Ever Heard of: Top of Sacral Vertebrae Fused S4/S5?

[AmandaSanD]

As part of a lengthy lameness investigation which I won’t get into here, I ended up with an X-Ray of my horses’s sacrum that shows the “top parts” of her S4/S5 vertebrae fusing. Those two vertebrae lean together, fused at the chunky top parts, while the rest curve gently towards the tail as normal, spaces in between the top parts.

I realize the sacrum itself is fused, which makes googling “fused equine sacral vertebrae” or similar an exercise in futility. I will post X-ray when I get the CD. Anyone have experience with or heard of this type of abnormality?

[IPEsq]

I haven’t heard of this…do you mean the top of the sacral spines are fusing? Like kissing spine of the sacrum?

[Lady_Eboshi]

“Hunter’s Bump.” Not necessarily an unsoundness if it’s “old.”

[AmandaSanD]

The S4 is leaning the wrong way, so the top is squished against the S5. I drew a circle and little arrow in the image.

http://s23.postimg.org/delf8anqz/vertebralcolumn_5.jpg

[AmandaSanD]

South of where a “hunter’s bump” would be. It is not visible on the rump. Count four vertebrae up from the tail.

[Lady_Eboshi]

I have a horse with something visible at about that spot out in my field right now, and he’s sound as a dollar. Is this just an incidental “finding,” or do they think it’s the source of his lameness?

I should imagine that might depend on whether it’s fully fused, or in the act of fusing. Why do they think it decided to fuse?

[AmandaSanD]

This is not visible to the eye - shows only on X-ray.

Source of lameness is still unknown. The vets have not seen this particular abnormality before, which was curious.