Dr Henning Röhl, as Head of the Department of Orthopedics, Trauma and Reconstructive Surgery at Diako Mannheim, is highly experienced in the use of artificial joints for the knee, hip, shoulder and ankle. The specialist in endoprosthetics has a wealth of experience, particularly in so-called replacement and revision surgeries. When it comes to reconstructions or corrections, for example of the leg axis, his expertise is frequently sought after beyond the region. In an interview with the Leading Medicine Guide, Dr Röhl discusses the possibilities of modern revision arthroplasty – a highly topical subject that is becoming increasingly important in orthopedics.
Leading Medicine Guide: Dr Röhl, what exactly is revision arthroplasty?
Dr Henning Röhl: Revision arthroplasty – that is essentially the replacement of the replacement. It involves replacing a joint prosthesis. This may be necessary for various reasons. Firstly, due to wear and tear of the prosthesis. The patient may then notice, for example, that their knee is swelling or becoming unstable. We document and monitor the situation using X-rays and then make a diagnosis. A second reason for replacing the implant may be a prosthesis that is becoming loose at the connection to the bone; the bone recedes, and the symptoms are similar to those described above. A third reason for replacement may be an infection. Fortunately, this does not happen often. The patient then complains of pain. In this case too, we replace the joint prosthesis with a new implant. In some cases, the mechanical function of the replaced joint is simply not restored to the patient’s satisfaction after the initial procedure; this reason can also lead to the need for revision surgery.
Leading Medicine Guide: It is common medical knowledge that one should be as old as possible before having a joint replacement. Precisely because replacing it is not so straightforward.
Dr Henning Röhl: Neither of those statements is true today. That view stems from an earlier era, when artificial joints were indeed expected to last only about ten years. Nowadays, the results achievable with joint replacement are constantly improving, meaning our patients with joint wear are getting younger and younger. This places new demands on endoprosthetics. Today, research has developed material compositions that, in the majority of cases, last a lifetime. Innovations can, for example, involve specifically doping the plastics in prostheses with vitamin E or other substances, which helps to slow down the aging process of the material within the body. In addition, our surgical techniques have become increasingly precise. We make small incisions, preserving muscles and tendons. The patient undergoes surgery at ten o’clock and by three o’clock is already walking and able to put full weight on the prosthesis. And replacement is also taken into account today; modern prostheses are designed – should the need ever arise – to be easily replaced.
Leading Medicine Guide: What materials are the prostheses mainly made of?
Dr Henning Röhl: That depends on where they are used. In hip implants, titanium has proven to be very well tolerated for the part that is connected to the bone. The joint component, on the other hand, is made of ceramic or polyethylene. The body’s fluids then form a capillary film over the joint head, allowing the joint to move as if on a film of fluid in a plain bearing. We use ceramic prostheses particularly for younger people because these materials are extremely advanced. Today’s complex ceramics have high hardness properties and are resistant to wear. The risk of ceramic fractures, which is sometimes still mentioned, has virtually disappeared in practice with the ceramics used today.
Leading Medicine Guide: Are the same materials used for knee implants?
Dr Henning Röhl: The knee joint is constructed differently; it has a fundamentally different surface structure. Here, chromium-cobalt steel is used for the implant, or metals with ceramic-coated surfaces are employed. This is due to the different operating principle. The knee is simply the more demanding joint and its function depends heavily on the fit of the prosthesis – this is influenced by the surgeon and their experience. What we endoprosthetists do is akin to a craft; it is mechanically quite challenging, and routine and understanding play a major role. When inserting the knee prosthesis, several axes of movement must be precisely aligned. We test this during the operation itself to achieve the best possible result.
Leading Medicine Guide: How do you find the right implant for each patient?
Dr Henning Röhl: My experience naturally plays a major role when advising patients. I am familiar with the advantages and disadvantages of a wide variety of prostheses, and I am aided by a prosthesis register which now records almost all prosthesis models implanted in Germany, along with all modifications and outcomes. A petite 80-year-old lady has different requirements for her implant than a strong, active 50-year-old man. With the elderly lady, there is a greater risk of dislocation – that is, the joint popping out; the man needs a prosthesis that is as robust and durable as possible. It has been shown that a sensible, experience-based balance between innovation and conservatism is what best helps the patient. After all, every prosthesis model is individually tailored. It is essentially a small machine which, once inserted into the body, is intended to function maintenance-free for several decades.
