AVATAR #1: Paraplegia

Sigourney and Sam

IT MUST BE (BELATED) CHRISTMAS

A miracle has occurred! I get to blog about characters played by two of my favorite actors! Sigourney Weaver and Sam Worthington! Both in Avatar! Yippee! Although there are some disturbing racial themes to this film(1), there's also dramatization of the forces behind aboriginal genocides, great action, and a decent story that ends "happily" (but doesn't really.)

REVISITING PARALYSIS

Jake Sully (Sam Worthington) is a paraplegic ex-marine, replacing his dead twin brother on a mission to a moon called Pandora, orbiting a planet called Polyphemus. Jake sustained a spinal cord injury in combat. Symptoms and signs of spinal cord injury will vary with the amount of damage to the cord (complete or partial) and the location of the damage.

Generally speaking, nervous function will remain above the level of the cord lesion. Function below the injury will be absent or diminished. It's hard for me(2) to tell from the movie, how much control Jake has over his hip muscles.

A variety of deep and superficial flexors of the hip, from an old copy of Gray's Anatomy, 1918.

Don't worry, muscles haven't changed that much in the last ninety-two years.

It is easy to see that Jake clearly has no control over knee or foot movement. If we use the chart below, which I lifted from the Merck Manual online, we can assume that Jake's injury is at the spinal cord, between the 11th and 12th thoracic nerves. This is an area between the lower thoracic vertebrae, where the floating ribs attach(3).

Effects of spinal cord injury on the body, from the Merck manual online.

I love the Merck as a resource.

Grouping #2 in this illustration shows the thoracic nerves.

The lowest of these are T11 and T12.

We see in the film that Jake does not have the use of his legs, which have atrophied due to lack of use. I understand that James Cameron's production crew cast prosthetic legs for Jake from a paraplegic man who was of Worthington's build. I thought they did a really great job of making Jake's atrophied legs blend with Worthington's body. I have no idea how they did that.

MORE HUNKY YOUNG MEN

If you want to watch a film that will educate you about different types of disability, spinal cord injury and the variables of paralysis, I highly recommend Murderball. This documentary is about exactly the types of character Jake Sully represents: young, competitive, loaded with testosterone, and male. It humanizes victims of spinal cord trauma in a way I've never seen before. It made me cry(4). I show it to my pathology classes.

Athletes playing wheelchair rugby, a.k.a. murderball, from the movie.

Where does Sigourney Weaver come in to all this? Wait for my next post about Avatar....

1. There is a very strong message that it takes a white guy to "go native" and save an indigenous population that clearly can't save itself.

2. It doesn't look like he has control over any of the gluteals, adductors, tensor fascia latae, etc. The way he moves his body in relationship to his legs, it appears that he has psoas function, but I'm not a doctor (I just watch one on TV.)

3. See the 12/30/09 post for more on floating ribs.

4. What can I say? I cry at the movies unless they're stupid.

SMORGASBORG #7: Endoskeletons part B

What do Sam Worthington, Peter Weller, and Will Smith have in common? They're all dreamy, and they all play characters in movies who have devices implanted into their bodies. In their films the only issues they seem to have with their artificial parts are emotional ones, but putting a foreign object into a human body without adverse physical effects is actually pretty hard to do.

Marcus.

Note the chiseled endoskeletal cheekbones.

Marcus (Worthington) in Terminator Salvation, is apparently the lone humanoid organism to have survived Skynet's experimentation to build a cyborg with a metallic endoskeleton. Why would this be so hard? (Other than the fact that a machine dominated society using humans as lab rats wouldn't really care that much if there were a lot of casualties.) Living tissue and many types of metals have problems getting along together.

YOU PUT WHAT, WHERE?

Metals for making cyborgs, or hip or knee replacements, have to be corrosion resistant and biocompatible. If you have an allergy to nickel, you sure don't want a nickel implant, or a nickel belt buckle, or a phone with nickel in it.

The consequences of nickel allergies.

Metals shed ions. In order for the body to tolerate the metal well, it can't leach too much into the surrounding tissue. Although your body uses some metals for metabolism (copper, iron, magnesium, etc.), too much can cause toxicity. You don't want that metal plate in your head shedding too much of anything near your brain(1).

So you can imagine that corrosion resistant types of metals, plastics, or ceramics, would be a good idea. Using incompatible metals could interfere with normal tissue growth near the implant(2). Blood acidity and ph balance can have a corrosive effect on metals. If metals shed into the bloodstream, your whole body may have a (systemic) reaction. Organs that filter blood, like the liver and kidneys may accumulate unhealthy amounts of metal ions, which is bad. And don't forget cancer! You have to be careful that whatever you're implanting isn't carcinogenic 20 years after you've implanted it.

Cobalt-chromium alloys, stainless steel, and titanium have been reported to have minimal tissue reactions in rabbits, dogs, and people. If Terminator Salvation was going to be really accurate, we should have seen some rabbit cyborgs hopping around killing humans.

Kelli Doyle's Cyborg-Bunny puppet

Although there are always many things to consider, many people enjoy their artificial joints (made of plastics and metals) or eye lenses (plastics), or boobs (silicone) and never have any problems. 300,000 women per year receiving breast implants can't be all wrong, can they(3)?

Lens implant

CYBORG FATIGUE

Once you find biocompatible materials to implant in the body, you also want them to last. Fatigue resistance is important. You don't want parts to break or bend like a lug nut on an airplane wing.

