Short-term temporal alterations in magnetic resonance signal occur in primary lesions identified in the deep digital flexor tendon of the equine digit

Reasons for performing study: Primary lesions of the deep digital flexor tendon (DDFT) within the digit are an important cause of lameness diagnosed using magnetic resonance imaging (MRI) but appearance of these lesions over time has not been documented. Objectives: To determine whether the magnetic resonance (MR) appearance of different primary DDFT lesions alter over a 6 month period and whether lesion type is a determinant of these changes. Methods: Cases included had lameness attributable to a primary lesion involving the DDFT in the digit diagnosed on MRI. Lesions were typed into parasagittal, dorsal border and core lesions. Approximate volumes and intensitieswere quantified for each lesion type using T2* scan sequences. Follow-up examinations and measurements were repeated at 3 and 6 month periods following conservative management. Results: Twenty-three horses fitted the inclusion criteria. Lesion distribution included: parasagittal (n = 7), dorsal border (n = 11) and core lesions (n = 5). No associationwas found between age of horse, degree of lameness and lesion type. Only dorsal border lesions showed statistically significant reduction both in volume(initial scan: 0.18 +/- 0.14 cm(3)) at 3 months (0.11 +/- 0.10 cm(3), P< 0.05) and 6 months(0.05 +/- 0.05 cm3, P< 0.01) andratiometric intensity (initial scan: 4.06 +/- 1.54) at 6 months(2.00 +/- 0.43; P< 0.01). Parasagittalandcorelesionsshowednodifferencein lesionvolumeorratiometricintensity. Lamenessimprovedin all lesion types following conservative management. Conclusions: Dorsal border lesions of the DDFT show reduction in both volume and intensity whereas parasagittal and core lesions do not. Potential relevance: Lesion typing may be important in predicting lesion behaviour and short-termoutcome using MR imaging.