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/metatarsophalangeal 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.

A Case Series of Five Horses with Superficial Digital Flexor Tendon Lesions in the Carpal Canal.

This case series discusses the clinical presentation, ultrasonographic findings, treatment, and outcome of 5 horses with superficial digital flexor tendon (SDFT) lesions within the carpal canal. The horses' ages ranged from 11-28 years, and presented with an acute, unilateral forelimb lameness which worsened following proximal limb flexion. The presence of a lesion within the SDFT of the carpal canal was accompanied by a mild swelling of the palmar carpal region in most cases. Diagnostic anesthesia of the ulnar nerve, when performed, abolished the lameness. Ultrasound evaluation revealed an increased cross-sectional area (CSA) of the superficial digital flexor tendon compared to the contralateral, sound limb and a loss of tendon fiber architecture within the palmar aspect of the affected tendon, most readily identifiable upon longitudinal ultrasound images. Three out of the five horses returned to their previous level of performance, and two were euthanized. A back at the knee carpal region conformation was associated with a poorer prognosis in these cases. An intratendinous fibroma was identified on histopathological analysis of one-horse following euthanazia, which has been recorded in a complementary short communication.

Intratendinous Fibroma of the Superficial Digital Flexor Tendon within the Carpal Sheath of a Horse.

A 20-year-old British Warmblood gelding was presented for a progressively worsening right forelimb lameness which developed following an intense dressage training session. Initial ultrasound examination revealed a triangular, intrathecal, hypoechoic region within the superficial digital flexor tendon (SDFT) in the proximal, palmar carpal region distal to the accessory carpal bone (ACB), extending 7cm distally into the proximal metacarpal region. No significant improvement in clinical presentation was observed following an eight-week rehabilitation programme. Repeat ultrasound examination revealed an enlarged cross-sectional area of affected tendon. Due to a poor clinical response to conservative treatment, combined with increasingly marked severity of the lameness, the horse was humanely euthanised and the affected SDFT was submitted for macroscopic and histopathological examination at the University of Liverpool. This revealed an approximately 70mm-elongated, focally extensive mass located within the SDFT. On cross-section, the mass was poorly delineated, irregularly triangular, focally haemorrhagic, firm, 15 × 12mm wide and eccentrically placed towards the palmar aspect of the tendon. Histopathological examination identified a moderately to highly cellular, infiltrative, poorly demarcated mesenchymal neoplasm comprised of streams of moderately atypical spindloid cells including bizarre mitoses. Intratendinous fibroma is an uncommonly recorded human neoplasm and this case represents the third reported case of this entity in the horse, the first in an adult horse and the first to be identified in the SDFT.

Evaluation of the Olecranon Bursa: An Anatomical Structure in the Normal Horse.

This study aimed to determine whether a true synovial structure exists over the olecranon tuberosity, which could be attributed to a noninflamed olecranon bursa. Contrast radiography, gross anatomical dissection, and histopathology were used to evaluate the olecranon bursa in horses with no previous elbow pathology. The radiographic study revealed that the contrast was positioned subcutaneously, superficial to the long head of the triceps and its insertion on the olecranon tuberosity and did not extend cranial to the triceps tendon. The contrast region was consistent in shape, size, and location. Gross anatomical dissection of the area revealed a potential bursal space overlying the tendons of the lateral and medial heads of the triceps brachii and the tensor fascia antebrachii in the normal horse. Histopathology confirmed a bursal lining, which was of mesenchymal origin and suggestive of a single-cell membrane, lined by fibroblast-like synoviocytes.