Maurice E. Müller is an almost legendary figure in orthopaedics. Nevertheless, he is very much in touch with reality and works tirelessly in the cause of his specialty. The simplicity of his welcome contrasted with the sophistication of the facilities at the M.E. Müller Foundation in Berne, where

we visited him, to obtain an interesting overview of his career as a surgeon. The following is an extract of an all too brief interview, which inevitably fails to reflect the full warmth and friendliness of this sterling character.

M.O. When did you become aware of your surgical vocation?

M.E.M. From the age of eight, my only ambition was to become a surgeon. I should mention that my father had been a surgeon in the States, but had to give up his career to live in Switzerland, because his wife did not want to move to the USA. At the age of 20, after some psychometric tests, my choice of profession was approved by the experts. They told me that their tests had identified a three-dimensional gift, which could be used to advantage in orthopaedic surgery. After my state medical examinations in 1944 I worked as a locum GP for three weeks. Two patients made a particular impression on me. The gait of the first was normal. He told me he had fractured his femur during the war between Finland and Russia in 1940, and that a German military surgeon named Küntscher had operated on him at the front and inserted a long nail. Less than two weeks later he was walking comfortably with just one stick. At that time, this was amazing. He had only come in to find out where he should go to have his nail removed. The other patient was having trouble walking with a stick. When I suggested that he must be in great pain he replied: “No, I am extremely well. Two years ago I had a Leveuf hip arthroplasty. Before that I had been in excruciating pain both day and night; my hip had seized in a very poor position. It’s true that my hip is now unstable and I can’t walk without a stick, but at least I can move it and it doesn’t hurt. This operation has changed my life.” Two weeks later I had decided to devote my surgical career firstly to fracture fixation and secondly to hip surgery. I was convinced that one of these fields would eventually revolutionise orthopaedic surgery. During the next 15 years, they became the most important aspects of orthopaedics, and my workload increased accordingly.

M.O. Tell us about your training as a surgeon.

M.E.M. My career started in Autumn 1944 at the Balgrist Hospital in Zurich. This had 150 beds and was the largest orthopaedic centre in Switzerland. At that time, fractures were not exclusively dealt with by orthopaedic specialists. As for hip operations, in 18 months I saw only half a dozen fusions and about 10 osteotomies of the femur, generally by the Ombredanne technique for upward dislocations. In 1946 I went to Ethiopia for 18 months with a Swiss surgical team. It was there that I really learned to operate. Not on fractures, as these were generally treated by the local healers with wooden splints, as in the days of Confucius. There were some self-styled nurses who used plaster bandages, a treatment which generally led to pressure sores, infection and amputation. After returning to Switzerland, I became senior registrar at Liestal Hospital in October 1947 for two years. At the beginning of 1950 I worked as a visiting registrar at Leyden in Holland with the famous Van Nes, a specialist in hip and back surgery. When I returned to Switzerland I was appointed senior registrar in general surgery at Fribourg and was able to operate on all fractures in the department using the Danis technique. In the Spring of 1951 I came full circle by returning to Balgrist Hospital, in the post of senior registrar for 5 years. Then in 1960 I became consultant at St. Gall, where I was able to set up my school, in a new ultramodern hospital.

M.O. To what extent were you able to pursue your particular interests?

M.E.M. During my first period at the Balgrist in 1945 I wrote a thesis on the 25-year outcome of patients with Legg-Calvé-Perthes disease. In Holland I published my first major article in a German orthopaedics journal, concerning the indications for Smith-Petersen cups and Judet prostheses. During that same period I spent a few days with Professor Danis in Brussels, who taught me the principles of stable fixation and painless active mobilisation, starting immediately after the operation. At Fribourg Hospital I was able to demonstrate the advantages of bone fixation followed by good physiotherapy. At the Balgrist I was involved only in elective orthopaedic surgery. Operations on the hip became more and more common. My monograph on osteotomies of the hip appeared in 1957, so that I became well known particularly in the German-speaking countries. I became a Privatdozent at the University of Zurich. In the same year I left the Balgrist to concentrate on the invasive treatment of fractures without postoperative immobilisation. Around thirty surgeons, who were senior consultants in Switzerland, asked me to demonstrate my technique and instrumentation for osteotomies of the hip and the fixation of recent fractures.

In this way I got to know Hans Willenegger, consultant at Liestal, Robert Schneider of Grosshöchstetten, and Walter Bandi in Interlaken. After forming a friendship with Martin Allgöwer in Coire, we decided in November 1958, with a few friends, to set up an Arbeitsgemeinschaft für Osteosynthesefragen (Association for the Study of Internal Fixation), known as AO/ASIF. In November 1960 I was appointed to the department of traumatology and orthopaedics in St. Gall with 200 beds. From then on, almost half the beds were occupied by patients with fractures or disease of the hip. Every day surgeons from other countries visited us, in particular to see for themselves how our directives and recommendations were applied in practice within the department.

