The collateral ligaments of the distal interphalangeal joint: magnetic resonance imaging and post mortem observations in 25 lame and 12 control horses.
BACKGROUND
Magnetic resonance imaging (MRI) is used with increasing frequency to diagnose injuries of the collateral ligaments (CLs) of the distal interphalangeal (DIP) joint, but the results have not been verified by histology and the mechanism of injury is poorly understood.


OBJECTIVE
Abnormal signal intensity and tissue contour represents change in tissue structure detected on histology.


OBJECTIVE
To compare results in horses free from and those with chronic lameness and to describe possible progression of lesions.


METHODS
One or both feet of horses free from lameness (Group N: n = 12) and with foot-related lameness (Group L: n = 25) were examined using MRI and by gross post mortem examination. The magnetic resonance (MR) images were graded. Sagittal sections from the proximal and distal aspect of each CL were examined histologically and each ligament assigned a score. Scintigraphic images from lame horses were also evaluated.


RESULTS
In Group N, 25 CLs were graded normal on both MR images and histology, 2 CLs were grade 1 on MR images, but were histologically normal, and 2 CLs had MR abnormalities verified histologically. However, 2 CLs appeared normal on MR images but were histologically abnormal. In Group L, 18 CLs were deemed normal on both MR images and histology, and 54 CLs had MR abnormalities verified histologically. However, 13 CLs appeared normal on MR images but were graded abnormal histologically. Lesions appeared to be degenerative, characterised by extensive fibrocartilaginous metaplasia and development of multiple, intercommunicating fissures within the degenerate collagen in severe lesions. There was an association between increased radiopharmaceutical uptake and a higher histological score.


CONCLUSIONS
High-field MRI is reasonably reliable for detection of lesions of the CLs of the DIP joint, but may underestimate their prevalence.


CONCLUSIONS
Collateral ligament injury appears to be a primary degenerative process, which may explain the poor response to conservative treatment and a need for promotion of regeneration.
Dyson
S
S
Centre for Equine Studies, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK.
Blunden
T
T
Murray
R
R
D000818:Animals; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D017885:Collateral Ligaments / Q000000981:diagnostic imaging / Q000473:pathology*; D003937:Diagnosis, Differential; D006734:Horse Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D006736:Horses; D007150:Immunohistochemistry / Q000662:veterinary; D007794:Lameness, Animal / Q000145:classification / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000662:veterinary*; D011877:Radionuclide Imaging / Q000379:methods / Q000662:veterinary; D014033:Toe Joint / Q000000981:diagnostic imaging / Q000473:pathology*