Computed tomography and magnetic resonance imaging of the normal distal limb in sheep (Ovis aries)

Prevalence of lameness associated with distal limb affection is frequently reported in sheep. Lameness diagnosis requires a systemic orthopedic examination associated with a convenient imaging modality. Computed tomography (CT) and magnetic resonance imaging (MRI) are the most popular and accurate diagnostic modalities, providing high quality bone and soft tissue imaging. Consequently, this study aimed to combine CT and MR images with their correlative anatomical cross-sections for a comprehensive assessment of normal osseous and soft tissues in fore (n = 6) and hind (n = 6) distal limbs of lameness free sheep cadavers. These limbs were scanned using a multi-detector helical CT scanner and 1.5 tesla MRI magnet. The examined limbs were sectioned into sagittal, dorsal, and transverse slices. The acquired CT and MR images were identified and compared with the cross sections.

The CT and MR images provided better visualization of the soft and bony structures of the distal limb in sheep. However, the CT images showed higher definition of the bony structures and a much clear demarcation of the trabecular pattern of the cancellous bone. These bony structures including the cortical, subchondral and cancellous bones. While, the MR images offered a valued delineation of the articular cartilage, which could not be evaluated using CT. The soft tissues in sheep distal limb including tendons, ligaments, interphalangeal joints, and interdigital gland were clearly visualized on CT and MR images. However, they were remarkably defined on the MR images.

CT and MRI, with the help of gross sections, admitted a comprehensive evaluation of normal soft and bone tissues constituting the distal limb in sheep. CT was appreciated to evaluate the osseous structures, while MRI was found to be the most effective for assessment the articular cartilages and soft tissues. The clinicians have to choose the appropriate modality, CT, MRI, or both, according to the clinical situations.