Hello. My name I Anders Odgaard and I am a consultant orthopaedic surgeon and clinical lecturer at Copenhagen University Hospital in Gentofte. My subspeciality is degenerative knee conditions and their surgical treatment, including treatment of complications. Most procedures, that I perform, are either primary or revision knee replacements. My intention is to give you a brief overview of issues related to the treatment of chronic deep infections around joint replacements. This lecture will briefly discuss what the symptoms are, how we establish the diagnosis and what kind of treatment we use, in different phases of the infection. When a joint is destroyed by disease or injury, the joint becomes painful, tissue destruction progresses and functional loss is seen. In an attempt to regain function, an artificial joint can be implanted. Most people know, that artificial joints are inserted into hips and knees, but artificial joints are also used in shoulders, elbows, wrists, fingers, ankles and toes. There are even replacements for the intervertebral discs in the spine and for the jaw joint. When joint replacements were first introduced in the hip, it was soon realised that infection was a major risk and a serious complication. In order to minimise the risk of infection, a number of preventive means were introduced. One of the pioneers in this process was Sir John Charnley, who advanced theatre techniques in an attempt to reduce the risk of infection. A deep infection in or around a joint treated with a joint replacement is a serious complication. In some cases, bacteria from the the infected joint spread throughout the body causing a life-threatening infection known as septicaemia or blood poisoning. In less dramatic cases, the infected joint becomes painfull, and the implant may loosen from its seating in the surrounding bone, neccessitating removal of the implant. Sometimes, the removed joint can be replaced by another implant in an attempt to restore joint function, but in other cases, the joint function will be lost forever. Now, lets look closer at the infection. Joint replacements may become infected during surgery or
after surgery. It is known that approximately two thirds of infections are diagnosed within the first year post surgery. A number of preventive measures are in general use. Among these are 1) laminar airflow, which intends to decrease airborne contamination, 2) space suits, which are meant to reduce bacterial contamination from the skin and scrubs of the surgical team 3) double gloves reduce the risk of contamination related to glove perforations, 4) restricted acces to operating theatres reducing the number of people in the theatre, 5) ultraviolet light, which is known to inactivate bacteria thereby cleaning air and surfaces and 6) prophylactic antibiotics reducing the risk of a manifest infection even in cases of contamination of the surgical field. The paradigm for joint replacement infection may be formulated as follows. When bacteria find their way to tissues or debris in or around a joint, and the bacterial load overwhealms the host response, an infection becomes established. When the infection has existed for a sufficiently long time, a biofilm forms over at least a part of the implant. When the biofilm has formed, the only possible way to eliminate the infection is to remove the implant, meticulously clean the area of infected material – also known as debridement - and treat the infection before a new artificial joint can be implanted. The symptoms of an acute periprosthetic joint infection are the classic symptoms of redness, pain, swelling and disturbed function, also known as rubor, dolor, calor and functio laesae. The chronic infection may, however, present without any of these classic signs of inflammation. There may only be tenderness or swelling or radiographic signs of loosening. The diagnosis of an infection is mainly based on a constant vigilance on part of the general practitioner, the physician or the surgeon, who sees a patient with a painful joint implant. When confronted with a patient with a painful artificial joint, it is important to review the history leading to joint replacement. Has the joint been surgically treated prior to the arthroplasty? Is there any reason to suspect infection related to previous procedures around the joint. It is also important to review the time following the joint replacement operation, especially the immediate postoperative period. Was there any sign of infection? Does the patient recall fever? Were stitches or staples removed at the planned time? Was fluid discharge or prolonged oozing from the wound observed? Were antibiotics prescribed by the GP? These are all possible indicators of an immediate postoperative infection, which may have become chronic. In case the immediate postoperative period was uneventful, the surgeon should turn his interest to the more recent history. Has there been fever? Has the patient felt generally unwell? Has there been general symptoms preceding the joint problem? Has the patient undergone any invasive medial investigation? All of these may be indicative of a joint infection caused by bacteria that have spread to the knee via the bloodstream – a socalled haematogenous infection. The history should always be followed by a thorough physical examination. This should consist of the classic investigations relating to the joint in question, but should also focus on signs of inflammation including swollen glands. Bloods should be taken for an examination of inflammatory markers, of which CRP – short for C-reactive protein - appears to be the most sensitive. Some surgeons also get the erythrocyte sedimentation rate and white blood cell counts. In many cases, the diagnosis may be almost certain based on the history, physical examination and bloods, but additional imaging studies may be of help. These consist mainly of isotope scans and PET-CT scans. As expertise and equipment vary among hospitals, you should probably consult with