White Line Disease, Inflammation, or What?

What do you think this is and what else can I do?

I have a horse that is lame intermittently.  In the beginning I thought it was an abscess.  Animalintex was used and the horse got better.  Then the lameness came back.  Last weekend apparently she was quite lame.

The veterinary was called and x-rays were taken.  They are attached.
The vet found what she thinks is white line disease, the black line from the quarter into the toe area on the left front foot. All this started after the owner did a long ride over rocky terrain without the hoof boots she normally puts on her horse.  The vet and I are wondering if it's the result of trauma.

In any case, I saw the horse tonight and the foot looks very clean.  The vet had scrapped the white line looking for infection and found none.  I scrapped the sole just beside the white line a bit and found some small black areas.  I didn't want to dig holes and create more problems.  Both front feet were hot but no pulses.  She had been walked about 1km to get to the yard from her field.  Tapping didn't indicate a cavity.  I'm not sure she was positive with the hoof testers as she was very agitated (the horses in the barn where getting their feed).  The vet said she had a pulse on the weekend and she thought she tested positive with the hoof tester at that time.

We washed the foot, sprayed it with Thrush Ender and put a Sole Mate Therapeutic pad on it with a vet wrap.  The owner is going to do a Clean Trax on Saturday.

This horse has had laminitis two times in the past (last time 3 years ago).  She also was treated with acid around her coronary bands on her front feet when she was a trotter.  This damaged the CB and the hoof wall is very uneven as a result.

What do you think this is and what else can I do?

My response:

As you may know, I am not a veterinarian and I do not look at x-rays from a veterinary diagnostic perspective, but rather from the perspective of an equine podiatrist. That being said, I do offer my opinion when asked to do so, in the hope that you and your veterinarian, working as a team will be successful in helping this horse. I have reviewed the x-rays, and I will agree with the veterinarian that something is going on in that quarter.
Inflammation and gas pockets appears as dark areas on x-rays, and bone health (density) appear as varying shades of gray. With this in mind, rarefaction (low density) of P3 at the location the veterinarian suspects white line disease suggests that this could be chronic inflammation or possibly a lesion, and could explain the intermittent lameness.

rarefaction and inflammation 

Trauma from riding without the boot could be responsible for flare up of inflammation. The inflammation may or may not result in abscessing, but I don’t think it will. Conformation or way of going can have a lot to do with this type of chronic inflammation. Does this horse land balanced or does conformation result in dynamic imbalances while going? The rarefaction of P3 suggests that whatever has caused the inflammation has done so repeatedly. Once this horse is comfortable and relatively sound, I suggest you tape a pair of Sole Mates on this horse and then walk and trot the horse in hand for ten or fifteen minutes. Remove the pads and examine the impression.

Pad impression

Training your eye to see foot fall is important, taking advantage of available diagnostic tools is smart. This will give you a good idea as to how this horse loads during the stride. If this horse does not land dynamically balanced, you will have to try and figure out why. You did all the right things by treating the symptoms, now let's figure out the why of it so you can work up how to protect or prevent further trauma in that foot moving forward.