Transplants: from hands to heads
We’ve considered robotic exoskeletons, and an implantable replacement pancreas, but sometimes a prosthesis isn’t right for a range of reasons and a transplant of human tissue is the best option. One example is when a person loses a hand or a limb. But not only are there psychological obstacles to overcome with this sort of surgery, practitioners were initially also worried about the challenge posed by immune rejection. For this reason it’s only within the last 20 years that doctors have carried out the first hand transplant. Now it’s gathering pace, and Alexandra Ashcroft heard how, from Leeds University hand surgeon Simon Kay, who is also Director of the UK Hand Transplant Programme...
Simon - When you lose an upper limb, or part of an upper limb, the options are to live with what you have, to create a prosthetic, or to have a limb transplant, and limb transplantation is very new. You take a hand from a recently deceased person who’s on the donor register, just as you would for a kidney or a liver, and you transplant that onto the limb that’s deficient. But then that limb lives and has nourishment from its blood supply and its function begins as the nerve regeneration occurs in the limb.
Alex - You said that it’s quite novel, what sort of surgical advances have you and others made to get to the point where you can transplant limbs or hands to other people?
Simon - The first hand transplant took place in ‘99, and the most important hurdle that we didn’t appreciate in the very early days is the behavioural one or the psychology of the patient. The other main hurdle that was much vaunted but was actually proved to be very easy to deal with is the immunological rejection risk. That is to say, just as you can reject a kidney or a liver, you can reject the limb. So that barrier that we thought was enormous has actually begun to recede. The great thing about a limb transplant that has skin is that when it begins to reject you can see it immediately as a rash, so we found that the issue of immunological rejection is relatively straightforward to deal with. The other barrier has been understanding whether the long term regeneration of the nerves, and the recovery of movement and feeling in the limb is going to be at level that we would think is useful and, I’m pleased to say, that’s proved to exceed our expectations as well.
Alex - Are donors a problem?
Simon - Nobody really cares what their liver or their kidney looks like as long as it does the job. In hand transplant it really is important because one of the functions of the hand is that it’s on view all the time. Although we have a small volume of recipients in the UK and a large volume of donors matching, not just immunologically but also in size, approximate age, and skin characteristics makes the pool much smaller, so finding the right donor is a challenge.
Alex - How do these limb transplants in terms of the outcomes that they achieved, how do they compare to people who’ve had prosthetics?
Simon - Comparing transplanted limbs with prosthetic limbs is very interesting. They’ve been, as it were, in competition between transplant and prosthesis. In our view that’s not appropriate because they do very different things. The vast majority of patients will be improved and functionally improved by prosthesis alone. The great benefit of a prosthesis is that you don’t need to give the patient drugs and immunosuppression in order to use it. However, the limitation of a prosthesis is that it’s not human and one of the things about the hand is that it’s one of the very defining attributes of a human being. So it’s warm and sensate; we gesture with it, we stroke with it, we feel with it; that humanity you won’t get from a prosthesis. You do get it from a hand transplant; you get the cosmetic, the aesthetic, and the functional, and also the humanness of it, but it is at the cost of immunosuppressive drugs.
Alex - And they have pretty severe side effects I understand?
Simon - I think rather than saying they have severe side effects, they have significant side effects which can, because we now have a great choice of drugs, we can chop and change, mix and minimise the side effects. But, there’s not doubt that for a young person having a hand transplant, if we assume they keep that transplant for the rest of their natural life and they’re on immunosuppression for the rest of their natural life, that life will be slightly shortened. So when you’re contemplating a hand transplant, just as with any other major medical decision about treatment, you have to weigh the benefits of the treatment very carefully against the disadvantages. And, because we haven’t done hand transplants until ‘99, we’re still beginning to fill in the boxes on either side of that risk/benefit equation.
Alex - Where do you think your field will be in the next decade to come?
Simon - I think the proof of concept is now virtually done. These things move in a slow pace, but I think it is becoming understood and accepted that hand transplantation is reliable. And, furthermore, that it produces very good and useful results that are enduring and those have been very important bridges to cross.
Alex - Shifting the focus a little bit to Sergio Canavero’s first attempt to do the World’s first human head transplant in December; what do you think about this?
Simon - I think it’s a thing that needs to be debated and the ethics very carefully considered. But when we’re talking about head transplant, what we’re really talking about is a body transplant. The internal human being resides within the cranium and if you have an alert, active human brain and you have a body that is failing then there is a logic to saying well, can I replace the body? And there’s no theoretical reason why you can’t. So, if you had a quadriplegic with organ failure, what you might say is well, the body is an inert support mechanism for the brain and I’d like to exchange that. Of course, it’s conceptually a head transplant because that’s a smaller part. But I see no overriding technical reason this can’t be conducted as long as you’re not expecting the body to function mechanically and get up and walk.
Alex - Because of connecting the spinal cord?
Simon - Because connecting the spinal cord is the “holy grail” of spinal surgery and that’s nowhere near at the moment...