Combined standing low-field magnetic resonance imaging and fan-beam computed tomographic diagnosis of fetlock region pain in 27 sports horses.

Abstract

Background: There is no description of comparative magnetic resonance imaging (MRI) and fan-beam computed tomography (CT) findings in the fetlock of lame sports horses.

Objectives: To document low-field MRI and fan-beam CT diagnoses in the lame and nonlame limbs of sports horses with fetlock region pain, and to evaluate whether combined imaging provides superior information to either technique alone.

Study design: Retrospective descriptive study.

Methods: Clinical records of sports horses with pain causing lameness localised to the metacarpo/metatarsophalangeal joint region that had undergone fan-beam CT and low-field MRI were reviewed. Images of both lame and nonlame contralateral limbs were assessed subjectively.

Results: Images of 52 limbs (lame n = 31, nonlame n = 21) were analysed. In 16 lame limbs of 13 horses, the most significant abnormality was in the subchondral and trabecular bone of the proximal phalanx (sagittal groove n = 14, medial fovea n = 1, sagittal groove and medial fovea n = 1). All had hyperintense STIR signal that was more extensive than CT abnormalities; CT provided useful information in all limbs. In five lame limbs, the most significant lesion was in the metacarpal condyle(s): an incomplete fracture (n = 1) or resorptive lesions (n = 4); the fracture and two resorptive lesions were not detected using MRI. In nine limbs of eight horses, lesions in multiple locations possibly contributed to pain. In one limb, abnormalities in the medial proximal sesamoid bone and in the palmar ligament were the main findings.

Main limitations: Small numbers of limbs with specific abnormalities. Comprehensive imaging of the contralateral limb was not performed in all horses. Absence of follow-up information.

Conclusions: Fan-beam CT and low-field MRI provided complementary information and yielded diagnoses and conclusions in some horses that could not have been achieved when using one modality only. Resorptive subchondral bone lesions in the fetlock may be present without associated low-field MRI abnormalities.