Management of Traumatic Injuries to the Hoof Capsule

Management of Traumatic Injuries to the Hoof Capsule Written and presented November 2005 by R.F. (Ric) Redden, DVM

Foal Injuries One of the most common injures to the foot may occur hours to days from birth. Mares occasionally step on their foal's foot while it is recumbent, often causing serious damage to the hoof capsule, soft-tissue and digit. Traumatic wall injuries demand immediate attention and thorough first-aid care.

Exam and Debride Many times the wall will be separated from the underlying laminae and sole corium. It is very important to determine the extent of damage and note if any of the germinal centers have been disrupted. The coronary papillae are of great concern, as they are responsible for tubular horn growth.

A frequently asked question is, "Should the wall be sutured back on in places where it has been pulled away?" This question has two answers. When the papillae remain inserted in the coronary groove, it is best to leave the wall. The exception is when the traumatized laminae become septic. If the papillae have been displaced from the coronary groove, it is best to remove the corresponding section of wall. Attempting to suture the wall back in place disfigures the papillae, which results in disfigured horn growth, delayed healing and the creation of a bacterial reservoir beneath the detached wall.

Radiographs are always indicated with traumatic foot injuries, as fractures are common and often very extensive. When taking radiographs, remember that a foal that is only a few hours or days old requires a very low MAS due to low foot mass and density of the bone. Creating a soft-tissue exposure chart for foals of varying ages is helpful, as over-exposure is often a common problem.

General Rules for Caring for Injured Foal FeetRemove all horn that has been detached from the dermis.Remove all bone fragmentsPreserve the coronary papillae and gently direct them downward into the natural direction normal tubules grow.Use firm but very forgiving compresses over all exposed corium to prevent exorbitant granulation.Use a mild iodine solution (less than 2%).Avoid any and all caustic agents that are often used to dry the foot.Protect the fragile vascular bed.Application of a light, short-limb cast that incorporates the foot can also be helpful. Pin casts for severely damaged feet can offer a more favorable healing environment.

Iatrogenic Wall Avulsions It is quite common to have foals that walk on their toes at birth. Most respond well to Tetracycline, bandaging, splinting and/or casting depending on the severity of the deformity, size and strength of the foal. Applying a very aggressive toe extension shoe as an aid to stretch the deep digital flexor tendon (DDF) can case catastrophic damage to immature laminae. The result is partial and/or full wall avulsions.

If this occurs, debride and bandage the exposed dermis. Protect the digit from being fully loaded by applying a pin cast. Short-limb, bi-valve casts can be easily changed and are useful once the pins are removed. The sole and laminae will cornify within days. New horn wall will grow from the coronary plexus and will totally replace the hoof wall over the course of a few months. Protecting the digit from load is the key to obtaining a functional, healthy hoof capsule. Normally, the new hoof will not be as healthy and tough as the original one, but most cases will have a good prognosis for use as brood animals.

Joint Ill Associated Avulsions Joint Ill involving the coffin joint may occur with contracted cases and go undetected in the early stages of splint and cast application. Foals apparently have a high pain threshold and often do not demonstrate an initial pain response to coffin joint sepsis. Therefore, extensive damage can occur. Damage can include PIII fractures and wall avulsions.

Septic coffin joints demand emergency treatment, as the cartilage, collateral ligament and tendon attachments can quickly lose their connections and slough, leaving the bone totally detached. The author reports having three cases that required complete removal of PIII. Two of these cases regrew a large majority of their respective coffin bones, and both patients lived to raise several foals. The remaining case presented at 17 days old with multiple fractures of PIII and a fully detached wall. Wall and the fragmented PIII were removed, and the digit was protected with a cast until the hoof capsule regrew around PII. Last contact with the patient was at age two.

Fractures Many different types of fractures have been previously described. The scope of this paper is not to describe in detail the etiology and treatment of various fractures, but to help point out the most commonly encountered fractures and useful treatment protocols.

Parietal Fractures Parietal groove fractures occur commonly in foals (AAEP 1987). The precise location and size will vary considerably. Normally, the medial wing will be the predominant site; occasionally the lateral wing will also be involved. It is not uncommon to find all four feet with fractures of various sizes. These areas were once thought to be separated ossification centers. However, the work of Dr. Andy Kaneps concluded that separated osseous bodies were in fact fractures.

