Discussion

Aims: To evaluate the type and distribution of lesions diagnosed using magnetic resonance (MR) imaging in hind feet of lame horses; to compare with previous results reported for front feet; and to determine the prognosis for return to athletic performance. Methods: Horses were selected for inclusion if they had hindlimb lameness abolished by plantar (at base of proximal sesamoid bones) nerve blocks and no diagnosis was reached using conventional imaging. Low-field or high-field MR images were reviewed by both authors until consensus was achieved. Each abnormality was recorded and a primary lesion was defined for each horse as the most likely cause of pain and lameness. If >3 structures were equally affected the horse was classified as having multiple injuries. Follow- up information was obtained by telephone questionnaire. Horses were classified as performing at the same or higher level than before injury, performing at a lower level, or retired. Results: There were 38 horses. Primary collateral sesamoidean ligament (CSL) injury was identified in 9 horses. Nine horses had multiple injuries, 8 had primary bone pathology, 5 had collateral desmitis of the distal interphalangeal joint, one had primary deep digital flexor tendonitis, 2 had navicular bone pathology and 4 had lesions involving other structures within the foot. Seven horses were subjected to euthanasia shortly after diagnosis because of poor prognosis, 4 of which had primary bone lesions and 2 multiple lesions. Follow-up information was available for 24 horses. Twelve and 3 horses returned to previous or lower level of performance, respectively; 9 horses were retired because of recurrent lameness. Five of 8 horses with CSL injury returned to previous performance and 2 at a lower level. Conclusions and practical significance: Collateral sesamoidean ligament injury and primary bone pathology were over-represented in hind feet compared with front feet. The prognosis for CSL desmitis in hindlimbs is reasonable.