Although an uncommon condition, keratoma formation beneath the horse’s hoof wall or sole can cause lameness, recurrent abscesses and damage to the laminae and coffin bone.

Because of the potential for serious medical consequences, keratoma diagnosis, removal and treatment requires either the close collaboration between farrier and veterinarian or the involvement of a veterinarian skilled in farriery.

The Condition

FARRIER TAKEAWAYS …

  • Keratoma is a non-cancerous mass that grows slowly under the hoof wall or sole. Lameness slowly advances as the keratoma presses against sensitive tissues.
  • Diagnosis, removal and treatment of keratoma require that a farrier and veterinarian work closely in concert to avoid serious medical problems.
  • The formation must be completely removed surgically and support must be provided for the hoof and off-limb. Infection prevention methods also must be employed.
  • The therapeutic shoeing plan for a horse after hoof wall or sole resection requires a skilled farrier.

The name keratoma implies a keratin-derived tumor, but while the involved tissues are generally mostly keratin, the cells themselves are hyperplastic rather than neoplastic — meaning they have multiplied but aren’t truly cancerous. Keratomas grow slowly over time, but do not spread to other parts of the body.

The keratoma is a spherical or cylindrical mass of keratin that grows between the hoof wall and sensitive laminae or beneath the sole. Lameness develops slowly and sometimes intermittently as the mass begins to press against sensitive structures.

While most keratoma formations are thought to be associated with injury or irritation to the hoof capsule or coronary band, such as a laceration, penetrating hoof injury or abscess, the exact cause is unknown in most cases.

Keratomas can affect horses of any breed, age or gender and generally develop over a long period of time. Typically, only one foot is affected and horses with more than one keratoma, such as the case below, are rare.

Treatment involves the complete surgical removal of the mass, hoof support, off-limb support and prevention of infection.

Keratoma Started In Yearling

Raul Bras, an equine veterinarian in the podiatry clinic at Rood and Riddle Equine Hospital in Lexington, Ky., sees more than the normal share of keratoma patients. He offers this look at an interesting case involving two keratomas in the left hind foot of a young Thoroughbred.

The patient is a 2-year-old gelding and future racing prospect, which was referred to Bras for a defect in the dorsal hoof wall of the left hind with recurrent abscesses at that site and in the sole, as well as mild, intermittent lameness.

By the time Bras saw the horse, the condition “had been going on for at least a year, on and off. So, it started at least as a yearling, maybe before.”

“It’s quite rare,” Bras says, “to see keratomas in such a young horse.”

All photos courtesy of Dr. Raul Bras

FIGURE 1

FIGURE 2

FIGURE 3

This horse had abnormal scar tissue along the dorsal hoof wall (Figure 1) that extended above the coronary band, giving Bras a clue as to the possible location of a lesion. However, this horse had another suspect area on the same foot. The previous farrier had pared out a sole abscess just lateral and cranial to the apex of the frog (Figure 2), and abnormal tissue could be seen in the pared out area.

Radiographs revealed the causes of both the dorsal and solar abscesses — two masses (Figure 3), a cylindrical keratoma on the dorsal aspect of the hoof capsule and another that can be seen as a well-defined circle defect (dark) over the caudal aspect of the coffin bone. The presence of both the cylindrical keratoma under the dorsal hoof wall and the spherical keratoma beneath the sole presented a problem for Bras.

“When you pare out the sole, you can see the abnormal tissue,” he says. “I was tempted to take it out, but I didn’t.”

In Bras’ estimation, the more pressing problem was the dorsal hoof wall lesion. The extent of the hoof capsule defect, from the ground to above the coronary band, made the severity of the mass obvious even before radiographs were taken. 

The presence and locations of two keratomas in the hoof created a series of concerns even before surgery began.

Bras worried that removing both keratomas at once could overly compromise the hoof.

“I only removed the dorsal wall keratoma because I thought it would be too much to do both,” he explains. “I wanted to preserve the structure of the hoof capsule.”

The scar tissue on the dorsal wall helped Bras make his decision.

“This case was more straightforward than normal because it had the well-demarcated scar tissue,” he says. “My only concern was that it went above the coronary band.”

