|
 |
|||||||||||||||||||
|
|
|||||||||||||||||||
The 30th Meeting of the West of France Orthopaedics and Traumatology Society (S.O.O.) was held at Pont-l'Abbé last June. There, we met Alain Dambreville, the Society's dynamic President.
M.O. Do you come from the west of France?
A.D. Not at all - I come from Lille, in the North. I settled in Quimper 21 years ago, in '76, and immediately joined the West of France Orthopaedics and Traumatology Society, the S.O.O. That society had been going for nine years, and I was a very, very junior newcomer. So I had never known the great pioneering days of the S.O.O.
A.D. No one was more surprised than I was. What you have to realize is that, for five years, whenever I submitted a paper to the S.O.O. it would be rejected, while the French society SOFCOT and the East of France Orthopaedics Society (SOTEST) would accept my papers. This left me wondering whether the S.O.O. was not a bit of a closed shop. And then, two years ago, without me doing anything at all, they come and ask me to be Vice-President. In fact, one of the rules in the S.O.O. statutes is that the presidential office should go turn and turn about to a surgeon from a teaching hospital, and to one from outside academia.
A.D. I had decided early on that as soon as I was through my specialty training, I would choose where to live. I love the North, but I wanted somewhere a little less harsh. My wife comes from the east of France, so Brittany was a good compromise. I found a post at a private hospital in Lorient. That was in September '76. (...)
A.D. In the end, they did not. However, by then two things had happened. Firstly, the atmosphere at the hospital had become tense; and secondly, a new and beautifully equipped private hospital was looking for an orthopod. So I took a decision, and went into the private sector. I had been happy at the hospital. When I first went there in '76, it was more or less a 19th century workhouse; but then it developed into a modern hospital with excellent facilities and a very pleasant working environment. The work there was teamwork, and it was fun helping to develop the hospital. Now, Quimper Hospital is a huge place that serves the entire region.
A.D. No, I don't. However, it's not been the same at the private clinic. There, it's everyone to himself. At Quimper Hospital, we really worked as a team.
A.D. When I first came here, I was mainly wanted for trauma work. I had had excellent training in traumatology, because I had been in Pierre Decoulx' department, where the volume of trauma work was huge. These skills got me known in the region. Before my arrival, traumatology had been practised by non-orthopods, and when I started using the techniques I had been taught at Lille, things improved noticeably. I rapidly built up a practice, and I realized that there was a lot of hip disease in this part of France. And hip surgery eventually came to play a major rôle in my work as a surgeon.
A.D. Initially, I was jack-of-all-trades. Very quickly, though, I realized that hands and kids weren't really my forte. Like all surgeons, I had always wanted to be able to do only what I am good at. So I asked Mr. Loddé to do the hand surgery, and Mr. Louppe to do paediatric orthopaedics. I was doing a bit of spinal work, but that was about it. When I went into the private sector, I asked Bernard Kerboul, who was a Senior Registrar in Brest, and who had been trained by Senegas, to come and join us. Also, I had no arthroscopy training, and had no great urge to do arthroscopy, because I did not like it overly much. I was looking for a surgeon who would do arthroscopy, but I didn't know whom to contact. The rehab people at Tréboul said, "Just go and ask Jean Yves Dupont, the Secretary of the Arthroscopy Society; he is bound to know someone." So I wrote to him, and 48 hours later he phoned me and said, "I do indeed know somebody - myself." That came as a complete surprise, because he was very well known. He came out to Brittany, because it's a beautiful part of the world, and because our centre is very well-equipped. Conditions here are really excellent.
A.D. There is an awful lot of dysplasia of the hip around here. That is not a myth, that is a fact. Prof. Masse, of Rennes, has written a very instructive article on this region, with a map showing the distribution of developmental dysplasia of the hip; this shows that the condition is concentrated in bigouden country, around Pont-l'Abbé. Quimper is outside that area, its' in what is known as glazik country - something quite different. It is astonishing to see how the region is criss-crossed by boundaries between lots of small areas, each with its own traditions and customs, and each with its own disorders. For instance, there is a marked difference between Northern Finistère and Southern Finistère. In the south, in bigouden country, around Pont-l'Abbé, that's where you get a really high rate of DDH.
