Hind foot lameness: results of magnetic resonance imaging in 38 horses (2001-2011).

Abstract: The distribution of lesions detected using magnetic resonance imaging (MRI) of hind feet has not been reported. Objective: To evaluate type and distribution of lesions detected using MRI in hind feet of lame horses and to compare the findings with those reported in front feet; to document follow-up information. Methods: Horses were selected if hindlimb lameness was abolished by plantar nerve blocks performed at the base of the proximal sesamoid bones. Magnetic resonance images were acquired using either a low-field or a high-field magnet, and all images were evaluated retrospectively by both authors. A primary diagnosis was defined as the most likely cause of lameness, based also on clinical findings and results of other imaging techniques. If ≥3 structures were equally affected, the horse was classified as having multiple injuries. Follow-up information was collected by telephone questionnaire; outcome was classified as return to former level of athletic function, working at a lower level or retired. Results: Thirty-eight horses were included. Primary collateral sesamoidean ligament (CSL) injury was identified in 9 horses. Nine horses had multiple injuries, 8 had primary bone pathology, 5 had collateral desmopathy 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; 6 as a result of poor prognosis and one as a result of post anaesthetic complications, 4 of which had primary bone lesions, 2 multiple lesions and one distal interphalangeal joint pathology. Follow-up information was available for 24 horses. Eleven horses returned to previous performance and 2 to a lower level of performance; 9 horses were retired because of recurrent lameness. Five of 8 horses with CSL injury returned to previous performance and 2 to a lower level. Conclusions: Collateral sesamoidean ligament injury and primary bone pathology are commonly observed on MRI examination of hind feet, and the prognosis is reasonable.