Winter’s life began with a phenomenal stroke of bad luck.6. Pin the Tail on the Dolphin
Winter’s life began with a phenomenal stroke of bad luck.
In December 2005, when the Atlantic bottlenose dolphin was just a few months old, she was swimming with her mother in Mosquito Lagoon, along central Florida’s Atlantic coast. Somehow, she got herself tangled in a crab trap. An eagle-eyed fisherman spotted her struggling and called in a wildlife rescue team. They found the calf gasping for air, her heart racing. The volunteers gently positioned the dolphin on a stretcher, carried her out of the water and drove her across the state to the Clearwater Marine Aquarium.
She was in bad shape when she arrived – exhausted, dehydrated and sporting numerous cuts and abrasions. She could barely swim, and trainers stood in the tank with her, holding her little body up in the water. No one knew whether she’d make it through the night. But she was a survivor, lasting through those initial hours and the following days, too.
Slowly, with bottle feeding and round-the-clock care, the team nursed the calf back to health. As Winter began to stabilize, though, other problems emerged. A line from the crab trap had been wrapped so tightly around her tail that it had cut off the circulation. The tissue was necrotic: The dolphin’s skin started peeling off, and the tail itself began to decay. One day, Winter’s caretakers found two of her vertebrae at the bottom of her pool. Winter was getting her strength back, but her tail was clearly a goner. And what kind of future could there possibly be for a dolphin without a tail?
Though she didn’t know it, in one way, Winter was lucky – she was born in the twenty-first century, and there has never been a better time for an animal to lose a body part. Materials ranging from carbon-fibre composites to flexible, shape-shifting plastics are making it possible for us to design artificial appendages for patients that fly, trot or swim; prosthetists have succeeded in creating a new beak for an eagle, a replacement shell for a turtle and a false foot for a kangaroo. Surgical techniques are enabling vets to give cats and dogs bionic legs that are permanently implanted in their bodies, and advances in neuroscience hold out the promise of creating prostheses that can be directly controlled by the brain.
Whereas affixing sensors and tags to animal bodies could help save entire species, artificial tails and paws represent the other end of the spectrum, a way to provide a (sometimes literal) leg up to unlucky individuals. Prosthetic devices aren’t appropriate for every animal – indeed, one of the challenges prosthetists face is determining what’s in the best interest of bodies that look nothing like our own – but when we get it right, our custom-designed and individually engineered devices are helping us aid animals one life and limb at a time.
If there’s any place to begin an investigation into the power of animal prosthetics – and the challenges involved in creating them – it’s the Clearwater Marine Aquarium. Home to dolphins, stingrays, sea turtles, otters and assorted other marine creatures, the facility is located on an island just off Florida’s Gulf coast. The bright blue building sits right at the harbour; on a sunny spring morning, a dozen small boats bob among the docks. Inside, cheesy but cheerful island music plays on an endless loop. A few stairs lead from the main lobby to an open-air deck, where two dolphins frolic around in a large tank. It’s easy to pick out Winter – instead of a long, full tail, she has a little curled stump that hangs off her torso like a comma.
Even with her abbreviated tail, Winter looks at home in the water, gliding and playing just like any other cetacean. She’s adapted to this unique body by adopting some unusual swimming techniques. Dolphins typically use their pectoral fins for balance, but Winter ‘cheats’ and uses these fins as little oars. And without the pair of flukes that normally adorn the end of a dolphin’s tail, Winter lacks a dolphin’s normal system of propulsion. So Winter learned how to swim like a fish, moving her body from side to side, rather than up and down, as dolphins normally do.
Unfortunately, this fish-like swimming posture puts pressure on Winter’s spine, causing it to curve unnaturally. And in the months after the dolphin’s rescue, Winter’s caretakers began to worry that her strange method of swimming would cause permanent injury. In September 2006, an aquarium official mentioned this concern in an interview with National Public Radio, which was airing a segment about Winter. A prosthetist named Kevin Carroll happened to be in his car, radio tuned to NPR, when the segment aired. As Carroll listened to Winter’s saga, he thought: I could put a tail on that dolphin. A prosthetic tail, Carroll believed, might prompt Winter to start swimming like a dolphin again and stave off a lifetime of disability.
