Read The Rise and Fall of Modern Medicine Online
Authors: James Le Fanu
The Rise and Fall of Modern Medicine (17 page)
There are two things that can be done to provide relief from the misery of hip arthritis. The first is to fuse the hip by cutting away the top of the femur and ramming it into the pelvis to form a bony union, as when a fracture heals. This will abolish the pain but necessarily it also abolishes the mobility of the hip. The second possibility is to interpose some material that will reduce the pain by preventing bone rubbing on bone. The femoral head can be cut away and replaced by a metal prosthesis and the pelvic cup can be replaced by one made of plastic. The logical extension of this principle is to replace both surfaces with a total hip replacement or arthroplasty (from the Greek
arthro
for âjoint' and
plasty
for âform', i.e. the formation of a movable joint).
From the 1930s onwards many surgeons developed arthroplasty operations, including Marius Smith-Petersen of Boston, who claimed âgood' results in half his patients after four years.
Philip Wiles of the Middlesex Hospital in London designed a stainless-steel total hip replacement â which he inserted in six patients in 1958 âwith some degree of success'. Another British orthopaedic surgeon, Kenneth McKee in Norwich, developed a total hip replacement made of cobalt. Then there was the Judet arthroplasty, devised by two brothers, Jean and Robert Judet of Paris, whose initial results were exceptionally good though they did not last. The prosthesis cracked and had to be removed.
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The prevailing view in the mid-1950s on all these operations was summarised by the opening speaker in a debate â âIn the opinion of this house, all methods of arthroplasty of the hip have failed to achieve their purpose' â that took place at the annual meeting of the British Orthopaedic Association in Buxton in 1954.
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He drew attention to four failings: serious post-operative complications; early deterioration; the expense of the seemingly endless physiotherapy subsequently required; and, crucially, âthe faulty conception of the operation due to ignorance of the true pathology'. The arthroplasty was doomed to failure, he argued, because no one properly understood the biomechanics of the hip. The debate was notable for the intervention of a rising star in the orthopaedic world, 43-year-old John Charnley. A North Country lad, born and bred in the industrial town of Bury where his father kept the same chemist's shop in the centre of town all his life, Charnley was, according to a friend, âvery bright, very clever and very good company'. After war service in the Middle East he returned to Manchester to become the protégé of the godfather of British orthopaedics, Professor (Lord) Harry Platt. Small in stature, he was an exact man with what would now be described as elitist views. As for hip replacements, he expressed the opinion in the debate that their record was so poor and unreliable that it was much more
sensible â at least from the patients' perspective â to perform the simpler operation of fusing the hip, which at least was guaranteed to relieve pain, even though it resulted in a stiff leg.
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Within seven years of Charnley's intervention in this debate he had made âthe most significant development in orthopaedics this century' with a paper published in
The Lancet
in 1961: âArthroplasty of the Hip: A New Operation'.
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The stimulus that seems to have led him to change his mind and take up the challenge of developing a new hip was the arousal of his intellectual curiosity by a chance observation made by a patient attending his orthopaedic clinic at Manchester Royal Infirmary. This man had had a Judet prosthesis (an artificial head of the femur) inserted elsewhere. He told Charnley that his artificial hip had squeaked so loudly whenever he leaned forward that his wife avoided being in the same room with him whenever possible. The squeak lasted only a few more weeks before disappearing, from which it was only natural to infer that the movement of the artificial hip had become smoother. Charnley, however, drew the opposite conclusion and described his thinking as follows:
The starting point was the well-known observation that after the Judet operation the hip squeaks. The squeak indicates that frictional resistance to sliding is so high that the surfaces are seizing together. Hence it seemed likely the plastic of the Judet prosthesis had adverse frictional properties when sliding against the bare bone of the arthritic acetabulum. It seemed possible too that the loss of sensation of squeaking might be a sign not of improved lubrication but of loosening of the attachment of the prosthesis.
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Charnley inferred that if a total hip replacement was to work the frictional resistance between the two components had to be
as low as possible. He proceeded to rethink every aspect of the problem, coming up with three brilliant innovations concerned with lubrication of the joint, cementing the prosthesis in place and designing a socket with maximum stability.
Charnley started by investigating the nature of friction within the normal joint. Frictional resistance occurs when an object is moved tangentially with respect to the surface of another contrary object and is measured as âthe coefficient of friction'. When experimenting on a freshly amputated knee joint Charnley found this to be quite extraordinarily low, at 0.005 â better than that of a skate sliding on ice. Clearly the friction coefficient in an artificial joint similarly had to be as low as possible. This is best achieved by the juxtaposition of two materials â durable metal for the femoral prosthesis and some slippery substance to replace the damaged cartilage of the acetabulum. Charnley was advised that the recently developed Teflon would be suitable.
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The femoral prosthesis had to be made of metal if it was to be durable, but this raised the question of how to fix it in such a way that it would not become loose. It was customary to âfix' prostheses with screws, but Charnley came up with an entirely different suggestion which he later described as his âmost significant breakthrough'
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â the use of acrylic cement. He was not the first to use the material, but the first to understand its properties and how to use it properly. The function of the acrylic cement was not to act as a âglue' to hold the prosthesis in place, but rather as a âgrout' transferring the load of the prosthesis over the whole inner surface of the bone. In this way the fixation of the femoral prosthesis was increased by a factor of 200.
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Finally, for the hip replacement to be stable the femoral prosthesis had to articulate within its Teflon socket as firmly as possible. Charnley's brilliant solution was to reduce by an inch both the diameter of the head of the femoral prosthesis and the
diameter of the acetabulum cup.
