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Chuck Maker D.V.M
Chad Roeber D.V.M
Louise M. Shuman D.V.M
Martha Rideout D.V.M
Darlene Berkovitz D.V.M
Michelle Schmidt D.V.M
17776 Highway 82
Carbondale, CO 81623
Phone: 970-963-2371 Fax: 970-963-2372
Providing complete medical and surgical care for your animals needs since 1970
http://www.alpinehospital.com/
Logo and content copyright Chuck Maker 2004
Lameness diagnosis
Whether your horse competes in FEI level dressage or national working cow horse competitions,
few problems can be more worrisome as a sudden lameness of unknown origin. While a clinical
exam and hoof tester application is often all that is needed to diagnose a routine sub solar abscess,
many of today’s athletes are affected by more serious injuries. Often times with today’s equine
athlete, multiple soft tissue conditions present affecting different limbs simultaneously, thereby
confounding the diagnosis. Sequential regional anesthesia or nerve blocks and repeated gait
analysis are often required to define and “un-couple” these conditions. Once localized to a region
or regions, the imagining methods used today to define the cause of lameness range from digital Xray and ultrasound to nuclear medicine, computed tomography (CT) and magnetic resonance
imaging (MRI). Unequivocally defining the exact location and nature of your horse’s lameness
issues with advanced imaging techniques better enables veterinarians to design the best treatment
plan and quickest route back to the show ring. We devote this month’s newsletter to the region
most affected by lameness conditions in the horse-The foot.
Laminitis (founder)
Laminitis is a painful
condition characterized
by inflammation of the
laminar tissue holding
the coffin bone to the
inside of the hoof. The
term laminitis is used to
describe the sudden
onset of laminar
inflammation, while the
term founder is
commonly applied to
long-standing (chronic)
laminitis. The more
severe the laminitis is at its onset, the greater the chance for chronic
problems and recurrence.
Lameness
Diagnosis-the foot
Laminitis-the area of
greatest research need
according to AAEP
members
Sub solar
abscesses
Case of the
Month
Open House Client Educational
and Social Event-May 6th and 7th
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In normal horses, two forces influence the position of the coffin bone within the hoof: the
downward push of the horse’s body weight and the upward pull of the deep digital flexor tendon as
it attaches the sole surface of the coffin bone. In horses with laminitis, when the downward force
is greater than the upward pull of the flexor tendon, the coffin bone sinks in the hoof capsule.
More commonly, inflammation of the laminae at the dorsal surface (front side) of the coffin bone
results in downward rotation of the toe due to loss of adhesion between the hoof
capsule and the coffin bone and the backwards pull of the deep digital flexor tendon.
In addition, inflammation of the laminar tissues results in swelling and edema which increases the pressure within the rigid hoof.
This increased pressure causes further damage to the blood vessels that supply nutrition to the laminar tissue, resulting in a cycle of
damage to the laminae that are
critical to the function of the equine foot.
Clinical Signs of Laminitis:
The most obvious signs in horses undergoing acute episodes of laminitis are marked lameness, often non-weight bearing, increased
digital pulses (pulses are palpable along the back side of the
pasterns), and warm feet. Radiographs of the feet may indicate no change in the position of the coffin bone in early or less severe
cases, or more commonly indicate rotation and/or sinking of
the coffin bone in relation to the hoof capsule. Acutely laminitic horses show pain upon
application of hoof testers around the toe region of the sole and frog.
Horses with chronic laminitis or founder often have hooves with characteristic grooves along the toe, which indicate past episodes of
laminar inflammation. The toes of affected hooves do not grow as quickly as the heels grow, resulting in toes that flare upward and
tend to separate away from the sole, widening the white line area. This predisposes the foot to chronic (long-term) or
recurrent infection of the white line area (“seedy toe”) or subsolar tissues (abscess formation).
Cause of Laminitis:
Lamintis can occur with no apparent cause, but often there is some identifiable underlying cause. The underlying condition can often
be cured, but the laminitis may persist, leaving the horse with chronic founder which often requires life-long special management.
The following factors are known to contribute to the onset of laminitis:
 Imbalance of exercise or food intake. A fit (lean) athletic horse that is worked harder than usual on a hard surface can
develop “road founder”. A cresty-necked pony or horse with a propensity for being overweight, that eats too much lush
pasture grass, or that eats too much grain can develop laminitis.