Carroll grew up near a hospital in Roscrea, a small town in County Tipperary, Ireland. Seeing the ailing and injured children come and go inspired an interest in fixing the human body. He trained in prosthetics in Dublin, visited the US, and never left. Today, Carroll is the vice president of Hanger Prosthetics and Orthotics based in Austin, Texas, and one of the world’s leading prosthetists. He is constantly on the road, crisscrossing the country as he outfits injured patients with artificial limbs. He consulted on the case of Oscar Pistorius, the double-amputee sprinter from South Africa, has worked with world-class mountain climbers, and regularly watches his patients compete in the Paralympic Games.
Carroll’s main focus is on helping humans, but every once in a while, someone will walk into his clinic with a three-legged dog or a beakless bird and ask for his help. As an animal lover, Carroll finds himself unable to resist donating his weekends to the cause. Over the years, he has worked with his Hanger colleagues to make prostheses for a veritable menagerie of animals: dogs, ducks, sea turtles, ‘whatever comes our way’, he says. ‘I’ve sort of become the Dr Doolittle of prosthetics.’
The aquarium agreed to let Carroll take a crack at a prosthetic dolphin tail, and he began assembling his team. He knew who he wanted for a partner: Dan Strzempka, a prosthetist in Hanger’s Florida office. Strzempka, who has worn a prosthetic leg since he was run over by a lawn mower at age four, is a Florida native with a passion for the ocean and the creatures that live there. But he wasn’t sure what to make of Carroll’s proposal to take on Winter as a patient. ‘At first, I thought he was joking’, Strzempka recalls. ‘Or I thought he was crazy.’ As soon as he realized that Carroll was serious, Strzempka decided he was up for the challenge. One way or another, the men would give that little dolphin a tail.
Carroll and Strzempka have agreed to meet me at the aquarium and walk me through how they tackled the task. They are an odd pair; Carroll is slight and cue-ball bald, with a white beard, while Strzempka is tall, tanned and solidly built. The staff beam when they see the prosthetists arrive, embracing them like family, and we slowly make our way to Winter’s pool, stopping to greet more people every few feet. When we get to the dolphin tank, Strzempka leans up against the railing and calls to Winter: ‘Hey, girl! What’s up, buddy?’
‘Good marnin’!’ Carroll shouts out to her in his Irish brogue.
Over the past five years, the men have spent countless hours standing here beside this tank. Winter was unlike any other patient they’d treated before, so the first task was to understand the dolphin body. Carroll and Strzempka began a crash course, reading up on dolphin anatomy and physiology and watching slow-motion videos of the cetaceans swimming to understand their biomechanics. Though animal prosthetists can draw upon human medicine, success often requires a degree of ingenuity; knowing how to build a leg for a human amputee won’t get you far if you want to replace an elephant’s missing foot or outfit a dog with a faux paw. So prosthetists often find themselves MacGyvering each animal appendage, custom designing and individually engineering it. Sometimes they end up inventing materials or techniques that have never been used in prostheses before.
In Winter’s case, the basic plan seemed easy enough – Carroll and Strzempka decided to create a plastic tail that would slip over what remained of Winter’s peduncle, the muscular back half of a dolphin’s body that normally runs from the dorsal fin to the tail flukes. The challenge, they realized, would be figuring out how to keep the prosthesis on. Winter would be putting an incredible amount of force on the tail while swimming but wouldn’t be pressing the entire weight of the body into it, as a human does with a prosthetic leg. ‘Water’, Strzempka reminds me, ‘is a totally different environment.’ What’s more, dolphin skin is slippery, sensitive and delicate – and very easily injured.
Human amputees commonly use soft liners to cushion their stumps and shield their skin, and Carroll and Strzempka decided that Winter would need something similar. But the standard human liner wouldn’t do – for Winter, they’d have to create a brand-new material, soft enough to protect her skin, sticky enough to stay put on a slick surface and strong enough to withstand daily use and abuse in a tank full of salt water.
