Surgery for Triple-Level Spinal Cord Compression

Spinal cord compression in the neck, more technically known as cervical vertebral stenotic myelopathy or CVSM, can cause notable incoordination and affects about 2% of racing Thoroughbreds. Probably the most well-known horse affected by CVSM was Thoroughbred champion racehorse and sire Seattle Slew, whose successful surgeries were well-publicized. But Slew had only two affected joints in his neck, and some horses have three joints compromised by CVSM. Only four reports of successful outcomes of surgery on such cases had been published as of November 2007, but a report of 12 cases was presented at the convention.

"Affected cases have a narrowing of the vertebral spinal canal (stenosis), which causes incoordination, inappropriate rigidity, paresis (impaired movement), and weakness," explained Nicholas Huggons, DVM, a veterinarian with the San Luis Rey Equine Hospital in Bonsall, Calif. "It's most frequently seen in young, rapidly growing, well-fed horses. Surgical management aims to stop repetitive trauma to the spinal cord. Horses that don't receive therapy have a poor prognosis because of the continuous damage done to the cervical spinal cord."

stabilizing cervical vertebrae

Surgery was done to stabilize three joints on each horse, primarily between cervical vertebrae C3-4, C4-5, and C5-6 (shown here).

The surgery usually consists of inserting metal cylinders through the adjacent bones on one side of the joint, effectively immobilizing the joint. Huggons conservatively estimated that more than 1,000 horses have undergone this procedure for one or more joints since the surgery was developed in 1979 for horses.

In this 12-case series, the average age of onset was two years, and all cases were males (eight of 12 were geldings). Five were Thoroughbreds, with the rest being of various breeds. Surgery was done to stabilize three joints on each horse, primarily between cervical vertebrae C3-4, C4-5, and C5-6, although two horses had C6-7 fused. Five horses had the original stainless-steel baskets placed, five had Kerf Cleaning Cylinders (also known as Seattle Slew implants), and two had bone grafts.

All but one horse recovered; that horse was euthanatized due to incisional complications. One later died in a paddock accident, but the rest improved at least one neurological grade and 75% had improved by two grades at one year after surgery. Overall, 67% of horses returned to their intended athletic function. Four horses were intended to race, and two did (one won a stakes race). Three of the six other horses intended for pleasure riding or showing have been used thusly, and two are entering training. The implant type used made no difference in outcomes.

"Triple level fusions have similar success rates to single and double fusions," he concluded. "Affected patients can live productive and/or competitive lives with no danger to themselves or their handlers, and they do not require daily medications."

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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