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Thus Charnley's hip is not so much a replacement as a âreconstruction', in which, in order to ensure maximum stability and range of movement he redesigned nature's original to take account of the properties of the materials that were being used. The credit was certainly not entirely Charnley's, and he duly acknowledged the help of his engineering colleagues.
Charnley's 1961 paper describing his new operation is a masterpiece of non-technical lucidity. The results after just one year were very encouraging, with grossly disabled patients being able to return home within two months having shown they could âwalk the length of the ward without sticks and with only a slight limp'.
And then the following year disaster struck. Some time in 1962 it became clear that Teflon was not a suitable material for the âcup' component of the hip replacement. First, it was simply not tough enough and over a period of three to four years the Teflon lining had almost completely worn away. Second, the minute particles of Teflon generated a severe inflammatory reaction, loosening the cup in the pelvis so the hip became painful again.
There was no alternative other than to try and repair the damage and, according to one of his assistants, âevery time he did a revision operation it was like observing a monk pouring ashes over his head'. Charnley's biographer, William Waugh, describes this difficult period:
At home Charnley was in a state of despair and the failure was the main topic of conversation. He would arrive back from hospital without a smile even for his young children. He fell asleep from sheer mental exhaustion, and would wake in
the early hours. His wife, Jill Charnley, remembers him sitting up in bed with his head in his hands. She felt that âeverything was grey and there was an all-pervading gloom'.
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Charnley's despair was, however, mitigated by the surprising reaction of the patients. Once the news got out that the operation offered only temporary relief from their symptoms, he had expected that the number of new patients coming forward would fall off dramatically, but this did not happen. They filled the waiting room in his outpatients clinic just as before and even though told the operation only lasted for two years, they were still prepared to have it. âThere were others,' recalls Charnley, âwhen told they would have to have the operation repeated with a new socket of a different plastic material, who made such remarks as “well it was worth it, it was the best few years of my life”.' These reactions certainly emphasised the pain and suffering caused by hip arthritis and how people were prepared to do virtually anything for it to be relieved. But where was the plastic material to replace the failed Teflon to come from? If it could not be found, then Charnley knew he would have to abandon his operation.
A couple of months after the disastrous revelation of Teflon's unsuitability, a most peculiar thing happened. The hospital supplies officer rang Charnley's technician, Harry Craven, to say that he had recently met a Mr V. C. Binns, who was selling gears for weaving machines in the Lancashire textile factories made from a new type of plastic manufactured in Germany. Binns, it emerged, did not know very much about the qualities of this plastic, known as High Molecular Weight Polyethylene (HMWP), but he gave Craven a piece to test on his machine for investigating the wear of different materials. Craven duly showed the material to Charnley, who dug his thumbnail into it and
walked out expressing the opinion that Craven was wasting his time. But
Craven had a stubborn streak and persisted with the test: after the first day there were no signs of wear; and only 1/2000th of an inch at the end of two days which was incomparably better than Teflon. Meanwhile, Charnley went to a four-day meeting in Copenhagen and on his return he recalled: âMy office door opened to reveal Craven, who asked me to come down to the lab . . . down I went to see the HMWP. After running day and night for three weeks this new material, which very few people even in engineering circles had heard about at that time, had not worn as much as Teflon would have worn in twenty-four hours under the same conditions. There was no doubt about it â we were on.
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Not quite. Besides its poor durability, Teflon had also induced a severe inflammatory reaction. How could Charnley be sure that HMWP might not have the same effect? He duly injected a piece under his own skin along with a small piece of Teflon. He reported the result in
The Lancet
: âAfter several months the Teflon specimens are clearly palpable as nodules about twice the size of the original implant. The HMWP cannot with certainty be detected by palpation which I take to indicate that no reaction has been produced by this material.' Not only was HMWP remarkably robust, it was much less likely to produce the inflammatory reaction that had cursed the Teflon implant.
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As soon as he had obtained sufficient supplies from the German manufacturer, Charnley was off again. Over the next three years 500 patients were given the new hip. These became the âfirst 500' though Charnley, not wishing to tempt fate, waited a further seven years â till 1972 â to publish his results.
And what results they were! The average amount of pain before operation was âsevere on attempting to walk, prevents all activity'. This became ânone'. The average degree of walking disability was âtime and distance very limited with or without sticks'. This became ânormal'.
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There were failures and complications â infection, loosening of the prosthesis, âunexplained' pain â but the overall success rate of the operation Charnley put at, typically precisely, 92.7 per cent. His new hip had a further advantage. It not only dramatically relieved the symptoms of hip arthritis, but it also lasted. Charnley deliberately performed his first operations on patients in their late sixties in anticipation that the hip would only have to last at the most twenty years, which indeed it did. Patients reported that their new hips carried on doing sterling work, with almost all remaining completely âpain-free'.
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John Charnley died in 1982 at the age of seventy-one. An editorial in the
British Medical Journal
summarised the monumental nature of his achievement:
Despite the Charnley hip being one of the first joints to be used in large numbers twenty-five years ago, it still reigns supreme â the gold standard. Not one of the dozens of newer, more expensive implants being used by surgeons can match the figures obtained with the Charnley hip in skilled hands.
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More than any of the other definitive moments of post-war medicine, the development of the Charnley hip would seem to conform to the commonly accepted view of how science works. Take a well-defined problem â hip arthritis â devise some appropriate experiments to investigate the difference between the healthy and the pathological, and then, with
fastidious attention to detail, come up with a solution whose progress is then monitored in a way that generates reliable and replicable results.