They enlisted the help of a chemical engineer, who tinkered with the recipe for a gel liner common in human prosthetics, trying to create a version more suitable for a dolphin. The first few prototypes he made were promising, but their performance was inconsistent, and there were several dramatic failures, including a fire that burned a warehouse to the ground. (‘It was a small ware house’, Strzempka assures me.) Finally, the engineer nailed it.
‘It’s incredible material’, Carroll says, as we sit inside the trainers’ office at the aquarium. He hands me a sheath of the rubbery gel, which is white, jiggly and slightly gummy to the touch. It resembles nothing so much as a supersized piece of calamari. Technically, the material is a thermoplastic elastomer – a mixture of plastics that begins as a liquid and can be moulded into a variety of shapes when heated – but everyone just calls it the ‘dolphin gel’. Eager to show off its properties, Carroll takes a half-metre strip of the dolphin gel and hands the other end to Strzempka. He starts walking backwards. One, two, three metres – the material just keeps stretching. Finally, Carroll lets go. His end whips back across the room. Strzempka holds up the gel; it looks as good as new, neither distended nor deformed. The men beam, and I get the sense that this is a well-rehearsed stunt. The gel also provides serious cushioning, which Carroll demonstrates by wrapping his hand in the liner and beating it furiously with a heavy mallet, before breaking into a grin and pulling out his unharmed hand.
To make sure that Winter didn’t reject the strange material, the dolphin’s trainers introduced it slowly, giving Winter a piece of the gel to examine, then gently touching her body with it, and eventually wrapping it around her entire stump. They repeated the process with the prosthesis itself, starting by attaching a tiny, lightweight contraption to Winter’s peduncle, working up to larger and heavier devices.
Winter’s an old pro now, happily wearing a full-size, anatomically correct prosthetic tail. To put the device on, a trainer balances on a platform suspended in Winter’s tank. With one swift command, Winter gets into position, head down towards the bottom of the pool and peduncle sticking up out of the surface of the water. A trainer rolls a sleeve made of the dolphin gel onto Winter’s stump. Then comes the prosthesis itself, which Carroll and Strzempka carefully constructed after taking a series of three-dimensional images and scans of Winter’s body. The prosthesis has a flexible, rubberized plastic ‘socket’ that slips on over the gel liner, hugging what remains of the dolphin’s peduncle. The socket tapers into a thin carbon-fibre strip, which is bolted onto a pair of fake flukes. Suction keeps the entire apparatus on.
Though the device is modelled on a dolphin’s natural tail, it’s made of all sorts of unnatural materials, and Winter has to be supervised while she’s wearing it. Winter’s caretakers need to make sure that the tail doesn’t suddenly start to slip off, for instance, or catch on something in the pool, and that the metal pieces don’t accidentally injure one of her dolphin playmates. So Winter doesn’t wear the tail all the time. Instead, it’s reserved for her daily therapy sessions, when trainers lead the prosthesis-wearing dolphin through a series of drills designed to build up her muscles and reinforce proper swimming posture. (During these sessions, the trainers also use gentle pressure to stretch and straighten the muscles in Winter’s stump.) The artificial tail helps keep Winter’s spine in proper alignment, and with it on, Winter does, indeed, flick her tail up and down, rather than from side to side. ‘It’s just beautiful to see her swim with it’, Carroll says.43 Winter’s scoliosis has improved since she started wearing the device, and Carroll hopes the prosthesis, combined with regular therapy, will help the dolphin lead a long, healthy life.
Despite this progress, Winter will spend the rest of that life in an aquarium; a dolphin without a tail, or with a human-fashioned one, is not a great candidate for survival in the wild. There’s no telling how the prosthesis would hold up to years of constant use, whether it might fall off or fall apart, and Winter will need continuing access to trainers to reinforce proper swimming posture and doctors to monitor the alignment of her spine. Winter will need prosthetists on hand to repair damage to the tail, as well as to make other refinements. In fact, Carroll and Strzempka are still making several new tails a year for Winter, who has not yet reached her full adult size, tweaking the design as her body changes and her muscles develop. They also dream of making more dramatic improvements to the prosthesis. For instance, Strzempka says he would love to figure out how to incorporate a vacuum device that pumps air out of the tail whenever Winter moves it up and down. The result would be an even tighter seal and a constantly self-adjusting prosthesis.