M.O. How did you come to manufacture your own fixation equipment?

M.E.M. I noticed in 1951 that Van Nes and Danis were using a number of instruments which they had developed themselves. So, in 1951 I arranged for a number of technicians and small manufacturers to make some spike retractors, a set of chisels and elevators, Schanz screws, twin external fixators, etc.

Eventually, a stainless steel importer recommended a very capable technician who had never made surgical instruments before, but who would certainly be able to understand my ideas. This was Mr Mathys, who agreed not to sell my instruments until they had been evaluated for 4 years. I immediately decided to work exclusively with him. This was in April ‘58 and in November of the same year, when the instrumentation had been completed, we founded AO/ASIF, which was to subject the devices to systematic testing for more than 3 years.

M.O. How did you manage the financial aspects of the sale of your instruments?

M.E.M. In 1958 we decided not to market the equipment. It was sold only from 1963 onwards, that is, after the publication of our first book on fracture fixation according to AO/ASIF principles. Like the founder members of AO/ASIF, all those who wanted to become members of our association had to sign the charter, which required them to keep records of all patients undergoing surgery, and at the same time to waive any remuneration for the current and future equipment. All receipts from the sale of instruments went from the outset into the public company Synthes, which operated as a charity without remuneration of any kind. No dividend was paid and all the money received was to be used in research and education. Synthes was created before anyone had had the opportunity to buy these tools and implants. We initially allowed the hardware to be sold only to those who had attended a theoretical and practical AO/ASIF course. The first of these training events was held in December 1960. At that time there was, throughout the world, a wide variety of instruments; and in particular so many different screws that it was necessary to have an incredible range of screwdrivers to hand when an implant was being removed. Our plan was to produce a range of hardware with a basic screw and a basic screwdriver. The rest you know. Our hexagonal socket-head screw was to be used all over the world.

M.O. Where did this screw come from?

M.E.M. In 1957 I was very fed up with slot-head and cross-head screws. Everyone had difficulty in removing them. I did try Phillips heads, but here again I had problems. The hexagonal socket was used in industry, but only for very large screws. One day, while I was changing a car wheel that had screws of this type, I decided that we could try applying this principle to orthopaedic screws. No-one encouraged me in this project - quite the contrary. Mr Descamps, who was with me in 1960, even told me: “You won’t succeed; the French would never want to use such a specialised screw and one which no-one uses anywhere in the world.” I replied: “Well, my friend, I could certainly convince everyone in Switzerland, and if all the Swiss surgeons are persuaded, the French might like to follow suit.”

M.O. Where did your ideas on fixation originate?

M.E.M. I was fairly well steeped in the ideas of Lambotte, Danis and Charnley. When I started, there was no question of carrying out any sort of fixation, which was a dangerous procedure at that time, unless its function could be guaranteed. One of my slogans was: “Life is movement, and movement is life.” The first rule of the group was that immediate and painless mobilisation of the limb must be possible from the day after fixation. Occasionally, casting was allowed, but only when joint mobility had been achieved, that is, after the first 8 to 10 days. With this immediate exercise treatment, the results were generally excellent. We were convinced that postoperative plaster casts were associated with oedema, muscle contractions and joint stiffness, necessitating prolonged physiotherapy to achieve perfect mobility.

M.O. In that case, why did you prefer plates to nails?

M.E.M. But nails were my first choice. The plates only came later. If you read my book published in 1957, you will see that apart from angled osteotomy plates, there was no mention of any fixation plate. In the treatment of non-union of the leg we used the tension plate; this means that the plate was positioned on the tensile side of the bone. So, for non-union in varus it was placed on the lateral aspect of the tibia. For fractures to the lower extremities, compression between the fragments was achieved by screws, the plate being used only to neutralise the fracture site. Apart form fractures to the forearm, in the emergency treatment of injuries I have never fitted a plate except for neutralisation purposes. I am always amazed to learn that one of the main things which people remember about AO/ASIF is the plate.

M.O. You were at that time convinced that fracture sites should be subjected to compression?

M.E.M. The compression was to obtain a completely stable construct. Compression of the fracture site was the only technique which gave us a sufficiently firm result. The aim was to allow active mobilisation of joints after all fixation procedures. Perfect immobilisation of the main segments seemed to us to be essential. It is important to understand what is happening at the histological level. If AO/ASIF succeeded, it was because it proved that, where the site is perfectly immobilised, the union which takes place is different from normal osteogenesis, that is, there is healing without formation of a callus. This is also what happens “naturally” in fractures which are stabilised spontaneously by impaction of the fragments, as in certain compression fractures of the vertebral column. There, too, you have primary healing. This type of union is possible only at an absolutely stable site. If there is mobility of more than 5 microns between fragments, there is a risk of non-union.

