Proximal suspensory desmopathy in hindlimbs: Magnetic resonance imaging, gross post-mortem and histological study.

BACKGROUND: There have been no previous studies correlating high-field magnetic resonance imaging (MRI) findings with gross and histological post-mortem examination in horses with hindlimb proximal suspensory desmopathy (PSD).

OBJECTIVES: To determine if adhesions between the suspensory ligament (SL) and adjacent tissues could be detected using high-field MRI and if collagen, adipose tissue and muscle pathology could be differentiated.

STUDY DESIGN: Retrospective study.

METHODS: Nineteen horses with hindlimb PSD were humanely destroyed; 12 limbs of 11 horses with PSD underwent high-field MRI. All lame limbs were examined grossly and all SLs were examined histologically. The MR and histological images were graded blindly. Statistical analysis used a numerical Bayesian approach to simultaneously determine a pathology rating and the contribution of each MRI, gross post-mortem and histological observation to this measure.

RESULTS: Signal intensity (SI) in the collagenous tissue was abnormal in 2/12 limbs. Abnormalities of SI in the adipose tissue and muscle were identified in 6 and 11 limbs, respectively. Adhesions between the SL and adjacent tissues were suspected in eight limbs, but only confirmed in six limbs. Histopathological observations of abnormal muscle tissue were associated most closely with the measure of disease used in the study and were abnormal in every limb. Gross adhesions were also a sensitive indicator, along with changes to nerves which were observed in 10 limbs. Assessments of adipose tissue signal intensity and muscle tissue signal homogeneity in both lobes of the suspensory ligament were the MRI indicators most closely associated with the measure of disease.

MAIN LIMITATIONS: Small sample size. Model assumption that all abnormalities reflected degrees of a single disease.

CONCLUSIONS: Adhesion formation between the SL and adjacent structures was detected by high-field MRI with reasonable accuracy. Muscle and adipose tissue pathology was identified either alone or in association with collagenous tissue pathology.