The authors of this paper found that most fractures occur in foals from 4-6 months of age and when the ground is very soft due to excessive rain. Foals trimmed extremely short (which is common in the thoroughbred racing industry) also had a higher incidence of fractures than those with greater foot mass.

Using the 4-point trim to enhance foot mass and applying Keratex Hardener daily to the soles during wet weather reduced the incidence of fractures in one farm study from 80% to 4% in two consecutive sessions. Further studies with a large populous of foals are needed to prove the hypothesis that the lack of foot mass and excessive moisture act adversely on the hoof capsule causing parietal fractures.

Treatment Only a small percentage of fracture victims experience lameness. Those that do are often 4/5 lame: typical abscess lame. When very close examination with a hoof knife fails to locate a suspicious abscess area, a parietal fracture should be high on your list.

Radiographic examination confirms the fracture. A 65 degree DP view taken with a low MAS and a perpendicular film-beam relationship clearly reveals the size and location of the fracture.

Tracking the healing patterns of a number of fractures, the author found that the majority healed over the course of 6-8 months. The fractures are space-occupying lesions, as the bone fragment is displaced into the adjacent laminae. The location of the healed, displaced piece of bone is often well defined on the 65 degree DP view when the patient reaches age 2 and 3. This area is often misdiagnosed as pedalostitis. Pedalostitis has a relative homogenous pattern along the quarter margins. The healed fracture has a very distinct line of demarcation that clearly defines the location of the pressure fracture.

Some professionals advocate special shoeing as a means to treat this type of fracture. Having observed several hundred cases, the author found that all fractures healed in a 6-8 month period. Special shoes were not used on any of the observed cases.

Lameness, when observed, was only evident for a few days and was quickly alleviated with stall rest. The significance of this type of fracture remains unclear. Since it is a space occupying lesion, it may be a precursor for medial quarter bruising and subsequent quarter cracks in speed horses. More studies are indicated.

Sagital Fractures Young, maturing horses, yearlings and two-year-olds, are more susceptible to sagital fractures than older horses. A quick, hard blow to one side of the foot apparently causes this type of fracture. Horses that experience this fracture become acutely lame, 4/5 to 5/5, and can remain very lame for several days. Radiographic examination verifies the fracture. The 65 degree DP view with soft and medium penetration reveal the extent of the fracture through the palmar margin, as well as the articulation. The DP view taken with a grid is also a very informative view, as it reveals the degree of sag or step that often occurs at the articular surface.

Treatment - Surgical The lag screw technique has been described in the literature, but it has failed to offer consistent, favorable results due to sepsis and other post-surgical complications. Dr. Yukka Houttu of Finland developed a technique that was never reported. It offered a more consistent pattern of healing. Treating several dozen sagital fractures in Finnish racing standardbreds, he found the large majority healed well and returned to racing soundness. His technique involved placing a lag screw in the fragment, followed by placing the sterile wall plug back into the hoof and sealing it with Equilox. Apparently, this prevented invading organisms from entering the surgical site.

In emergency cases, elevate the palmar angle to 20 degrees to significantly reduces the pull of the DDF and prevent the distal displacement of the two fragments. Subsequently, this will also reduce the intense pain response.

Treatment - Non-Surgical The author has treated several cases using a rim shoe and a 20 degree palmar angle adjustment heel. One two-year-old thoroughbred horse treated with the Redden Modified Ultimate™ and Advanced Cushion Support™ with the breakover modified to produce a self-adjusting 20 degree palmar angle. The devise was glued on with an adhesive for a period of 90 days. The foot was radiographed and trimmed at 45-day intervals. During resets, the horse was never allowed to load the foot without the mechanical aide of the shoe. Following 90 days in the Redden Modified Ultimate™, he was shod with a rockered rail shoe (15 degree - 18 degree PA) for an additional 45 days, followed by 30 days in a flat, steel bar shoe. The fracture healed nicely with very little arthritic change. The horse remains became pasture sound within 3 months.

