Where Are We Now?
Prosthetic joint infection (PJI) is a devastating complication of hip and knee arthroplasty . Although the incidence remains low (0.5% to 3%), the total annual numbers are growing quickly as the frequency of THA and TKA increases . The resulting morbidity, mortality, and economic burden are substantial . The ideal management strategy for an established, chronic PJI is controversial. The two most common techniques for eradicating these chronic infections are the two-stage procedure  and the one-stage procedure [2, 3, 6]. Success rates for the two-stage technique have been reported to range from 80% to 95% at mid-term follow-up . A common critique of this technique is the morbidity and costs associated with a prolonged convalescence and a second operation. The one-stage technique avoids these problems by performing the débridement and reconstruction in a single operation. One-stage and two-stage procedures have been reported to have similar results [8, 17]. Two meta-analyses reviewed a large number of studies comparing the one-stage and two-stage techniques for hip and knee PJI and found no significant difference in success rates between the two techniques [10, 11].
Patient selection appears to be imperative to consistent outcomes of the one-stage technique . However, this has become an area of controversy . For instance, there seems to be general agreement that the minimum criteria for a one-stage exchange are preoperative identification of the infecting organism and susceptibility of the infection to antibiotics [6-8, 14, 16, 17]. Some have also argued that in order to consider a one-stage procedure, there must be an adequate soft-tissue envelope and the host must not be immunocompromised [7, 14]. Others have recommended a one-stage procedure only for prosthetic hip infections with good bone stock that does not require bone grafting and definitive implant fixation with antibiotic-loaded bone cement . These varying criteria for patient selection have made comparisons across centers more challenging.
The recent work by Dombrowski et al.  has raised important questions regarding patient selection. Only 19% of their cohort met the International Consensus Meeting criteria  for a one-stage procedure. These findings highlight the difficulty in comparing results between the two techniques without strict, well-defined criteria. The data should also caution us that most patients presenting with chronic PJI are not candidates for a single-stage exchange.
Where Do We Need To Go?
Several important questions remain unanswered. Foremost is the question of who is the ideal candidate for a one-stage procedure? A center with vast experience with the one-stage technique reported that 85% of patients with PJIs were candidates for this procedure . In contrast, another group found that only 28% of their patients were candidates for a one-stage procedure . The current study  found that only 19% of patients met the criteria for a one-stage procedure. These differences seem to be related to patient selection. It is important to identify reproducible criteria that identify the appropriate candidate for a one-stage procedure. Additional questions revolve around specific inclusion and exclusion criteria. What constitutes immunocompromise? Some have defined immunocompromise as the presence of rheumatoid arthritis, diabetes, anemia, or cancer, without the requirement of immunosuppressive medications . What type of soft-tissue defect is acceptable for a one-stage exchange? Does the presence of a sinus tract remove a patient from consideration?
When we have determined which patients are the most likely to benefit from one-stage exchange, we will need to determine whether the one-stage or two-stage approach is the most effective for eradicating infection, restoring patient function, and reducing morbidity, mortality, and cost.
How Do We Get There?
Several centers have been diligently working on these questions. One group found no recurrence of infection in 28 patients treated with one-stage exchange at a minimum of 3 years . These authors reported very strict inclusion criteria: preoperative identification of a single organism, susceptibility to antibiotics, a soft-tissue envelope that could be closed primarily, and an immunocompetent host. These inclusion criteria appear to offer a pragmatic approach by offering the benefits of a one-stage procedure to those whose infection is the most likely to be eradicated. It is important to test these criteria in large, multicenter, randomized trials. Two such trials are currently underway. A large, multicenter, prospective trial in the United States is comparing one-stage and two-stage exchange to treat chronic PJI of the hip and knee . The study uses similar inclusion and exclusion criteria to those proposed by the International Consensus Meeting , as well as the criteria of a previous study . The INFection: ORthopaedic Management (INFORM) trial is a multi-center, randomized study comparing one- and two-stage revisions for PJI of the hip . Enrollment is complete and results are anticipated soon.
If the results of these trials indicate there is a cohort of patients who can be successfully treated with one-stage exchange, additional studies can then test various inclusion criteria. This will help us continue to define the best candidates for this technique and potentially expand to a larger patient population. Additionally, well-controlled studies can compare patient-reported outcome measures, cost, and ability to reduce the morbidity and mortality of PJI.
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