your local department of nuclear medicine. Depending on the clinical situation, a joint aspiration can be necessary. A positive culture from an aspiration will guide the surgeon in his choice of antibiotics, and may be indicative of surgical choices available in case of a later reinfection. An aspiration of a high white blood-cell count, also is indicative of infection. The presentation, differential diagnoses and treatment differ with different types of periprosthetic infection. The following classification is generally accepted, although it exists in a number of modifications: Type I: acute postoperative infections occurring within the first few weeks after surgery. Some set the time limit at four weeks, others at six weeks. This type is considered to be the result of intraoperative contamination. Type II: A chronic infection irrespective of aetiology. Type III: An acute, late-occurring infection seen in a previously well-functioning joint replacement, usually secondary to haematogenous spread Type IV: Positive cultures from biopsies taken during a revision procedure to a joint replacement without previous evidence of infection. The generally accepted treatment for periprosthetic infection depends on the classification, but it is important to realise that the principles should follow directly from the infection paradigm, that you have explicitly formulated to yourself and your colleagues. There is no need to memorise details of treatment, you only have to 1) have a clear mental picture of how an infection occurs, 2) know that you have to know your enemy in order to win the battle, and 3) understand that most bacteria form biofilm. The guiding principle of an early, acute infection, i.e. type 1, is that all necrotic and avascular tissue has to be removed to reduce the bacterial load. The old surgical rule “Ubi pus ibi evacuat!”, meaning “where there is pus, it should be evacuated” is also valid for joint replacements. It follows from this simple principle that it is necessary to operate and perform a meticulous debridement of the joint and its soft-tissue envelope. In cases when a modular implant is used, one may exchange parts of the implant. This is for instance the case, when a modular polyethylene in a knee replacement can be taken out to clean up a potential dead space under the polyethylene. It is important to get good representative biopsies that can guide the choice of antibiotic treatment, even in cases where there may have been positive preoperative cultures. The debridement should be followed by long-lasting antibiotic treatment. It is probably best to consult with the local department of clinical microbiology for selecting the antibiotic, its frequency, its route of administration and the duration of treatment. However, expect no treatment to be shorter than 8-12 weeks. Also, it is important to explain to the patient, that they are at risk for a chronic infection, and that a cure cannot be guaranteed. If you don’t, you will loose the faith of some of your patients. For late infections, i.e. type 2, the guiding principle is that a biofilm has formed The biofilm cannot successfully be defeated by antibiotics only, and consequently the surgeon has to remove infected material and the biofilm mechanically. This is done by removing the implant and performing a thorough debridement as above. The classical method has been to implant an antibiotic-impregnated cement spacer followed by antibiotic treatment for weeks before a new, permanent joint implant is eventually inserted. This classic method has, however, been challenged by regimes, where a new implant is inserted directly after debridement in the same operation. The benefit of the cement spacer is that insertion of a permanent implant is postponed until the infection has been eradicated, thereby minimizing the risk of reinfection. The disadvantage is the fact that two operations are needed, usually weeks apart. If an infection occurs months or even years after the original joint replacement was inserted, it may under certain conditions be reasonable to consider it to be an acute haematogenous infection, i.e. a type 3 infection. This may be the case, if the joint symptoms occur hours to days after an obvious infection, like pneumonia, or a surgical procedure, like dental extraction. A true late infection is probably a rare event, but it does occur. If all indicates a true late infection it should be treated as the early postoperative infection of type 1 And finally, sometimes one receives a positive culture report following a revision of a joint, that was not suspected of being infected. The unexpected positive culture taken during an unsuspected revision, is classified as type 4, and should be treated with prolonged antibiotics. Let’s look at the outcomes of these treatments. With the aggressive treatment outlined above and adhering to strict guidelines for treating periprosthetic infections, success rates of 80-90% are usually quoted. There is unfortunately a small group of patients, in whom the infection is never eradicated, and where permanent removal of the implant, possibly by arthrodesis or amputation, becomes the final solution to the infection. In other patients, it is chosen to give the patient life-long antibiotics. The risk of having an arthrodesis after knee replacement varies between countries and within countries. The average Danish figure is in the order of 0.1%. In conclusion, periprosthetic infections can be treated, but it requires an aggressive surgical attitude and sound principles. You should among your colleagues discuss your impression of infections. Discuss your brilliant ideas, and discuss your uncertainties. Successful treatment requires an organization that agrees on the basic paradigm and the guiding principles. Such an agreement only exist in an organization, if the principles are explicitly stated. The starting point for a discussion among your colleagues might for instance be this course series. Thank you very much for listening.
