**4.2 Future prospects**

The detection of bacterial RNA rather than DNA by reverse transcription PCR is a potentially useful new approach to arthroplasty infection (Bergin et al., 2010). On one hand, RNA should be present only in viable bacteria and therefore indicate infections more accurately than DNA. On the other hand, the much shorter half-life of RNA should make its presence as a contaminant less likely. It remains to be seen whether this concept will prevail.

Rapid identification of bacteria and fungi to the species level by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is utilized increasingly. There are already promising data on the detection of *Staphylococcus epidermidis* in tissue samples of patients with periprosthetic joint infections (Harris et al., 2010). It appears that it should even be possible in the near future to prove clonal identity of strains from the same species isolated from different tissue samples with this technique. This should facilitate the decision whether bacteria isolated from multiple tissue biopsies are likely to be involved in infection or rather reflect contaminating strains.

clinical symptoms radiological signs laboratory markers

joint aspiration

pediatric blood culture vial (14 days incubation)

pain, hyperthermia joint loosening elevated CRP

5 x culture (14 days incubation) 5 x histology

tissue biopsies

Fig. 3. Sampling algorithm for suspected periprosthetic hip infection. If joint aspiration cultures are negative but the risk assessment suggests indicates septic implant failure, pre-

In stable implants, we do not undertake the risk of causing joint damage by blinded tissue biopsy. Instead, joint aspiration culture is performed, which has shown accuracy of 89%

The pre-operative diagnostic approach of combined tissue culture histology has shown an accuracy of 98.6% compared to the definitive results obtained during revision surgery (Fink

The detection of bacterial RNA rather than DNA by reverse transcription PCR is a potentially useful new approach to arthroplasty infection (Bergin et al., 2010). On one hand, RNA should be present only in viable bacteria and therefore indicate infections more accurately than DNA. On the other hand, the much shorter half-life of RNA should make its presence as a contaminant less likely. It remains to be seen whether this concept

Rapid identification of bacteria and fungi to the species level by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is utilized increasingly. There are already promising data on the detection of *Staphylococcus epidermidis* in tissue samples of patients with periprosthetic joint infections (Harris et al., 2010). It appears that it should even be possible in the near future to prove clonal identity of strains from the same species isolated from different tissue samples with this technique. This should facilitate the decision whether bacteria isolated from multiple tissue biopsies are

likely to be involved in infection or rather reflect contaminating strains.

operative tissue biopsies are drawn additionally for culture and histology.

(Fink et al., 2008).

**pre-operative sampling** 

**risk assessment** 

**intra-operative sampling** 

**4.2 Future prospects** 

et al., 2008).

will prevail.

Fig. 4. Sampling algorithm for suspected periprosthetic knee infection.