If we're talking about hip replacements, "... chrome is favoured if tensile and fatigue strength are required, titanium is favoured if load sharing with adjacent bone (uncemented prostheses) is required (titanium has a similar modulus to cortical bone)(4)." So it really depends on what you're going to do with that hip and whether you glue the prosthetic, or just jam it in there really tight.

Bo Jackson, cute enough to be a cyborg, and a super-human athlete.

The metal and the bone it's embedded in, making up the structure of an artificial joint, are able to withstand normal physical stresses. Professional athletes with joint replacements often end up with complications because they put super-human stress on their bodies. The metal may bend, the bone holding it may break, or the prosthetic starts to work its way lose. For this reason, RoboCop with his combination of exoskeleton and implanted sensory parts, Spooner and his entirely prosthetic limb, and Marcus with a full body endoskeleton are the creme de la creme of the Hollywood Cyborgs.

1. Which is why they use titanium or niobium in the skull.

2. This can lead to chronic inflammation and scarring in the area.

3. Women with breast implants do not qualify as cyborgs.

4. Page 394 from Imaging of the Hip and Bony Pelvis: techniques and applications, by Arthur Mark Davies, Karl J.Hohnson, Richard Wihehouse. Read it on Google books, otherwise it costs over $200!

TERMINATOR SALVATION - Spoiler Alert #1

Being a science fiction fan and a lover of the first and second Terminator movies, I went to se Terminator Salvation with my screenwriter friend, Todd Alcott, who was in town for the weekend. I'll leave script analysis to the experts, but since I watch a doctor on TV, I consider myself fully qualified to probe the parameters of cyborg medicine.

Here's the basics of the plot from the Sony Pictures Official Website. My commentary is in italics:

"'Terminator Salvation' is set in post-apocalyptic 2018, where John Connor (Christian Bale - His character is a self-important jerk.) is the man fated to lead the human resistance against Skynet and its army of Terminators. But the future that Connor was raised to believe in is altered in part by the appearance of Marcus Wright (Sam Worthington - Yummy!), a stranger whose last memory is of being on death row. Connor must decide whether Marcus has been sent from the future, or rescued from the past (Connor doesn't care about Marcus' past. It's not an issue for him). As Skynet prepares its final onslaught ("Final" indeed!), Connor and Marcus both embark on an odyssey that takes them into the heart of Skynet's operations, where they uncover the terrible secret behind the possible annihilation of mankind. (Yes, there's a "secret", but it's established pretty early. "Possible" annihilation doesn't seem that exciting, does it?)

The movie has lots of good action, but lacks in plot. It's not entertaining enough to keep me from dwelling on trivia that wouldn't even get my notice on a better film. Like the dweeb that I am I took notes in the theater - for my blog, which makes me dweeb-concentrate. Today's entry covers the first entertaining distraction I encountered in the film.

Giant Robot

DROPPING PEOPLE INTO CAGES CAUSES INJURY - Don't try this at home!

Giant humanoid-shaped robots scoop people (like Jane Alexander) up in their mighty, bone crushing hands and drop them into cages on "human transport vehicles." The puny humans are dropped from a height of a minimum of 15 feet, to either land on other people (ouch!), or land on the floor of what looks like a cattle car. The citizens of the future have incredible righting reflexes and manage to land on their feet more often than not.

Human Transport Vehicle

Landing on one's feet from extreme height can result in a fracture-dislocation, where the lower bone of the ankle, the talus, is driven up between the two leg bones, the tibia and fibula. Usually there is some breakage of the fibula, and if you try hard enough, you can break your tibia, too! Depending on the direction of the force, the foot can also be displaced to the side(1). This type of injury is incredibly painful. Suddenly, a person with this type of fracture is a few inches shorter when standing on his broken foot, as compared to the healthy side.

Ankle Anatomy

Above is a picture of normal alignment between the tibia, fibula, and talus at the right ankle.

Here (below) is a dislocation-fracture of those bones. Notice the way the talus is now in between the bones of the lower leg. The fibula, on the left, is also broken but the break is not visible in this xray(2). Gruesome, isn't it?

Another variation can happen when the foot is displaced laterally (eversion) and the fibula is broken. This is called a Pott's fracture, pictured below. When comparing the two photos, be aware that the fibula is on the left side, and the tibia is on the right side in the xray above. In the illustration below, the fibula is on the right and the tibia is on the left. These are both right feet, but xrayed from the front and drawn from the back.

You'll notice that when the people are dumped out of the transport cars (in a scene vaguely reminiscent of Soylent Green with Charlton Heston) no one is limping, visibly in pain, or three inches shorter on one side because his foot has been shoved up his leg. Let's face it, Jane Alexander looks great but she is getting older, and she should be a little gimpy at this point in the film.

Is there more than ankle fracture to this movie? Oh yes! So much more! Next time, I write about Marcus' cybernetic brain, hair that will not burn, and child safety.

1. Dupuytren's fracture and Pott's fracture both present as variations on this scenario. I remember being told by a professor that one of these injuries is nicknamed "Paratrooper's fracture" because these types of injury are common if you land wrong when sky diving. This is, providing your parachute opens. If it didn't then you would really be "landing wrong!"

2. Xray is from the article by: Adla, Deepthi Nandan, Rachael Joanne Hutchinson, and Ian R. Scott. "An Unusual Fracture-Dislocation of the Ankle." Journal of Bone & Joint Surgery, American Volume 86.10 (Oct. 2004): 2287-2289.