Winter’s tail has earned the dolphin fully-fledged celebrity status. There are books, video games and documentaries about her, and in 2011, Warner Bros. released Dolphin Tale, a 3D movie based on her story. (The prosthetist, or ‘mad scientist character’, as Carroll calls him, is played by Morgan Freeman.) The aquarium’s website and gift shop is chock-a-block with Winter gear: T-shirts, postcards, magnets and dolphin plush toys that are also missing their tails.
But Winter has become much more than a powerful marketing tool – she has also become an ambassador for prostheses. Children with artificial arms and legs regularly visit the aquarium, and many are invited into the tank with Winter. The encounter can do wonders for a kid’s psyche, Carroll tells me. ‘The psychological aspect of it is just incredible, for a child [who’s] lost a limb’, he says.
Winter has helped human amputees in more concrete ways, too; as word spread about the so-called dolphin gel, prosthetists began ordering it for their human patients. The material, which grips the skin better than the liners commonly used with people, has proven especially useful for amputee athletes, whose replacement limbs start to slide off when they sweat. Strzempka, an avid golfer, became a convert the first time he tried the gel in his own artificial leg. ‘The stickiness is a huge benefit, especially in Florida’, he says. ‘If you’re golfing thirty-six holes a day, your skin becomes like a dolphin’s – slippery.’ It didn’t take long for Hanger to start selling ‘WintersGel’ liners to everyone from seasoned triathletes to eleven-year-old girls. ‘Animals give back to us all so much’, Carroll says. ‘We learn so much from working with them.’
Injured animals easily capture our hearts, and it’s natural to want to heal their wounds. Bringing home a bird with a broken wing or an ailing, tick-covered stray is practically a childhood rite of passage. (My stray was a sickly, starving Dobermann puppy, who I found wandering in the woods. His skin was so wrinkled and loose that we named him Raisin.) We naturally empathize with animals that are suffering; some neuroscience research has revealed that the brain regions that are active when we see fellow humans in distress also light up like arcade games when we see an animal in pain.
Animals have all sorts of ways of communicating their distress – they may cease to eat or groom themselves, or may pace, whimper, cry or obsessively lick or rub parts of their bodies. Sheep in pain curl their lips, horses sweat excessively, apes and monkeys roll their eyes. Mice make grimaces, and scientists have developed a ‘mouse grimace scale’ so researchers can assess their rodents’ discomfort. But animals can also be incredibly ‘stoic’, and since they can’t talk to us, it’s not always obvious whether they need medical attention.
Not everyone thinks that prosthetists are doing the right thing when they intervene in the lives of injured animals. Though Carroll and his colleagues are driven entirely by the desire to help their patients, human-designed, factory-manufactured appendages still represent a radical refashioning of animal bodies. And Carroll often encounters naysayers, other prosthetists or members of the public who insist that his devices won’t work or that they’ll cause wild creatures undue distress.
Some of the critics’ concerns mirror those faced by the scientists who use electronic tags to track the movements of wild animals: Will this device cause physical or psychological discomfort? How will the animal adjust to having a foreign object attached to its body? Vets and doctors must weigh the answers to these questions against the potential medical consequences of not giving an animal a prosthesis. The Clearwater Aquarium could have spared Winter the medical scans, tail fittings and training sessions that her prosthesis required, but the tradeoff might have been a lifetime of deformity and pain.
Not every case is so straightforward. When I visited Carroll at one of his clinics, he showed me photos and X-rays of a California sea lion missing part of its left flipper. The mammal’s caretaker had just called, wanting to know whether a prosthesis was an option. Carroll ultimately decided to pass on the project because he thought the sea lion was doing just fine and wasn’t sure a false flipper would improve her quality of life. But there’s no way of knowing, for sure, whether that was the right decision.
