Monday, October 31, 2011

Vehicle versus the Vulture

About a month and a half ago, we got a call from some good samaritans telling us about a turkey vulture (Cathartes aura) that had just been hit by a car on I-10.  He was struggling on the side of the road and his wing appeared badly injured.  Unfortunately, the vulture was feeding on some road kill itself and got too close to the traffic.

The interesting thing about turkey vultures is that they feed primarily on carrion and they have an extremely acute sense of smell which they use to pick up the scent of a carcass.  This sense of smell is INCREDIBLY unique in the avian world and they are particularly good at picking up the scent of ethyl mercaptan (a gas produced by animals beginning to decay).  The olfactory lobe of a turkey vulture is well developed when compared to other avian species which helps allows a turkey vulture to actually detect odors up to 12 miles away.

When our patient arrived at the Tucson Wildlife Center he was very painful and dehydrated.  Lou Rae quickly addressed his pain management, gave fluids, and stabilized his wing with a figure-8 bandage.  He was then placed in a warm, dark incubator and allowed to rest.

When I arrived at the center, Lou Rae and Warren helped me perform a physical examination.  Unlike raptors, vultures have a wicked bite and they aren't extremely dangerous with their talons.  You have to be careful though when you handle a vulture (WARNING: ONLY PROFESSIONALS SHOULD EVER HANDLE WILD ANIMALS), because they all tend to vomit or regurgitate as a deterrent.  It definitely is effective, believe you me!  We carefully unwrapped his wing and immediately we all noticed that he had broken his humerus (the human equivalent can be visualized here).  We decided to take radiographs to see how bad the the fracture really was...

Ventrodorsal view - right humerus

AP view - right humerus

Looking down on a chicken skeleton,
showing the relation of the humerus.

An anteroposterior (AP) view is just a fancy way of us shooting the x-ray beam through the front and out of the back (of the feathers) of the wing, as the vulture is positioned next....

So the fracture itself can be considered a mid-diaphyseal fracture of the humerus which is mildly to moderately displaced.  It was going to be a tricky repair!!!  We scheduled surgery for the next morning and fasted the vulture prior to be anesthetized...follow the pictures below for the rest of the story.

First, the vulture is given a pre-med to
calm him down and allow for less gas
anesthesia to be used.  Here, isoflurane is
being given to induce anesthesia.
Once asleep we have to then intubate all
of our patients to provide a direct path
for airflow and anesthesia

We have now intubated the vulture, meaning
a tube goes from his mouth, down his trachea
and supplies gas anesthesia and oxygen to his
respiratory tract.  Notice the "red head" which
is why they are called, Turkey vultures.

The patient is then prepped to go to surgery.
The machine at the right of the picture is our
gas anesthesia machine.

I had to make a small skin incision at one end of his humerus
and then use a surgical drill to place an "intramedullary" pin
for resisting "bending" forces.  We will go over this in a bit.
A few other pins were drilled through the bone at different areas
on either side of the fracture site to add "rotational" stability.

Close up of surgery site

Close up of surgery site - labelled
Clearly not showcasing my artistic talents

We then placed a rubber drain over the pins,
and filled it with an epoxy to add support to the
external fixator (much like the bobcat jaw repair!)

The vulture was then recovered from anesthesia carefully, extubated, and when he was fully awake given a meal.  The fixator needed to stay on for at least 6 weeks and then would be reassessed via radiographs prior to removal.

Approximately 6 weeks post op

Let's briefly discuss intramedullary pins and the "bending" and "rotational" forces that a veterinarian has to be aware of when fixing a fracture on an animal.  

Intramedullary pins simply enter the "middle" cavity of a bone; most commonly a long bone.  This middle cavity is called the medulla and a pin should be approximately 60-75% of the width of the cavity.  To illustrate this, review the image below....

Once you put an intramedullary pin, into the medullary cavity... that bone will no longer be able to bend at the fracture site easily.  Consider, very lightly, a corn dog and a stick.  The hot dog in the middle would be equivalent to the medullary cavity and the outer bread covering would be the bone.  Without the stick in the middle of the corn dog, you can very easily bend and break it; but with the stick through the entire corn dog it resists "bending" forces a lot better.  Even though this stick (analogous to the intramedullary pin) provides resistance to "bending" forces, the corn dog can still rotate quite easily around a 3-dimensional axis.  This is less than ideal if a corn dog has a fracture because then it would never heal if it constantly moved!  So then to provide that "rotational" stability, you place external fixator pins through the corn dog to secure fix it along an axis to provide complete fixation.  If that doesn't make sense or you don't like corn dogs...leave a comment below and I'll try my best to come up with another food group; or if you wanted to read about this in medical terminology, follow this link about intramedullary pins and this link regarding external fixation.

To date, the vulture is doing very well and currently has his external fixator off!  The volunteers, along with Lou Rae, Warren, and Lisa have also been performing routine physical rehabilitation on his wing to help strength his muscles.  He is even starting to fly short distances in one of the flight cages!  He currently lives with Egor (a Black Vulture) and while I was trying to record a video of our patient flying, Egor didn't take kindly to candids of his friend and chased me out of the cage... (I'll try again in the near future and post it if I get a good shot!)

1 comment:

  1. I am a student studying veterinary medicine in France. We love your writings!