University of Southern California Staging System for Prosthetic Joint Infection

 

Parameters:

(1) infection type

(2) systemic immune status

(3) local extremity status

Parameter	Finding	Rating
infection type	early postoperative infection (<= 4 weeks after surgery)	I
	acute hematogenous infection	II
	late chronic infection (> 4 weeks postoperative)	III
systemic immune status	no systemic compromising factors	A
	1 or 2 systemic compromising factors	B
	> 2 systemic compromising factors	C
	>= 1 significant comorbid conditions	C
local extremity status	no local compromising factors	1
	1 or 2 local compromising factors	2
	> 2 local compromising factors	3

 

Clinical stage = (infection type) - (systemic immune status) - (local extremity status)

 

Systemic compromising factors:

(1) systemic inflammatory disease

(2) immunosuppressive drugs

(3) infection

(4) renal and/or liver failure

(5) diabetes mellitus

(6) cardiopulmonary compromise

(7) malnutrition

(8) metastatic disease not of immune origin

(9) chronic indwelling catheter

(10) alcoholism or smoking

 

Significant comorbid conditions:

(1) absolute neutrophil count < 1,000 per µL

(2) CD4 lymphocyte count < 100 per µL

(3) intravenous drug abuse

(4) chronic infection at other site

(5) dysplasia or neoplasm of immune system (malignant lymphoma, etc.)

 

Local compromising factors:

(1) reflex sympathetic dystrophy

(2) multiple incisions from trauma

(3) soft tissue loss from trauma

(4) synovial cutaneous fistula (draining sinus)

(5) large subcutaneous abscess (> 8 square cm)

(6) vascular disease

(7) previous fracture or trauma above joint

(8) prior local radiation to region

(9) prior infection > 3 months before