 Endotoxins from illness. Certain bacteria can produce endotoxins, which damage the laminar blood vessels. Endotoxins can
be produced in such diseases as severe colic, uterine infections, diarrhea, and pneumonia.
 Cortisone release or use. Stress causes the release of the hormone, cortisone, which can result in laminitis. This stress can
be acute (over a few days) or chronic (over several weeks). Stressful situations for your horse may include training,
competition, and shipping. Any cortisone type of drug should be used only under veterinary direction, as large doses can
result in laminitis. Some older horses develop hormonal disorders that result in hormone imbalances which may predispose
a horse to laminitis (i.e. Cushing’s disease or hypothyroidism).
 Conformation or genetic predisposition. Heavy horses or ponies are more likely to develop laminitis. Also, horses with thin
or flat soles do not have as much protection of
the coffin bone.
Treatment of Acute Laminitis:
Preserving the normal hoof wall-coffin bone relationship, decreasing pain and inflammation, and preventing or minimizing recurrence
are the goals of laminitis/founder treatment. This requires prompt identification of foot-sore horses and intensive treatment of acute
episodes. Any horse with sudden onset of lameness with warm painful feet requires emergency evaluation. The majority of drugs
used to decrease laminar inflammation and improve the blood supply to the laminar tissues are most effective prior to the onset of
noticeable lameness (prodromal stage); this fact makes it difficult to identify horses while in the prodromal stage and effectively
prevent damage to the laminar tissues. Therefore, prevention is the key: identification of horses at risk for laminitis and treating any
underlying conditions before the feet become affected. Prophylactic
treatment is often used in sick horses known to be at risk for developing laminitis.
Once the horse becomes lame, there are drugs that can help prevent further damage and techniques to prevent further coffin bone
sinking or rotation. Use of vasodilating drugs are commonly used to help maintain or improve blood supply to the laminae and use of
anti-inflammatory drugs help relieve pain and laminar injury. Using Styrofoam pads, lily pads (frog
support pads), or sand stalls have been beneficial in providing support to the foot.
Management of Chronic Laminitis:
Regular foot care with frequent trimming is required for all horses with laminitis; some horses recover from an acute episode with
little or no recurrence of foot problems, the majority, however suffer from chronic foot problems that require regular attention. Some
horses can be maintained with regular trimming and dietary changes alone, other horses require special shoeing to keep them
comfortable and prevent acute laminitic episodes. Once the coffin bone has rotated, new hoof wall needs to be formed in order to
return the hoof wall-coffin bone relationship to normal. On average, it takes one year for a new hoof to grow; therefore, repeated
laminitic episodes must
be prevented during this time period.
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Dietary changes for all laminitic horses includes use of grazing muzzles for horses kept on pasture during the spring and fall seasons
and during other times when pasture grass is lush. Affected horses should not be fed concentrated feeds such as sweet feed or corn.
Grass hay is the
ideal feed for affected horses, as alfalfa hay can also precipitate laminitis in affected horses.
Horses with underlying hormonal imbalances such as Cushing’s disease or hypothyroidism should be placed on medication for such
disorders in order to minimize the likelihood of further laminitic episodes.
Hoof Abscesses
Hoof abscesses are probably the most common cause of acute lameness in horses. Foreign matter (such as gravel, dirt, sand, etc.) or
infectious agents such as bacteria or fungal elements gains entry into the hoof through a separation in the sole-wall junction (white
line). This foreign debris will migrate in the hoof to the sensitive subsolar or submural tissue leading to infection. Another common
cause of subsolar abscesses is penetration of the bottom of the foot (sole) by a sharp object. Infection may also gain entry into the foot
by way of a hoof wall crack or multiple old nail holes.
Hoof abscesses are less likely to occur with a solid sole-wall junction (white line). Conditions that cause mechanical breaks or
weakness in the continuity of the white line are hoof imbalance (long toe-underrun heel syndrome, excessive toe length, heels too
high) hoof wall separations (white line disease, seedy toe), aggressive removal of sole and chronic laminitis. Excessive moisture or
dryness may also contribute to weakness in the white line. If left untreated, the subsolar abscess will follow the path of least resistance
up the hoof wall, rupture and then form a draining tract at the coronet. This often leads to a permanent scar in the hoof wall.
