Understanding the disease progression of abnormal hoof anatomy, Part 3

Understanding the disease progression of abnormal hoof anatomy, Part 3

Solving the mathematical needs of a Grade IV laminitic foot
Mar 01, 2012

Figure 1: A typical coronary band rupture. Note the use of a reverse wedge tenotomy trailer rail shoe.
Grade IV cases are the bad boys of laminitis. These cases can involve edema and separation of the laminar structures that surround the dorsal face of the distal phalanx (P3), with seromas that rupture through the coronary band dorsally (Figure 1), medially or laterally or penetrate the sole (solar prolapse). The final sequela is often fatal sinker syndrome with hoof capsule loss. Complications that I have seen (as if the aforementioned were not bad enough) are rupture of the distal interphalangeal (DIP) capsule, fatal emboli, P3 fractures, ankylosis of the DIP joint, gangrene and unusual infections within the hoof capsule such as botulism.


For the sake of simplicity, I divide Grade IV cases into two categories—the rotators (cranial rotation cases) and the sinkers (fatal sinker syndrome, or FSS).

All horses with Grade IV laminitis are in extreme pain. They are recumbent and rarely stand unless asked to. I have seen these horses walk in on their hind legs, rather than place weight on their forefeet. I have also watched them walk out of their hoof capsules. Grade IV cases of the forefeet will always have a degree of laminitis in the hind feet as well, so be sure to radiograph all four feet when starting your work-up.

Figure 2: A venogram of an intermittent constriction of smooth wire around a limb that resulted in a Grade IV laminitic event. The venogram shows complete absence of the dorsal and circumflex circulation.
Cases of Grade IV laminitis of the hind feet (originating there first) are rarely bilateral and are often less complicated than forefoot cases, but they can also become euthanasia cases rapidly if not taken seriously—especially if the laminitis has a supporting limb etiology. (Remember to radiograph the forefeet as well.) Horses with a fractured hind leg or severe pain of any origin are candidates for supporting limb laminitis. I have also seen smooth wire fencing become a tourniquet when wrapped around the leg during a struggle in the fence line. When the wire is placed in such a way as to allow intermittent blood flow, laminitis can be a sequela (Figure 2 and Figure 3).

Figure 3: A lateral radiograph of the limb in Figure 2 showing the separation of laminae in the dorsal and solar regions of the hoof capsule that was prognosticated by the venogram.
Grade IV laminitis has a series of pathologic events that avalanche to final cases that may be beyond salvage. The Grade IV case can present in 24 hours or five or six weeks. The usual course becomes more critical over a longer period as the structures within the hoof capsule collapse slowly. It is common to see a case "recur" five to six weeks after the acute phase, when in actuality this is simply the final stage of the original case.