Magnetic resonance imaging of distal sesamoidean ligament injury.

Distal sesamoidean ligament injury is a recognized cause of lameness but diagnosis using ultrasonography is sometimes difficult. Herein, we describe the normal appearance of the distal sesamoidean ligaments on magnetic resonance (MR) images and the changes that occur when the ligaments are injured. The appearance of the distal sesamoidean ligaments on MR images from 66 control horses and 58 horses with distal sesamoidean desmitis were described and the cross-sectional area and signal intensity of the ligaments measured. In control horses, the ligaments had a characteristic appearance and strong left-right symmetry, and the lateral oblique sesamoidean ligament was larger and had higher signal intensity than the medial ligament. Cross-sectional area and signal intensity were significantly greater in injured straight sesamoidean ligaments compared with the controls. Signal intensity increased significantly with oblique sesamoidean desmitis compared with the controls. Lesions of the distal sesamoidean ligaments were considered the sole cause of lameness in only 2 of 58 horses. Eighty percent of lesions in the distal sesamoidean ligaments were not detected using ultrasonography.