00:00
Now let’s move over to the ulnar nerve. The
ulnar nerve passes close behind the medial
epicondyle of the humerus, and then it runs
again within the anterior compartment of the
arm alongside the ulnar artery. It doesn’t
pass through the carpal tunnel, but it runs
superficial to the flexor retinaculum in Guyon's
canal or the ulnar canal to go and supply
some muscles within the hand. But damage to
the ulnar nerve and this can be as it passes
posterior to the medial epicondyle, are likely
placed, or compression at the elbow or Guyon’s
canal can lead to damage. Sensory loss,
this will be at the medial surface
of the palm, the medial one and a half fingers,
those fingers that were preserved when we
had median nerve damage. So the median nerve did
three and a half. The ulnar nerve is redoing
the remaining one and a half for finger 5
and the medial surface of 4. So you’ll lose
sensation there. You’ll also have paralysis
of the vast majority of those intrinsic
hand muscles. So the medial to lumbricals, the
interossei, the hypothenar eminence muscles,
these will be paralyzed with the effects on
functionality. The hand will be deviated to
the radial side when a fist is formed because
flexor carpi ulnaris is no longer able to
make a even flexion of the wrist. So the
radius via the flexor carpi radialis muscles
will pull it towards the radial sides so it
have radial deviation.
01:37
And you’ll have an inability to flex fingers
4 and 5, and also the distal interphalangeal
joints. And these are what supplied by flexor
digitorum profundus, the ulnar belly, the
ulnar nerve supplying the bellies to these
digits. So this time, when a patient forms
a fist, digits 4 and 5 remain extended at
the distal interphalangeal joint, yet the
remaining fingers are flexed. Then you have
what’s known as claw hand.
02:07
If we now move on to the radial nerve, the
radial nerve passes to the posterior compartment
of the arm where it supplies triceps, and
then it supplies the posterior surface of
the forearm, where we can see it here. It’s
passing from the posterior cord. It passes
the triceps muscle which it innervates. It
then runs onto the posterior surface of the
forearm supplying the extensor compartment.
Damage to the radial nerve can be via a knife
injury perhaps in the axilla or a humeral
fracture where the shaft of the humerus
is damaged. Paralysis, well, if the damage
to the radial
nerve occurs superior to the origin of the
branches that supply triceps, then triceps
brachii, brachioradialis, supinator, and the
extensors of the wrist will all be damaged.
03:00
So if the lesion is high up, say it’s a
humeral fracture before it has given off the
branches to triceps, then every muscle distal
that it supplies will be affected.
03:11
And this can have the effects of what’s known as
wrist drop. We can see we’ve got an inability
to extend the wrist because the extensor muscles
in the forearm are damaged. You may also have
an inability to extend the forearm at the
elbow joint if triceps is damaged.
03:29
So you’ve got wrist drop primarily as the
problem with a radial nerve lesion. This
is due to paralysis of the extensors, and
therefore, you have unopposed tonic contraction
of the flexor muscles, and that leads to this
flexed wrist drop position. Sensory loss is
going to be over the lateral aspect of the
dorsal of the hand, and you can just see a
small little region here which is affected by
the sensory loss due to damage to the radial
nerve. So let’s have a look at the
axillary nerve.