This has been happening since mid December? If this is truly a founder case, she is likely within the "chronic" phase; the majority of rotation (and pain) has already occured. The horse will still be sore, but generally less than the subacute or acute phase. Abscesses are likely to still be forming. Often, you will see excessive bruising in the sole and further prolapsing. She will still benefit from being kept in a deeply (12") bedded stall.
Coffin bone rotation 100% can not be reversed. You can only hope to manage it. Depending on radiographs and the horses' tolerance, they may need boots or shoeing to help them stay pasture sound. Mini's are typically pretty light on their feet and can often tolerate bony changes easier than standard-sized horses, but they need to be aggressively managed (ie: diet/weight). I cannot stress the serious implications of founder enough to horse owners.
The cause of laminitis and founder are either; insulin resistance (Cushing's, EMS, diabetes, etc), carbohydrate overload (grass, hay, grain, etc), or the incomplete delivery of a placenta.
What is laminitis and founder?
Laminitis is the beginning or "acute" stage of founder (and when the vet should be called to intervene). The limb is shunting oxygenated blood away from the foot, resulting in inflammation and necrosis in the laminae (the live tissue within the foot). The horse will assume the "founder stance" with their hind feet underneath themselves to help shift weight off of their front feet. There will be pain, heat, and swelling primarily at the toe and front aspect of the coronary band. Laminae will be damaged, but no rotation occurs.
Founder is the physical separation and rotation of the coffin bone away from the hoof wall. The "subacute" phase is where most of the boney separation and tearing of the laminae is going to occur. The horse will be in constant pain, the affected legs will have a bounding pulse, and there will be heat and swelling in the coronary band and pastern region. Your horses body condition is likely to deteriorate.
[Since horses have a natural resting balance of ~60% on the forehand and 40% on the hind quarters, laminitis and founder tend to affect the front feet more than the hinds.]
Hoping for the best. I've seen some pretty nasty looking cases that radiographed beautifully (comparatively).
Stay safe, and Happy New Year!
