Low-Field Magnetic Resonance Imaging Findings of the Fetlock Region of Nonracehorses

Low-field, magnetic resonance imaging (MRI) is an advanced imaging modality widely used to diagnose distal limb pathology in horses, but there are limited data regarding lesion distribution within the metacarpo/meta-tarsophalangeal joint (MCP/MTPJ) region in lame nonracehorses. The aim of this study was to describe the low -field MRI findings and lesion distribution in nonracehorses with MCP/MTPJ region pain. Clinical records from horses undergoing MRI of the MCP/MTPJ region between July 2016 and March 2023 were reviewed. Horses were included if pain causing lameness was localized to this region and conventional imaging failed to provide a definitive diagnosis. Eighty-four horses met the inclusion criteria. Soft tissues were affected in 76 (90.5%) horses, with suspensory ligament branch injuries being the most frequent (60.7%) soft tissue pathology identified. Osseous pathology was diagnosed in 51 horses. The subchondral bone (SCB) of the distal third metacarpal/ metatarsal bone (MC3/MT3) was the osseous structure most frequently affected (40.5%), with 79.4% of these horses having lesions on the dorsal aspect of the bone. Osteoarthritis was present in 48 (57.1%) horses. The main limitations of the study were the lack of a standardized diagnostic analgesia pattern due to varying veterinary surgeon involvement, and the absence of bilateral magnetic resonance (MR) sequences in all limbs. MRI is a useful diagnostic tool to assess soft tissue structures in the MCP/MTP region, especially in horses with thick skin, which may make ultrasonographic imaging unreliable.

Automated summary

This study investigated the low-field magnetic resonance imaging (MRI) findings and lesion distribution in nonracehorses with MCP/MTPJ region pain. The results showed that soft tissue injuries were more common, with suspensory ligament branch injuries being the most frequent. In terms of osseous pathology, the subchondral bone (SCB) was most frequently affected, with the majority of lesions located on the dorsal aspect of the bone. The main limitations of the study were the lack of standardized diagnostic analgesia pattern and the absence of bilateral MRI sequences in all limbs.