Low-Field Magnetic Resonance Imaging Findings of the Fetlock Region of Nonracehorses.
Authors: Auth Adel K, Hinnigan Guy J, Smith Meredith A, Owen Kathryn R
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Low-Field MRI Findings in the Nonracehorse Fetlock When conventional radiography and ultrasonography fail to identify the source of fetlock lameness in nonracehorses, low-field MRI offers valuable diagnostic clarity—particularly in animals with substantial soft tissue coverage that compromises ultrasound image quality. This retrospective analysis examined MRI scans from 84 nonracehorses presenting with localised fetlock pain and inconclusive conventional imaging findings, cataloguing the distribution and prevalence of both soft tissue and osseous lesions within the metacarpo/metatarsophalangeal joint region. Soft tissue pathology predominated (90.5% of cases), with suspensory ligament branch injuries accounting for the majority at 60.7%; osseous involvement occurred in 51 horses, most frequently affecting the subchondral bone of the distal cannon bone (40.5%), predominantly on its dorsal aspect (79.4% of subchondral lesions). Nearly three-fifths of the cohort (57.1%) displayed concurrent osteoarthritic changes, highlighting the multi-factorial nature of chronic fetlock dysfunction. For equine practitioners managing diagnostic uncertainty in fetlock lameness cases—particularly where anatomical thickness or poor ultrasound windows limit soft tissue visualisation—MRI emerges as a robust imaging modality capable of characterising lesion location and extent, thereby informing targeted therapeutic and farriery interventions, though inconsistent diagnostic analgesia protocols across the cohort represents a practical limitation when extrapolating findings to individual cases.
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Practical Takeaways
- •When conventional imaging doesn't identify the cause of fetlock lameness in nonracehorses, low-field MRI is highly likely to reveal soft tissue lesions—particularly suspensory ligament branch injuries—that require targeted rehabilitation and management
- •Expect subchondral bone lesions to occur primarily on the dorsal aspect of the distal cannon bone; these lesions are common in this population and correlate with osteoarthritis development
- •MRI is particularly valuable in horses with thick skin or poor ultrasound visualization, where soft tissue imaging quality may be compromised by conventional methods
Key Findings
- •Soft tissue pathology was identified in 90.5% of lame nonracehorses with MCP/MTPJ pain, with suspensory ligament branch injuries being the most common lesion at 60.7%
- •Subchondral bone of the distal metacarpal/metatarsal bone was the most frequently affected osseous structure at 40.5%, with 79.4% of lesions on the dorsal aspect
- •Osteoarthritis was present in 57.1% of horses with MCP/MTPJ region pain
- •Low-field MRI successfully provided definitive diagnosis in cases where conventional imaging failed