Dr. Carlo Romanò
Responsible of the Center of Reconstructive Surgery and Osteoarticular Infection
Galeazzi Orthopaedic Institute IRCCS, Milan (Italy)
The wide range of preformed spacer includes 18 variants. Four typology of stem combinable with 3 sizes of head and 2 options of antibiotic (gentamicin or vancomycin + gentamicin).
The whole range of preformed spacer for knee includes 7 variants: 3 with gentamicin and 4 with vancomycin and gentamicin
The Preformed spacers for shoulder are available in 2 sizes
What is a periprosthetic joint infection (PJI )?
Joint prosthesis within the human body may act as a foreign material. Although in the majority of the cases they are well accepted by our body, in same patients joint implant can be colonized by bacteria and become infected.
Which is the probability to have a PJI ?
The overall risk of a PJI is relatively low, ranging from 0.5 to 3 %. However, some conditions may enhance the risk. These include: previous surgeries on the same joint, diabetes, smoke, alcool or drug abuse, peripheral vasculopathies, renal insufficiency, corticosteroids treatments etc.Recent reports show that PJI is the first reason for failure of knee prosthesis and the third for hip prosthesis in the usa. Even in europe, with slight differences among countries, PJI is among the first three reasons for revision surgery.
Are there risk factors predisposing to PJI ?
As mentioned above, the risk of developing an infection following joint prosthesis implant is related to a number of risk factors. The occurrence, in the same patient, of two or more risk factors, increases the risk esponentially. Risk factors have also a strong prognostic value. Most of the patients that develop a PJI will need further surgery to overcome the septic process around the implanted material. In our and other case series, the majority of patients that will have infection recurrence after treatment are compromised hosts, with one or more risk factors for infection. For this reason it is strongly recommended that risk factors that can be corrected are taken into consideraiton, including smoking habits, glycemic control, nutritional status, etc..
Which are the symptoms of a PJI ?
PJI may be associated with typical inflammatory signs and symptoms: local redness and warmth, swelling, pain and joint stiffness. In some cases persistent wound drainage or a draining fistula may appear. Unfortunately, however, these clinical signs may be missing and the only complaint is local pain and eventually stiffness of the affected joint. For this reason, a PJI should always be suspected in the presence of a painful joint prosthesis until it can be reasonably be ruled out through suitable tests and a convincing alternative explanation of pain
Which are the most suitable diagnostic methods to confirm the presence of a PJI ?
The diagnosis of a PJI relies on a multi-modal approach, that includes clinical examination, laboratory tests (blood tests), joint aspiration and imaging techniques. More and more sophisticated tests are now coming on the market and our diagnosis will hopefully increase to a large extent in the near future. An efficient microbiology department, able to perform the most recent analyses of the retrieved implants and peri-prosthetic bone, is currently necessary to perform revision surgery in failed joint prosthesis. A number of previously considered non infected failed prosthesis are now, in fact, discovered to be infected, thanks to a better microbiological and diagnostic analysis. This is obviously of utmost importance in view of the treatment choice and the final outcome.
Which are the treatment options in case of PJI ?
A PJI usually requires a combined medical and surgical approach. In some cases a salvage procedure of the implant can be undertaken, combining surgical debridement and a targeted antibiotic therapy. In the majority of the cases, however, the infected prosthesis needs to be removed and a new prosthesis is reimplanted in the same procedure or in a second stage. In these latter case, that is actually the most performed approach worldwide, an interval antibiotic-loaded spacer is implanted at the time of the infected prosthesis removal and, usually after 8 to 12 weeks, when the infection has been cleared, a new prosthesis is implanted. This procedure, although long and expensive, may lead to an eradication rate exceeding 90%. In case of repeated failures and in the most severe cases, an arthrodesis or even amputation may be required.
When is it possible / necessary to undertake a suppressive antibiotic therapy?
When the removal of the prosthesis in not possible or refused by the patient, expecially in a well fixed infected prosthesis, with microrganisms that are sensitive to oral antibiotics, a "suppressive" prolonged antibiotic therapy can be proposed. The main limits to this approach are, however, the high risk of side effects of the prolonged drug therapy, the possibile occurrence of resistant bacteria and the recurrence of the infection after some time from antibiotic therapy suspension.
