J Korean Radiol Soc.  2002 Dec;47(6):657-664. 10.3348/jkrs.2002.47.6.657.

Experimentally Induced Pyogenic Arthritis of Rabbit Knees: Comparative Study of MR Imaging and Pathology

• Hong SH
• Koh SH
• Chung HW
• Lee KW
• Kim CJ
• Kang HS

• KMID: 2103687
• DOI: http://doi.org/10.3348/jkrs.2002.47.6.657

Abstract

PURPOSE
To compare the MR imaging findings of experimentally induced pyogenic arthritis of rabbit knees with the corresponding histopathologic findings.
MATERIALS AND METHODS
Infection was induced in 20 rabbit knees by direct intra-articular injection of Staphylococcus aureus. The animals were divided into four groups of five rabbits each, and spin-echo sagittal T1-and T2-weighted images were obtained 3 days, 1 week, 2 weeks, and 4 weeks, respectively, after staphylococcal inoculation. MR-pathologic correlation was performed, with emphasis on intra-and extra-articular soft tissue lesion characteristics. Soft tissue lesion signal intensity (SI) was classified as low, iso, or high on the basis of that of muscle, and high SI was further subdivided into three categories.
RESULTS
At T2-weighted imaging, all soft tissue lesions showed high SI. Pathologic examination revealed the presence of inflammatory cell infiltration (n=2), abscess (n=1), granulation tissue (n=3), fibrosis (n=11), edema (n=4), congestion (n=9), and joint fluid (n=11). Except for the abscess, these lesions were irregular in shape and had variable SI (grade 1-3) and at T2WI could not, therefore, be differentiated. In nine kness, extraarticular soft-tissue lesions were demonstrated at T2WI and correlated with infectious soft tissue lesions such as inflammatory cell infiltration, abscess, granulation tissues and fibrosis; and non-infectious reactive soft tissue changes such as edema and congestion.
CONCLUSION
In pyogenic arthritis, the MR imaging features of soft tissue lesions varied and were nonspecific, depending on the histopathologic abnormalities observed. Our results indicate that in assessing the extent of pyogenic arthritis with MR imaging, caution is required.

Keyword

Arthritis, septic; Knee, MR; Animals

MeSH Terms

Abscess
Animals
Arthritis*
Arthritis, Infectious
Edema
Estrogens, Conjugated (USP)
Fibrosis
Granulation Tissue
Injections, Intra-Articular
Joints
Knee*
Magnetic Resonance Imaging*
Pathology*
Rabbits
Staphylococcus aureus
Estrogens, Conjugated (USP)