Septic Osteitis--One Laminitis Complication

Septic osteitis (SO, inflammation of bone beginning in the periosteum, or membrane surrounding bone) of the third phalanx or coffin bone can be a problematic complication of laminitis. SO has historically been regarded as a problem that called for an extremely guarded prognosis or even euthanasia, but Bruce Lyle, DVM, a primary care equine veterinarian in Aubrey, Texas, has a slightly different take on it. He discussed the problem of SO in complicated laminitis cases at the 2002 Bluegrass Laminitis Symposium on Jan. 21; his first point was that it is essential to differentiate SO from osteomyelitis, which is a bone inflammation beginning in the inner medullary cavity.

“The SO horse will be very painful on the infected foot,” he explained, “and after the foot is derotated and balanced, he’ll fail to improve despite maximum mechanics (mechanical shoeing correction), antibiotics, and pain medication. In very critical cases, the horse’s respiratory pattern and behavior might be similar to a horse with anoxic or septic abdominal crisis (flaring nostrils, heavy sweating).”

Lyle said that in the horse with SO, one might see on radiographs progressive thickening of the horn-lamellar zone (distance between the laminae and the outside of the hoof wall, which is not exclusive to SO), loss of sole depth in the affected area, asymmetric collapse of the proximal hoof wall into the coronary band of the affected area (unless it was recently trimmed and balanced), and a gas density adjacent to the bone.

Digital venography (injecting radio-opaque dye into a blood vessel to measure blood flow in the foot) has been the most helpful tool to deciding if surgery is indicated for treatment, he commented. On some of these horses, the blood pressure in the foot is very high because of the inflammation. When trying to do a venogram on such horses, he sometimes can’t get the normal amount of dye into the vessel because the pressure within it is too great.

“The tissue’s not going to live without blood supply,” he explained. “We have to do venograms so we can see if there is any blood to the area.

“Large areas of bone not encased by the corium’s vascular web should be removed,” Lyle continued. “Smaller suspicious areas can be surgically approached, and if bone is exposed it can be curetted, or treated locally and observed.” Following surgical treatment, the area is packed with dimethyl sulfoxide (DMSO)-soaked sponges and amikacin (or hydrogen peroxide).

“The bottom line is that SO is curable,” Lyle concluded.

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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