Prolonged microbiological culture for 2 weeks is promising because it yields signs of periprosthetic infection in a significant proportion of patients that would otherwise remain unidentified.

We analysed the serum C-reactive protein level, synovial fluid obtained by joint aspiration and five synovial biopsies from 145 knee replacements prior to revision to assess the value of these parameters in diagnosing late peri-prosthetic infection. Five further synovial biopsies were used for histological analysis. Samples were also obtained during the revision and incubated and analysed in an identical manner for 14 days. A total of 40 total knee replacements were found to be infected (prevalence 27.6%). The aspiration technique had a sensitivity of 72.5% (95% confidence interval (CI) 58.7 to 86.3), a specificity of 95.2% (95% CI 91.2 to 99.2), a positive predictive value of 85.3% (95% CI 73.4 to 100), a negative predictive value of 90.1% (95% CI 84.5 to 95.7) and an accuracy of 89%. The biopsy technique had a sensitivity of 100%, a specificity of 98.1% (95% CI 95.5 to 100), a positive predictive value of 95.2% (95% CI 88.8 to 100), a negative predictive value of 100% and an accuracy of 98.6%. C-reactive protein with a cut-off-point of 13.5 mg/l had a sensitivity of 72.5% (95% CI 58.7 to 86.3), a specificity of 80.9% (95% CI 73.4 to 88.4), a positive predictive value of 59.2% (95% CI 45.4 to 73.0), a negative predictive value of 88.5% (95% 81.0 to 96.0 CI) and an accuracy of 78.1%. We found that biopsy was superior to joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements.

Cementless two-stage revision of infected total hip prostheses lacks the possibility of local antibiotic protection of the implant at the time of reimplantation, which leads to the concern that this protocol may not sufficiently eradicate periprosthetic infection. Moreover, early implant loosening as much as 18% and stem subsidence as much as 30% have been reported. To determine whether a cementless revision could eradicate infection and achieve sufficient implant stability, we prospectively followed 36 patients with two-stage revisions for septic hip prostheses. We used a uniform protocol of a 6-week spacer interval, specific local and systemic antibiotic therapies, and cementless modular revision stems. The minimum followup was 24 months (mean, 35 months; range, 24-60 months). In one patient, the spacer was changed when the C-reactive protein value failed to normalize after 6 weeks, and the reimplantation was performed after an additional 6 weeks. No infections recurred. There was no implant loosening and a 94% bone-ingrowth fixation of stems. Subsidence occurred in two patients. The Harris hip score increased from a preoperative mean of 41 to 90 at 12 months after reimplantation and later. Using cementless prostheses in two-stage revisions of periprosthetic infections of the hip in combination with a specific local and systemic antibiotic therapy seems to eradicate infection and provide implant stability.

Many concepts have been devised for the treatment of late periprosthetic infections of total hip prostheses. A two-stage revision with a temporary antibiotic-impregnated cement spacer and a cemented prosthesis appears to be the most preferred procedure although, in recent times, there seems to be a trend towards cementless implants and a shorter period of antibiotic treatment. Because of the differences in procedure, not only between studies but also within studies, it cannot be decided which period of parenteral antibiotic treatment and which spacer period is the most suitable. The fact that comparable rates of success can be achieved with different treatment regimens emphasises the importance of surgical removal of all foreign materials and the radical debridement of all infected and ischaemic tissues and the contribution of these crucial procedures to the successful treatment of late periprosthetic infections.