Laminitis and founder aren’t easy concepts to understand and comprehend, but every horse owner will benefit from having a basic understanding of these conditions, and knowing how to recognize them.
Though used interchangeably among horsemen, there is a difference between laminitis and founder. Laminitis describes inflammation of the supportive tissues that join the inner foot bone — also known as the coffin bone or third pastern bone (P3) — to the hoof wall. This inner bone is suspended within the hoof capsule by tiny, highly innervated and vascular connective tissue fingers called laminae. These sensitive laminae interdigitate with corresponding insensitive laminar fingers from the hoof wall to form a strong, durable bond between the hoof wall and coffin bone, suspending the horse’s axial skeleton.
Normally, the front of the third phalanx is parallel to the hoof wall and its lower surface is roughly parallel to the ground surface. When structural integrity of the laminar connection is disrupted, separation results and movement of the coffin bone within the hoof capsule can occur. Radiographic imaging is used to identify the position of the coffin bone within the hoof capsule following laminitis. Rotation, sinking, or a combination of both rotation and sinking can occur to varying degrees.
Laminitis refers specifically to inflammation of the laminae — a very painful and debilitating condition. Any shift, sinking or displacement of the coffin bone from its normal, well-anchored position within the hoof capsule influences the horse’s way of going leading to lameness and unsoundness. This displacement or sinking of the coffin bone within the hoof capsule is known as founder.
The mechanism of laminitis remains unclear and is currently the subject of much debate and research. Its underlying cause is usually a disturbance elsewhere in the horse’s body. There are multiple triggers and can be either mechanical or systemic. Overindulgence on grains/grasses, frosted grasses, concussion, metabolic derangements, neglected hoof care, inappropriate shoeing, systemic infections, colic, supporting limb lameness, ingestion of toxins or medication intolerances are all potential inciting causes of laminitis.
The progression and consequences of laminitis is influenced by many factors, of which early recognition is key. Initially the horse will appear uneasy, shifting its weight backward in an attempt to ease its sore feet, especially in the toe region. The horse will be reluctant to move forward, gingerly shuffling its forelimbs.
As inflammation and discomfort escalate, the horse may shift its weight entirely onto its hindquarters, camping out and even choosing to lay down. Other clinical signs include increased temperature of the hoof, a bounding pulse in the digital artery, and increased vital signs. Many laminitic horses develop a characteristic sole pack as a natural aid to support the ailing hoof. The horse’s front feet are affected more commonly than the hind feet, although any hoof may be afflicted.
Early intervention is of utmost importance to minimize inflammation, separation and tearing of laminar structures. Immediate veterinary involvement is advisable to address the inciting cause(s) and relieve the driving trigger(s) for inflammation.
Cold therapy/icing is tremendously beneficial to interrupt the destructive cycle of inflammation. Mechanical support is necessary as well to aid stabilization of the internal structures of the hoof. Soft, cool ground is forgiving and supportive to the internal structures of the hoof and sole. Judicious use of analgesics is indicated. Pain relief without a means to limit the horse’s movement is controversial as unmitigated movement can cause further damage to internal structures. The laminar structures need to heal and it is of great advantage for the horse to periodically lay down, which allows healing to restore the disrupted laminae. Over the next six to 12 months, the foot will be in the process of rebuilding its internal structures.
Co-operative efforts between owner, veterinarian and farrier offer the best possible outcome. Addressing the primary problem and secondary problems such as hoof abscess, supportive footing, purposeful hoof care, and nutritional coaching are necessary to direct the horse along the path of healing.