AO Trauma Symposium at DKOU on October 27, 2011, ICC Berlin
The prevention and treatment of infections in cases of osteosynthesis and joint replacement.
19 January 2012
Hansjörg Oestern, Chairman of AO Germany, opened the symposium and welcomed the delegates, who numbered almost 200. Unfortunately, the room was far too small and well over 100 people had to stand in the foyer and listen to the lectures over loudspeakers.
Nikolaus Renner, Chairperson of AO Trauma International, pointed out that a start was made years ago on the preliminary work for a new Clinical Priority Program (CPP) on the subject of bone infection. Following an open call for tenders, the projects submitted are currently undergoing the peer review process, on the basis of which the best projects will be selected in December. It will then be possible to start the actual research work next year. Expertise in the field of infection research at the AO Research Institute (ARI) in Davos has been increased accordingly in recent years through the development of a separate research group.
Geoff Richards, Director AO Research Institute Davos, explained the mechanism involved in the formation of biofilms and how difficult it is to get rid of these. He expressed his astonishment that courses hardly ever provide training in debridement any more. Research at AO into improving resistance to infection focuses on implant design, materials and surface treatment. The ultimate aim is to reduce the "dead space." Richards spoke of the difficulties of developing appropriate research models, since almost 90% of the various biofilms cannot currently be simulated in models. He emphasized that antibiotics applied directly to an implant in the hospital will not work, since, without coating, the antibiotic does not come into direct contact with the bacteria. This is because the body coats the implant with proteins on insertion and this would block any antibiotic directly bound to an implant surface. A biodegradable coating would protect the antibiotics that would be released over time and would not be disturbed by the proteins on the coating. Richards finished by issuing an invitation to work with AO Research Institute Davos eg, as an AO Research Fellow in Davos.
Gerhard Schmidmaier emphasized the importance of preventing, or at least reducing, the formation of biofilms. In this regard, implants are only one part of the overall treatment (Diamond Concept). He presented intramedullary nails coated with gentamicin. The antibiotic is released over the course of six months, starting with an initial peak. He then presented a series of cases involving the tibia and femur, relating to both the treatment and prevention of infections.
Mathias Herrmann emphasized that, with regard to microbiological principles, the essential problem is the lack of host defense, which is therefore of greater importance than the formation of the mucous or biofilm. He then spoke about the significance of the small colony variants (SCVs) that result in the development of highly resistant organisms. In the context of the previous speaker’s presentation, it is significant that SCVs can particularly be induced by gentamicin treatment. With regard to diagnosis, he explained that sonication is a method that is currently very much in vogue, but that is very costly. There are also certain problems associated with the interpretation of the results.
Consequences for diagnosis are:
Fistula secretions and surface material from acute surgical wound infections are not suitable. Synovial fluids and tissue biopsies are good.
Direct samples are less useful. Tissue biopsies are required. Here he said that you need at least 1 cm3 and several biopsies – 5.
He recommended that, wherever possible, several tissue samples should always be taken (a minimum of 5) and that there should be an incubation period of more than 14 days.
The relevance of molecular diagnosis, eg, nucleic acid amplification technology (NAT), is not yet clear in all areas, but is probably most important in the case of patients who have undergone prior treatment with antibiotics.
He warned of the need to be careful of molecular techniques such as PCR that can give false negatives and referred back to my talk that intraoperative diagnosis development would be very useful, especially since cultures are also not always possible.
Christian Friesecke presented the therapeutic procedure for prosthetic infections. Infections often go unnoticed or are detected too late. It is important to establish whether the infection is an early-onset (<3 weeks) or a late-onset infection. It is only possible to avoid replacing the prosthesis in the case of an early-onset infection, although all non-cemented prosthetic components should be replaced. With late-onset infections, single-stage replacement leads to better functional results with the same success rate (80–90%) regarding the recurrence of infection. However, this should only be performed if it is possible to isolate the pathogen preoperatively and if antibiotics are available in a powder form that can be added to the cement. He uses Lavasept for the jet lavage, but believes that, for recent infections, the pulsation is more important than the substance used. There is a lack of good studies into both the substance used for lavage and the lavage procedure itself, eg, whether the pulsating process for treating chronic infections could, in fact, actually cause the infection to spread.
Christoph Josten gave a lecture about osseous reconstruction techniques. Bone defects should be addressed as early as possible. Extremity shortening is acceptable for bone defects up to a maximum of 3 cm. Autogenous grafts can be used for defects up to 3–4 cm and have a shorter healing period than the transport methods. Spongiosa may only be used to fill defects that have no biomechanical stability requirements. Christoph Josten is of the opinion that segment transport is far superior to spongiosaplasty due to the better biomechanics. Calcium sulfate spacers have only low initial stability and take too long for the osseous restoration to occur. He finished by presenting various cases involving segment transport.
Peter Vogt spoke about the possibilities of plastic soft-tissue reconstruction. Plastic reconstruction should be performed as early as possible. Flap losses occur primarily in tertiary centers, but not in reconstruction centers. The patient should therefore be transferred as quickly as possible. With free flaps, early mobilization can be started after three days. The final, very animated discussion, chaired by Norbert Haas, clearly showed just how topical this subject matter is in day-to-day practice.