A.D. It's thought to be due to a genetic factor. The population in this area is somewhat inbred, and that would have selected the defect.(...) Inserting the femoral component is not that difficult either, since there are special implants for dysplastic hips. The difficult bit is to control lengthening and the orientation of the implant. This is difficult because there is major malrotation in the lower limb, with the femur often in internal rotation, and the bones of the leg in external rotation, with a risk of dislocation and a knock-kneed gait, etc. I have done a lot of this kind of surgery, and I am full of admiration when I hear Marcel Kerboul say that when he has done a prosthesis in a DDH patient, that patient will not limp any more. I would not claim that sort of result - I merely note that the patients are better after surgery.
A.D. I often start with a trochanter slide. That is to say, I detach the greater trochanter with the gluteus medius and vastus lateralis muscles in continuity, to make for easier reinsertion. Bringing the hip down is not easy, and I am baffled by statements in papers that "two inches of lengthening is readily obtained." I have had problems with sciatic nerve palsies, and with patients who were none too happy with their overtightened muscles etc. I try not to do too much lengthening, especially since these patients are used to walking on legs of different length, and it would be quite wrong to give them legs of equal length.
A.D. This is done mainly at surgery. With the patient lying on their side, knee flexed and leg vertical, one establishes the 0 plane of the femur; and that, in principle, is when I insert the implant in the horizontal plane. However, one needs to test the ROM very carefully, because there is a major risk of dislocation in either direction.
A.D. I used to be all for customized prostheses, because I thought that that was the way forward, and that what was needed was implants that exactly matched the medullary cavity. However, we had financial constraints imposed, which limited the number of these implants that we could do; and I also realized that the real problem was not the adaptation of the prosthesis to the femur: Even with standard uncemented devices, one can get very good primary stability. The real problem is the control of anteversion. Of course, with a customized implant, the pre-operative CT scan will show the pattern, and any excess anteversion can then be corrected; however, the same result may be obtained with a standard device that has an adjustable neck. I think that one should have implants that come in three parts - a stem, a neck, and a head; and such devices are now commercially available. That way, once the stem has been inserted, one can adjust the neck as required.
A.D. The Americans have certainly stressed the risk inherent in a modular design - corrosion, possible breakage, deterioration of the implant in the long term. However, I think that these are rather academic risks. Femoral heads on Morse tapers have been used for more than 20 years, and there have been no problems. There is a Swedish publication showing a completely eroded spigot - that can happen, but it would be very, very rare. I think the same goes for adjustable necks. Bousquet started using such devices a long time ago. I don't agree with his implant design, with a stem that is screwed into the femur; however, I do not think that there are many reports of breakage of the fixation system attaching the neck to the stem. There have been problems with pain, and with difficult removal of the implant, but not with the modular concept as such. I think it is important to realize that what is published in the American journals may be vastly different from our experience in Europe. I think that for the management of DDH patients, modular implants are very useful; while customized devices are becoming unimportant in this kind of surgery.
A.D. My thesis was on femoral varus osteotomies. At that time, we were getting good results in early OA of the hip; patients with more advanced disease, however, were inherently unsuitable, and the results were poor. There are only very few osteotomies being done nowadays. I sometimes do a varus osteotomy in a young patient (under 50) with DDH, with coxa valga and an early stage of OA. Joint space loss must not be greater than 50%. Once the OA has become severe, there is a 50% risk of a poor outcome.
A.D. I do more shelves than osteotomies, because this is a less drastic procedure. A varus osteotomy means two and a half months off weight-bearing, at least six months of rehab, and walking with a limp for one year. With a shelf, it's three weeks' walking with two aids, and then two or three months' rehab. The dysplasia must be mainly acetabular, with lateral and above all anterior loss of coverage. However, it's the defect on the false profile (the Lequesne view) that is the most important; and this dysplasia must not be associated with major OA. I don't think it makes sense to do this in patients over 60.
