Let’s look at the anterior compartment first.
We can see here, there are a number of muscles.
There are three which we’re going to cover
and this lie on the anterior compartment.
They actually really lie lateral to the tibia.
So we can see the tibia here. This is a right
leg. We can see the lateral aspect here by
the fifth digit, and we see the medial
aspect here. We can see we’ve got tibialis anterior
that’s passing down onto the foot. And we’ve
got extensor digitorum longus, and then deep
to these two more superficial muscles, we
have extensor hallucis longus. Let’s have
a look at the details of these muscles.
So tibialis anterior, this is coming from the
lateral condyle, the lateral surface of the
proximal tibia and the interosseous membrane,
and it’s passing through the medial cuneiform
and base of the first metatarsal. So we can
see here it’s coming from the lateral condyle
of the tibia, and it’s passing down and
attaching to the base of the first metatarsal
and the medial cuneiform. If we look at extensor
digitorum longus, this is also coming from
the lateral condyle of the tibia. It’s coming
from the anterior surface of the fibula and
interosseous membrane. This muscle is passing
to the middle and distal phalanges of digits
2 to 5. So we can see it’s passing all the
way down extensor digitorum longus, and it’s
splitting into these tendons which are passing
to the distal phalanges and the middle phalanges
of digits 2 to 5. We then finally look at
extensor hallucis longus, and hallucis means
the great toe or the first digit. This muscle
is coming from the anterior surface of the
mid-fibula, and also the interosseous membrane.
But as we can see, it’s actually coming
from deep. It’s coming from deep to tibialis
anterior and extensor digitorum longus.
And this muscle passes specifically to the distal
phalanx of the great toe digit 1. All of these
muscles are supplied by the deep fibular nerve.
And we also have another muscle which is in
the anterior compartment. But we can’t see
it on this diagram and we’ll come back to
it in a later slide. But this is fibularis
tertius. The fibular muscles are normally
located within the lateral compartment, except
the fibularis tertius. And not everybody has
this muscle. It’s located in a few individuals,
fibularis tertius. We’ll come back to it.
It does come from the anterior surface of
lower fibula and the interosseous membrane,
and it passes on to the base of the fifth
metatarsal. And this is, again, supplied by
the deep fibular nerve. So, all of the muscles
within the anterior compartment of the leg
are supplied by the deep fibular nerve. Their
primary function is to extend the digits and
dorsiflex the ankle. So, if we look at tibialis
anterior, this is involved in dorsiflexion
of the ankle, and it also has an important role
in everting the foot. The extensor digitorum
longus is important in extending digits 2 through
5, and also dorsiflexing the ankle.
Extensor hallucis longus, this is important
in extending the great toe, and also assisting
in dorsiflexion of the ankle. Fibularis tertius
actually is involved in dorsiflexing of the
ankle and it supports eversion. And this is
a common movement of the fibular muscles.
But this time, this muscle just happens to be
in the anterior compartment. Remember that
these muscles in the anterior compartment
primarily involved in dorsiflexion of the
ankle and extending the digits are supplied
by the deep fibular nerves, so these anterior
compartment muscles. If we look at them in
more of an anatomical view, we can see here
we’ve got the anterior kind of edge of the
tibia. We can see its medial surface running
down here. And then lateral to it, we have
these three muscles. We have tibialis anterior,
then we have lateral to it, extensor digitorum
longus, and we can see passing between extensor
hallucis longus. If we look at this, we can
see that these are innervated via the deep
fibular nerve and they’re supplied by the
anterior tibial artery. We can also see that
we have a small muscle that’s running down
in this direction here. We can just see the
tendon of it, and this is, in this view, our fibularis
tertius tendon; that muscle I mentioned
a few slides ago. Its muscle belly coming
from the lower parts of the fibula and the
interosseous membrane is coming from the anterior
compartment. So just like in the upper limb,
we also have some thickenings of the deep
fascia that creates superior and inferior
extensor retinacula. On the screen, we can
see the image of the anterior compartment
of the leg again. And we can see this inferiorly
positioned Y-shaped band, and this is extending
from the calcaneus, we can see here, all the
way across to the medial malleolus.
So we can see a portion of dropping down here as
well. And this is your inferior extensor retinacula.
This is important in creating a strong loop
around fibularis tertius and extensor digitorum
longus holding those tendons in place. We also
have a more superiorly positioned thickening,
and that’s not visible on this diagram, but
it would be approximately in this position.
And it’s quite separate, but again, a thickening
of the deep fascia. And that is your superior,
a broad band extending across from the tibia
to the fibula and this prevents bowstringing
of all of the tendons from the anterior compartment.