White-Line Disease
click on images for detail

Description

The most characteristic diagnostic sign of this condition is that one heel bulb is swollen in comparison with the other. The condition is extremely painful.(click image)

On examination of the sole, the earliest sign will be hemorrhage in the white-line area. (See anatomy)

Infection moves upwards beneath the wall in a track starting from a lesion in the white line.

Structures close to the track become involved and complications will result. (click image)

Complications

• A septic arthritis of the toe joint.
• A necrotic deep flexor tendon.
• A retroarticular abscess.

(click image) at left. Claw removed to show septic track.

This disease is frequently confused with foot rot. If medical treatment does not produce improvement within a few days, the claw should be examined very carefully for a white-line lesion.

There is considerable risk that complications will get out of control.

Cause

This disease is a very common complication of sub-clinical laminitis which causes softening of the horn.

Excessive moisture underfoot will continue the softening process.

The white line contains the softest horn in the claw.

The precipitating cause of this condition is trauma.

This region (the heel) bears the first impact of locomotion. (click image)

When subjected to the pressure of weight-bearing, the digital cushion expands sideways, tearing the wall from the sole.

Treatment

All black marks in the white line should be explored to their final depth. In some cases it may be necessary to remove the overlying wall.

There is so much elastic tissue in this area that natural drainage is virtually impossible and drainage tubes must be inserted.

Once infection has penetrated into the navicular bursa (See anatomy) or a retroarticular abscess has developed, prompt surgical intervention by a veterinarian is imperative. Once this stage has been reached, disintegration of the joint and surrounding tissues is very rapid.

When one heel bulb is larger than the other, it can be assumed that a retroarticular abscess is present. A radiograph may show the presence of gas or joint infection. An arthrodesis or joint fusion can be performed by a veterinarian.

Unfortunately, these cases are not always caught at the early stage and the tendon and navicular bone become necrotic. In these cases a tendon resection can be performed.

The foregoing procedures are expensive and for this reason amputation of the affected digit is frequently recommended.

Claw trimmers must refer these cases to a veterinarian once the wound starts to bleed.

In my experience this is a frequently misdiagnosed disease. Prolonging medical treatment allows the pathology to progress to a point at which nothing but drastic surgery will bring about a resolution.

Control

If the annual incidence of this disease exceeds 5%, it must be assumed that the herd is affected with sub-clinical laminitis.

When this is the case, the nutritional status of the herd should be investigated and appropriate control measures instituted.