A.D. Like most surgeons, I put in the implants I had been taught to do. I put in Müller banana stems, with 32 mm heads, and cemented, of course. Then, in '79, I found out that Müller was allowing some "chosen few" in the surgical fraternity to use his self-locking prosthesis. I was among the first to be able to insert it, and I thought it was great the way one could wedge the implant in the femur. However, at the time, Langlais told me that he was dubious about this technique, because there was an uneven cement mantle, and direct contact between the implant and the host bone both medially and laterally, and a lot of cement at the front and back. Like a fool, I did not really believe him, and for ten years or so I thought that what had been designed and created by our elders and betters was the Truth, and I did not want to contest that Truth. When I was putting in a Müller prosthesis, I was doing my patient the best possible service. However, as time went by and follow-up lengthened, I realized that the implants were coming loose. So I thought that perhaps one could do better. At the time, the cement was being blamed for everything, so I wanted to go cementless. The implants available were the Parhofer and then the Harris stems, i.e. devices with diaphyseal fixation. There were problems - thigh pain and early loosening. That was in the early '80s. By trying to do something better, we had actually finished up doing something worse. However, we learned from this experience what not to do: One must not insert a long stem that wedges itself in the shaft, and which may rotate. So, in '85, I decided to go for stems with metaphyseal fixation.
A.D. We did think initially that all the loosening was the fault of the cement. However, we then realized that the chief problem was the response to polyethylene debris. We took a long time to master cementless fixation, but we got there in the end, and the technique came of age in 1990. We had learned two things: Firstly, how to handle the technique, which made surgery very straightforward (in fact, if one decided then to add cement, this was only an unnecessary complication); and secondly, we had come to the conclusion that hydroxyapatite-coated implants with metaphyseal fixation had many advantages, which go beyond the cementless nature of the arthroplasty: Stress transmission occurs in the metaphysis; microparticles are prevented from tracking along the interface; removal is made easy and less damaging. I shall have more to say about these advantages in a minute.
A.D. At first, I thought of an implant that would be fixed in the femoral neck; however, this idea proved too difficult. When one looks at a femoral neck that has been cut at the top, one sees that the cortices form a U shape, with the rounded calcar at the bottom, and comparatively straight anterior and posterior cortices. I Therefore designed a prosthesis that would come in different sizes and thickness, so that it would exactly match the shape of the neck. There were flattened metaphyses, and wide metaphyses. This implant was technically difficult to insert, and did not win over too many surgeons. So I went on to look at metaphyseal fixation. I adopted a modular concept, i.e. the implant comes in two parts, a stem, which is, of course, underdimensioned with regard to the femoral shaft; and a metaphyseal portion, which, as the term metaphyseal fixation implies, is stabilized in the metaphysis. Apart from the design features of the implant, and the surgical technique required, one vital point is the surface coating. Even if primary stability is excellent, the long-term results will not be good unless secondary stability can be obtained through osseointegration. For four years, I used implants with metaphyseal fixation that had been made from grit-blasted titanium. The results were quite good, with 92% implant survivorship at ten years; but there was still an 8% early failure rate. The trouble with cementless fixation is that it's a race against time - you need to get there first with osseointegration, before the implant yields to the mechanical stresses acting on it. If the bone stock is poor and the coating is not very bioactive, the implant may loosen before osseointegration has occurred. This is why good bioactive coatings are so important. With hydroxyapatite, osseointegration is achieved within one month - so one wins the race against time. This is why, in 1989, I started using HA coatings, and since then I have not had any more problems with early loosening.
