00:00
Now let’s turn to the common fibular
nerve, and we know the common fibular nerve
bifurcates from the sciatic. It then runs
along the lateral border of the popliteal
fossa, and it divides into the superficial
and deep fibular nerves - the superficial
nerve supplying the lateral compartment, the
deep fibular supplying the anterior compartment.
00:23
So here, we can see that the neck of the fibula
has the common fibular nerve wrapping around
it. Now we know from a previous lecture that
the neck of the fibula and the head of the
fibula are very superficial and can easily
be palpated. So this means that the common
fibular nerve is prone to injury, as it’s
located superficially around the neck of the
fibula on the lateral aspect of the leg. Damage
to the common fibular nerve is going to lead
to flaccid paralysis of muscles in the anterior,
the dorsiflexors, and the lateral elevators
of the leg in the leg compartments, the anterior
and lateral leg compartments. Those are responsible
for dorsiflexion and eversion. With no dorsiflexion,
you’re unable to lift your foot up. So you’re
unable to lift your toes up keeping your heel
on the floor, and therefore, you have foot
drop. The foot drop assumes this permanent
plantarflex position. So when you go to walk,
you’re likely that your toes in this plantarflex
position will drag along the floor as the
limb becomes too long and it’s difficult for
your toes to clear the ground. To compensate
for this, you have this waddling gait where the
body moves to the unaffected side, therefore,
giving you clearance. You have a swing-out
gait where the leg is excessively abducted
to avoid the toe sitting in the floor. And
you have this stepping gait where you have
increased thigh and knee flexion to raise
the foot higher up so it can then clear the
ground.