MRI evaluation of infectious and non-infectious synovitis: preliminary studies in a rabbit model.
BACKGROUND
Literature on magnetic resonance imaging (MR) evaluation of inflammatory joint effusions is sparse.


OBJECTIVE
To describe an animal model for studying infectious and non-infectious joint effusions with magnetic resonance imaging.


METHODS
Ten rabbit knees with septic arthritis and four with talc synovitis were imaged with MR. Contralateral knees injected with saline served as controls. Fat saturation T2-weighted and gadolinium-enhanced T1-weighted images were assessed for joint effusion, and periarticular and adjacent intraosseous increased signal or enhancement. Each knee was cultured and underwent pathologic examination.


RESULTS
Both Staphylococcus aureus and talc produced effusions in all knees. The degree of periarticular signal and enhancement was greater in infected knees than talc-injected knees. No abnormal enhancement was seen within bone. Pathologic examination showed a greater degree of inflammation and joint destruction in the infected knees, but no evidence of osteomyelitis.


CONCLUSIONS
A greater degree of abnormal signal and enhancement seen on MR suggests a more vigorous inflammatory process, as seen with septic arthritis. In spite of advanced septic arthritis, no enhancement was evident within bone, suggesting that enhancement within bone is not an expected finding in isolated septic arthritis and should raise concern for osteomyelitis.
Strouse
P J
PJ
Section of Pediatric Radiology/F3503, C.S. Mott Children's Hospital, University of Michigan Health System, Ann Arbor, MI 48109-0252, USA.
Londy
F
F
DiPietro
M A
MA
Teo
E L
EL
Chrisp
C E
CE
Doi
K
K
D000818:Animals; D003937:Diagnosis, Differential; D004195:Disease Models, Animal; D005122:Exudates and Transudates; D007091:Image Processing, Computer-Assisted; D007717:Knee / Q000382:microbiology / Q000473:pathology; D008279:Magnetic Resonance Imaging; D011817:Rabbits; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000302:isolation & purification; D013583:Synovial Membrane / Q000382:microbiology / Q000473:pathology*; D013585:Synovitis / Q000139:chemically induced / Q000175:diagnosis* / Q000382:microbiology; D013627:Talc / Q000633:toxicity
D013627:Talc