Athletic potential is based on the extent and location of arthritic changes. The prognosis for pasture soundness appears to be quite good based on a limited number of cases studied.

Protecting the opposing foot is always a concern. Contra-limb laminitis is often manifested within 3-6 weeks from the initial injury. Using the Modified Ultimate as a prophylactic tool can reduce the incidence of contra-limb laminitis (AAEP 2003).

Wing Fractures Fractures that involve the wings of PIII are predominantly found in the medial wing of the right front foot and the lateral wing of the left front foot of racehorses that race counterclockwise. The fracture is often quite painful for a few days, but it seldom causes the degree of pain found with an articular fracture. The majority of these fractures never heal with a complete bony union, even when given 4-5 months of stall rest. However, they apparently become non-sensitive after a few months of rest. A bar shoe that prevents excessive frog compression seems to work well as an aide for treating this type of fracture.

Speed horses at their peak are often nerved and remain in training. The efficiency of this protocol needs further study.

Articular Wing Fractures Articular fractures through the wings are quite painful and can remain very painful for several days and/or weeks. The 65 degree DP, the 65 degree 45 degree oblique, and the DP with the grid are radiographic views that clearly reveal the limits of the fracture, as well as the displacement, that is often described as a "step fracture."

Observing the characteristics of the step fracture reveals that a large segment of PIII is displaced distally when the foot is loaded. It is the hypothesis of the author that the DDF pulls the larger segment distal when the foot is loaded. The other segment is significantly smaller and has less DDF attachment; therefore it is not influenced by the pull of the tendon.

The pain response appears to be due to the grating effect of the larger segment on the smaller one. Applying a shoe that offers a minimum 20 degree palmar angle significantly reduces the DDF pull, therefore significantly reducing movement and displacement, and subsequently the pain. Using this shoeing protocol for more chronic fractures may reduce the pain response, but it is unlikely that it will correct the displacement.

Most of these fractures appear to heal radiographically in 4-6 months, but after observing several dozen post mortem cases on older horses, the author found none of them to have a solid bony union. Several of these horses apparently sustained fractures as racehorses years earlier and prior to their death as aged breeding stallions. All had a cartilaginous zone separating the fragments, as well as a large overlapping callous on the dorsal surface. This gave a radiographic perception that the fracture had healed.

Most horses that experience these fractures become athletically sound with 6-8 months of rest; 4 months stall bound and 4 months of limited exercise. Unfortunately, most sport horses will step down in class apparently due to varying degrees of arthritic changes. Nerving may be performed as a means of improving training soundness, however, sequestrum fractures have been found to be associated with articular fractures in horses that were nerved and kept in training. Septic sequestrum deep within the foot can become life threatening.

Palmar Margin Fractures Thin-soled horses turned out on frozen ground are subjected to excessive trauma to the sparsely protected coffin bone. Racehorses and other sport horses let down for the winter often have their shoes pulled for winter turnout. Their feet are vulnerable to sever bruising and rim fractures simply due to the lack of healthy sole depth. Bi-lateral bruising and or fractures along the palmar margin appear clinically much like a laminitic case; and subsequently, they are misdiagnosed as such.

Clinical Signs of Acute Lameness Unilateral versus Bilateral Many days following the initial trauma, the sole often appears soft and necrotic, and the sole corium is exposed. At first glance, this may appear as penetration of PIII, especially when the sole is exceptionally thin. It is common to find racehorses with a mere 6mm of sole that remain in training. This is far from the healthy 15mm required for adequate sole depth.

Very low MAS radiographs clearly reveal the fracture along the palmar margin. The 65 degree DP and 45 degree 65 degree DP Oblique views best reveal the extent of the fracture. Film taken for bone detail will invariably burn through the thin fractures and obscure the evidence of their existence.

Treatment Application of a hospital plate shoe prior to debridement facilitates the treatment protocol. The majority of these cases can be debrided using good sedation, as the necrotic area is normally desensitized. The small slivers of bone can often be removed without using a local block.

Once the area is debrided, apply firm pressure by packing the defect and sole with Betadine impregnated gauze to prevent excessive granulation. The treatment plate will adequately protect the sole and often provide adequate positive pressure to control bleeding in the site.

