Berbari et al identified risk factors associated with infections involving prosthetic joints. This can help identify patients who may require closer monitoring or additional prophylaxis. The authors are from the Mayo Clinic.
Risk factors:
(1) postoperative surgical site infection (not involving the prosthesis)
(2) NNIS score
(3) systemic malignancy
(4) history of previous total joint arthroplasty
where:
• The NNIS (described in the chapter on Infection Control) ranges from 0 to 3 with the risk for surgical site infection increasing with higher NNIS. One of the 3 factors measured is clean (0 points) vs dirty/contaminated (1) surgery; in orthopedic patients therefore the maximum score would usually be 2.
• A history of previous total joint arthroplasty involves both revisions of the same joint and an arthroplasty on a separate joint.
Risk Factor
Odds Ratio
95% CI
p value
postoperative surgical site infection
35.9
8.3 - 154.6
<= 0.01
NNIS score 1
1.7
1.2 - 2.1
<= 0.05
NNIS score 2
3.9
2.0 - 7.5
<= 0.01
systemic malignancy
3.1
1.3 - 7.2
<= 0.01
previous total joint arthroplasty
2.0
1.4 - 3.0
<= 0.01
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