Both the diagnosis and treatment of Prosthetic Joint Infection (PJI) can be challenging. The International Consensus meeting on PJI primarily defined joint infection as having two culture samples with phenotypically identical organisms or the presence of a sinus tract. Positive histology is only considered as one of the minor criteria of which 3 are required for diagnosis.
We developed a retrospective, multicentre database of prosthetic joint revision procedures where tissue samples were halved and sent for both microbiology and histology. 9% had only one histology sample sent. The correlation between microbiology and histology was observed with the aim of identifying what role histology has to play in the diagnosis.
208 revision procedures for all causes were analysed between 2012 and 2018. 152 (73%) were single stage revisions. In 132 (63.5%) cases, the histology matched the microbiology result. Of the 76 cases in which histology contradicted the microbiology, 48 (63%) helped support a conclusion of a 'contaminant' with a single false positive culture. Histology correlated well with both CRP and ESR on 66% of occasions and at least one on 83% of occasions in which the microbiology results differed.
Histology is beneficial in the confirmation of infection when intraoperative samples fail to culture. Histology indicating 'no infection' is also very useful in the presence of possible contamination in which only one sample developed positive culture or there were differing cultured organisms. Histology gives no additional information in the obviously infected joint such as those with sinuses. All the results however should be interpreted alongside other investigations such as inflammatory markers and pre- operative aspirates.
The authors agree that histology is one of the minor criteria for PJI, but would encourage samples be sent to help with decision making in the presence of negative or inconclusive cultures.