Intra-Operative Frozen Section
We recommend the use of frozen sections of peri-implant tissues in patients who are undergoing reoperation for whom the diagnosis of periprosthetic joint infection has not been established or excluded.

Rationale
Eight Level I studies were identified that evaluated the use of frozen sections to help diagnose peri-implant infection.3, 21, 30, 32, 54, 59, 75, 96 Three studies excluded patients with known underlying inflammatory arthropathy.30, 54, 96
 
Six of the eight studies used intraoperative cultures, while two studies used a combination of test results as the gold standard for diagnosis against which the frozen sections were compared. All studies based the histologic diagnosis of probable infection on the tissue concentration of acute inflammatory cells, usually defined by two variables: 1) the number of neutrophils in a high magnification (400X) microscopic field, and 2) the minimum number of fields containing that concentration of neutrophils. At least three studies excluded neutrophils entrapped in superficial fibrin.
 
Four studies used 10 or more neutrophils per high power field, and three of the four required 10 more neutrophils in at least 5 fields. The remaining study required 10 or more neutrophils in any given area. Our meta-analysis of these studies indicated that frozen section is a very good “rule in” test (i.e., a positive result has a high likelihood of infection; LR+: 23), but is a relatively low value “rule out” test (i.e. a negative result does not have a high likelihood of absent infection; LR-: 0.23).
 
Four other studies used 5 or more neutrophils per high power field; several of these specified at least 5 microscopic fields but the other studies did not. Meta-analysis indicated that when compared to a 10 PMN/HPF criterion this lower inflammation threshold may have similar sensitivity, but slightly lower specificity (i.e. a higher frequency of false positive results).
 
There is insufficient information to distinguish 5 from 10 neutrophils per high power field as the best threshold needed for diagnosis. Insufficient information is available to determine the efficacy of frozen sections in patients with an underlying inflammatory arthropathy.