Lucy and Modern-Day Surgery: Australopithecus afarensis
OUR BODIES ARE made up of components that, after billions of years of trial and error, have become closely related to each other at macroscopic, cellular and molecu-lar level. To understand them, you need knowledge of several natural sciences, including biology, biochemistry and genetics. They are so complex that it is easy to overlook the fact that many of those components work surprisingly simply. The venous valves in our veins, which prevent the blood from flowing in the reverse direction, are a good example. The explanation of how they work may seem a little technical, but with some knowledge of gravity and pressure, they are easy to understand.
On the inside of each of our legs, a long vein runs just below the skin, from the ankle right up to the groin. This is the great saphenous vein, or GSV for short (one origin of the word ‘saphenous’ is saphon, the Latin for ‘cable’). Together with a number of smaller veins, the GSV comes out in the groin in a short, curved section of vein resembling a shepherd’s crook, called the saphenous arch. In the saphenous arch, there is a small valve. This is nothing out of the ordinary, as all veins below this point have valves, to stop the blood from flowing back downwards under the influence of gravity. Strangely enough, however, there is not a single valve to be found in the long stretch of veins above the saphenous arch, from the groin to the heart. In an adult human, during the day, that one small valve in the saphenous arch therefore has to resist the pressure of a column of liquid some 50 centimetres long. That is five times greater than the pressure on any of the other valves in our veins. A lot to expect from a valve that is otherwise completely normal, not especially strong or built to withstand such high pressure. As a result, the small valve in the saphenous arch can sometimes malfunction. It no longer stops the backflow of blood and starts to ‘leak’. This can cause varicose veins.
Varicose veins are abnormally enlarged subcutaneous veins through which the blood flows upwards too slowly, does not flow at all, or even flows back downwards. They are not only unsightly, but can also cause problems, such as pain, itching and eczema in the surrounding skin. They usually start with a leaking valve, often the valve in the saphenous arch, as that is most under pressure. If the valve fails, the pressure is relocated downwards to the following valve, around ten centimetres lower down the leg. This valve then has to cope with the column of liquid, which is now ten centimetres longer. If that valve also fails, there is even more pressure on the next one. In this way, the pressure steadily rises and the GSV will gradually blow up like an elongated balloon. Eventually, all the valves will leak and the GSV, normally no thicker than half a centimetre, will enlarge to form varicose veins, which can in some places grow to the size of a bunch of grapes.
So the cause for varicose veins is that one small valve in the saphenous arch is too weak for the job it is supposed to do because, for some mysterious reason, there are no valves in the large veins above it. The obvious question is: why? The answer is staggeringly simple.
To find it, we have to go back 3.2 million years, to Lucy, a twenty-five-year-old Australopithecus afarensis. Lucy and the other members of her species were among the first of our ancestors to walk on two legs. Lucy, by walking upright, is at the root of half of modern-day surgical practice. Parts of her skeleton were found in Ethiopia in 1974 by paleoanthropologists Donald Johanson and Tom Gray. They called her after the Beatles’ song ‘Lucy in the Sky with Diamonds’, which was playing on the radio when they were digging. Lucy is currently to be seen in the national museum in Addis Ababa and replicas can be found in museums all around the world.
Let us assume that Lucy’s mother still walked on all four legs. That meant that the liquid column in the major veins between her groin and heart was horizontal. And because no pressure builds up in a horizontal liquid column, Lucy’s ancestors did not suffer from varicose veins. Valves in the major veins ‘above’ the saphenous arch would have been pointless for the simple reason that they were not above it.
Varicose veins are therefore as old as the modern human. The first report of varicose veins is from Egypt and is more than 3,500 years old. The earliest illustration dates from the golden age of Athens, and Hippocrates was the first to treat them with bandages. The Roman Celsus described the removing of varicose veins by making an incision and drawing them out with a blunt hook. According to Plutarch, consul Gaius Marius, the uncle of Julius Caesar, was more affected by the pain of this operation than by the result, and refused to allow his second leg to be operated on. Pliny tells us that this tough-guy statesman was the only one to undergo the operation standing up, refusing to be bound to the operating table. Tough indeed, but also a little foolish as, because of the higher pressure in the vertical liquid column, much more blood spurts out of the open varicose veins during the operation than if the patient is lying down.
The valves in the veins were not described until after the Middle Ages. Even so, that does not mean they were understood. Ambroise Paré was the first surgeon to think of tying off the GSV with a ligature high in the upper leg. We now know that doing this cannot cause any real harm, as there are plenty of veins to take over the work of the GSV – but did Paré know that?
In 1890, German surgeon Friedrich Trendelenburg described the high ligature in greater detail and was the first to display some insight into varicose veins being caused by the leaking of the venous valves and the increased hydraulic pressure. This marked the step to functional treatment. The position of the patient on their back, with the operating table tilted with the head down and the feet up, is named after him. In the Trendelenburg position, the hydraulic pressure is reversed, becoming negative in the legs and positive in the heart. The increase in pressure in the heart is favourable for patients in shock and the low pressure in the legs is better for performing varicose vein operations.
At the end of the nineteenth century, Australian surgeon Jerry Moore perfected the methods of Paré and Trendelenburg. He understood that you should not tie off the GSV as high as possible, but go one step further and tie off the saphenous arch. This became the standard method in modern times, and is known as a crossectomy, after the French for a shepherd’s crook, crosse. The procedure not only allows the existing, visible varicose veins to be treated, but also prevents the problem from reoccurring.
