Treat Hoof Punctures Early
- May 1, 2002
It seems like such a mild problem, a nail or splinter in the tough hoof. The solution also seems simple--take the object out, clean the foot up, give the horse some time off, and everything will be all right. For superficial hoof wounds, that's pretty much all it takes. "But a deeper puncture wound that penetrates any of the synovial structures that are underneath the frog (the coffin joint, navicular bursa, or digital sheath) or that penetrates the navicular bone or coffin bone can be difficult to treat and life-threatening," states Stephen B. Adams, DVM, MS, Dipl. ACVS, Professor of Large Animal Surgery at Purdue University.
Deep puncture wounds are marked by superficial puncture sites with deeper tissue injury, explains Claude A. Ragle, DVM, Dipl. ACVS, ABVP, Associate Professor of Large Animal Surgery at Washington State University's College of Veterinary Medicine.
"Puncture wounds of the equine foot are common and can be very serious when deep structures of the foot are involved and sepsis ensues," says Ragle. "With deep punctures, there is penetration into the deep collagenous connective tissue in the foot. This connective tissue blends with the deep digital flexor tendon, which forms the ventral (lower) border of the navicular bursa. When the dense collagenous tissue is penetrated, it becomes inflamed and subsequently collapses the puncture site and tract. With trauma to deeper structures, damaged blood supply and devitalized tissues can provide an anaerobic environment favoring the growth of clostridial (bacterial) organisms (that were introduced by the penetrating object). Deep structures within the foot can also be directly penetrated and become septic depending on the location and depth of the puncture."
Infections of the synovial structures can be painful for the horse and difficult to control. Elizabeth M. Santschi, DVM, Dipl. ACVS, Chief of Large Animal Surgery and a Clinical Associate Professor at the University of Wisconsin-Madison, explains, "These structures have to glide past each other; infection damages those sliding surfaces, resulting in friction, pain, and inflammation." The end result can be loss of use of the joint; for example, a coffin joint infection can result in serious arthritis, then loss of use of the joint, creating severe, chronic lameness.
"The same can happen with navicular bursitis; if left unmanaged, it can cause erosion of the navicular bone and the tendon that rides or slides over the navicular bone (the deep digital flexor tendon), leading to serious disease of that area and chronic pain," says Adams. In some cases, the damaged areas become so permanently painful that euthanasia is the only humane option.
Additionally, serious lameness in one leg can lead to overloading on the other leg. "If the horse starts to use the other leg excessively, the other leg bears a tremendous amount of weight, and it can break down," Adams says. "The horse can get laminitis in that other hoof, or he can have tendon breakdown, so then you're left with a horse that has only two good limbs. A horse with only two good limbs has difficulty standing, and euthanasia is often performed."
Early recognition and veterinary treatment are required for a satisfactory outcome of any hoof puncture wound, states Sarah le Jeune, DVM, an equine surgery resident in the Large Animal Clinic at the University of California, Davis. "The reason is that these wounds are very close to the ground and become soiled with urine and feces, quickly leading to infection."
The most common clinical sign of a puncture wound to the hoof is lameness. When the penetrating object remains in the hoof, it's obvious what has occurred, but often the horse steps off of the foreign object and it does not remain in the foot, leaving the owner to guess about what might have happened to cause the lameness.
While superficial wounds might cause subtle clinical signs, deeper punctures involving the synovial structures can be immediately pronounced, or initially present as a mild lameness that quickly progresses in severity as the septic processes become established.
Some horses have lameness so severe that they are non-weight-bearing, and some horses toe-walk, says Ragle. "Horses tend to hold the affected foot forward and walk asymmetrically in order to protect the injured area."
If the infection is well-established, distal limb edema, swelling, and draining can occur, Ragle says. "The affected foot may also be warmer than the contralateral foot (the opposite foot), and digital pulses in the affected foot may be increased."
Because infection can advance rapidly, the veterinarian should be summoned quickly if the owner knows the horse has stepped on a foreign object or if the horse suddenly comes up very lame, Adams urges.
There's some debate on what the owner should do while awaiting the veterinarian. Some veterinarians recommend leaving the penetrating object in the wound until the veterinarian arrives. This allows the veterinarian to take radiographs of the foot with the object in place, showing the extent of the penetration and potential involvement of important structures, explains le Jeune. (For more information, see article Quick Find #3280 at www.TheHorse.com.)
