An ultrasound-guided, tendon-sparing, lateral approach to injection of the navicular bursa
Nottrott, C. De Guio, A. Khairoun and M. Schramme
To develop a novel technique for injecting the navicular bursa that avoided penetration of the deep digital flexor tendon, four cadaver limbs were used for development, before a study was conducted using a further 62 cadaver limbs sectioned at the fetlock joint. These were positioned on a 60° incline radiographic block (Hickmann block) before injection of the navicular bursa with 1.5 ml of the contrast agent, meglumine ioxitalamate, under ultrasonographic guidance.
Then 0.2 ml of methylene blue was injected into the bursa and a further 0.3 ml injected as the needle was withdrawn to show its pathway through the tissues. Successful injection of the navicular bursa was achieved in 58 out of 62 limbs. Of these, 49 showed contrast agent in the bursa alone. In the remaining nine, contrast agent was also observed in the distal interphalangeal joint. Contrast agent was not detected in the digital flexor tendon sheath, either radiographically or by methylene blue staining in tissue sections. In approximately one-quarter of limbs, extravasation of contrast agent into adjacent soft tissues was observed, although this was faint in the majority of cases.
In an in vivo study, 26 Standardbred horses without lameness were assigned to one of two clinicians who performed ultrasound-guided navicular bursa injection on both forelimbs under sedation and local anaesthesia, with the limb held or positioned in a block in a flexed position. Contrast radiographs confirmed injection of the navicular bursa in 88% of limbs, with agent being present in the bursa alone in 77%. Where agent was also present in other locations, this tended to be faint compared with marked opacity visible in the navicular bursa. Between one and two injection attempts were needed in most cases. There was no significant difference in outcome or number of needle redirections between cadaver and live limbs. Successful injection was found to be significantly dependent on the quality of the ultrasound image.
Bottom line:
This lateral approach to injection of the navicular bursa under ultrasonographic guidance is successful in the majority of limbs with minimal attempts and avoids the need for radiographic exposure.
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