And there’s even trickier territory: the use of prostheses to alleviate an animal’s mental anguish. Take the dog owner Gregg Miller, for example, who swears that his beloved bloodhound Buck was downright depressed after getting neutered. According to Miller’s recollection, Buck came out of surgery, went to clean himself, noticed his missing bits, and then looked up mournfully at his owner. ‘Good God, it was horrible’, Miller recalls. In those awful first days after the operation, a novel thought occurred to Miller: Maybe he could buy some fake balls and use them to make Buck look whole again. ‘Don’t they make artificial testicles so it can reduce my trauma in neutering Buck and Buck’s trauma at losing a body part?’ he wondered.
When Miller discovered that no one made prosthetic dog testicles, he decided to create them himself. ‘People thought I was nuts’, he says. ‘No pun intended.’ Working with veterinarians over the course of two years, Miller developed ‘Neuticles’, and launched the CTI (Canine Testicular Implantation) Corporation to sell them. The implants are shaped like oversized butter beans and are designed to perfectly replicate the ‘texture and firmness’ of the genuine articles. (I’ll have to take Miller’s word for it.)
The first dog received his counterfeit gonads in 1995.44 The Neuticles were popped in while the pooch was on the operating table having his real testicles removed, adding just a few extra minutes to the surgical procedure. When the dog came to, it looked as though he’d never even been neutered. (As CTI’s slogan asserts: ‘It’s like nothing ever changed.’) The prostheses come in an assortment of sizes and materials; prices range from $109 (£70) for a ‘petite’ pair of the original Neuticles to $1,299 (£830) for a set of extra-extra-large, top of the line NeuticlesUltraPLUS. The company also sells models designed for cats, horses and bulls, and more than 250,000 pets in forty-nine countries have now received fake balls.
That’s a lot of animals that have been spared the humiliation of emasculation. Perhaps. It’s hard to know what the dogs think of the implants, or whether they’d even notice if they suddenly vanished. That’s the challenge involved in outfitting animals with prostheses: Other species can’t weigh in on whether and how they want their bodies to be remade. Though brain imaging lets us witness animal minds in action, as one neural circuit or another lights up, we’ll never truly comprehend what life is like, on the level of subjective experience, for a member of another species.45 (We have enough trouble imagining what life is like in another person’s shoes.)
In his famous essay ‘What Is It Like to Be a Bat?’ the philosopher Thomas Nagel expounded on this very problem. As he wrote:
It will not help to try to imagine that one has webbing on one’s arms . . . which enables one to fly around at dusk and dawn catching insects in one’s mouth; that one has very poor vision, and perceives the surrounding world by a system of reflected high-frequency sound signals; and that one spends the day hanging upside down by one’s feet in an attic. In so far as I can imagine this (which is not very far), it tells me only what it would be like for me to behave as a bat behaves. But that is not the question. I want to know what it is like for a bat to be a bat. Yet if I try to imagine this, I am restricted to the resources of my own mind, and those resources are inadequate to the task.
Neutering may well be traumatic. Surgery is stressful and recovery can be painful. A dog’s gonads produce sex hormones, and removing them can cause behavioural changes, especially a reduction in mounting, marking and aggression. But just because neutering alters sexual behaviour doesn’t mean that it causes a crisis of sexual identity. As the Humane Society of the United States explains in an online guide to spaying and neutering, ‘Pets don’t have any concept of sexual identity or ego’. And behavioural changes don’t necessarily equal distress. Miller says that he finds neutering to be ‘a creepy, creepy thing. You’re modifying your dog, you’re kind of playing God.’ But Neuticles don’t unmodify the animal – they merely add a second alteration on top of the first.
Though I have yet to find any peer-reviewed research on whether Neuticles can prevent neutering-related trauma in dogs, a study of monkeys provides a hint. Scientists studying the effects of monkey castration used Neuticles as a control – after removing the testicles of half the animals, they inserted silicon imposters. That way, all the male monkeys would continue to look identical to the other members of their social group. However, the prosthetic balls didn’t prevent the neutered primates from behaving more submissively than their intact counterparts. The finding suggests that it’s the absence of hormones, not some sexual identity crisis that results from looking like a eunuch, that causes behavioural changes in neutered animals. And Neuticles don’t restore a male dog’s normal hormone levels, nor do they spare him the trauma of the surgery itself.
