00:01
Now, let's move on to
posterior knee dislocation.
00:05
This is an incredibly high-yield
and important clinical entity.
00:10
Classically, it’s associated with a
direct force to anterior knee
in an anterior-posterior trajectory.
00:15
What’s the most common scenario for this?
Just like this dummy in a vehicle.
00:20
The dashboard hits the knee
causing a posterior knee dislocation.
00:27
On physical examination,
there may be laxity of the ligaments
holding our knee joint together.
00:32
There can be significant pain
and sometimes obvious deformities,
including a posterior dislocation.
00:41
Imaging shows
a clear demonstration of
a posterior dislocation
on the right side of the screen.
00:48
You can see on physical examination
on the left side of the screen
that knee is incredibly edematous and swollen.
00:54
Additionally,
you see an obvious deformity,
likely a posterior dislocation.
01:00
And surgery is usually
necessary in these situations.
01:04
Again, we like to reduce and immobilize.
01:08
These patients often
have a knee immobilizer,
so there's no actual flexion
or extension of the knee,
allowing the bones to heal
as well as the ligaments.
01:17
Remember what are they
at high risk for for periods of –
long periods of immobilization?
That's right.
01:24
DVTs and pulmonary embolism.
01:27
Let's now discuss popliteal artery injuries.
01:30
Popliteal artery injury is
incredibly important to recognize
and you should have a
high index of suspicion
whenever a patient has
a posterior knee dislocation.
01:40
It’s so commonly associated
with posterior knee dislocation
that whenever I have a patient
that have the dislocation,
I always seek to make sure
that the patient does not also have
I always seek to make sure
that the patient does not also have
a concomitant popliteal artery injury.
01:53
Warm ischemia time
is critical to limb salvage.
01:55
What does that mean?
Warm ischemia time is the time
where the tissues distal to the artery injury
is not getting oxygen.
02:04
This is different than cold ischemia time,
which is talked about in transplantation.
02:10
Cold ischemia time is when organs
are preserved in solutions
and put on ice.
02:15
The theory behind cold ischemia time is
there may be a better chance of salvage
if something is put on ice
and the metabolism has been lowered.
02:25
You must suspect a
patient of popliteal artery injury
if there's a posterior knee dislocation.
02:32
Remember that mechanism of injury.
02:34
That dashboard on a head-on collision
has intruded on to the patient
and pushed the knee back with enough force.
02:42
Therefore,
it's not difficult to imagine
that the popliteal artery,
as you can see on this image,
can become injured.
02:49
Reducing the knee joint is the first step
if distal pulses are absent.
02:53
Pulses normally return immediately
post-reduction,
but if they remain absent, urgent
operative treatment may be required.
03:01
Now, let's revisit some
important clinical pearls
and high-yield information.
03:06
Remember,
any significant fracture,
particularly long bone fracture,
demands evaluation of the associated vessels.
03:15
You should always consider the potential
for vascular injury in these situations.
03:20
Now, let me ask you.
03:21
How would you assess for
vascular injury in these patients?
I’ll give you a
second think about this.
03:28
That's right.
03:29
You feel the patient's pulses.
03:31
There is a caveat, however.
03:33
There’s an additional test
called the ankle brachial index,
particularly for the lower extremities.
03:38
We generally have a differential pressure
between our ankle systolic blood pressure
and our arm systolic blood pressure.
03:45
Any index less than 0.9 warrants
additional vascular injury workup.
03:53
High-yield information for your examination.
03:55
Remember, fat embolism after long
bone fracture is a classic association.
04:01
However, it’s difficult to diagnose.
04:03
Therefore,
you must have a high index of suspicion.
04:06
Treatment, though, is largely supportive.
04:08
And again,
the diagnosis depends on
your index of suspicion.
04:13
Unfortunately, there's no confirmatory study for this.
04:17
I would recommend, however, that
on a clinical scenario,
with a patient having a long bone fracture
and mental status changes
and hypoxia,
your answer choice
should be fat embolism.
04:30
Thank you for joining me
on this discussion of classic fractures.