Discrepancies between frozen and paraffin tissue sections have little effect on outcome of staged total knee arthroplasty revision for infection.

BACKGROUND: Intraoperative analysis of frozen tissue samples has been used to diagnose periprosthetic joint infection in revision total knee arthroplasty, but the precision and reliability of this test throughout staged revision arthroplasty have not been well characterized. We undertook this study to determine the rate of discrepancy between frozen and permanent histopathologic samples in the diagnosis of periprosthetic infection at both the index total knee arthroplasty revision procedure and the attempted reimplantation.

METHODS: Seventy-six patients who underwent staged revision of a total knee arthroplasty for apparent infection had samples for frozen and permanent sections obtained at both the index revision procedure and subsequent reimplantation attempts. We investigated the rate of discrepancy between these frozen and permanent sections. The clinical and radiographic outcomes of patients with and without concordance between the frozen and permanent sections were reviewed.

RESULTS: Concordance was noted between 297 (97.7%) of the 304 frozen sections and the permanent sections. Seven discrepancies between diagnoses based on frozen and permanent sections were noted; however, additional samples in these patients were positive and management was not affected. Fewer discrepancies were found during the initial revision procedure (one of 92, 1%) compared with reimplantation (six of 212, 3%). The mean time to reimplantation was similar between patients with and without a discrepancy in diagnosis between the frozen and permanent sections (185 compared with 157 days). The rate of discrepancy between frozen and permanent histopathologic sections was low, and no discrepancy affected the final outcome of any patient.

CONCLUSIONS: The rate of discrepancy between frozen and permanent histopathologic samples was low for both index revision and reimplantation procedures. In rare instances of discrepancy, management should be unaffected provided a sufficient number of samples were collected.