So are Neuticles really for dogs? Or are they for humans, a way for us to atone for the castrating we put our pooches through? Most of his customers, Miller says, are ‘freaking out over neutering their dog.’ The possibility of testicle implants soothes their psychic pain, and some animal welfare groups have endorsed Neuticles because they may spur pet owners who are on the fence about castration to go ahead and get their pets fixed.46 (In fact, when Miller heard that President Bill Clinton had expressed hesitation about neutering Buddy, the First Dog, he did something that required both literal and figurative cojones; he asked the leader of the free world to give some thought to a prosthetic package.)
I never considered Neuticles when I got my dog, Milo, neutered, perhaps because I’m a woman. According to a survey of nearly sixteen thousand Australian dog owners, men are twice as likely as women to believe that neutering fundamentally changes a dog’s ‘maleness’.47 It occurs to me that Neuticles might be a lot like ‘truck nuts’, those fake plastic testicles men sometimes affix to the back of their vehicles – there to telegraph the virility and manliness of the owner. Indeed, one male customer reported that his only disappointment with Neuticles was that he and his wife hadn’t bought their dog a bigger size. According to one scholar of gender studies and human-animal interactions, ‘many men continue to view their male pets as personifications of their own egos and libidos’.
Neuticles are a bit, well, nutty, they don’t strike me as cruel. Especially when we compare them with some of the other things we do to dogs’ bodies. Take tail docking, for instance, in which the last several inches of a puppy’s tail are removed, usually without anesthesia, sometimes with extremely crude instruments such as scissors or razors. While the Kennel Club of the UK has banned tail docking in dogs (with a few limited exceptions), its American counterpart, the American Kennel Club (AKC), prefers boxers, Rottweilers, Cocker spaniels and dozens of other breeds to have docked tails.48 In other words, the ideal American specimen of these dogs is one that’s been surgically reshaped by humans.
Speaking of surgery, some vets are now giving dog owners the opportunity to have their pooches nipped and tucked. Pet plastic surgery can have a medical rationale – nose jobs can make it easier for some breeds (such as pugs) to breathe, face lifts can eliminate folds of skin that trap bacteria, and doggy braces can alleviate sores caused by crooked teeth. But one veterinary surgeon in Brazil says he has no problem performing the procedures for purely cosmetic purposes. ‘Why shouldn’t a dog be beautiful?’ he told the BBC. ‘Beauty is desirable. We all like talking to someone who looks good and smells nice. It’s the same with dogs.’ But does the search for beauty alone, especially in the eye of a human beholder, really justify putting these canines under the knife?
Neuticles provide another way for us to project our own aesthetic ideals onto our pets, but the false balls also represent something more complicated than that. While few would argue that docking a Cocker spaniel’s tail makes the animal happier, hundreds of thousands of customers think synthetic testicles are good for their dogs. (One pet owner’s silly silicone sac is another’s medical miracle.) Neuticles – and the strange mixture of motives that may prompt their purchase – illustrate how hard it can be to untangle our own interests from what best serves an animal.
Even Kevin Carroll, who says his work is motivated purely by a love of other creatures, faces critics. But he is undaunted by those who say that animal prostheses are a waste of time and money. ‘We try to work around positive people [who] think there’s options out there, that there are solutions that can help an animal get back up and walk again’, he says. ‘I think it’s critical to take care of our animals and to help rehabilitate them when they get injured. Mostly the ones that we see, it’s humans that have injured them, and I think it’s important that humans put them back together.’
Carroll and his colleagues have worked with animals for whom prostheses have been lifesaving. After Winter’s story appeared in a local newspaper, Carroll got a call from Lee Fox, who runs Save Our Seabirds, an avian rescue and rehabilitation facility in Sarasota, Florida. Sandhill cranes commonly come into Fox’s care; the birds are often hit by speeding cars and wayward golf balls, irreparably damaging their delicate legs. Because of how the birds are built – with long, thin legs and big, heavy bodies – a crane with a bum leg is usually a crane that will be euthanized.
