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Understanding the Phases of Laminitis in the Horse

By Adam Whitehead, Resident Farrier UFVMC

Grossly defined, laminitis is inflammation of the sensitive laminae in the hoof of the horse, caused by stressful events, trauma, infection, or parturition. This definition sheds little light on the destructive process that occurs within the hoof. Laminitis is commonly known as a secondary process and is a result of a variety of primary processes. Some of the primary causes that initiate laminitis are starch-overload, colitis, colic, diarrhea, Cushing’s disease, retained placenta, exhaustion, direct hoof trauma, excessive weight bearing on a single limb, change in diet or environment, and stressful travel. Once the laminetic process has begun it can be classified into the developmental, acute, and chronic phases.

Developmental Phase
The developmental phase typically begins with the onset of the primary process (e.g. hoof trauma or colic). Symptoms such as elevated digital pulse and warmth in the hooves are typically mild and generally present within 12-24 hours. Treatment for horses in the developmental stage of laminitis should be proactive, not reactive, and based largely on the probability of the disease occurring. Most treatment goals are aimed at eliminating the cause of the episode, preserving circulation, and providing hoof support.

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Abscess on the sole of a lamitetic horse. The PIII bone has penetrated through the solar corium (tissue between the sole and PIII bone of the foot) and has therefore pushed the sole outward in the the center of the foot.
Acute Phase
The acute stage begins with the onset of pain and lameness, typically within 24-48 hours, and lasts until the pain and lameness subsides and the horse recovers or displacement (rotation, sinking or both) of PIII (the distal phalanx) occurs. Horses in the acute phase generally exhibit common signs such as, elevated digital pulse, warm hooves and painful response at the toe to hoof testers. Loss of appetite, limited intake of fluids and the typical laminetic stance (transferring weight off of the front hooves) are also commonly observed signs. In this phase the inflammatory process is at its climax and blood supply to the digit may be severely compromised. This hypoperfusion within the digit may lead to ischemia, necrosis, and edema compromising the integrity of the laminae. sential in establishing a baseline for treatment as well as to monitor for displacement of PIII.
Aggressive treatment during the acute phase generally provides a more favorable outcome and may preserve the integrity of the laminae. Use of non-steroidal anti-inflammatory drugs (NSAID’s) such as Bute to control pain is a common practice. Treatment should also target reducing the biomechanical forces that further compromise weakened laminae. No system has been proven universally effective, yet the goals are simple. Reduce the lever arm the toe creates; apply heel elevation combined with caudal sole support and limit the horse’s activity. Radiographic examination is also essential in establishing a baseline for treatment as well as to monitor for displacement of PIII. 1
Same horse after surgery to the deep digital flexor. The foot has been de-rotated and a shoe has been glued on. A hoof wall reconstruction has also been performed.

Chronic Phase
The chronic phase begins when clinical or radiographic signs of displacement are noted. This rotation and/or sinking of PIII occur as a result of failed laminar bond, which suspends the bone within the hoof capsule. This displacement compresses the corium at the coronary band as well as under the tip of PIII, resulting further compromised perfusion, abnormal hoof function, and chronic pain. Treatment of chronic laminitis is primarily based on therapeutic trimming and shoeing, while continuing to control pain and the initial trigger. Goals of therapeutic shoeing, aided by radiographs, are to restore PIII’s orientation to the ground establishing proper boney alignment and helping to restore normal function of the hoof. Dramatically reducing the biomechanical exertion of the deep digital flexor tendon (DDFT) is paramount to successful treatment as well. These efforts allow new laminae to generate as the hoof grows, eventually providing stability to PIII. It is important, however, to note that the amount of damage incurred during the early stages is directly related to how well a horse will recover. Surgical interventions may include a deep digital flexor tenotamy on horses that exhibit progressive rotation despite interventions and/or on horses in which PIII has or is about to penetrate the sole.
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Side view radiograph of a horse that has developed laminitis. As you can see, the PIII bone has rotated and has basically penetrated through the sole of the foot. This picture is before any treatment was performed. Back view radiograph of the same horse after therapeutic shoeing and surgery were performed.


Treating laminitis at any stage can be emotionally trying for all involved. Awareness by owners, veterinarians and farriers of horses that are high risk as well as early diagnoses and treatment according to the probability the disease occurring rather than waiting for laminitis to occur may certainly provide the most favorable outcome. It is also important to recruit a vet/farrier team that keeps realistic goals in mind such as, maintaining comfort of the horse, preserving and/or restoring adequate perfusion to the hoof and reducing the biomechanical influence of the DDFT.

 

 

Adam Whitehead is the resident farrier at the University of Florida Veterinary Medical Center. Whitehead completed farrier school in Tennessee and studied animal science at Abraham Baldwin Agriculture College in Tifton, Ga. Prior to joining the UF team, Whitehead successfully practiced in the field for 10 years.

 


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