Managing Severe White Line Disease
White line disease is a bit of a misnomer as it doesn’t actually affect the white line along the bottom of the hoof wall. Rather, it’s a disease process that sets up within the inner, nonpigmented section of the hoof wall, called the stratum medium, that can also erode into the stratum internum (where the sensitive laminae attach the hoof wall to the coffin bone). In severe cases, white line disease can damage the lamellar apparatus to the point that the horse develops laminitis.

Mike Steward, DVM, APF, of Shawnee, Oklahoma, discussed the intricacies of treating and shoeing horses with severe white line disease during the 2017 International Hoof-Care Summit, held Jan. 24-27, in Cincinnati, Ohio.

Diagnosis

One of the big challenges in treating white line disease is that its cause is unknown. The disease process usually begins with separation of the hoof wall’s insensitive laminae from the underlying sensitive laminae attached to the coffin bone. Bacteria, fungi, and dirt can then enter the space and cause infection, which is often difficult to treat due to its location and the lack of blood flow to this area.

Veterinarians typically diagnose white line disease by looking for abnormal wall separation or wall conformation, tapping the hoof wall to listen for a hollow sound, and applying hoof testers to the sole. A veterinarian or farrier can use a hoof knife to cut away the diseased part of the hoof wall to get a better idea of the extent of infection and separation. Radiography is a useful and less-invasive diagnostic tool, Steward said.

Treatment

Treatment—although lengthy—is relatively simple, said Steward. When dealing with these cases, he removes the dead hoof wall with a hoof knife, Dremel tool, or half-round nippers. This allows oxygen to reach the anaerobic bacteria (which thrive without oxygen) that are degrading the hoof wall. It also helps reduce stress on the diseased hoof wall that are causing the separation. He emphasized the importance of cutting away the entire infected area. Then he said he usually applies a topical medication to treat the infection.

If the hoof wall deficit is particularly large, Steward said he might mix powdered copper sulfate with impression material, place it within the deficit for support, and wrap the foot with a cast. He added that some farriers also apply super glue to the cleaned lesions’ edges to help to seal them and prevent more damage.

Steward stressed the importance of stabilizing the hoof wall and coffin bone. If possible, he trims and rolls the affected toe and might then use a wedge pad or clog pads to help take some of the load off the diseased area. These wedging and breakover modifications can help reduce pressure on the deep digital flexor tendon attached to the coffin bone to help prevent (or relieve pain associated with) laminitis. He sometimes applies ethylene-vinyl acetate (memory foam) to help lessen concussive forces on the foot, especially if the horse will be walking on hard ground or concrete.

Shoeing

Farriers can use various shoeing methods depending on their knowledge of shoe mechanics and the individual foot’s needs, Steward said. For example, they might apply a wide web shoe, a pad, and sole impression material to redistribute the horse’s weight to the back of the foot and protect the painful toe area.

“The toe soreness can be a result of the white line disease’s damage to the lamellar apparatus, resulting in laminitis,” said Steward.

Some of Steward’s favorite shoes for stabilizing the hoof and redistributing weight include heart bars, egg bars, square-toed shoes, and full roller motion shoes. In more severe cases, he might use a clog similar in design to that of the “outlaw shoe” for horses with laminitis.

“The concept of the wooden shoe (such as Steward’s eponymous Steward Clog) is utilizing mechanics in an orthotic (an artificial support) to alter the hoof’s engineering to enhance healing,” he said. “Stability and mobility are uniquely balanced in such a manner they allow the hoof to function in an optimum manner when normal. Altering one of these entities will inversely affect the other, and these are just two of many things that need to be considered when altering mechanics to enhance healing of white line or other hoof pathologies.”

If the foot requires more mobility, Steward recommended using a “taller” shoe to move the point of breakover (the moment the heel lifts off the ground) back. He cautioned that horses wearing tall shoes should be confined to smaller spaces where they can’t move at speed. Doing so can increase the pressure and forces on the collateral ligaments, potentially resulting in injury.

Steward concluded that while farriers have many shoes to choose from when treating white line disease, they should select the one that meets the individual horse’s mechanical needs. The goal is to stabilize and protect the hoof and enhance healing.