When is it possible perform irrigation and debridement?
Salvage procedures, that include surgical debridement and prosthesis retention, associated with systemic antibiotic therapy, are usually indicated in early (within 4 to 6 weeks) onset of the infection after prosthetic implant.
This approach can also be considered for acute infections that may happen after years from prosthetic implants and that are thought to be due to a late contamination of the prosthesis via haematogenous spreading of bacteria from a distant septic focus, for example from a teeth granuloma or pneumonia, etc..The chance of success of debridement and irrigation, with prosthesis retention is approximately 46% at 4 years, according to our recently published metanalysis (romanò cl et al., 2012)
When has the prosthesis to be removed?
Removal of the prosthesis is the procedure of choice to cure a PJI . This procedure should be performed in all those subjects in which there are no general or local contraindication and particularly in painful prostheses
Which are the therapeutical options when the prosthesis has to be removed?
After the removal of the infected prosthesis and of the cement and any other foreign materials eventually present, there are different options: it is possibile to reimplant a new prosthesis in the same surgical procedure (one-stage procedure) or an antibiotic-loaded cement spacer can be put in place and joint reimplantation will then be performed in a second stage, usually after 8 to 12 weeks (two-stage procedure).
What determines the choice of removing the implant in one or two stages? What does the literature say on this subject?
There are no comparative studies concerning one- or two-stage procedures. At the moment meta-analyses do support two-stage as a more successful procedure, compared to one-stage, especially as far as knee prosthesis are considered (romanò cl et al., 2012). However, two-stage procedure is obviously associated with a longer time to recovery and to increased costs. To reduce inability between stages, it is then important to use, whenever possible, antibiotic spacers that allow partial weight-bearing and some range of movement of the affected joint. This is permitted by using the preformed antibiotic-loaded spacers, which have been in the market for more than 10 years. Two-stage revision with preformed spacers and uncemented prosthesis provided, in our experience, an eradication rate of 94% at 10 years follow-up (romanò et al, 2012). Similar results are reported in other centers, even if with a shorter follow-up (degen rm et al., 2012; wan z et al; 2012).
What does it happen if the infection is not eradicated of if it recurs?
In most cases it is possible to repeat the procedure and change the spacer, or perform a two-stage re-revision. It should be noted, however, that the more interventions are made on the same joint, the more bone and soft tissue defect will be encountered, making re-revisions one of the most challenging procedures in orthopedic surgery.
Is mobility important during the period in which the spacer is implanted?
The spacer choice matters. A spacer that allow some degree of joint mobility between stages will allow to maintain muscle efficiency, will prevent joint stiffness and reduce bone loss, making reimplantation of the prosthesis easier. For all of these reasons i personally use and recommend whenever possible to use a dynamic spacer instead of a static one.
How are the functional parameters of the limb affected by the presence of the spacer?
We have performed a computerized gait analysis study, recently published (logoluso n et al., 2012), that showed how patients with a dynamic knee or hip spacer do preserve a normal gait, even if in the slower range, compared to normal subjects.
Which factors do influence the time of implantation of the spacer?
The spacer is intended for a limited time use. In this period its function is to preserve joint space and, possibly, function as much as possible, while being protected by colonizing bacteria eventually present by the local antibiotic release. This function is needed for 2 or 3 months. After this period there is no need to wait more to implant a new prosthesis. Only in cases in which there are local or systemic contraindications to perform the second stage within three months, the spacer can be left in place. To our knowledge, even long-term spacer retention, up to 8 years in our experience, has not caused any measurable side effect. However, since the antibiotic release from the spacer decreases with time, reimplantation should take place as soon as there is sufficient evidence that the septic process has been adequately eradicated.
How is it decided to allow or not partial weight-bearing?
Normally a patient with a preformed spacer may walk with partial weight-bearing and two crutches without pain. In some cases, due to severe bone loss or to an instability of the spacer, that is most often related to large bone defects and/or ligament imbalance, weight-bearing can be restricted or prohibited.In our experience this occur in approximately 15% of the cases, but it should be noted that, as a referral centre for bone and joint infections, we are often required to treat challenging cases.Standard cases do not require particular weight restrictions, except for the use of two crutches.