Soon after starring on Horse & Hound’s front cover earlier this year (9 July), small tour dressage gelding Boston Deluxe was diagnosed with a keratoma.
Successful treatment of these hard-to-access hoof tumours requires scrupulous removal of the affected tissue and no small amount of patience, as Boston’s owner Jane Lavington discovered…
“Boston comes in lame from the field and looks suspiciously ‘footy’,” says Jane. “He’s hopping lame by the morning and the vet releases a small pocket of pus from the sole of his left forefoot, which we then poultice. It’s the first abscess Boston has ever had. We’re hoping it clears up in time for the Hickstead premier league show at the end of the month.”
After returning to soundness, Boston, a part-Clydesdale, once again goes badly lame.
“This time our farrier, John Stern, releases more pus from the same spot,” says Jane. “Unfortunately, Hickstead is now off.”
When the abscess fails to resolve, Boston is taken to Bell Equine Veterinary Clinic in Kent for X-rays.
“We think he may have trodden on something that has penetrated deep to the tip of his pedal bone,” says Jane.
A larger hole is made in the sole to access the infection and Jane is careful to keep the hoof clean.
Further hospital investigations reveal that the problem is not an abscess but a keratoma.
Vet David Sinclair explains: “A keratoma can sometimes put pressure on the pedal bone and starve it of its blood supply, so that the bone is resorbed — a process called pressure necrosis. We X-rayed Boston’s pedal bone from above to see if this had created an obvious groove or ‘nibbled’ appearance, which would indicate the presence of a keratoma.
“We could see the dark hole where the sole had been pared away and a tract containing debris running up inside the hoof, but as this is not conclusive in itself, we confirmed the diagnosis with an MRI scan.”
“I’m actually quite relieved,” says Jane. “A keratoma is serious and does require surgery, but at least this can be done under standing sedation without general anaesthetic.”
Boston is sedated and prepared for a dorsal hoof resection. His hoof is nerve-blocked and a tourniquet applied around the fetlock to control the bleeding.
“Using a pair of half-round hoof nippers or a saw, we removed a vertical strip of the hoof wall,” explains David. “We started over the point where the infection had broken through the sole and worked up to the coronary band. It is possible to leave a ‘bridge’ of horn at the coronary band and bore into the wall from underneath, but the most important thing is to remove the entire tumour to limit the possibility of recurrence.”
The exposed tumour can then be extracted carefully from the surrounding tissue.
“Boston’s keratoma shells out beautifully and we removed a core of discoloured tumour tissue,” adds David.
Boston stays in hospital overnight.
“We packed the gap with iodine-impregnated swabs to control any bacteria and to ‘leather up’ [toughen] the tissue,” says David. “After two weeks we used dry dressings until horn growth started to appear at the coronary band. Antibiotics should not be necessary if the hoof is kept covered — it can often be counter-productive.”
Jane discusses treatment options with her vet and farrier. Some cases benefit from a bar shoe, with or without a flat ‘hospital plate’ applied to the sole, to stabilise the hoof capsule. Because Boston has been barefoot for some years, Jane is reluctant to have him shod if it is not essential.
Back at home, Boston is on box rest. Jane tries an alternative treatment, cold laser therapy, to encourage horn growth.
Healthy, healing granulation tissue is appearing, but at the first trim John notices a split at the top of the hoof, at the coronet band, that moves when Boston puts weight on it.
John fits an aluminium plate across the gap in the hoof wall, sealing the protruding screw heads with glue.
Bandages are at last removed and Boston is allowed to graze in a small pen.
“Having his foot wrapped up for 10 weeks and being on box rest has had disastrous effects on the rest of his hoof,” says Jane, who protects the hoof wall with cotton wool and duct tape to allow his heels to breathe. “Both front frogs have shrivelled and we’ve had minor thrush issues, but things will hopefully now improve.”
Boston now has access to a larger pen for longer periods.
“I’m still plugging the hole daily with cotton wool and soaking the foot twice a week in sterilising fluid,” says Jane. “It’s difficult to see exactly what’s happening under the plate, although new, healthy horn is appearing at the coronet.”
Three months after surgery, John removes the plate and David trims away excess granulation tissue. Regrowth now reaches a third of the way down the hoof, but Boston is not out of the woods. Hoof horn grows at about 1cm a month, making rehab a long process, and there is a small chance the tumour will reappear.
“It’s now a matter of time,” says David. “The hope is that Boston will have a more positive New Year and be able to return to full work.”
“A keratoma is a relatively rare, benign tumour of the keratin or horn-producing part of the hoof wall,” says David Sinclair MRCVS. “Classically cone or cylinder-shaped, the tumour originates in or just beneath the coronary band where the horn is produced and grows vertically down the white line of the hoof. When it reaches the floor, the integrity of the joint between the sole and hoof wall is lost and infection sets in.
“Deformity of the hoof or local pain may indicate a keratoma, but the most common sign is an abscess that fails to resolve or recurs after treatment. While X-rays can reveal the mass itself and any damage to the pedal bone, an MRI scan will more clearly define the extent of the abnormal tissue.
“Various theories as to why a keratoma forms include local irritation, trauma or stretching of cells that produce keratin. There is no particular susceptibility among differing ages, types or breeds, nor among shod or unshod feet.
“While there is a strong feeling that maintaining proper hoof conformation should help prevention, this is by no means the whole story. Development of a keratoma is somewhat unlucky, but prognosis is good as long as all traces of the tumour are removed and healing of the hoof wall is successful.”
Ref: Horse & Hound; 26 November 2015