Adams suggests leaving the foreign object in the wound for the same reason, as long as the veterinarian can get there within an hour and the object is not protruding where the horse could step down and drive it in farther. Otherwise, remove the object, noting where the object entered the hoof.
However, Santschi prefers otherwise. "This has never made much sense to me. If your horse has a nail in his foot, pull it out so it doesn't go any deeper, then take a hoof knife and dig out around the spot it entered so the veterinarian can find it later. Save the nail and show us how far it went in. As long as you can find the spot, that's all we want."
Regardless, while waiting for the veterinarian, the owner should bring the horse to a clean environment with dry footing, le Jeune recommends. Being in a clean environment will reduce the risk of packing more dirt and manure into the wound. Santschi also suggests placing a bandage or regular wrap around a wound that has significant bleeding or a skin flap to protect the injury from further trauma.
Owners might wish to soak the injured foot in Epsom salts, although the benefit is minimal. Says Adams, "Soaking won't treat the injury, but it might offer minor help as long as you clean the bottom of the foot first. There's no sense in putting a foot covered with dirt and manure into a bucket of Epsom salts: That'd be like soaking the foot in a septic sewer!"
Nailing the Diagnosis
Often, it's not obvious even to the veterinarian that the horse has suffered a puncture wound. Explains Adams, "The horn of the sole is somewhat elastic and has a high water content, so the horn substance tends to close, making it very difficult to see a puncture wound."
Consequently, in the absence of a visible penetrating object, the veterinarian utilizes a variety of procedures to secure a definitive diagnosis of the cause of lameness.
First, lameness is isolated to the foot via hoof testers, pain response, and/or nerve blocks. "Once we know the pain is localized to the foot, we'll pare the foot down to nice, healthy, fresh sole and frog, remove the shoes, and look carefully for any puncture wounds," Adams says. A probe might reveal the puncture site, which might appear as a black spot or crack in the hoof.
Next, radiography determines the direction and depth of the puncture as well as changes that might have occurred.
"Knowledge of wound depth and direction are valuable in determining the possible involvement of underlying structures of the foot and to institute appropriate therapy," says Ragle. "If the foreign body is still in place upon presentation, it should be left in place and radiographs taken to assess the spatial relationship of the foreign body to the deep structures of the foot; contrast radiography may still be required to determine the true depth of penetration. Puncture tracts without a foreign body present can be radiographed following the insertion of a sterile, flexible, blunt probe or infusion of sterile contrast media into the foot."
If there are still questions regarding the involvement of the synovial structures, the veterinarian might use other imaging techniques such as magnetic resonance imaging (MRI), ultrasound, or nuclear scintigraphy. Says Ragle, "MRI, when available, can offer extremely accurate information regarding injury to the foot. Ultrasound has been used to evaluate communication of deep punctures with the navicular bursa, but the navicular bursa is difficult to image and proper interpretation is essential. Inflammation of the navicular region has also been evaluated by nuclear bone scintigraphy; however, this technique does not specifically identify septic processes."
Additionally, the veterinarian might do an arthrocentesis (surgical puncture of a joint to withdraw fluid for examination) of the coffin joint or the navicular bursa to sample and analyze fluid from these structures for evidence of infection, says Adams.
Tending to wounds that don't involve critical structures is fairly straightforward--the veterinarian will use aseptic cleaning, lavage, and debridement. A culture might be performed to help direct antimicrobial selection.
"The veterinarian should administer a tetanus shot to make sure the horse is protected against tetanus, open the wound so it can drain, and apply some sort of protection to the foot so debris, moisture, urine, and feces from the ground can't enter the wound," Adams states.
Protective devices can include a very simple bandage secured with duct tape, a protective rubber boot worn over a wrapped foot, or a hospital plate (a shoe with a full solid pad or plate underneath it to protect the bottom of the foot).
"The plate can be taken off easily," explains Adams. "There are usually screws that release the plate from the shoe so the veterinarian can examine the wound, treat it, perhaps pack it with ointment or an antiseptic, then put the plate back on."
Many veterinarians use systemic antibiotics for minor puncture wounds. "There is a little controversy about whether or not antibiotics help or not," Adams says. "It usually doesn't hurt."
