Magnetic resonance imaging of equine stifles: Technique and observations in 76 clinical cases

Magnetic resonance imaging (MRI) of equine stifle disorders is challenging. We describe a routine technique for low-field stifle MRI under general anaesthesia in clinical cases and report the main findings. We hypothesised that MRI can be safely and routinely performed and portray bone and soft-tissue pathology. In this retrospective study, medical records of 76 stifles with positive response to intra-articular anaesthesia without abnormalities on conventional diagnostic imaging were reviewed for breed, age, gender, MRI anaesthesia time and findings. Under anaesthesia, limbs were extended in a rotating MR gantry. Different sequences in several planes were acquired in an average time of 62 min. In all horses, the stifle examinations were successful and complete. Typical MRI lesions included bone marrow lesions, osseous cyst-like lesions, cruciate desmopathy, meniscal tearing or a combination thereof. Retrospective reviewing confirmed that initial radiographic and ultrasonographic images failed to identify these lesions. Surgically accessible lesions were confirmed in arthroscopy if exploration was indicated. However, MRI was useful to estimate extent of cruciate and meniscal pathology as well as bone marrow lesions and bone cystic-like lesions more thoroughly. Our protocol allows for routine stifle MRI, independent of breed, age and gender. Based on our preliminary results, low-field stifle MRI is safe and can delineate bone and soft-tissue pathology. Low-field MRI appears to be a promising approach for better understanding stifle pathology and thus treatment and prognosis.