Quantitative Magnetic Resonance Imaging and Histological Comparison of Normal Canine Menisci

Abstract

Objective The purpose of this observational study was to establish normative data for the canine menisci using magnetic resonance imaging (MRI). Methods Ten fresh stifles from five normal male Beagles were obtained from animals with no known lameness. Conventional MRI and ultrashort echo time (UTE) imaging were performed and T2* values calculated. Five stifles were assessed histologically. Results The caudal horn of the medial meniscus had significantly prolonged T2* values (4.6 ± 1.27 ms; p = 0.002) as compared with the cranial horn of the medial meniscus (3.25 ± 0.86 ms), and the cranial (3.06 ± 0.54 ms) and caudal (3.64 ± 0.72 ms) horns of the lateral meniscus. Histology demonstrated normal tibial, femoral, interior and peripheral meniscal margins, and normal cellularity. The medial meniscus was noted to be obliquely oriented to the scan plane compared with the relatively perpendicular orientation of the lateral meniscus as compared with the bore of the magnet in a limb-extended orientation. Clinical Significance Variability of MRI UTE T2* is seen in the normal canine meniscus, with prolongation of the caudal horn, medial meniscus. Prolongation may be due to magic angle effects, as the medial meniscus of the Beagle is not perpendicular to the axis of the main magnetic field. Canine meniscal injury is a common sequela to cruciate tear, and detecting meniscal damage is important for directing patient care. The non-invasive quantitative MRI technique of UTE imaging can be used for the evaluation of collagen orientation, while acknowledging inherent regions of prolongation.

Histological Findings and T2 Relaxation Time in Canine Menisci of Elderly Dogs—An Ex Vivo Study in Stifle Joints

“…These findings suggest that there can be different degrees of degeneration in the menisci of older dogs before clinical signs of lameness or radiographic evidence of osteoarthritis develop. Meniscal degeneration has been studied in dogs before, but only a minority of these studies performed both histological and magnetic resonance imaging (MRI) [ 25 , 26 , 27 ]. Collagen fibers and proteoglycans are important components of the meniscal extracellular matrix.…”

“…It allows both short and longer TEs. Short TEs are useful for the assessment of menisci and longer TEs may be useful to assess other joint structures, for example the articular cartilage [ 9 , 26 , 31 , 32 ]. T2 mapping can thus be a good tool to detect early matrix changes in joint structures.…”