Reasons for performing study: There is limited information on magnetic resonance imaging (MRI) findings in the carpus and proximal metacarpal region of lame horses.
Objectives: To document MRI findings in horses with lameness localised to the carpus and/or proximal metacarpal region.
Methods: Clinical records of horses that underwent MRI of the carpus and/or proximal metacarpal region at the Animal Health Trust between January 2003 and September 2010 were reviewed. Magnetic resonance images of all horses and available radiographs, ultrasonographic and scintigraphic images were assessed. When possible, MRI findings were related to the results of other diagnostic imaging techniques.
Results: Seventy-two MR studies of 58 lame limbs in 50 horses from a broad range of work disciplines and ages were reviewed. The most commonly detected primary abnormality was decreased signal intensity in T1- and T2-weighted images in the medial aspect of the carpal bones and/or the proximomedial aspect of the metacarpal bones (n = 29). Nine horses had syndesmopathy between the second and third metacarpal bones. In 6 horses the primary abnormalities were identified in the palmar cortex of the third metacarpal bone (McIII). Significant abnormalities of the suspensory ligament (SL) with associated lesions in the adjacent palmar cortex of the McIII were seen in 4 limbs. Ligament and associated osseous abnormalities between the second and third carpal bones and second and third metacarpal bones were detected in 4 limbs.
Conclusions and potential relevance: Magnetic resonance imaging enabled diagnosis of a variety of lesions not detected by conventional imaging in horses from a wide range of work disciplines. The distribution of injury types differed considerably from previous studies.