Sacroiliac Injection Technique

The sacroiliac joint, which forms the articulation between the pelvis and the spine, is often considered a location of elusive pain in horses. However, its deep location and, thereby, limited accessibility make diagnosis (via nerve blocks) and injection-based treatment difficult. At the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla., Florent David, DVM, DES, MSc, Dipl. ACVS, ECVS, a large animal surgeon at the University College Dublin in Ireland, presented the results of a study (performed when he was at the University of Montreal in Canada) that evaluated four different ultrasound-guided approaches to injecting this difficult joint.

After describing equine sacroiliac anatomy, David described the various techniques that were used (cranial, craniomedial, medial, and caudal--from the head direction, head/midline, from the midline outward, and from the tail direction, respectively). All approaches used a 20-cm, 18-gauge needle manually curved to a 40� angle, and all techniques were performed on 14 cadaver pelvises using different colors of latex (2 mL per injection) to distinguish them.


Illustration of sacroiliac joint location

Problems that occur in the sacroiliac joint region include osteoarthritis, ilial wing stress fractures, tuber sacrale asymmetry, desmitis (ligament inflammation), and muscle strain.

No technique resulted in injection within the virtual joint space, but most injections were very close to it (from 1.1 cm away with the caudal approach to 2.4 cm away with the craniomedial approach). In live horses, diffusion of medical substances (such as regional anesthesia or joint therapies such as corticosteroids) into the joint would occur. The caudal approach resulted in injection closer to the sacroiliac joint itself, making it the best choice for joint medication. However, he noted that this approach does carry a risk of puncturing the gut if the needle is inserted too deeply.

The caudal approach isn't ideal for everything; David noted that this approach resulted in injections farthest from neurovascular structures. Therefore, this approach, and the medial approach should not be used to anesthetize the sacroiliac area. The cranial and craniomedial approaches are better for that.

He reported that half of the cranial, craniomedial, and medial approaches resulted in injections within the interosseous (situated between bones) sacroiliac ligament, so they are all options for treating desmitis (inflammation) of this ligament or joint instability.

David concluded that ultrasound guidance was of great help to perform injections extremely close to the sacroiliac joint margins without depending on variable external landmarks. The veterinarian can choose one or a combination of approaches to anesthetize or medicate the sacroiliac area, depending on the suspected problem.

The full article will be available in Equine Veterinary Journal (Equine Vet J. 2007 Sep 24; [Epub ahead of print]).

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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