In the twentieth century, the crossectomy was combined with ‘stripping’, a method by which the GSV can be removed subcutaneously completely and in one go. This was – and remained until around 2005 – the standard procedure for treating varicose veins, the whole operation taking no more than fifteen minutes per leg. Theodor Billroth, one of the greatest names in the whole history of surgery, was vehemently opposed to varicose vein operations, without bothering to explain why.
And then came Sven Ivar Seldinger, a Swedish radiologist who turned the whole of vascular surgery on its head. In 1953, he invented a method that made it possible to treat blood vessels endovascularly – from the inside. Thanks to the Seldinger method, in 1964 another radiologist called Charles Dotter invented percutaneous angioplasty, a brilliantly simple idea for the treatment of narrowed arteries by stretching the blood vessel from the inside with a small balloon. In the twenty-first century, the Seldinger method is used to treat not only arteries, but also varicose veins. The GSV can be seared from the inside with laser or microwave treatment to seal it off. And all without the need for a scalpel.
Circulation
The heart consists of two halves. The right half pumps blood from the body to the lungs under slight pressure. The lungs are delicate and cannot withstand high pressures. The left half of the heart pumps the blood from the lungs to the rest of the body. Here, the blood pressure is much higher. Arteries transport the oxygen-rich, bright-red blood from the heart to the furthest edges of the body. Veins collect the blood from the whole body and carry it back to the heart. The workings of the heart and the blood vessels – the circulation – was a complete mystery until 1628, when the Englishman William Harvey spent several hours looking at the beating heart of a dying deer, which he had cut open while it was still alive. He described his findings in a treatise entitled Exercitatio Anatomica the Motu Cordis et Sanguinis in Animalibus. No one had ever understood the body’s circulatory system before mainly because, after death, blood coagulates, so that the blood vessels of a corpse seem to mainly contain air. The return of the blood to the heart occurs through a combination of the movement of the limbs and the valves in the veins. This is known as the skeletal-muscle pump. The suction power of the chest also helps this process. When we breathe in, negative pressure is created in the chest cavity, drawing blood up out of the abdomen and the limbs. The veins of the digestive system and the spleen are an exception in the circulation system. Known as portal veins, they transport the blood to the liver, rather than back to the heart.
Lucy brought humankind even more problems. If she did not happen to have three small blood vessels in her rectum that kept her anus watertight (the haemorrhoidal veins), she would probably have changed her mind after her first few steps and gone back to walking on four legs. The act of defecation has never succeeded in adapting: we still have to bend our hips at 90 degrees to do it. The fact that this now requires much greater pressure leads to typical human problems like haemorrhoids, prolapses and constipation.
Another regular feature in the daily work of a surgeon that we have Lucy to thank for is the inguinal canal. This is a weak spot at the bottom of the abdominal wall, exactly where it should be at its strongest. Gravity continually forces the contents of the abdomen against the inside of this weak spot. That can lead to a hole, known as an inguinal or groin hernia, an opening that evolution seems to have forgotten. But if we imagine ourselves on four legs again, the inguinal canal then appears to be higher than the centre of gravity of the abdomen, not lower. So no problem for our four-legged friends, but a real design flaw for us bipeds. Because we walk upright, modern men have a 25 per cent chance of developing a groin hernia in their lifetimes. And that means plenty of work for the surgeon.
The transition from quadruped to biped also meant of course that the hips and knees had to bear twice as much weight. And the intervertebral discs, which separate the individual vertebrae in the spine, went from supporting practically nothing (horizontally) to carrying half the body weight (vertically). This excessive load on the knees, hips and back led to the development of a sister discipline of surgery – orthopaedics. Orthopaedic surgeons spend a large part of their time replacing overburdened hips and knees with prostheses and removing hernias in the back.
The most conspicuous fault can be seen in the arteries running to the legs. They still make a 90-degree bend characteristic of quadrupeds, deep down at the back of the pelvis. This bend was necessary because the hind legs of an animal are at right angles to the trunk. Since we spent most of the time we were evolving from primitive land animals to humans walking on four legs, natural selection has made the 90-degree bend in our arteries wide, spacious and gradual. That causes the least possible turbulence in this stretch of the circulation system, which is important for our survival, as turbulence in the arteries can cause damage to the artery wall. Because we now walk upright, however, after making the gentle, gradual bend of the quadruped, the leg arteries now have to bend back another 90-degrees in the groin. This is not a smooth curve, but a sharp kink that has not adapted and does cause turbulence. That leads to hardening of the arteries (arteriosclerosis), resulting in narrowing of the blood vessels near the kink. And that is why hardening of the arteries in humans is most common in the groin. If the arteries gradually become narrower, the legs receive insufficient oxygen-rich blood at the moment that they need it most – during exercise. That causes pain when walking, which disappears immediately again when standing still. This condition is known medically as intermittent claudication (from the Latin claudicare, ‘to limp’), but in Dutch it is appropriately called ‘window-shopping legs’, referring to the fact that the pain of walking down the street will subside every time you stop to look in a shop window. Eventually, the legs can die off, causing gangrene. This is not something quadrupeds have to worry about.
And so we have accumulated quite a list of complaints treated by modern-day surgeons that can be traced back to Lucy. Varicose veins, haemorrhoids, groin hernias and narrowing of the arteries account for perhaps half the work of the average surgical practice. In other words, a large part of the work of the surgeon consists of patching up what went wrong when Lucy decided to walk on two legs. Incidentally, Lucy was given a second name, in Ethiopian – Dinqines, which means ‘you are amazing’. Surgeons can agree with that.