With breached synovial (joint or tendon) structures, early and aggressive intervention is critical for recovery. Failure to do so could result in permanent lameness or breakdown of the other leg. Says Santschi, "If I see these wounds quickly before bacteria has damaged those critical structures, I can usually deal the bacteria a serious blow, right now. But there's nothing I can do about damage that happened before I saw the horse."
Adds Ragle, "A multitude of conditions may result from a deep puncture wound to the foot as a result of any lag-time allowing colonization of bacteria, tissue destruction, and movement of infection between synovial cavities. Due to the close proximity of the structures, damage may be simultaneously induced or infection may extend through tissue planes."
Septic navicular bursitis can occur within hours. Infection can destroy fibrocartilage on the flexor surface of the bone, leading to destruction of the subchondral bone and infective osteomyelitis (inflammatory bone disease marked by local death and separation of tissue) that, in turn, can extend into the distal interphalangeal (coffin) joint. Infection and inflammation that extends into the coffin joint and flexor tendon sheath can result in septic arthritis and tenosynovitis, respectively. Tendon rupture, dislocation of the distal interphalangeal (coffin) joint, fracture of the navicular bone and/or distal phalanx, and laminitis in the contralateral foot can also occur secondarily to deep punctures of the foot.
Wounds involving the navicular bursa or deep structures often require surgery at a veterinary hospital with the horse under general anesthesia in order to create proper drainage, flush the wound, and debride dead tissue. Says Adams, "We do this by arthroscopy or with a classic procedure known as a street-nail operation, which is basically cutting a window out of the frog and flexor tendon and going right into the navicular bursa to establish drainage. Arthroscopy allows you to go into the navicular bursa, clean it up, flush it, then inject antibiotics in there without creating a big hole in the bottom of the foot."
If the bone is involved, it should be curetted (surgically scraped or cleaned) and all necrotic tissue should be removed since it can harbor infection, le Jeune says. Some surgeons advocate packing the defect with a bone graft to promote wound healing.
Additionally, these horses often are placed on a regimen of systemic antibiotics and intravenous regional perfusion (pumping of fluid and antibiotics into the area).
"This procedure really makes a big difference in treating infections," says Santschi. "We instill antibiotics directly into a vein in the horse's leg and apply a tourniquet for a period to confine the antibiotics to that area. This procedure delivers higher levels of antibiotics into areas that might not be well infused because of inflammation damage."
After surgery, the wound is packed with antibiotics and wrapped in a waterproof bandage or covered with a treatment plate shoe, says Ragle. (Santschi prefers a short foot cast to a treatment plate.) "Phenylbutazone is administered to decrease inflammation and pain and to reduce the risk of laminitis developing in the contralateral foot. Fresh bandages should be applied daily or more frequently as determined by the amount of fluid discharge."
Prognosis for full recovery for minor hoof involvement is about 95%, says Adams. "With a simple puncture wound that didn't breach critical areas, often the horse can be put back into work within five to seven days."
For wounds that penetrate the synovial structures, the outlook is less cheery, generally ranging from fair to guarded depending on how quickly treatment is initiated. Convalescence for serious involvement can extend up to 12 months, says le Jeune.
With so much riding on an accurate diagnosis and prompt treatment, lameness that progresses or does not resolve quickly should be given serious and timely veterinary attention.
A simple nail in the foot might not be so simple after all.
According to various studies, reports Claude A. Ragle, DVM, Dipl. ACVS, Dipl. ABVP, Associate Professor of Large Animal Surgery in the College of Veterinary Medicine at Washington State University, soundness following puncture wounds in various scenarios was seen in the following percentages:
- 93% success in horses referred less than one week following initial injury;
- 62% success in horses referred more than seven days, but less than 30 days following the initial injury;
- 95% success in horses with hoof penetration outside the frog region;
- 50% success in horses with a deep puncture through the frog;
- 31.6% success in horses with punctures of the navicular bursa;
- 7% success in horses suffering from subluxation of the distal interphalangeal joint;
- Those with septic arthritis of the distal interphalangeal joint were reported as "frequently euthanized."--Marcia King
About the Author
Marcia King is an award-winning freelance writer based in Ohio who specializes in equine, canine, and feline veterinary topics. She's schooled in hunt seat, dressage, and Western pleasure.
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