Handling Non-Weight Bearing Lameness in the Field (AAEP 2012)
One of the most common calls an ambulatory equine practitioner receives is that from a panicked owner whose horse becomes three-legged lame seemingly overnight, said Ryan Penno, DVM, a practitioner at The Equine Clinic at Oakencroft, in Ravana, N.Y. Whether the cause is a simple abscess or a complex fracture, Penno described how to manage acute-onset, non-weight-bearing lameness cases during his presentation at the 2012 American Association of Equine Practitioners (AAEP) convention, held Dec. 1-5 in Anaheim, Calif.
Veterinarians regularly encounter the most common causes of such lameness--penetrating hoof injuries, subsolar hoof abscesses, cellulitis, laminitis, fractures, and soft tissue injuries--so they must feel comfortable diagnosing and treating them, said Penno.
Severe lameness cases often present as a Grade 4 ("obvious lameness with a marked nodding, hitching, or shortened stride") or 5 ("lameness produces minimal weight-bearing in motion and/or at rest, or a complete inability to move") lameness on the AAEP's five-point scale, he said.
Penno said obtaining a complete history on the horse is crucial when dealing with acute lameness; details such as prior lamenesses or recent farriery care can help narrow down differential diagnoses (conditions that cause similar clinical signs--essentially, a list of rule-outs). He also recommended observing the horse from a short distance away to gauge his attitude, apparent distress level, and respiratory status without the added stress of a veterinary examination.
Next, Penno suggested completing a "brief but thorough" physical exam. To do this, he said, the horse should be fairly clean and not wearing a blanket, as mud, dirt, and blankets can potentially hide important signs. He suggested looking for any swelling, hemorrhage, or trauma before beginning the hands-on exam. He also recommended taking the horse's temperature, pulse, and respiration rate, which can alert the veterinarian to systemic disease--especially in more stoic patients.
After the physical exam, the veterinarian can begin examining the affected limb closely. While there are certain aspects that should always be included in a lameness exam, Penno said each veterinarian will arrive at a diagnosis in his or her own manner.
"Each practitioner has his or her own procedure for performing a lameness examination, and it should be the goal of the new practitioner to develop a system that works well for him or her," he said. "No one method is superior, provided that all structures are thoroughly examined and palpated and the same procedure is followed with each subsequent case, reducing the possibility of missing a subtle lesion."
During lameness exams, Penno said, veterinarians should ensure they:
Other tools veterinarians can use after the lameness exam to reach a diagnosis include imaging and nerve blocks, he added.
Once the lameness exam is complete, the veterinarian can put his or her findings together, develop a list of differential diagnoses, and formulate a treatment plan. If the injury warrants more intensive care, veterinarians should consider referring the patient to an equine hospital or clinic. Additionally, Penno said, veterinarians shouldn't hesitate to ask for a second opinion from another practitioner if they are in doubt about anything.
Finally, he touched briefly on handling the most common causes of acute-onset, non-weight-bearing-lameness in the field.
Penetrating solar injuries generally present as peracute (very sharp) severe lameness, Penno said, in horses with no other history of lameness. In most cases, a foreign body in the foot will be evident. When called to these cases, he recommended veterinarians tell the owner not to remove the object or move the horse. If necessary, suggest they provide wooden blocks for the horse to stand on to prevent the foreign body from traveling any deeper into the hoof.
These horses generally have little to no swelling, but they often have increased digital pulses. Penno recommended veterinarians use radiographs in these cases to determine the course of the object's penetration and what internal structures have been impacted (for instance, whether a nail the horse stepped on has penetrated deeply enough to damage the coffin bone and/or joint). Additionally, he said, ultrasound might be useful for determining if the horse's digital flexor tendon sheath has been affected.
Penno said typical treatment protocol includes removing the penetrating object, paring out the object's tract through the hoof sole, and flushing the hole with saline and disinfectant. In most cases veterinarians prescribe 10-14 days of antibiotics for the horse, in addition to non-steroidal anti-inflammatory drugs (NSAIDs) and a tetanus shot. The owner should continue wrapping the foot to keep the open tract clean, and in most cases they should have the veterinarian out to check healing progress.
In more severe cases, veterinarians might use regional limb perfusion (RLP). This involves applying a tourniquet to isolate a vein that supplies blood to the lower limb, then injecting one or more antibiotics into the vein. Practitioners might also opt to refer the horse to a hospital for treatment and/or surgery, if necessary.
Subsolar hoof abscesses are generally straightforward to treat once the veterinarian locates the abscess location with hoof testers. Next, the veterinarian pares the sole to allow the abscess to drain ("The resultant fluid is typically light gray to black in color and ranges from profuse watery discharge to a thick, tarlike consistency and is often malodorous," Penno said).
Abscess treatment protocol varies among practitioners, Penno said, but the ultimate therapy goal is to drain the abscess while allowing the affected hoof structures to heal. Some common abscess treatment recommendations, he said, include:
Regardless of the treatment protocol, the owner must continue wrapping the horse's hoof to keep it clean until the wound heals.
Cellulitis--a diffuse bacterial infection of the skin and associated tissues--is common in horses, and Penno said it can be difficult to diagnose and treat. Horses often have a small wound present along with limb swelling, heat in the affected limb, significant pain on palpation, and variable lameness, he said. Cellulitis is more common in hind limbs than forelimbs, he added.
Veterinarians often diagnose cellulitis using a combination of laboratory work (including a complete blood count and serum chemistry), radiographs, ultrasound, and clinical signs, he said.
Penno said treatment often includes NSAIDs and antibiotics, along with corticosteroids. Owners should exercise affected horses; Penno recommended walking the horse for 20 to 30 minutes, two to three times daily; "Owners can walk (horses) in hand or under tack unless the severity of the lameness is prohibitive," he noted.
Horses also might benefit from the owner cold hosing the affected leg and/or applying clay poultices. Additionally, he said, compression wraps can help control limb swelling.
Penno stressed that acute-onset, non-weight-bearing lameness is, and will continue to be, one of the most common emergencies ambulatory practitioners diagnose and manage in the field. Staying abreast of new diagnostic and developments, and brushing up on treatment methods, should remain a top priority for field veterinarians
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.
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