foot (with peroneus tertius)

Question 13

Name the four retinaculums of the foot

Answer 13

Superior extensor retinaculum
Inferior extensor retinaculum
These pin down the tendons of the anterior (extensor) muscles.

Superior Peroneal Retinaculum
Inferior Peroneal Retinaculum
These pin down the tendons of the peroneal (lateral) muscles

Question 14

What is the clinical purpose of Retinaculum?

Answer 14

Holds down tendons to prevent bowstringing of muscles and tendons. If not held in place tendons could rub on bone (eg peroneal tendons on distal fibula) and snap.

Question 15

Where would you find a pulse for foot?

Answer 15

Dorsalis Pedis pulse: just lateral to EHL tendon on dorsal surface of 2nd metatarsal

Posterior Tibial Artery pulse: arch of foot

Question 16

What are the three main arteries that trifurcate off the popliteal artery to supply the leg?

Answer 16

Peroneal Artery: supplies lat. compartment
Anterior Tibial Artery: supplies anterior compartment
Posterior Tibial artery: supplies posterior compartment

Question 17

What is interesting clinically about the anterior tibial artery?

Answer 17

It passes anteriorly through the interosseous membrane to supply ant. comp. At the ankle joint it crosses deep to the EHL tendon (midway through malleoli) to become Dorsalis Pedis. DP can be used to find a pulse ( that isn’t always around boob)

Question 18

What does the sciatic nerve bifurcate into at the popliteal fossa?

Answer 18

Common peroneal (runs laterally around femur) and tibial nerve (stays post)

Question 19

What are the two lateral compartment muscles

Answer 19

Peroneus Longus

Peroneus Brevis

Question 20

Dorsal Foot Muscles are? And what is their common origin?

Answer 20

Extensor Digitorum Brevis
Extensor Hallucis Brevis

They originate at the inferior extensor retinaculum and calcaneous

Question 21

Extensor digitorum brevis
Extensor hallicus brevis
insertion and action

Answer 21

• Base of big toe (extension of great toe)

- phalanges of lateral four toes (extension of toes)

Question 22

What are the five p’s of compartment syndrome?

Answer 22

1) Pain
2) Pallor
3) Pulseless
4) Paresthesia (nerve cut off)
5) Paralysis

Question 23

Why would you get paresthesia in C S?

Answer 23

When the pressure builds to a certain level and cuts off the nerve supply to the limb

Question 24

What would be the appearance of a lower extremity if suffering long term from CS?

Answer 24

Grey and dusky. Pallor due to arterial supply being cut off.

Question 25

Where could you check for Compartment syndrome

Answer 25

In the 2nd meta tarsal of the foot, as there is no arterial supply you will not find a dorsalis pedis pulse.

Question 26

What is the order in which the blood vessels will be compressed?

Answer 26

1st Veins (weaker walled vessels) 
2nd Arteries