Magnetic resonance imaging and histopathological evaluation of equine oblique sesamoidean ligaments

Lesion Distribution in the Metacarpophalangeal and Metatarsophalangeal Region of 341 Horses Using Standing Magnetic Resonance Imaging

Pain localised to the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) region represents a frequent cause of lameness in sport horses, and standing magnetic resonance imaging (MRI) of these regions is increasingly being acquired. This multicentre retrospective study describes the ranges of abnormalities identified on standing MRI of the MCP/MTP region and compares patterns of abnormalities between forelimbs, hindlimbs and different sports disciplines. In total, 341 MRI reports were reviewed. Subchondral bone plate irregularities, condylar and proximal phalanx pathologies were frequently identified with subchondral bone defect, sclerosis and increased intensity on STIR images often described. Medial pathology was frequently identified in the forelimbs, and more lateral pathology was reported in the hindlimbs, which could potentially reflect differences in the loading patterns. Significant differences in MRI findings were found between different sports activities, with MCP/MTP bone pathology occurring more frequently in MRI reports from race and endurance horses and MCP/MTP soft tissue injuries being reported more frequently in dressage and show-jumping horses, particularly in the suspensory apparatus, including the distal sesamoidean ligaments. The findings of this study identify patterns of MCP/MTP abnormalities detected using standing MRI, with differences seen between forelimbs and hindlimbs and between different sports disciplines.

When radiography and ultrasonography are not enough: the use of computed tomography and magnetic resonance imaging for equine lameness cases

MRI and CT have enhanced our diagnostic abilities for equine lameness beyond what is available using radiography and ultrasonography. This has allowed veterinarians to better prognosticate and treat lameness conditions, improving patient outcomes. This article discusses the basic principles behind MRI and CT, their advantages and disadvantages, the different types of equipment available for clinical use in horses, the typical diagnostic workup prior to pursuing advanced imaging, and common regions where MRI and CT are used clinically. The companion Currents in One Health by Spriet, AJVR, July 2022, discusses even more advanced equine imaging in the form of positron emission tomography. Combined, these future directions of MRI, CT, and positron emission tomography may include improved ability to image standing horses or screen for injury prevention.

Retrospective analysis of oblique and straight distal sesamoidean ligament desmitis in 52 horses

BACKGROUND

Injuries to the oblique (ODSL) or straight (SDSL) distal sesamoidean ligaments are a recognised cause of distal limb lameness in the horse. However, there are only limited publications addressing common diagnostic features and prognosis.

OBJECTIVES

(a) Report findings on ultrasonography and standing low-field magnetic resonance imaging (sMRI) in horses with ODSL or SDSL injury; (b) Identify clinical variables associated with lesion type and (c) Identify factors associated with return to soundness in horses with ODSL or SDSL injury.

STUDY DESIGN

Retrospective case series.

METHODS

Horses with a primary diagnosis of ODSL or SDSL injury confirmed with a combination of diagnostic analgesia and detection of a lesion on imaging (ultrasonographic ± advanced imaging) were included. Return to soundness and performance follow-up data were obtained.

RESULTS

Fifty-one horses were included. SDSL injuries were more common in the forelimb (13/21, 62%), while ODSL injuries had equal frequency in fore- (15/30, 50%) and hindlimbs (15/30, 50%). ODSL injuries were more likely than SDSL injuries to affect the proximal third of the ligament (OR =13; 95% CI 2.3-74.3; p = 0.004) and often presented with periligamentar swelling (20/30;67%) and focal pain (22/28;79%). Lesions were frequently detected using ultrasonography (35/42;83%) and sMRI examination (18/25;72%). Only 27/49 cases (55%) returned to soundness, with only 15/49 (31%) returning to intended use. There were no significant associations between outcome and clinical features or treatment.

MAIN LIMITATIONS

There was no comparative "gold standard" to validate lesions such as high-field MRI or histopathology.

CONCLUSIONS

In contrast to previous studies, ODSL and SDSL injuries were readily identified ultrasonographically using appropriate views, and with sMRI. Given the limited availability, cost and general anaesthetic risks associated with high-field MRI, more focus should be placed on optimising the ultrasonographic examination. Owners of affected horses should be informed of the guarded prognosis for return to full use.

Chronic Collateral Sesamoidean Desmopathy in Draft Horses: Magnetic Resonance Imaging and Histopathological Findings

Desmopathy of the collateral sesamoidean ligament (CSL) is an unusual disorder in draft horses. This study records the magnetic resonance imaging (MRI) features of chronic CSL desmopathy in eight draft horses and confirms these features by histopathology. The recorded chronic CSL desmopathy has usually affected the forelimbs (100%) and commonly bilateral (62.5%). All horses showed positive proximal digital nerve block, positive front digital flexion test, and negative interphalangeal extension test. Radiography revealed no osseous abnormalities in all feet. MRI features of chronic CSL desmopathy included thickening of the ligament with increased moderate intensity in fast low-angle shot, T1 turbo spin echo, and proton density images in the affected part of the ligament. Chronic CSL desmopathy was concomitant with deep digital flexor tendon injury and distal sesamoidean impar desmitis. In most chronic cases of CSL desmopathy, heterogeneous signal intensities were seen with multiple foci of low signal intensities interlaced with increased moderate signal intensities of thickened CSL. Histopathology confirmed the MRI findings and revealed separated bundles and fascicles by septa of less organized and loose connective tissues containing fibroblasts and loose collagen fibers. Multifocal islands of cartilaginous metaplasia, mineralized areas, and dystrophic calcification were observed in the injured ligament. In conclusion, chronic CSL desmopathy may progress to cartilaginous metaplasia and dystrophic calcification. MRI is a beneficial diagnostic and prognostic tool for chronic CSL desmopathy, and histopathology is a gold standard to document the MRI findings associated with CSL dysmopathy in draft horses.