Fox was, she says, ‘truly, physically sick about having to put down one sandhill after another’, so she began outfitting her birds with prostheses she rigged out of some PVC pipes and sink plugs. When she met Carroll, he fashioned a more comfortable, permanent solution, taking plaster casts of the legless birds and making prostheses out of lightweight plastic. The recipients included a crane named Chrisie, and Fox vividly recalls the day Carroll first put his device on the bird: ‘Chrisie walked in hers like it was her own leg.’ The birds even use their artificial limbs to scratch themselves, something healthy cranes do with their natural legs. As Carroll notes, ‘Animals are wild, so they’re very adaptable to their situation. We help them and they get along with their little lives.’
Cranes aren’t the only creatures that could be saved by a well-engineered false limb. Horses are usually put down when they break or seriously injure a leg, and while some dogs career around just fine on three paws, not all adapt as easily. A corgi, for instance, with its long, tubby body, can’t manage on three legs, says Noel Fitzpatrick, a veterinary orthopedic surgeon with his own practice in Surrey. Fitzpatrick thinks vets have been too willing to euthanize pets facing the loss of a limb. ‘Animals deserve a good quality of life’, he says. ‘I’m not saying that you shouldn’t put a dog to sleep if there’s no other option. But there are circumstances, lots of them, where prosthetics really should be used.’
There’s especially no excuse today, he explains, given the advances in veterinary and materials sciences that are giving injured creatures more options than ever. Feline and canine anatomy present unique challenges for prosthetists – just as Winter’s body did. Though dogs and cats can wear devices that strap on to the outside of their bodies, they don’t always do well with them. Below-the-knee amputations in these species don’t leave much muscle or flesh for an external apparatus to grab on to, and their rounded bones are difficult for an artificial limb to grip. Above the knee, the animals have too much muscle, and lots of loose skin, surrounding their bones; even when a socket prosthesis is tightened all the way, cats and dogs can sometimes pull their legs right out. What’s more, pets often kick, chew or claw off a strap-on device.
Fitzpatrick has been pioneering an alternative kind of prosthesis that gets around many of these difficulties.49 His approach, known as osseointegration, involves implanting one end of a prosthetic leg in an animal’s stump and fastening it to whatever bone is left. The metal implant then passes through the skin and can be attached to a specially engineered foot or paw, creating what Fitzpatrick calls ‘a bionic dog’.
Fitzpatrick knew that osseointegration was not without risks: A bone-anchored prosthesis breaks the skin barrier, jutting out through a patient’s stump, providing an easy entrance for bacteria and leaving the patient susceptible to serious infections. Fortunately for the vet, Gordon Blunn, a biomedical engineer at University College London, thought he had a solution to this very problem. Blunn believed that surgeons could learn from deer antlers, one of very few cases in nature where skin and bone are tightly bonded. The secret to this strong marriage, one of Blunn’s PhD students discovered, is that antlers are covered with tiny pores. Collagen fibres grow into and through these openings in the bone, creating a permanent connection between the antler and the surrounding skin. A pore-pocked prosthesis that mimicked deer antlers, Blunn proposed, might interface with the skin to create a protective seal against infections.
Using antlers as inspiration, Fitzpatrick and Blunn designed a medical device for legless animals: the intraosseous transcutaneous amputation prosthesis, or ITAP. By 2007, they were using it in pets. One of the first patients was an American bulldog named Coal, who had a tumour in his front left paw. The normal treatment would have been full amputation of the leg, but Coal had arthritis in his other limbs and was likely to struggle as a three-legged dog. So Fitzpatrick agreed to give Coal an ITAP. With the dog under anesthesia, Fitzpatrick inserted a rod made of a titanium alloy into the centre of what remained of Coal’s radius. As the rod emerged from the bone, it opened up into what resembled an upside-down umbrella. Fitzpatrick stretched Coal’s skin over this rounded cap, which was dotted with small holes, much like a deer’s antler. Then the surgeon sewed the bulldog up, hoping that Coal’s soft tissue would grow into and through the implant, creating permanent links between skin, metal and bone. Fitzpatrick left a short segment of titanium jutting out from Coal’s stump, into the open air. When the dog’s wound healed, his owners could then pop an artificial paw on and off the metal rod.
