LOW-FIELD MAGNETIC-RESONANCE-IMAGING OF EARLY SUBCHONDRAL CYST-LIKE LESIONS IN INDUCED CRANIAL CRUCIATE LIGAMENT DEFICIENT DOGS

Six healthy adult male mongrel dogs underwent cranial cruciate ligamen t transection in the left stifle. Survey radiography of both stifles a nd low-field (0.064 T) MRI of the left stifle were performed preoperat ively and at 2, 6, and 12 weeks postoperatively, Focal changes in sign al intensity were seen with MRI in the subchondral bone of the medial tibial condyle at 2 and 6 weeks postoperatively, At 12 weeks postopera tive, a cyst-like lesion was detected using MRI in the subchondral bon e of the medial tibial condyle in 4 of 6 dogs and a less defined lesio n at this site in the remaining 2 dogs. The cyst-like lesion was spher ical in shape and showed typical characteristics of fluid with low sig nal intensity on T1-weighted images, high signal intensity on T2-weigh ted images and high signal intensity on inversion recovery images. The lesion was seen in the subchondral bone of the caudal medial and/or m iddle region of the tibial plateau slightly cranial to the insertion o f the caudal cruciate ligament, No subchondral cysts were seen in the tibia on radiographs, Histopathologically, the tibia was characterized by a loose myxomatous phase of early subchondral cyst formation.