Ex Vivo Assessment of an Ultrasound-Guided Injection Technique of the Navicular Bursa in the Horse.

Synovitis of the navicular bursa is common in performance horses. The objective of this study was to describe an ultrasound-guided technique to inject a distended navicular bursa and to evaluate its feasibility for use by a clinician not trained in the technique. Twenty distal limbs of horses of various breeds and sizes were used. To produce synovial distension, the navicular bursa of each limb was injected with contrast medium using a lateral approach and radiography was performed to confirm that the contrast medium was distending the bursa. The digit was positioned with the distal interphalangeal joint in hyperextension. A microconvex ultrasound probe was placed in the hollow of the pastern, palmar to the middle phalanx and the region was assessed in a transverse plane slightly oblique to the horizontal plane. The ultrasound probe was rotated to visualize both the lateral and medial recesses and to select which side was more distended to inject. A 21G 0.8 × 50 mm needle was inserted abaxially to the probe in the plane of the ultrasound beam into the proximal recess of this navicular bursa and a methylene blue solution was injected. Following injection, dissection was performed to assess whether the navicular bursa had been successfully injected. This ultrasound-guided technique was reliably performed with a success rate of 68%. The success of injection is influenced by hyperextension of the foot, quality of ultrasound images and degree of distension of the bursa.

Computed Tomography and Magnetic Resonance Anatomy of the Normal Orbit and Eye of the Horse.

Traumatic and infectious diseases of the eye and orbit can occur in horses. For diagnosis and monitoring of such diseases, medical imaging is useful including computed tomography (CT) and magnetic resonance imaging (MRI). The aim of the current study was to describe CT and MRI anatomy of the equine orbit and ocular globe. The heads from four adult horses were scanned with a 6-slice Emotion 6 CT (Siemens, Erlangen), and a 3.0 Tesla Siemens Verio 6 MRI using T1 and T2-weighted sequences. To validate CT and MR reference images, these were compared with anatomical models and gross anatomical sections. The bony limits of the orbital cavity, the relationship of the orbit with sinuses and foramina of the skull were well identified by CT. MRI was useful to observe soft tissues and was able to identify adnexae of the ocular globe (eyelids, periorbital fat, extraocular muscles, lacrymal and tarsal glands). Although MRI was able to identify all components of the eye (including the posterior chamber), it could not differentiate sclera from choroid and retina. The only nerve identified was the optic nerve. Vessels were not seen in this series of cadaver heads. This study showed that CT and MRI are useful techniques to image the equine orbit and eye that can have clinical applications.