Quantification of neutrophil polymorphs in infected and noninfected second-stage revision hip arthroplasties.

AIMS: In the diagnosis of periprosthetic joint infection (PJI), a heavy neutrophil polymorph (NP) infiltrate (>5 per high-power field [HPF] by MSIS criteria) is characteristically seen in periprosthetic tissues. PJI is commonly treated by a two-stage procedure with surgical clearance of infected tissues followed by intensive antibiotic treatment before re-implantation; tissues are sampled at the time of second stage but whether MSIS histological criteria can be used to diagnose the presence or absence of infection in second stage samples has not been established. METHODS: Periprosthetic tissues from 31 cases of second-stage revision hip arthroplasty (including 3 cases fulfilling the microbiological MSIS criteria for PJI), were analysed histologically after haematoxylin-eosin and chloroacetate esterase (CAE) staining. The extent of the NP infiltrate was determined semiquantitatively and correlated with the microbiological diagnosis. RESULTS: CAE staining facilitated identification of NPs in arthroplasty tissues and showed that in those cases where an organism was cultured in 2 or more samples, meeting the MSIS microbiological criteria for definite diagnosis of PJI, there was a heavy polymorph infiltrate (>5 NP per HPF on average). It was noted that isolated or scattered NPs were seen in 42.8% of periprosthetic tissues from noninfected second-stage revisions. CONCLUSIONS: The MSIS histological criteria which support a diagnosis of PJI in specimens from a primary revision hip arthroplasty (i.e. >5 NPs per HPF on average) are also valid for the assessment of a second-stage specimens. NPs can be seen in samples of periprosthetic tissue from uninfected second-stage revisions, indicating that strict histological criteria should be used in evaluating their significance in this context.