So let’s have a look at the
Remember the axillary nerve passing through
the quadrangular space, we can see it here,
passing through the quadrangular space with
the posterior circumflex humeral artery to
go and supply deltoid. We can see this on
the posterior view of a right shoulder.
So damage to the axillary nerve could occur
as a fracture to the surgical neck of the
humerus, also due to compression of the muscles
that form the quadrangular space. So, if the
muscles that form the quadrangular space were
to become bigger, that’s a hypertrophy, then
this could compress the quadrangular space.
Now as we know passing through the quadrangular
space as I just said is the axillary nerve,
then this can compress this nerve leading
to functional deficits of the deltoid. If
there’s a fracture to the surgical neck
of the humerus, then as the axillary nerve
passes through here, then the same problems
will result. You’ll have paralysis of the
Paralysis leads to atrophy of the muscle, and
this can lead to loss of the rounded shoulder
contour as you lose the muscle mass. Now,
deltoid is involved in abducting the arm,
but it abducts it after the first 15 degrees.
So the first part of abduction is carried
out by supraspinatus, and that starts the
abduction as the first 15 degrees, and then
the deltoid muscle carries on. So the individual
will only be able to abduct their arm due
to supraspinatus by 15 degrees. You’d also
have sensory loss over a patch
of skin on the lateral arm which we can see here.
This little patch of skin over the lateral
aspect of the arm, shoulder region, is
due to the cutaneous branches coming from
the axillary nerve. And here, we can see that
they would be damaged. So you’d have loss
of sensory distribution from this region.
If we then look at the long thoracic nerve,
the long thoracic nerve comes away from the
brachial plexus and it runs down, we can
pick up the long thoracic nerve here. It’s
running alongside serratus anterior, and it
actually runs superficial to serratus anterior.
Here, we’re looking at the right side of
the thoracic cavity. This is anterior, this
is posterior, this would be deltoid here.
And we can just see the long thoracic nerve
running down here to supply serratus anterior.
So damage to the long thoracic nerve that’s
coming from the brachial plexus can be due
to damage to the lateral thoracic wall. This
can be due to a fight or it could be due to
surgery on the lateral aspect of the chest
wall. If there’s surgery on the breast or
if there’s removal of lymph nodes in this
region, then the long thoracic nerve could
be damaged. The effect is that the medial
border of the scapula would protrude through
the skin, especially when the patient is asked
to push against the fixed wall, and this is
known as winged scapula. So serratus anterior
is important in clamping
the scapula onto the posterior chest wall.
It holds the scapula onto the chest wall.
So damage to the long thoracic nerve would
paralyze this muscle, and therefore, when
you’d go to move your arm and you need your
scapula to be anchored to make it a stable
push off, then that’s not going to be possible,
and the scapula is then pushed into the skin,
and that gives the impression of a winged
scapula. The actual triangular shape of the
scapula is seen as an impression on the under
surface of the skin.
So in this lecture, we have looked at the
general nerve supply to the upper limb and
some typical locations of lesions and then
looked at their motor and sensory deficits.
We looked at the musculocutaneous nerve and
their deficits with damage to this nerve.
We looked at the median and ulnar nerve with
hand of benediction and claw hand.
We then looked at the radial nerve and wrist
drop and the axillary nerve, the ability through
damage this nerve to lead to failure of abduction
beyond 15 degrees, and the loss of shoulder control.
And then we looked at winged scapula in relation
to damage of the long thoracic nerve.