The only successful treatment for a keratoma is complete surgical removal. If part of the mass is left behind, the keratoma can grow back again. Bras discussed this concern with his client before the surgery. Knowing that he didn’t want to resect any part of the coronary band and that he was also concerned about the proximity of the lesion to the coffin joint, there was a possibility that complete removal of the mass might not be possible.

FIGURE 4

The radiographs provided some hope that the dorsal wall keratoma didn’t extend all the way to the coronary band. However, on the lateral view (Figure 4), Bras saw something else that made him wonder how difficult it would be to remove the entire mass.

“The bone proliferation at the dorsal surface of P3 on the lateral view was a concern,” he says. “I wondered if the keratoma had an attachment to it.”

Resection Needed

As both veterinarian and farrier, Bras was able to manage this case himself, but he stresses the need for teamwork in keratoma removal.

“This is a case when the vet and the farrier definitely have to work together,” Bras says.

He points out that the veterinarian is needed to radiograph the horse and to provide sedation and local anesthesia for surgery.

“You need a resection of the wall or sole, which sometimes the farrier does,” Bras says, “but usually the vet and farrier do it together, with the farrier resecting the horny tissue and the veterinarian performing the surgery within the capsule.”

The therapeutic shoeing plan requires a skilled farrier. The veterinarian is needed for follow-up treatment and prevention of infection.

Bras anesthetized the foot with an abaxial (at the level of the fetlock) nerve block, cleaned and trimmed the hoof as much as possible. He applied a light surgical scrub before beginning the resection.

“I dremeled around the scar tissue at the dorsal wall from just below the coronary band to the ground,” Bras says. “After I had the local area dremeled out, I went in with clean instruments and started peeling the keratoma out.”

The keratoma’s position against the dorsal laminae made removing it delicate work.

“You want to peel it off without disturbing the laminae,” he says. “If you disturb the coronary band, you worry about abnormal hoof growth.”

The bony proliferation Bras had seen on radiographs didn’t present a problem during surgery.

“I wonder if the keratoma caused inflammation and the bone responded,” he says.

Often pressure from a keratoma will cause the bone to resorb (break down). In this case, Bras says, “this horse had a lot of bone reaction.”

Fortunately, the keratoma did not extend as far proximally as the scar tissue suggested. Instead, the proximal extent of the mass was well below the coronary band.

“When I removed the hoof wall, I probably didn’t have to go that high,” Bras says. “But I wanted to because of the scar tissue. Plus, I wanted to make sure that I got all of the keratoma, because if you don’t, it’ll come back.”

Hoof Stabilization Critical

FIGURE 5
FIGURE 6

With the extensive hoof wall resection and removal of the keratoma complete (Figure 5), Bras’ next concerns involved stabilizing the hoof capsule and preventing infection.

He tightly packed the defect with Betadine-soaked gauze to prevent granulation tissue from filling in the site too quickly and trapping bacteria underneath. Bras also kept the horse hospitalized for several days to monitor for signs of infection or laminitis.

During that time, he soaked the foot daily in CleanTrax to keep the surgery site clean. The horse was also given a course of systemic antibiotics to reduce the risk of post-operative infection. Bras also stresses the importance of keeping the foot wrapped to ensure it is clean and dry.

In order to stabilize the hoof wall, Bras bridged the dorsal wall defect with an aluminum square (Figure 6) “that I shaped to the hoof capsule, glued to one side and braced over.”

He shod the foot with a SoundHorse Technologies Sigafoos Series II glue-on shoe that incorporates a fiberglass cuff that goes all the way around the hoof. The shoe covers the sole and part of the way up the hoof wall. To customize the shoe, Bras cut out the area covering the sole lesion and used a treatment plate to access the pocket that had been pared out over the solar keratoma. He also cut a window in the cuff over the dorsal wall resection to provide access to the surgery site.

These modifications also allowed Bras to decrease the pressure on the compromised areas of the hoof. By removing the cuff and attaching a bottom plate from the dorsal aspect, Bras says, “you unload that area. I put impression material in the sole, cut out from the spot (of the solar keratoma) and put no impression material at that dorsal aspect, so it’s unloaded even farther back from the toe.” The compromised regions will remain unloaded until hoof growth is complete.