Leading Medicine Guide: It is fascinating what is medically possible today to restore mobility to both older and younger people. Thanks to the relatively small surgical incisions, patients are mobile again shortly after the procedure. What does the rehabilitation involve?
Dr Henning Röhl: Rehabilitation should begin as soon as possible after the operation. It has been shown that the earlier the first exercises are started, the better the recovery. Following joint replacement, it is extremely important for effective rehabilitation to restore good mobility and coordination while ensuring effective management of swelling and wound healing. Patients and therapists often place too much emphasis on building strength. Muscle strength is the only aspect that should be put on the back burner for the first ten weeks. Once the wound has fully healed and everyday activities have resumed, strength usually returns naturally. The first few weeks of rehabilitation are dedicated to maintaining and restoring lost mobility, and to establishing a coordinated, ‘smooth’ gait.
Leading Medicine Guide: Are all sports possible again with an endoprosthesis?
Dr Henning Röhl: In principle, yes, though it naturally depends on the level of fitness and athleticism you had beforehand. You can take up many sports again, particularly recreational ones. Some high-impact sports, such as football or perhaps skydiving, are less suitable. However, I would generally advise against competitive-level sport following a joint replacement.
Leading Medicine Guide: Let’s talk once more about revision surgery, the replacement of the artificial joint. You mentioned earlier that wear and loosening can be reasons for a replacement. A third reason is infection. How does that happen? As a patient, one assumes that everything in the operating theater is highly sterile.
Dr Henning Röhl: That is true; procedures today meet very high standards and are completely sterile. But every person carries a lot of bacteria around with them, and so, unfortunately, even after a prosthesis has been inserted into the body, bacterial colonization of the prosthesis can still occur. And since the prosthesis is not a living organism and cannot defend itself against the bacteria without its own immune system, in isolated cases a veritable film of algae forms on the implant. Once this condition has set in, the implant can no longer be preserved and must be replaced.
Leading Medicine Guide: Would it not be possible to treat the prosthesis accordingly?
Dr Henning Röhl: Well, one could treat it with certain coatings as a precaution; this is already done in specific cases. At the same time, however, there are competing requirements for the surface of the prostheses. After all, the bone is supposed to grow onto the implant. However, if it is pre-treated, this process does not take place as intended, and unfortunately that is not in our interest either.
Leading Medicine Guide: How often can a joint implant be replaced?
Dr Henning Röhl: In principle, we can do this four or five times, or even more often. The limitation usually lies in the available bone stock. A revision prosthesis generally needs to be slightly larger than the primary implant, meaning that some bone is lost with each procedure. We therefore have to compensate for this loss with the prosthesis. If, beyond a certain point, this can no longer be achieved effectively, procedures such as bone grafting are used as an alternative or in addition. For this, we use biological or synthetic bone substitutes. Over time, these are remodeled by the body and replaced by the patient’s own bone. These grafts can also bear a full load immediately. Building up and regenerating bone mass is important during revision surgery in order to create a low-risk baseline for any future procedures that may be necessary. Even when inserting the first endoprosthesis, one should always aim to create a good baseline and consider a future replacement from the outset. This is achieved, for example, by using the smallest possible prostheses during the initial operation; the so-called short-stem hip prosthesis is one such implant.
Leading Medicine Guide: If you were asked: hip or knee – which presents the greater challenge for you in your work?
Dr Henning Röhl: I am, of course, always delighted when I can achieve a good outcome in the operating theater, particularly with complex cases, using the tools at our disposal. The primary hip prosthesis is, technically speaking, the ‘simpler’ joint. Consequently, we see a very high rate of satisfaction with the joint replacement among patients who have had hip surgery. Naturally, I need technical skill and a good planning strategy for all my operations. I regard the knee joint as a greater technical challenge; here, the outcome for the patient is determined even more by the surgeon’s experience and dexterity. The greatest challenge is usually presented by prosthesis replacements involving complex reconstruction. I thoroughly enjoy doing it all.
Leading Medicine Guide: Dr Röhl, thank you very much for these insights into the current state of affairs regarding joint prostheses, their use and replacement.
