The septic versus nonseptic inflamed joint: MRI characteristics.
OBJECTIVE
To differentiate the MR features of septic versus nonseptic inflamed joints.


METHODS
Thirty patients were referred for MRI with inflamed joints (19 were subsequently found to be septic and 11 nonseptic). At 1.5 T enhanced MRI five groups of signs related to joint space, synovium, cartilage, bone and peri-articular soft tissue respectively were assessed and compared between the septic and nonseptic groups.


RESULTS
The prevalence of MRI findings in septic versus nonseptic joints (respectively) was as follows: effusion (79% vs 82%), fluid outpouching (79% vs 73%), fluid heterogeneity (21% vs 27%), synovial thickening (68% vs 55%), synovial periedema (63% vs 55%), synovial enhancement (94% vs 88%), cartilage loss (53% vs 30%), bone erosions (79% vs 38%), bone erosions enhancement (77% vs 43%), bone marrow edema (74% vs 38%), bone marrow enhancement (67% vs 50%), soft tissue edema (63% vs 78%), soft tissue enhancement (67% vs 71%), periosteal edema (11% vs. 10%). The presence of bone erosions appeared to be an indicator for an infected joint (P=0.072); coexistence of bone marrow edema slightly improves the significance (0.068). A similar trend was obtained when combining bone erosions with either synovial thickening, synovial periedema, bone marrow enhancement or soft tissue edema (P=0.075).


CONCLUSIONS
The combination of bone erosions with marrow edema is highly suggestive for a septic articulation; the additional coexistence of synovial thickening, synovial edema, soft tissue edema or bone marrow enhancement increases the above level of confidence. Similar to conventional radiography, the single sign that appeared to show a significant trend was the presence of bone erosions. However, no single sign or combination could either be considered pathognomonic or exclude the presence of a joint infection.
Graif
M
M
Tel Aviv Ichilov-Sourasky Medical Center, Sackler School of Medicine, Tel Aviv University, Israel.
Schweitzer
M E
ME
Deely
D
D
Matteucci
T
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001170:Arthritis, Infectious / Q000175:diagnosis*; D001853:Bone Marrow / Q000473:pathology; D001842:Bone and Bones / Q000473:pathology; D002358:Cartilage, Articular / Q000473:pathology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007596:Joints / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000175:diagnosis*; D018805:Sepsis / Q000175:diagnosis*; D013583:Synovial Membrane / Q000473:pathology