Acute and chronic disease (especially osteoarthritis) of the sacroiliac joint(s) is not uncommon in competition horses and racehorses, affecting up to 8% of Standardbreds in training and 15% of competition horses (particularly hunters, jumpers, and event horses). However, it is difficult to localize a problem to one of these joints because of their deep location and relative inaccessibility. Emmanuel Engeli, Med.Vet., a surgeon at the College of Veterinary Medicine at Cornell University, presented a study at the 2002 AAEP Convention in which he developed a successful protocol for periarticular (medication placed immediately adjacent to the joint capsule) injection of the sacroiliac joint.

The sacroiliac joints are the junctions between the hind limbs (upper part of the pelvis) and the rump (sacrum, consisting of five fused vertebrae). "Clinical signs of sacroiliac arthritis are often non-specific and may include poor performance, refusal of jumps, lack of hind limb impulsion, poor croup muscling, back soreness, resistance to trot or pace at high speeds in Standardbred racehorses, and a low-grade or shifting hind limb lameness," said Engeli.

The ability to inject local anesthetic, one of the primary diagnostic tools used in lameness evaluations, into or just adjacent to the sacroiliac joint could greatly improve the diagnostic and therapeutic capabilities of veterinarians seeking to diagnose and treat the cause of the above clinical signs. This injection technique, if successful, would also allow injection of medication (such as corticosteroids) into this area, if needed. In human medicine, comparable injection techniques are used in patients with sacroiliac joint disease.

The researcher used 24 horses (of various breeds, ages, and sizes) to develop the injection protocol using custom-made, curved, 10-inch (25-cm) 15-gauge spinal needles. Reliable bony landmarks of the pelvis were used to locate the needle entry site just off midline between the sixth lumbar vertebra and the first sacral vertebra and for needle advancement toward the sacroiliac joint. The horses were injected with methylene blue dye while sedated and standing, then euthanized (for reasons unrelated to the sacroiliac or pelvic regions) and the sacroiliac joints examined to determine the location of the dye and thus, the success of the injection.

Due to anatomical constraints, the researchers were not able to access the joint directly with the needle, but they were able to place the dye immediately adjacent to the joint capsule. Location of the dye 2 cm or closer to the sacroiliac joint margin was considered a success; 88% of the injections fulfilled this criterion. The other goal was to place dye in the middle or caudal (rearward) third of the joint, the most common site for osteoarthritis of the sacroiliac joints; 96% of the injections were successful in this regard. No injections damaged the neurovascular (nerve and blood vessels) structures that pass through the nearby greater sciatic foramen (opening between the pelvis, sacrum, and the sacrosciatic ligament, located just at the rearward aspect of the joint). Age, weight, breed, or sex did not affect successful needle placement.

Additionally, the study mentioned a clinical trial in which four horses with pain apparently in the sacroiliac joint were injected with local anesthetic using this technique. Three were then less lame and had decreased caudal back soreness following the injection. With this technique the pain causing the lameness and back soreness was localized to the sacroiliac joint region in those three horses.

Engeli concluded that with this technique, needle placement was safe, reliable, and well-tolerated by horses, and it seems to be of value in the diagnosis and treatment of sacroiliac joint disease, although he recommended further research in this area.

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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