M.O. But the humerus consolidates well in a hanging cast?

M.E.M. The more unstable the site and the larger the callus. Nature produces a large callus in order to achieve stabilisation of the site before ossification. The most common example is that of the clavicle. Ossification proceeds at the ends of the two separate fragments to bridge the gap between them, after which the callus is mineralised and then ossified. People who treat tibial fractures in extension for 3 weeks or so have all seen patients with a mobile fracture one day and then overnight the site would become stable by mineralisation of the fibrocartilaginous callus. This is secondary healing. Our implants were designed to produce primary union.

M.O. Since the formation of your group you have invested a great deal in the evaluation of results.

M.E.M. We felt that this was essential, firstly to evaluate our instrumentation and secondly to evaluate the techniques of those who work with us. We wanted to develop instrumentation that would work no matter who was using it; so we needed to know how our tools and implants were being used by others. This evaluation was one of the main objectives of the AO/ASIF Documentation Foundation. I was president of this Foundation for 26 years. When the implants were marketed, the revenue allowed the foundation to function properly. But in the beginning, we ourselves financed our first foundation, the Laboratoire de Recherches Expérimentales (Experimental Research Laboratory). Each member regularly paid 10,000 SFr - to the dismay of our wives.

M.O. So were Swiss surgeons at that time so well off that they not only spent a great deal of their time evaluating results but also managed to finance a laboratory from their own funds?

M.E.M. Not well off at all. In 1957 I was earning 1,500 SFr a month as a senior registrar and paying 500 SFr for my house. You can imagine the financial state that we were in. We were motivated by the certainty of achieving something valuable; our enthusiasm was what drove us, and at that time it was impossible to do anything without using our personal funds. Fortunately our wives backed us up, as there were certainly some difficult moments.

As far as I am concerned, when I left the Balgrist Hospital in 1957, some patients immediately followed me, particularly private patients, who were able to pay for their operations. The first 13 members of AO/ASIF soon acquired patients who came not only from Switzerland but from other countries, since our surgeons had exceptional implants which were not yet for sale. This, needless to say, infuriated the rest of the surgical community. The definitive hardware was developed in '62, and our first book on fixation was published in 1963.

From that time onwards we were unable to monitor the technical expertise of the users of our devices, since anyone could now buy the implants. On the other hand, the question of finance became simpler since, as industry was earning money, it was able to finance research and education. By this time, most of the 13 original members had become consultants in fairly major departments.

M.O. Looking back, what contributed most to the success of your method of fixation?

M.E.M. This success was based on the quality of our experimental research in animals, the universal nature of our system, our thoroughgoing approach to evaluation, and our theoretical and practical AO/ASIF courses.

We had developed the hardware, but had also sought to teach surgeons how to use it. To date, more than 2,000 French surgeons have attended the Davos courses. More than 20,000 surgeons throughout the world have completed one or more AO/ASIF courses.

M.O. When did you move from bone fixation to arthroplasty?

M.E.M. Towards the end of the fifties I had already fitted some hip prostheses of the Judet or Merle d’Aubigné type, with Ostamer, a precursor of acrylic cement, which proved to be toxic. However, I had noticed that patients did better when the prosthesis was cemented. When Charnley published his results with methyl methacrylate cement I felt that this was probably the solution. I quickly developed my prosthesis, and in February 1960 fitted my first total hip prosthesis.

M.O. Why did you make your own?

M.E.M. First of all, we could not buy the Charnley prosthesis. I had heard about this prosthesis in 1960, but didn’t see the first one until 1962. Also, having had a head start in the manufacture of instruments and implants, we tended to personalise our products.

Within three months my first range of total prostheses was ready. In 1961, at an AO/ASIF course in Davos where John Charnley was talking about the biomechanics of fractures, I showed him my early results with about thirty prostheses.

We decided to continue to work together from 1963, and not to allow the sale of our prostheses outside our two groups before the SICOT Congress in Paris in 1966. Until 1966, the only prosthesis which could be used in France was therefore the MacKee-Farrar prosthesis. It was also a good thing that nobody apart from ourselves fitted Teflon cups, as this material wore very quickly. Polyethylene was not available until towards the end of 1963.

M.O. You were attracted by Charnley’s ideas, so why did you not use the small head?

M.E.M. I myself started with a small head. My first prostheses had a head diameter of 24 mm, and in any case I did not know the exact size (22.2 mm) of the Charnley head. But out of the first 50 cases we had 7 dislocations. Why was this? First of all, our cups were less deep than Charnley’s, and we paid less attention than Charnley to the position of the prosthetic components. In his department all patients treated surgically had prostheses; in ours, hip arthroplasty was performed in only 5% of patients.

