Subchondral Bone Lesions of the Metacarpophalangeal/Metatarsophalangeal Joint Diagnosed by Standing MRI in 23 Horses

Background: Subchondral bone damage is well described in race/sport horses. Data are lacking regarding subchondral bone damage of the metacarpo/tarsophalangeal joint (MCPj) in the general horse population. 

Objectives: To describe the clinical presentation, MRI findings and outcome of general pleasure/ performance horses diagnosed with subchondral bone damage of the MCPj. 

Study design: Retrospective descriptive study. 

Methods: Medical and imaging records of horses undergoing standing low field MRI of the distal limb between January 2014 and March 2021 were reviewed. Horses (excluding racehorses) were included if subchondral bone damage of the MCPj was diagnosed. MRI sequences were reviewed, and the features of subchondral bone damage described. Follow-up information was obtained by telephone questionnaire and/or medical records. 

Results: Twenty-three horses were included. Median lameness grade was 3/10 (range 0/10–7/10). All horses had a high signal intensity lesion of the subchondral bone involving the condyle (10/23-43%) or sagittal ridge (3/23-13%) of the third metacarpal/metatarsal bone and the glenoid (7/23-30%) or sagittal groove (3/23-13%) of the proximal phalanx. Concurrent trabecular bone damage was identified in 20/23 (87%) and osteoarthritis in 18/23 (78%). Follow-up information was obtained in 23/23 horses (100%) after 10 months–8 years. One horse (1/23- 5%) was sound at the previous level of exercise; 4/23 (17%) were sound at lower levels; 3/23 (13%) were intermittently lame in work; and 4/23 (17%) were retired. 8/23 horses (35%) had been euthanised due to persistent lameness/poor athletic prognosis, and one (4%) for other reasons. Two horses (2/23-9%) remain in rehabilitation. 

Main limitations: Small numbers and follow- up by telephone questionnaire/medical records. 

Conclusions: Subchondral bone damage of the MCPj was identified by MRI in the general horse population, often with concurrent trabecular bone damage and osteoarthritis. With extensive periods of rest, a small proportion became sound enough to work at a lower level. A significant proportion were euthanised due to persistent lameness. 

Ethical animal research: Research ethics committee oversight not required by this congress: retrospective study 

Informed consent: Not stated. 

Competing interests: None declared. 

Sources of funding: None.

[...]