Medial parapatellar arthrotomy and aspiration of the articular fluid to analyze with the aim of identifying the causing microorganism
Intraoperative photograph of a patient with an acute infection after total knee arthroplasty (TKA). Note the thickened synovial tissue
Synovial tissue and polyethylene (PE) insert removed
17.4 Risk Factors for Failure
17.4.1 Acute Hematogenous Infection
The treatment of acute hematogenous PJIs with ODPE has been shown to be successful in the majority of patients (76% survivorship at 2 years). Survivorship of the prosthesis was 45% for patients with a staphylococcal infection and 96% for patients infected with organisms other than Staphylococcus species. In patients who developed recurrent infection, the rate of success was less than 50%. Twenty-five percent of patients died within 2 years of the treatment of their infection, indicating that an acute hematogenous infection may be a marker of poor general health predisposing to this complication .
Vilchez et al.  reported that ODPE in patients with hematogenous PJI due to S. aureus had a worse outcome than early postsurgical infections (failure rate 58.7% vs 24.5%, respectively).
17.4.2 Virulence of the Microorganism
Many studies have reported that virulence of the microorganism was one of the risk factors for the failure. Silva et al.  reported in a systematic review that if the infecting bacteria are resistant, such as methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-resistant Staphylococcus epidermidis (MRSE), it would be better to consider a two-stage revision rather than ODPE.
In a multicenter retrospective study, Bradbury et al.  reviewed 19 cases of acute periprosthetic MRSA infection managed by ODPE and suggested that the total failure rate of ODPE in acute periprosthetic infection (<4 weeks) was 16 cases (84%). They recommended a two-stage exchange arthroplasty for periprosthetic MRSA infection.
Streptococcal PJI is associated with high recurrence rates, which are even higher than observed in staphylococcal PJIs. Zürcher-Pfund et al.  reviewed 599 published cases of PJIs treated with ODPE and found an overall recurrence rate of 47% with a significantly higher rate for streptococcal than staphylococcal infection 43/54 (79.6%) and 144/324 (44.4%), respectively (p < 0 0.01).
In a multicenter study of PJI managed by ODPE using rifampin for MRSA infections, Lora-Tamayo et al.  stated that it may have contributed to homogenizing methicillin-sensitive Staphylococcus aureus (MSSA) and MRSA prognoses.
The relatively poor results of staphylococcal infections are likely due to biofilm production and associated antibiotic resistance. Biofilm formation is enhanced in staphylococcal foreign body infections compared to streptococcal PJIs .
17.4.3 Sinus Tract
The presence of a sinus tract has been associated with treatment failure and is a contraindication to ODPE . Marculescu et al.  revised 99 PJI treated with ODPE. The PJIs that involved a sinus tract at presentation were associated with treatment failure of 39%, compared with 64% among those without sinus tract at presentation.
17.4.4 Polyethylene (PE) Exchange
PE exchange is usually recommended as a part of thorough debridement. Choi et al.  showed that not exchanging the PE insert was an independent risk factor for failure. They report 59% failures in cases without PE exchange resulting in a poor infection control rate. Infection control rates were higher when PE was exchanged than when it wasn’t (p < 0.001). Regardless of the causative organisms, lack of PE exchange resulted in poor outcome.
Kim et al.  reported that PE exchange was one of the factors affecting the success of ODPE. They performed PE exchange in cases of open debridement and did not perform PE exchange in cases of arthroscopic debridement. They report 58.8% failures treatment in cases without PE exchange resulting. They concluded that PE exchange can prevent the recurrence of infections.
17.4.5 Arthroscopic Versus Open Debridement
Arthroscopic debridement is a less invasive procedure than open debridement. Some authors have employed arthroscopic debridement in acute infections. Ilahi et al.  reported 100% success in seven patients, and Liu et al.  reported 88% success rate in 15 patients they treated, but others report a lower success rate when compared to open debridement. Waldman et al.  suggested that only 38% of infected knees were successfully treated using arthroscopic debridement and recommended the use of open debridement for infected TKA.
An ODPE procedure is difficult to carry out arthroscopically because this does not allow access to all compartments and some parts of the joint, especially the posterior compartment; it is impossible to exchange the PE insert and remove microorganisms present between the metal tibial tray and the PE liner . For this reason, it is not currently recommended in the treatment of PJI.
17.4.6 Single Versus Multiple ODPE
Most studies would regard the need for a further procedure as failure of the index procedure. Vilchez et al.  showed that the need for a second debridement (p = 0.002) was an independent predictor of failure. Therefore, repeated ODPE procedures are not recommended and indicate failure and the need for an alternative procedure. However, Mont et al.  performed one to three irrigation and debridement procedures based on systemic signs, knee symptoms, or the results of knee aspirations.
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17.4.7 Preoperative Erythrocyte Sedimentation Rate (ESR)
Kim et al.  reported that the preoperative ESR was one of the factors affecting the success of ODPE. The mean preoperative ESR in the success group (69.1 ± 35.5 mm/h) was lower than that in the failure group (103.5 ± 43.7 mm/h; p = 0.021). Kuiper et al.  demonstrated that ESR at presentation above 60 mm/L was one of the factors associated with failure of ODPE. More studies including a greater number of cases are needed.
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