This was why we changed to the 32 mm head, to reduce the number of these incidents. The 32 mm head is in my view as good as the 22 mm head if the thickness of the polyethylene in the cup is more than 10 mm. The polyethylene cups used by us from 1964 to 1966 lasted an exceptionally long time; this was also due to the sterilisation conditions.

At that time, sterilisation was chemical - and obviously efficacious, since we had no case of infection. But in particular, it did not damage the polyethylene, as is the case with the current gamma irradiation method.

As you know, a polyethylene cup must not be sterilised twice, as the second time the polyethylene disintegrates. If the polyethylene is that badly affected by two successive exposures to gamma radiation, it follows that a single sterilisation may not be totally without effect. When removing chemically sterilised cups after 20 years, we have found only 1 to 2 mm of wear, which is quite amazing.

M.O. Should we not reconsider our current sterilisation systems?

M.E.M. Nobody wants to. These days, surgeons have almost no say in the matter. It is the technicians, engineers and various manufacturers who have assumed a role which, personally, I would never have given them. The second important thing which has reduced the life of the cups is the opacification of cement. Cement was made radiopaque in 1966. To achieve this, metallic substances were incorporated - barium sulphate or zirconium oxide - which are even harder than the metal itself. If minute particles of cement became interposed between the two components of the prosthesis before 1966, with the radiolucent cement this did not matter, but with the radiopaque cement, the effect on the metal-on-metal system is disastrous.

M.O. How did you arrive at the self-locking prosthesis?

M.E.M. In the beginning, with the “banana” stems we observed a certain number of prostheses going into varus. This is why I developed the self-locking system in 1977. Each time I had a prosthesis to fit I tried my various 2 mm metal templates and assessed their fit in the diaphyseal cavity. Anatomical studies were also performed, and that was how the definitive shape was reached. This work also showed that the smaller prosthesis should have a shorter neck than the large diameter one. Most of the prostheses I know of do not follow this essential rule. One of the big advantages of the self-locking prosthesis is the simplicity of the template, with all the prosthetic dimensions on a single transparent foil; this allows accurate preoperative planning. The only drawback is that in view of the bone-prosthesis contact, the cementing technique with an intramedullary plug must be perfect. But, to judge from the follow-up, this does not seem to have posed insoluble problems.

M.O. How do you see the future of hip replacement?

M.E.M. As far as I am concerned, polyethylene is the weak point of the current prostheses. I have a small series of 50 cases of metal-on-metal prostheses which I did at St. Gall in 1966. These had been followed up partly by my former senior registrar, Mr. Weber, my successor at St. Gall, whose impression was very favourable. As a result, he has been fitting metal-on-metal prostheses for the last three years. According to our tests with different ultramodern metals, which started in 1981, the best combination is cast chromium-cobalt, the original material we used at the very beginning, known as Protasul 2.

M.O. What is your main activity at the moment?

M.E.M. I am basically concentrating on the documentation and evaluation of postoperative outcome. I am, thus, continuing what I started in 1967. At that time, all patients with implants were recorded on punched cards, to which miniaturised copies of their radiographs were attached. Fortunately information technology has now resolved the problem of data storage.

M.O. The systematic gathering and storage of data must still require considerable funds.

M.E.M. To begin with, the work was financed by the AO/ASIF, then by Protek, which was initially a foundation created to use the proceeds from the sale of prostheses. Since 1975 it has been the M.E. Müller Foundation which has supplied the funds. Our evaluation work has been the subject of several presentations, particularly at the last two SICOT conferences. We have proposed a number of definitions for clinical and radiological terms to be used by orthopaedic surgeons and rheumatologists. We have perfected the fracture classification system. We have developed computer evaluation programs. There is a Minor Program and a Major Program. In the Major Program, all the radiographs are digitised, while in the Minor one we store only analogue radiographs. 72,000 radiographs can be stored on one disk, but these cannot be manipulated. By contrast, digitised radiographs can be enlarged, the migration of prosthetic components measured, etc. The measurements are accurate to the millimetre, and no enlargement is necessary, because everything is based on the known diameter of the head of the prosthesis.

M.O. After so many years of evaluating prostheses, what is your overall impression of the success factors for implantation?

M.E.M. To be quite honest, I don’t think that the different prosthetic models play an essential part. I personally think that the most important factors are, firstly, appropriate patient selection; secondly, preoperative planning; and, thirdly, the technical expertise of the surgeon. You cannot use the same prosthesis in all indications. You cannot ensure the success of a procedure without meticulous preoperative planning. Finally, you cannot achieve optimum results, for example with cemented prostheses, without perfect cementing technique. Also, you must remember that evaluation is not an end in itself, but only a start. The aim is to guide us when making our choices, defining our indications and shaping our policies, in order to ensure a constant improvement in our surgical technique and in the quality of the outcome.