1. Supervised by Dr Tim Bracey
Review of Frozen Section Results and correlation with microbiology for revision joint replacement surgery
Dr R Hadden BSc MBBS
SpR Histopathology
Supervised by Dr Tim Bracey
Derriford Hosptial

2. Revision Surgery
Currently Frozen Section is considered by Orthopaedic surgeons as a vital tool in assessment of periprosthetic joint infections.
Main Indications – aseptic or septic loosening
Intraoperative decision on type of procedure
One stage
Two stage

3. Problems
No agreed Gold Standard single test for diagnosing periprosthetic joint infections (PJI).
International Consensus Meeting on PJI.

4. PJI Is Present When One of the Major Criteria Exists or Three Out of Five Minor Criteria Exist
Two positive periprosthetic cultures with phenotypically identical organisms, OR
A sinus communicating with the joint, OR
Minor Criteria
1) Elevated serum C-reactive protein (CRP) AND erythrocyte sedimentation rate (ESR)
2) Elevated synovial fluid white blood cell (WBC) count OR ++change on leukocyte esterase test strip
3) Elevated synovial fluid polymorphonuclear neutrophil percentage (PMN%)
4) Positive histological analysis of periprosthetic tissue
5) A single positive culture

5. Criterion
Acute PJI (< 90 days)
Chronic PJI (> 90 days)
Erythrocyte Sedimentation Rate (mm/hr)
Not helpful. No threshold was determined 30
C-Reactive Protein (mg/L)
100 10
Synovia White Blood Cell Count (cells/μl)
10,000
3,000
Synovial Polymorphonuclear (%) 90 80
Leukocyte Esterase
+ Or ++
Histological Analysis of Tissue
> 5 neutrophils per high power field in 5 high power fields (× 400)
Same as acute

6. Local guidelines
No universally agreed gold standard (even within local team)
Based on the number of polymorphs per high powered field in at least five separate fields
<5 - indicates no active infection and one stage advised
possible infection, surgeon preference along with clinical picture to dictate surgical management
>10 - indicative of active infection, requiring two stage surgical management

7. Recent Series Of 15 Patients
If “clear operative field” and <20neuts/hpf
an infection free outcome is possible after single stage re- implantation
If “poor surgical field appearances”, associated with >20neuts/hpf. 2 stage procedure done.
Confirms our anecdotal evidence that positive frozen sections are macroscopically abnormal (colour/texture/odour).

8. Conflicting evidence Cut off 10 or 20 neuts/hpf?
Do surgeons actually comply with local guidelines?

9. Results Of Our review including micro
Reports on 50 sequential samples were reviewed
The microbiology results were reviewed
Correlation between the two was assessed

10. Frozen results 8 positive (>10 neuts/hpf) 36 Negative
6 Equivocal (5-9 neuts/hpf)

11. Positive FS Of the 8 positive Frozen sections:
All confirmed on paraffin
4 grew organisms
1 on initial culture
3 on “enrichment”

12. Negative FS 34/36 confirmed on paraffin
2/36 cases 0 neuts on frozen, “small numbers” on later paraffin sections
Likely negative
24/36 grew organisms
1 on culture
23 on enrichment culture

13. Equivocal / Borderline
6 cases 5-9 neuts/hpf
4 with growth on enrichment culture
2 with no growth
All had no growth on initial culture

14. Results From Orthopaedic review of 138 cases
Negative frozen section
Equivocal frozen section
Positive frozen section
Single stage operation
110 4
Two stage operation 28 5 2
Other 1

15. Summary Negative result: 25% go on to have 2-stage procedure!
Equivocal result: 50/50 split – presumably based on clinical/other test results
Positive result: Good compliance (n)

16. Results From Orthopaedic review of 138 cases
Negative frozen section
Equivocal frozen section
Positive frozen section
Negative
Cultures
101 4 1
Positive 36 5 2

17. Results From Orthopaedic review of 138 cases
Negative frozen section
Equivocal frozen section
Positive frozen section
Required
Revision 17 2
No Further
121 7

18. 12% with negative FS required revision
22% with equivocal FS required revision
0% with positive FS required revision

19. Discussion Why do surgeons ignore negative result in 25% of cases?
What is the point of FS in these cases?
In equivocal FS cases, what determines the procedural outcome? Does FS really make a difference?
approximate costs of £15,000.

20. Histology concerns:
Anecdotally, positive FS correlates with macro findings.
In the Korean series, high numbers of neuts correlated with macroscopic impression.
The 0-5, 5-10, 10+ criteria are arbitrary and based only on one study.
Recent criteria use histology (not necessarily FS histology!) as only a minor criteria for PJI.

21. Microbiology concerns:
Correlation with microbiology results is difficult.
Confounding factors (pre/intraop abx).
Most growth is on “enrichment culture”, we do not know the significance of these results.

22. Learning points / Questions
Negative predictive value is published as the most important factor in intraoperative testing
Why did many –ve FSs have +ve micro? ?sampling or FS poor sensitivity
25% of negative frozen sections still had a 2-stage procedure
Is there another test or clinical parameter that “trumps” frozen section?
Targeted or limited use should be advised (JK agrees this – reaudit needed to confirm)