**4.1.3 Knee infections**

We perform pre-operative tissue biopsies rather than joint aspiration if it is clear that revision operation is necessary due to an unstable implant (Fig. 4). Five biopsies for culture are obtained in a blind fashion without instillating fluid in the intra-articular space (to avoid possible losses in sensitivity due to sample dilution). Afterwards standard arthroscopy is performed to rule out possible joint damage, and during this process 5 additional tissue samples are obtained for histological analysis.

We define infection using the same combined culture and histology algorithm as in biopsy samples taken during revision surgery. Our experience is that pre-operative biopsies are more sensitive than culture from aspirated synovial fluid (Fink et al., 2008).

Infections in Hip and Knee Arthroplasty:

**pre-operative sampling** 

**risk assessment** 

Challenges to and Chances for the Microbiological Laboratory 451

clinical symptoms radiological signs laboratory markers

stable implant?

no

joint aspiration

yes

tissue biopsies (blinded) tissue biopsies

(arthroscopic) 5 x histology

pediatric blood culture vial (14 days incubation)

5 x culture (14 days incubation)

pain, hyperthermia joint loosening elevated CRP

5 x culture (14 days incubation) 5 x histology

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

Achermann, Y.; Vogt, M.; Leunig, M.; Wust, J. & Trampuz, A. (2010). Improved diagnosis of

tissue biopsies

Atkins, B.L.; Athanasou, N.; Deeks, J.J.; Crook, D.W.; Simpson, H.; Peto, T.E.; McLardy-

periprosthetic joint infection by multiplex PCR of sonication fluid from removed implants. *Journal of Clinical Microbiology,* Vol. 48, No. 4, (April 2010), pp. 1208-1214,

Smith, P. & Berendt, A.R. (1998). Prospective evaluation of criteria for microbiological diagnosis of prosthetic-joint infection at revision arthroplasty. The

**5. References** 

ISSN 1098-660X

**intra-operative sampling** 

Fig. 3. Sampling algorithm for suspected periprosthetic hip infection. If joint aspiration cultures are negative but the risk assessment suggests indicates septic implant failure, preoperative tissue biopsies are drawn additionally for culture and histology.

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% (Fink et al., 2008).

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 et al., 2008).