Clinical Signs
Most affected horses show sudden (acute) lameness. The degree of lameness varies from subtle to non-weight bearing. The digital
pulse felt at the level of the fetlock is usually bounding and the involved foot will be warmer than the opposite foot. The site of pain
can be localized through the use of hoof testers. A small tract or fissure will commonly be observed in the white line where the pain is
noted. The wound or point of entry may not always be visible, as some areas of the foot such as the white line and frog are somewhat
elastic and wounds in these areas typically close. Sometimes pain will be noted over the entire foot with hoof testers and, in this case,
the veterinarian may want to rule out a severe bruise or a possible fracture of P3 (coffin bone)
Treatment
The object of treating a simple subsolar abscess is to open and drain the infection. The opening should be of sufficient size to allow
drainage but not so extensive as to create further damage. Establishing drainage is the most important aspect of therapy. Preferably,
this is done at the onset of lameness before the infection ruptures at the coronet. The offending tract or fissure is opened on the hoof
wall side of the white line using a 2 mm bone curette or other suitable probe. A small opening is sufficient to obtain proper drainage
and care must be taken to avoid exposing solar corium, as it will invariably prolapse through the opening and create an ongoing
source of pain. The draining tract is kept soft and drainage is enhanced by the application of an Animalintex® poultice for the first 48
hours. This is a self-contained, medicated poultice, which is commercially available through your veterinarian or tack shop. In most
cases, this eliminates the need for continued foot soaking. The horse should show marked improvement within 24 hours.
The hoof is kept bandaged with a suitable antiseptic such as Betadine® ointment or 2% iodine until all drainage has ceased and the
wound is dry. At this point, a small gauze plug is used to fill the opening of the tract and is held in place with super glue. This keeps
the affected area clean and prevents the accumulation of debris within the wound. The shoe is replaced when the horse is sound.
Many times the painful tract can be located but drainage cannot be established at the white line. In this case, the infection has
migrated under the sole away from the white line.
Under no circumstances should an opening be created in the adjacent sole. This only leads to a persistent, non-healing wound and
increased susceptibility to bone infection. Instead, a small channel should be made on the hoof wall side of the white line in a vertical
direction following the tract to the point where it courses inward. Drainage can be established here in a horizontal plane. Tetanus
immunization status of the horse should be determined. Use of systemic antibiotics is optional and based on the needs of the
individual horse.
Prevention
Prevention is achieved through proper hoof care and centers around promoting a strong, solid white line which resists penetration by
debris. Excessive toe length increases the bending force exerted on the toe, leading to a widening and weakening of the white line.
This, along with toe cracks and hoof wall separations, is the most common cause of foot abscesses.
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To prevent abscesses it is important that the foot be trimmed in a manner that accentuates a strong healthy foot. A few basic principles
can be used when trimming to create a strong foot and strengthen the white line. First, the bars of the foot are left untouched and the
heels are trimmed back toward the widest part of the frog, or as far back as possible. This allows a large amount of weight bearing to
occur in the posterior portion of the foot and not the toe area. Sole is only removed adjacent to the white line to identify excess hoof
wall to be removed. It is not necessary to concave the sole as this occurs naturally. The toe is then backed up from the dorsal surface
(front) of the hoof wall and/ or the breakover is set back accordingly. This assures that there is no excessive toe length. A good rule of
thumb to use when trimming the foot is to leave the last few rubs on the bottom of the foot. When applying shoes, fitting the shoes hot
may be helpful to seal the sole wall junction. The use of hoof hardeners (Keratix®) and bedding the horse on shavings or sawdust
may be useful to harden the feet during extremely wet weather or when the horse is being washed frequently such as during horse
shows. During dry weather, a hoof dressing such as a combination of cod liver oil and pine tar (mixed in a ratio of 3:1) painted on the
entire foot may help to contain moisture.
Preventing indirect penetration through the white line is therefore dependent on providing adequate protection to the underlying
sensitive structures. The hoof capsule has a natural ability to provide such protection and it is imperative that we strive to enhance
these strong features through proper trimming. Excessive removal of protective horn is a common practice, as emphasis is often
placed on eye appeal instead of functional strength.
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