Dear Lena: The item you present is not the horse's hoof, but rather the
coffin bone. This is a common confusion. The "hoof" means the keratinous,
epidermal "capsule"  which fits around the coffin bone. The hoof capsule
is composed of the capsule itself plus the other epidermal parts, i.e. the
sole and frog, which together constitute the horny covering of the distal
part of the limb.

As you probably know, each part of the epidermal capsule is secreted by an
underlying dermal or "live" ("sensitive") so-called corium, so that the
capsule itself is secreted by the cells of the coronary corium (located in
the coronary band, supported by the coronary groove); the frog by the frog
corium; the sole by sole corium.

The dermal "sensitive" and epidermal "insensitive" components of the frog
and sole are held together -- in other words, the frog and sole are held
on -- by thousnds of tiny papillae which protrude from the dermal layer
and are received in sockets of the epidermal layer.

By contrast, the dermal and epidermal capsule (i.e. toe, pillars,
quarters, buttresses and bars) interdigitate via laminae. The laminae of
the dermal layer are the modified periosteum of the coffin bone (some
books will tell you that "the coffin bone has no periosteum"; I have even
heard veterinarians say this. It's a good example of confusion induced by
terminology, possible only when the speaker has no knowledge of the
relevant embryology). The interdigitation is like two pleated curtains
hanging side by side; the pleats are oriented parallel to the outer
surface of the coffin bone. The interdigitation, which may involve
primary, secondary, or tertiary folding, is not in itself sufficient to
anchor the horny capsule; anchoring is provided by microscopic dots of
short collagen fibers which act as "rivets" that attach the opposing
dermal and epidermal sheets.

If the pleating which constitutes the interdigitation of the sensitive and
insensitive laminae of the hoof were to be stretched out or expanded so
that it lay flat, it is estimated that in a full-sized horse that wears a
no. 2 shoe there would be 8 square feet of effective attachment surface.
This is also a measure of the richness of the circulatory supply, for each
finely-divided pleat of the sensitive laminae carries a small artery and
vein, which within that pleat ramify to ensure an abundant supply of
oxygen and nutrients to the cells which maintain and produce the epidermal
daughter cells.

Likewise, each papilla which reaches out from the corium of the sole or
frog carries an incredibly rich blood supply.

Further, there is at the distal rim of the normal coffin bone a circumflex
artery, which receives supply via foraminae normally developed in the
coffin bone, and which ramifies just behind the edge to supply the area of
the distal hoof capsule and the outer edge of the sole, i.e. the area that
would normally lie just internal to a horse shoe.

This much anatomical information having been given, it is only necessary
to say of your specimen that it represents a fairly typical case showing
three phenomena. The first two reflect the remodeling of the bone because
in life the hoof capsule was allowed to become unbalanced medio-laterally;
this is what accounts for the fact that the specimen has greater
medio-lateral asymmetry than normal. The second change is the flattening
of the bone by lowering of the angles of the wall and toe, and the forward
shift of the posterolateral corners of the bone; these are due to the hoof
capsule having been allowed to get out of antero-posterior balance,
something referred to by modern horsemen as 'run under heels' or sometimes
'sand heels'.

The third change is a degree of necrotic destruction involving the distal
1/3 of the bone, especially at the toe. The disease that usually causes
this in modern horses is called 'founder' and the cascade of sequelae that
affect the hoof are called 'laminitis'. In the laminitic horse, the
disease process causes the destruction of the collagen rivets that hold
the laminae together, and as a result, the coffin bone sinks and rotates
within the horny capsule. It may rotate either mediolaterally or
anteroposteriorly, i.e. the coffin bone will get to where it is tipping
toward one side, and it normally sinks so as to become steeper at the toe.

Another sequel to laminitis is the disruption and (eventual) destruction
of the distal circulation. If the coffin bone sinks more than a minimum
amount at the toe, the circumflex artery will get squashed between the rim
of the coffin bone and the sole. It will initially attempt to compensate
by ramifying anywhere it can find space -- this will create abnormal
foraminae, usually several of them, and abnormal grooves on the surface of
the coffin bone which develop due to the pounding pulse associated with
the disorder. Finally, if the coffin bone continues to sink, the
circulation will die and then the periosteum, as well as the bone in this
area will also die and start to necrose. Not long after this, the horse
will get septic poisoning and/or gangrene and will have to be killed.

A horse operating with a coffin bone in the condition of the specimen you
present would not have been sound at any gait above a walk. This does not
say to me that the Roman owners would have avoided making the animal go
faster; it only means that if it went faster, there would have been a
pronounced limp. It might have been maintained with out-of-balance,
laminitic feet -- the "ski feet" one occasionally sees reported in modern
cases of criminal neglect -- for years before the disease tipped over far
enough to start the downward slide to necrosis. A ski-footed horse can be
kept in work by periodically sawing off the excessive growth at the toe. I
do definitely envision this animal having the heavy, lobelike laminitic
rings, and knock kneed-toed out stance.

What in the modern world typically causes laminitis is the feeding of
grain (rolled oats and maize corn, particularly; barley is much lower in
glycemic load and I would not look to ground barley as a culprit. If you
have teeth from this site and they are polished, you may assume, I think,
that the animals were being fed ground barley. If you have no polished
teeth, then I'd assume they were pastured/fed hay, and in that case, I'd
want to consult with the site paleobotanist as to which grasses were
likely to be found locally and/or in manure or stable refuse from the
site).

The other inducer of laminitis, and this would apply at all historical
periods and in all cultures, is the greening of the grass, especially in
springtime. "Sap" in grass is full of sugar, and the laminitis-prone horse
is one which, like a diabetic, can't handle a sugar overload, and reacts
symptomatically by the disruption of the distal circulation which is the
major feature of laminitis.

There is a huge amount of information on laminitis/founder in modern
horses: look up Dr. Bowker of Michigan State University on the Internet
and have a look through his bibliography. Also, look at Dr. Chris
Pollitt's published work; he has a website from which you can get a number
of free and very useful PDF's of published papers. His "Atlas of the
Equine Hoof" is indispensable.

From my own website at www.equinestudies.org you can click on "membership"
and then look up the "Inner Horseman" back issue disk for Year 2003. This
is essentially a book on "orthopedic principles in horseshoeing", and what
you'll be getting out of that for your $25 bucks is a 12-layer 3D virtual
dissection of the distal limb which I made, along with all the anatomical
detail pertaining to the musculoskeletal system, of which the above is
only a sketch. -- Have fun -- Deb Bennett, Ph.D., Director
Equine Studies Institute & the bone lady at Vindolanda




> Dear all,
>
> I have a horse hoof that is affected by some sort of pathology, probably
> infection of some kind. The hoof is worn unevenly, one side more than the
> other. I can't tell whether it's the medial or lateral side. The hoof
> almost seem to curve upwards on that side. The too-worn side has
> porosities and minor bone growth on the side facing the ground. Does
> anyone here have any suggestion as to what might have caused this, or seen
> similar pathologies elsewhere?
>
> The site is a rural Iron Age/Roman rural settlement in southern England.
>
> Pictures here:
> Front:
> http://i893.photobucket.com/albums/ac137/ossamentaDW/Benbilder/P1020525.jpg
> Base:
> http://i893.photobucket.com/albums/ac137/ossamentaDW/Benbilder/P1020526.jpg
> Pathological side:
> http://i893.photobucket.com/albums/ac137/ossamentaDW/Benbilder/P1020527.jpg
> Normal side:
> http://i893.photobucket.com/albums/ac137/ossamentaDW/Benbilder/P1020528.jpg
>
>
> ------
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>
>
>