Prof. Claudio Castelli
Director of the Operative Unit of Orthopaedics and Traumatology United.
Ospedali Riuniti di Bergamo
The preformed spacer for knee includes 7 variants: 3 with Gentamicin and 4 with Vancomycin + Gentamicin
What are the guidelines for treatment?
In the case of infection of total knee prostheses, the therapeutic approach changes according to its precocity or lack thereof.
When the infection is extremely precocious, it is possible to perform a conservative treatment, leaving the joint prosthesis in place and essentially relying on local cleaning associated with antibiotic therapy.
In most other cases, in order to treat the infection, the prosthetic implant must be removed.
In the case of removal, what are the indications for two-stage reimplantation?
When the prosthesis must be removed, in order to treat the infection, there are two therapy alternatives: immediately reimplant another prosthesis, that is, the so-called single-stage revision, or else after explantation allow a period to elapse during which the joint is left free of foreign bodies, and therefore of the prosthesis, which will be implanted at a later stage.
This second method, called two-stage revision, is by now used by most surgeons around the world since it offers a greater guarantee of results on eradicating the infection.
In the two-stage treatment, what advantages does the choice of a preformed and articulated spacer give the surgeon and the patient?During the interval period in the two-stage revision, the problem is to reach the second operation having local conditions at the level of the joint that allow for
a simpler surgery and therefore prefigure better functional results.
During this interval period, the patient can maintain joint function and therefore have a satisfying quality of life; that is the aim during the intermediate period between the two stages of the articulated spacer.
What are the contra-indications to the use of the spacer?
The contra-indications are chiefly local in character, in the sense that for a spacer to be effective from a mechanical point of view, the joint must have some ligaments intact, in particular the medial collateral, so that the spacer will be stable once it is implanted.
Another requirement is that once the infected implant is removed the bone defect must permit attachment and application of the spacer in the correct position.
This concerns most knee prostheses that are revised due to infection.
When is partial load allowed?That depends on the results achieved during the surgery.
If the intraoperatory kinematic results are satisfactory, and they can be respecting a few small technical details, there is not a big difference in the post-operative progress as compared to a normal implant.
Therefore partial load with supports can be allowed as early as the first days.
In any case it is useful to protect the knee at first with a brace.
After how much time are patients with spacers released?
Release depends more on the antibiotic therapy the patient must receive than on the post-operative period.
This therapy is a combination of the local release of antibiotic with which the spacer is equipped, and a systemic antibiotic therapy. When this is especially taxing and must be administered intravenously, it involves a certain delay in dismissing the patient. But the patient can be released as early as after one week or ten days from hospitalization.
After how much time is the spacer removed?That depends on results for the purposes of eradication of the infection. Parameters are used in any case to understand if the treatment of the infection
is effective or not (one is chemical, the other laboratory), for which two main indications are used, VES and PCR.
In my experience, in the case of the knee and in the absence of particularly complicated infections, the average period in which the spacer can be left in place, with a goal of eradicating the infection and achieving good mechanical results, ranges from eight to twelve weeks.
Are you satisfied with the results achieved?
Yes, I am satisfied because it has noticeably improved the overall functional result of the procedure, and at the same time maintained the quality of the results in terms of eradicating the infection.
Are the patients satisfied?I would say so, especially considering that the alternative to this type of method using an articulated spacer would be the implantation of a spacer block, which would create a period of rigidity for the knee with a noticeably reduced total load capacity.