A.D. There is an immediate ion exchange that brings bone onto the hydroxyapatite in the month after implantation and produces an intimate bond between the bone and the HA. This is good mechanically, biologically, and for implant removal. Mechanically, it is beneficial because stresses will be transmitted in the metaphysis. Radiological studies in the medium term of implants coated in such a way as to make the bone adhere only over the proximal few centimetres of the prosthesis have shown condensation of the cancellous bone in the metaphysis, which, in accordance with Wolff's law, is proof of stress transmission in that area. The longest follow-up is over seven years, and even in the earliest cases there is no evidence of stress shielding with such prostheses. All implants with diaphyseal fixation - be they cemented or cementless - are associated with thinning of the metaphyseal and proximal diaphyseal cortices; while this thinning does not normally cause loosening, it contributes to the decline in the quality of the bone stock around the implant, which will go on to major osteolysis. So, preventing this factor of bone stock compromise is actually very useful. Biologically, HA coating is helpful because it constitutes a barrier to the migration of PE particles. The bioactive coating produces an intimate contact between the implant and the host bone, without any interposed fibrous tissue of the kind routinely observed at cement/bone interfaces. This fibrous membrane provides a thoroughfare along which wear debris can travel around the implant, especially in the femoral shaft. This is what Schmalzried and Harris have called the effective joint space. Where the metaphyseal portion of the device has an all-round bioactive HA coating, debris is prevented from tracking, which is why femoral shaft lysis has never been seen, even at more than seven years' follow-up. And, finally, there is the advantage of ease of removal, with little tissue damage, as we have been able to observe on three occasions. Since the implant is coated only over the proximal few centimetres, it can be extracted without difficulty. A thin flexible blade inserted between the implant and the bone will readily detach the prosthesis. Removal is all the more tissue-sparing since osseointegration is achieved, not by the ingrowth of bone into nooks and crannies on the implant surface, but by bone ongrowth onto the coating. This way, there are none of the removal problems that bedevil the cementless implants with diaphyseal fixation, nor those of the cemented ones, where the removal of the cement leaves the bone fragile and devitalized.
A.D. It does - but it does so very slowly, over several years. How long it takes will depend on the thickness and on the physicochemical properties of the coating. What Bauer, Frayssinet, and Søballe have shown is that as the HA is resorbed, it is replaced by bone. So when all the HA is gone, there will be bone in direct contact with the implant. This way, the intimate contact with bone may persist even after the HA has been resorbed, provided that the metal under the HA has been textured.
A.D. I think that "metaphyseal fill" is another one of those concepts that need revising. It is not vital to fill the metaphysis. What one has to obtain is primary stability in the metaphysis, and that can be got with three-point support.
A.D. It does, but they don't matter if the implant is perfectly stable and if it is rapidly osseointegrated. Ray, who designed the ESOP device, the prosthesis that I am currently using, was well aware that it's not a question of putting the biggest possible implant into the bone - it's a question of putting in the first one that achieves stable fixation. As in all cementless surgery, the important point is that stability must be tested intra-operatively. And it must be tested in the three planes, coronal, sagittal, and axial. If primary stability is good, and if the implant is fixed in the metaphysis, there will be none of the thigh pain that is typical of implants with diaphyseal fixation. Thigh pain is felt at the front or the side, half-way down the thigh, radiating into the knee when walking. Thigh pain is now a matter of the past, we are not seeing it any more with implants fixed in the metaphysis. This has been documented not only by myself, but by all surgeons who use this type of implant.
A.D. Initially, I got it badly wrong by putting in large threaded cups, which, at the time, were uncoated. Of the 250-odd threaded cups I did, 150 had to be revised. They were Weil cups. Some are still in and doing all right, but don't ask me why. In '84-'85, I came across the Harris cup. At first, I thought that this cup with its little screws was a bit gimmicky. In actual fact, it's ingenious. The hemispherical acetabulum needs a hemispherical cup - elementary, you might say; it's just that nobody had done it before. And it also needed a surface coating to provide lasting stability through osseointegration.
