Bone marrow lesions of the distal condyles of the third metacarpal bone are common and not always related to lameness in sports and pleasure horses AbstractThe metacarpophalangeal joint is a common site of pain in horses. Little information is available about bone marrow lesions in the distal condyles of the third metacarpal bone in sports and pleasure horses. Aims of this prospective, retrospective, observational study were to evaluate the prevalence of bone marrow lesions in the distal condyles of the third metacarpal bone, to describe their anatomic distribution and to correlate lesions with the presence of lameness and the level and type of activity. All sports and pleasure horses undergoing standing low-field MRI of the front fetlock region between 2009 and 2016 were included and divided into three lameness groups according to the results of diagnostic analgesia. Bone marrow lesions were analyzed and graded by one reader. Grades were compared between anatomical locations and between lameness groups.A total of 166 horses were sampled. The prevalence of bone marrow lesions was 76.5% (127/166).The dorsal aspects of the medial condyle (31%, 39/127) and of the sagittal ridge (28%, 36/127) were the most commonly affected locations. There was no significant difference between both forelimbs (lame limb and non-lame limb) of the same horse. Lesion severity was neither significantly associated with the lameness group nor with the type or level of activity. The prevalence of bone marrow lesions in the distal condyles of the third metacarpal bone is high in this population and the clinical significance is not always clear. Further studies are required to elucidate the clinical significance of this finding in sports and pleasure horses. K E Y W O R D Sequine, fetlock, magnetic resonance imaging, subchondral

Background: Central tarsal bone fractures in non-racehorses are uncommon and their MRI appearance and follow-up have not been described. Objectives:To describe the clinical and MRI characteristics and follow-up of central tarsal bone fractures in non-racehorses. Study design:Retrospective descriptive case series. Methods:The low-field MRI appearance of central tarsal bone fractures in sports horses identified over a 9-year period, was reviewed. Follow-up MRI examinations, treatment and clinical outcome were included.Results: Four horses with five vertical fractures of the central tarsal bone were included.There were three Warmbloods, of which two were showjumpers and one a dressage horse, and one Quarter Horse used for western performance. All fractures could consistently be visualised on low-field standing MRI and were associated with marked sclerosis in the surrounding bone, with little to no associated bone marrow lesion of the central tarsal bone. One horse had bilateral fractures. Three fractures were complete (full-thickness) slab fractures and two were incomplete (partial-thickness) slab fractures.Fractures occurred in a consistent dorsomedial to plantarolateral oblique orientation and were non-displaced. Incomplete fractures occurred at the dorsomedial proximal aspect of the central tarsal bone. All horses were treated conservatively initially. The dressage horse with bilateral fractures and the Quarter Horse remained lame after conservative treatment and were subsequently treated surgically. Three horses returned to their previous level of performance, one horse in spite of persistent MRI evidence of a fracture line (non-union), while the Quarter Horse returned to a lower level of reining.Main limitations: Small number of horses. Conclusions:Standing low-field MRI is helpful in the diagnosis of central tarsal bone fractures. Central tarsal bone fractures occur in a dorsomedial to plantarolateral orientation in sports horses, can be complete or incomplete, unilateral or bilateral and remain nondisplaced. The prognosis is good for return to performance.

Computed tomography (CT)is increasingly available in veterinary referral practices; however, published studies describing CT lesions of the equine elbow are currently lacking. In this single‐center, retrospective, observational study, horses undergoing elbow CT at Equitom between July 2015 and October 2018 were reviewed. Subchondral bone sclerosis; resorption of the radius, ulna, and humerus; osteophyte; and enthesophyte lesions were graded. One hundred thirty‐nine elbows of 99 horses (16 with elbow pain and 123 control elbows) were included (median age, 9 years). Osseous cyst‐like lesions (n = 13), only seen in the proximomedial radius and medial humerus, were the most common cause of lameness in horses with elbow pain (n = 16), with significantly higher grades of bone resorption (including osseous cyst‐like lesions) in this group. One elbow had an avulsion fracture of the lateral epicondyle, two others showed signs of osteoarthritis. Significantly higher grades of sclerosis in the proximomedial radius were seen in horses with elbow pain; however, mild to moderate subchondral bone sclerosis was seen in all horses at the medial aspect of the joint. Osteochondral fragmentation lesions of the weight‐bearing surface of the medial radius (2/16 vs 1/123; P = .0025) and intra‐articular gas (4/16 vs 2/123; P < .0001) were significantly more common in horses with elbow pain compared to control horses. Mild linear resorptive subchondral bone lesions were often not clinically relevant (32/123 vs 5/16 in medial humerus; 19/123 vs 2/16 in medial radius). In conclusion, elbow CT is a feasible method for detecting clinically relevant lesions in adult Warmblood horses with elbow pain.