Dropped Sole

Horses with solar prolapse (when a rotated or dropped coffin bone causes the sole to bulge outward, seen here) might benefit from wooden clogs. | Photo: Courtesy Dr. Daisy Bicking

Laminitis itself is a precarious condition, but complications can make cases even more challenging to manage. Two of the most common complications veterinarians face are injuries to the subsolar tissues (the soft tissue located between the coffin bone and the hard/keratinized sole, in front of the frog) and sole, such as coffin bone penetration and subsolar abscesses.

At the 2017 American Association of Equine Practitioners Convention, held Nov. 17-21 in San Antonio, Texas, James Belknap, DVM, PhD, Dipl. ACVS, gave veterinarians tips on how to evaluate and manage these difficult scenarios.

Horses that develop complications typically exhibit more severe lameness (usually in one limb) and, possibly, an increased heart rate and increased recumbency (time spent lying down), said Belknap, a professor with a special interest in laminitis at The Ohio State University College of Veterinary Medicine, in Columbus.

“The question is whether the pain is coming from the sole or the lamellae,” he said.

To find out, he said veterinarians must examine the hoof, sole, and frog and determine whether the horse is painful in response to solar pressure (indicative of sole pain). Radiographs—dorsal-palmar (front to back), lateral, and solar margin views, specifically—can also reveal valuable information about what’s happening inside the hoof. Nerve blocks can help the veterinarian localize pain to the hoof (and numb the hoof for later treatment); however, Belknap said they won’t necessarily help differentiate solar from lamellar pain, because the same nerve block anesthetizes both structures.

After thoroughly evaluating the complications, the veterinarian can develop a treatment plan.

Subsolar abscesses

While owners might hope for an easy-to-treat abscess when their horses develop severe and sudden lameness, these painful infections can be bad news for laminitic horses. Belknap said one major concern is exacerbating laminar injury in the opposite foot (usually already damaged by the initial bout of laminitis) if the horse offloads weight from the abscessed hoof.

He said it is much more common for laminitis-related subsolar abscesses to be “underrun abscesses” (involving a large portion of the sole). Therefore, it’s important for the veterinarian to determine the extent of the sole involved and “establish multiple small openings (in the sole or hoof wall) to allow both drainage and active lavage of the abscess,” said Belknap. Once drainage is established, treatment begins with Epsom salt soaks and lavage once or twice a day. If the horse will not bear weight on the limb, Belknap recommended applying open-sole casts, which support the hoof while still allowing sole access for treatment.

He noted that products such as CleanTrax can aid in healing, but cautioned that while they work well when used for soaking, they can make horses sorer when used for lavage. If neither Epsom salts nor CleanTrax work, medical maggots can help eliminate diseased tissue and offending organisms, he added.

Though the condition is relatively uncommon, Belknap said it’s important to determine whether the horse has developed septic osteitis (infection of the coffin bone) in conjunction with the abscess. It’s likely to be a septic condition if a focal area of bone resorption (remodeling) is evident on X rays and must be treated; this requires surgical removal of the affected portion of the coffin bone either through the sole or the hoof wall. These animals commonly need foot care for four to eight weeks post-surgery.

Solar injuries

Injuries to the sole, such as prolapse (when a rotated or dropped coffin bone causes the sole to bulge outward) or perforation (when it penetrates the sole), present another management obstacle.

For mild prolapsed soles (or horses with pain in the toe region), Belknap recommended veterinarians or farriers apply a wooden shoe (clog), using a Dremel tool to create a gap in the clog’s sole surface where the prolapse is present, then filling it with a rubbery cushion support material (commercial silicon putty materials sold for hoof care). The advantages the wooden shoe offers include:

  • The wood material provides more “give” than traditional metal shoes; and
  • The beveled ground surface around the circumference of the shoe takes some of the physical stress off the affected hoof wall/laminae (lamellae).

For horses with solar perforation, he recommended applying an open-sole cast, which is essentially a half-limb cast (up to the knee) that encompasses the entire hoof, supporting the sole with cushion material but with an opening at the perforation site for treatment access. . In some cases, he added, a deep digital flexor tenotomy (transecting, or cutting, the deep digital flexor tendon, or DDFT, in the mid-cannon bone region) can benefit these horses. The DDFT runs down the back of the horse’s leg and attaches to the back of the coffin bone. Transection removes one of the main forces responsible for coffin bone rotation and could alleviate pain and further laminar injury by decreasing pull on the bone and inflamed lamellae.

Belknap told The Horse that not all horses can recover from this severe complication. However, in those that progress well through treatment, the solar tissue generally heals over six to 12 weeks.

Take-Home Message

Treating laminitis complications can be challenging, but not all are insurmountable. With proper diagnostics, correct treatment, and careful management, Belknap said many horses can overcome laminitis complications.

“To have the greatest chance of success, it is important for the owner to promptly involve the veterinarian and farrier at any time that there is a sudden increase in lameness in the chronic laminitis case in order for a rapid diagnosis and treatment of complications,” he stressed.