Because of the extent of the resection and the fact that the keratoma had clearly compressed and stressed the laminae (Figure 5), Bras was concerned about the possibility of P3 rotation in the affected foot.

However, after closely monitoring it, neither the affected foot nor the opposite hoof developed rotation.

Supporting limb laminitis is a post surgery concern, especially in a lame horse, Bras says.

“You have to check individual cases,” he says. “If this horse had gotten really lame from surgery, I would have had to come up with something for more substantial support for the other limb. But this horse did well. In this case, I applied a boot with impression material to make sure the horse was balanced and had something to support the other limb just in case.”

Follow-Up, Future Surgery And Prognosis

The horse was rechecked weekly by Bras and had the shoes and aluminum plate changed every 5 to 6 weeks. It initially was confined to a stall to monitor for lameness. Since the horse never went lame after surgery, exercise was gradually increased to hand-walking and limited turn out. It also was weaned off of non-steroidal anti-inflammatory (NSAID) pain medication.

ON THE WEB …

Learn how to assemble the Sigafoos Series II therapeutic shoe system by visiting www.americanfarriers.com/ff/0714.

This horse responded exceptionally well to the surgery, Bras says. Successful keratoma removal with no surgical complications generally results in a good return to full performance.

While this case initially was complicated by the rare presence of two keratomas, the large extent of the dorsal wall keratoma, and the bony proliferation seen on radiographs, the actual procedure was remarkably straightforward.

With these lesions, Bras says, there are a number of potential complications and concerns:

  • Damage to the laminae or bone.
  • Post-operative infection.
  • Rotation of P3 in the affected foot.
  • Supporting-limb laminitis.
  • Incomplete removal and recurrence of the keratoma(s).

Accurate diagnosis, usually by radiograph, but sometimes through biopsy, MRI and complete removal are critical for successful treatment. If any portion of the keratoma is left behind, it will reoccur.

Prevention of infection can be accomplished through packing the defect, systemic and/or regional antibiotics, and keeping the site clean at all times. Pain is generally managed with NSAIDs.

The remaining hoof capsule should be stabilized and the compromised area unloaded during the regrowth period. 

Keratoma cases provide an excellent opportunity for close collaboration between veterinarian and farrier.

After successfully removing the keratoma along the dorsal hoof wall, Bras is contemplating removing the second keratoma that is lateral and caudal to the apex of the frog. In a future issue, American Farriers Journal will update this case study and document the surgery, treatment and recovery.

Therapeutic Shoeing Method Takes Plenty Of Practice And Time

After surgically removing a keratoma mass in the dorsal hoof wall of a 2-year-old Thoroughbred gelding, Raul Bras knew he needed to stabilize the capsule. He turned to the SoundHorse Technologies Sigafoos Series II shoe.

“It’s an indirect glue-on shoe technique that I use quite often and am very comfortable with,” says the veterinarian and farrier at the Rood and Riddle Equine Hospital in Lexington, Ky. “It’s a custom-made therapeutic shoe that provides lots of protection and support.”

The shoe consists of two parts — a plate and cuff — that are fabricated using an exact tracing of the horse’s foot.

“You can modify it to any specification you might need,” Bras explains. “You can add treatment plates as needed and apply mechanics as well.”

Fabricating and applying the shoe can be time consuming and labor intensive.

“Like everything else, it’s the type of shoe you have to become familiar with and practice fabricating before you can become comfortable with it,” he says. “For someone who fabricates them only once in a while, it can easily take more than an hour. For someone who does them on a regular basis, it could take 30 to 45 minutes per shoe.”

Bras stresses that this shoeing technique was his preferred method for this case. It is not ideal for every farrier. He is a firm proponent of the journey and destination approach to farriery.

“I’m a strong believer that it’s not the actual shoe,” Bras says. “The most important aspect is the trim approach and the principle behind your shoeing. It’s important that we allow our farriers to use what they are comfortable with, as long as the principle reaches the same goal.”