Whatever their cause (trauma, insult, bad karma, etc.) solar abscesses are
characterized by an invasion of pathogenic bacteria and the presence of the
end products of the horse's body's efforts to fight the infection.  Those end
products (think "pus") consist mainly of incompressible fluids and can bring
tremendous pressure on the sensitive structures within the hoof capsule if the
fluids accumulate faster than the horse's body can absorb them.

In defiance of gravity and common sense, the line of least resistance for a
growing abscess in the sole is upward. The exfoliating sole, hoof wall, and P3
create an impenetrable barrier to fluids, the infection keeps churning out more
end products, so hydraulic pressure forces the infection upward until it encounters
tissue weak enough to penetrate - the coronary band.  Classic blow out!

Because the pain of the abscess is caused mainly by hydraulic pressure, when
an abscessbursts out, improvement is usually immediate.

If an abscess can be located and drained before it travels upward to the
coronary band, less tissue is affected, the horse normally heals faster, and the
prognosis for full recovery is usually better. On the other hand, it's easier to
treat a wound in the coronary band than a wound in the sole.  Hobson's choice.

[As an aside, horizontal defects in the hoof wall are thought to be caused by
swelling of the tissue near the coronary band which impinges on the blood flow to
the coronary corium; e.g., a blow to the coronary band, a wound, or a bursting
abscess. A wound to the coronary corium that results in the formation of scar
tissue invariably causes a vertical defect in the hoof wall.]

According to Dr. Tracy Turner at the Univ. of Minn., soaking an abscess is useless.  On
the other hand, Dr. Mike Heitmann of Katy Equine Clinic recommends soaking in
a hot, saturated solution of magnesium sulfate (epsom salts) to facilitate resolution.  It
is generally agreed that soaking is beneficial after the abscess is draining.  While some
folks feel an abscess bursting out at the coronary band is a bad thing, the release of
hydraulic pressure that takes place when an abscess bursts out at the coronary band
can sometimes take a horse from three-legged lame to sound within a couple  of hours.
Sound is considered a Good Thing here in Texas - and a wound  at the coronary band
is not subjected to the same environmental pressure as is a drain cut into the sole.

An owner should never attempt to cut a hole in the sole in order to drain
an abscess unless directed to do so by a veterinarian.   A hoof knife is not
an exploratory tool!  The inexpert use of a hoof knife or gouge can cause a
helluva lot more problems than it alleviates.   Leave the digging to
veterinarians and folks at their direction.

Soundness after opening a drain in the exfoliating sole will depend on the cause of the
abscess as well as the location, depth, and size of the drain.  The inexpert use of knife
or gouge can do more damage than an abscess;   sensitive sole prolapsing through a
hole in the exfoliating sole can be more difficult to heal than an absecss, but it happens
quite often when civilians start playing veterinarian.

A drain hole in the exfoliating sole exposes sensitive tissue to the horse's environment;
for this reason, protecting the wound site from environmental pressure becomes an
extremely important factor in achieving and maintaining soundness.  This is usually
accomplished by the application of a pad, hospital plate, or by forging a bulge in the
inner web of the shoe that covers the wound site.  These procedures also serve to hold
any medicated packing against the wound.

Any owner, trainer or stable manager who uses a hoof knife as an exploratory tool places
the horse  unnecessarily at risk.   The draining of abscesses is best left to equine
practitioners and folks working at their direction.