The antler-inspired device worked – Coal’s tissues gradually grew into the implant, forming a sturdy seal, and there were no signs of infection. The bulldog adapted beautifully to his new leg. ‘The ITAP didn’t just improve Coal’s quality of life, it gave him life’, his owner wrote in a testimonial. ‘Coal led a perfectly normal life after the operation, there was absolutely nothing he couldn’t do. He would use his prosthetic leg to bash at the door to be let out, and used it with his good paw to hold food and toys, as well as give you his “paw” when he wanted a treat. The most amazing thing was people never noticed he had a prosthetic leg until they actually looked closely.’
Coal has been followed by other successes, including a black cat named Oscar, who received two ITAPs after losing both his back paws in an unfortunate run-in with a mechanical grain harvester. Fitzpatrick, who was the subject of the BBC documentary The Bionic Vet, estimates that he’s done about two dozen of these animal ITAPs. The procedure has been so successful in animals that human trials of ITAPs are under way in the UK. (One of the first recipients was a woman who lost her arm during the 7/7 bombings of the London Underground.)
Fitzpatrick’s technique is just one approach to osseointegration, and a handful of other vets are trying out their own variations. Denis Marcellin-Little, a veterinary orthopedist at North Carolina State University, has a number of canine patients that are either overweight or very active and thus not good candidates for conventional, strap-on prostheses. With osseointegrated devices, Marcellin-Little has helped some of these formerly hopeless cases get back on their feet again. Meanwhile, one equine researcher is designing implants that could be used to build bone-integrated prostheses for horses; the devices might save the lives of race horses such as Barbaro, the Kentucky Derby champ who had to be euthanized after breaking a leg and suffering from an escalating series of complications. (Veterinarians tried to repair Barbaro’s leg, but it didn’t heal well, causing additional strain on his good legs. Eventually, these limbs, too, began to break down, leaving the horse literally without a leg to stand on.)
Animal prostheses, and the research and development required to create them, are not cheap, and Fitzpatrick says he’s sometimes asked why he’s spending so much time and energy designing a leg for someone’s dog. The endeavour is about more than just giving a pet a new limb, he says. ‘It’s about life and love. It’s about the bond of love between an animal and a human that is a small microcosm about how things could be better on Earth.’
Osseointegration is also a step towards building an even more futuristic kind of prosthesis – one that is not only a permanent part of the body but also works seamlessly with the nervous system. With such devices, patients will be able to move manufactured limbs more like natural ones, wiggling carbon-fibre fingers or toes just by thinking about it. There have already been major breakthroughs. Monkeys outfitted with brain implants have been trained to use just their thoughts to move external robotic arms – in one case, using an arm to feed itself marshmallows – and paralysed humans have performed the same feat. (Instead of eating marshmallows, the human volunteer used the robo-arm to give his girlfriend a high five.) Scientists at the Rehabilitation Institute of Chicago have succeeded with a different approach, taking the nerves that would normally control the movement of a missing arm and moving them into the muscles of the chest in several human amputees. Patients learned to use the nerve signals generated by the use of these muscles to control virtual arms on a computer screen, as well as motorized prosthetic limbs.
The main goal in developing these robotic limbs has been to improve the lives of human amputees or quadriplegics. In particular, the Defense Advanced Research Projects Agency (DARPA), part of the US Department of Defense, has invested a lot of time and money in this area of research, hoping to find better solutions for injured military veterans. However, just because animals aren’t the intended beneficiaries of this work doesn’t mean that they won’t benefit along the way. Prosthetic innovations flow back and forth across species lines, and it wouldn’t be surprising to see scientists refining nerve-integrated prostheses in injured animals or veterinarians borrowing tools and techniques being used in human patients. A variety of diseases and conditions cause hind leg paralysis in elderly dogs, for instance; by turning these canines into cyborgs, with brain-controlled prostheses, we could give them back control of their nervous systems.
Or we could do something even more extreme: build bionic animals and then take control of their nervous systems ourselves.