A.D. At the time, they were being put in. Also, the cups used were of the same size as the acetabula into which they were inserted. Once a Harris cup had been put in, we would drill the holes; trouble was that while the surgeon was picking up the screw, the cup would move a bit, and the screw hole would be out of line. This made me wonder whether one shouldn't go for a cup with spikes that could be impacted into place, and then there would no longer be a problem with screw insertion. This gave me the idea of the Atlas cup. I also thought that the cup should be split at the bottom, because since the semilunar portion of the acetabulum is springy, it was only logical to insert a cup that would be springy, too. I started using this device back in 1987, ten years ago; the results were excellent. What helped me greatly in the further enhancement of this implant was the fact that other surgeons started using it. I got a lot of feedback from them, especially from Louis Doré in Tours, who has put in over 1,000 Atlas cups - almost as many as I myself. In 1989, he said to me, "You know, if you put in a cup one size larger than the acetabulum, it will wedge itself, and then you can dispense with screws."
A.D. Yes, I would routinely fix the cup with screws, same as the Harris. Then I found that it worked very well without screws, so I stopped using them. At the same time, it emerged from work done at Compiègne Institute of Technology that when the polyethylene insert was placed in an elastic cup, the cup/insert unit would lose most of its elasticity. And that's where I was lucky. Having an elastic cup was no longer very relevant once the insert had been put in; however, it was crucial for achieving excellent primary stability on impaction. If one wants to make do without screws, which are fiddly and have many disadvantages, including the provision of a route along which debris can track, then the cup will need to be press-fitted, i.e. the cup will need to be one size larger than the final reamer. The problem is that impacting a rigid cup into a smaller acetabulum produces peripheral stresses that counteract the advance of the cup into the acetabulum, and which may cause microfractures, as shown by Adler and MacKenzie. However, with an oversized cup that is split, the shell will close on impaction, so the cup can be driven fully home; and then it will spring apart again, pressing itself against the host bone and assuring excellent primary stability. This stability can be readily checked at surgery, since even a very hard pull will not dislodge the cup. In order to be a successful inventor, one has to be serendipitous: I had had an idea, and - as luck would have it - this idea proved useful in a way that had not originally occurred to me.
A.D. There are lots of theories, but no evidence. If the bone is stressed at certain points only, then necrosis may occur. However, with this cup, the stress is distributed over the entire acetabular surface, and the implant bed is well vascularized. So there is no reason to assume that osteonecrosis will occur; and we also have our experience, gained from over 20,000 cups inserted over the past ten years, with excellent results and not a single instance of necrosis.
A.D. Someone else actually got there first - Spotorno. His cup was a few years before mine, but it had six splits. Having that many was not, perhaps, essential; one was quite enough. I was, in fact, the first to design a cup with only one split. Since then, there have been lots of others.
A.D. No, I don't. One cannot be sure that the problem has been definitively resolved. All we can say is that the implants have stood the ten-year test; we shall need to wait another ten years before we can be certain.
A.D. There is the question of the long-term fixation of the implant. Secondary stability is a function of the surface texture under the hydroxyapatite. The engineers tell us that, under the HA, we need titanium grit-blasted to a roughness of about 6 microns; apparently, that would be ideal in the interest of longevity. However, only the future will tell. The results are good at ten years; if they still are at 20 years, then we will be able to say that implant fixation is no longer a problem. There are also the questions of the material combination, and of the release of microparticles. Once again, we shall have to wait and see how it goes over the full 20-year period - although ceramic-on-ceramic or metal-on-metal look very promising. Some surgeons are convinced that they know the Truth with a capital T. However, I think that that is often only a coping strategy. Our job is very difficult, and hugely responsible - so people may sometimes keep their spirits up by telling themselves that they know the Truth. However, I think we must never lose sight of the fact that there is more than one truth, and that there are several ways of getting to the same goal. I think it's daft to think that the way one has chosen to do something is the only possible one. What goes for religion goes for medicine as well - the fundamentalists are wrong.
