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Biomet Cementing University


Therapy

At the Endo-Klinik in Hamburg, more than 6000 septic revisions, including 1000 septic knee revisions, have been performed over the past 25 years using the one-stage revision procedure. The current success rate of hip revision arthroplasties is about 88%. For septic knee revisions, the success rate with the one-stage revision procedure is about 75%.

The pathogenesis of periprosthetic infections gives us the proper approach to the therapy. If there is an infected foreign body on whose surface bacteria have colonised and are residing comfortably in a biofilm protecting them against the host defence and against systemic antibiotics, then that foreign part and all foreign material must be removed.

There is one exception. In the event of an immediate infection ­ one occurring within the first three weeks after implantation ­ there is a chance to save the implant by performing suction irrigation drainage combined with radical debridement of all infected tissue and postoperative administration of systemic antibiotics. The irrigation should not last longer than three days, as the danger of a secondary infection caused by other bacteria increases over time. In our patient group, the success rate of this procedure is nearly 60%. Another method for controlling an immediate infection is systemic antibiotic therapy with a combination of chinolones and rifampicin, as proposed by Zimmerli and co-workers.

In cases of late infection occurring later than three postoperative weeks it is not possible to eliminate infection with the prosthesis still in place. Removal of the prosthesis and all foreign material is essential. From the point of view of a microbiologist, it is not important whether the procedure is one-stage, two-stage or revision; only removal of the implant is important. In all described methods of revision, the foreign body must be removed completely

Reimplantation of a new artificial joint in the same session is possible only when the causative pathogen has been identified and an antibiotic-loaded acrylic bone cement is used. Surgical intervention must be radical, and debridement must include all infected bone and soft tissue as well as all components of the joint replacement and bone cement. Non-viable bone must be resected, and curettage of the remaining bone must be done with irrigation under pressure (for example, with jet lavage and the addition of antimicrobial agents such as Lavasept).

The choice of implant plays a crucial role. We have successfully reimplanted a primary implant in 60% of our septic knee and hip revisions. Normally this is done when a periprosthetic infection of a condylar prosthesis must be treated. In all cases we chose constrained hinge models such as the Total Hinge or the Rotation Knee to get good stability, as typically the ligaments and muscles are involved in the infection, resulting in severe instability of the joint.

In instances of severe bone loss or infectious involvement of bone, a secondary implant must be reimplanted. These implants have longer stems so that the bone that must be removed can be replaced by polyethylene or cement, and the stems reach deep enough into the remaining natural bone to provide sufficient anchoring for the implant. If it is not possible to preserve enough bone for anchoring the stem, and there is severe involvement of the soft tissue, then a tertiary implant must be used. We call these implants megaprostheses. Usually these mega-implants are total femur replacements, which include two or more joints (typically the knee and the hip, although other combinations, e.g., knee and ankle, are possible).

The last resort for controlling severe periprosthetic infection of a hip replacement is removal of the joint by exarticulation or amputation. In recent years, our amputation rate has decreased to less than 1%. We try to preserve the limb in all cases and by all means. Additional problems that can further aggravate the situation include complications of the soft tissues or the extensor mechanism.

Severe disturbance of wound healing or extensive soft tissue defects can be treated by a gastrocnemius flap and mesh graft, as shown here.

Postoperatively, systemic therapy is administered for five to fourteen days. The drainage tips are sent for bacteriological examination, and laboratory parameters are controlled at regular intervals. In cases where the result is uncertain, control aspirations are carried out.