Complications are rare, and most cases will heal within 30 days. The hospital plate should be used until the sole has fully cornified. Using a pad under the shoe for another 30 days will help prevent unwarranted bruising.

Traumatic Wall Injuries Bulb, heel and wall lacerations can be very minor or quite excessive. Metal objects, glass, fence and wire are the most common causes of lacerations. Other horses can cause serious damage and injuries, too. It is important to determine the extent of the injury by performing a thorough clinical and radiographic exam.

For wall ablation injuries, the author prefers to apply a custom fit hospital plate shoe prior to debridement. Make a cardboard template of the area that needs to be protected. Mark a piece of 1/4" aluminum and cut the sole plate and extension from one solid piece. Forge them to fit over the defect. Allow a 1/8"-1/4" space between the hoof and convex cover to facilitate proper fit. This will foster pressure on the debrided area. The goal is to provide positive pressure on the laminae and granulating wound, while preventing the soft tissue from protruding past the normal anatomical limits. The tissue will cornify regardless, but the most optimum results are obtained when cornification takes place at the base of the adjoining healthy wall.

Puncture Wounds - Indirect Sepsis that invades the soft tissue is a very common problem with horses that have a hoof capsule that is not healthy. Disruptions in the normal, healthy sole/wall junction allow moisture and bacteria to enter the sensitive, and highly vascular, corium and/or laminae.

Better know as abscesses, they often cause an acute and very painful response. An abscess can be far more painful than fractures and should always be high on the list when examining an acutely lame horse. Cleaning the foot up with a rasp will most always reveal linear, dark splits in the inner horn and sole/wall junction. Many times there will be several small, dark lines. Discreet use of a hoof tester will help locate the area that is most sensitive.

Opening the track through the wall offers tremendous advantages to going through the sole. The goal is to establish drainage without exposing any sole corium. Sole corium drainage can be established using a small curette (2mm), a horseshoe nail with a small hook on the end, or a custom screwdriver with a darning needle hook tip. Using the “small hole approach” prevents corium prolapse that can be a problem for weeks. It is easier to reopen the tract, if necessary, than it is to deal with a large, sensitive polyp of sole corium. Bandage the areas with Betadine to protect it from getting debris packed into the tract. Most cases will heal is a couple days. Those that fail to heal properly will remain painful for 5-7 days and should be radiographed for potential bone involvement.

Puncture Wounds - Deep Puncture wounds involving the DDF and/or navicular bursa and bone are life threatening until proven otherwise. They should be treated as an emergency case. Evaluate the structures involved using a sterile probe, in conjunction with radiographic information.

There are several methods for treating deep wounds; each has merits and drawbacks. The general rules of thumb that have helped me with many serious cases are:

Establish drainage.Remove any and all necrotic tissue.Totally unload the DDF using an adequate hospital plate/raised heel shoe that creates a 35 degree - 40 degree PA.Treat with a broad-spectrum antibiotic until culture sensitivity has returned.Use adequate protective mechanics to prevent contra-limb laminitis in the opposing foot.Apply firm pressure to the site to prevent excessive granulation.

Extensive Heel Bulb Lacerations Wire and metal induced lacerations are often very extensive. The majority will involve the heel and lateral cartilage. In this case, thorough debridement is indicated. Deep lacerations should not be sutured due to the pooling effect. Many of these cases will heal well in a foot cast that limits motion.

Most heel bulb lacerations also disrupt the coronary groove, which causes permanent scaring and subsequently chronic quarter cracks. Athletic horses with permanent scars often require stability patches on this area to remain sound for training.

Catastrophic Lacerations Lacerations involving the majority of the vascular supply of the digit are fatal. Amputation of the digit is a viable option provided it is performed in a timely fashion, the goals and dedication of the client are clearly defined, and adequate equipment and experience compliment the procedure.

The prognosis for a reasonable quality of life is good for hind feet, while a higher-degree of risk is associated with front feet. Rim casts are a tremendous adjunct to therapy for all amputation cases. Frog implants in the granulating stump tissue have also been a tremendous aide in creating a tough stump pad. Prosthetics are used until the stump has matured. More permanent, fitted prosthetics are indicated for long-term cases.