Ted S Stashak, DVM, MS, Diplomate ACVS, Professor Emeritus Surgery, Colorado State University

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1 4. Avulsion and penetrating injuries of the foot Ted S Stashak, DVM, MS, Diplomate ACVS, Professor Emeritus Surgery, Colorado State University Avulsion injuries Avulsion of the foot region is a relatively uncommon injury that may seriously limit function and in some cases euthanasia may be advised. The avulsion may be complete where the tissue is totally removed or incomplete where a border remains intact. It may involve the hoof wall, the coronary band, the pastern region, sole and structures deep to the hoof capsule (e.g., distal phalanx). Generally, the deeper the avulsion and the more complete it is, the more serious the injury. However, even with significant loss of germinal tissue, the foot has the capacity to heal, although slower than other tissues, with complete reformation of hoof wall structures if treated properly for a long enough period. Since the foot region has limited ability for wound contraction, the wound heals primarily by epithelialization and reformation of the corium. These processes require a healthy bed of granulation tissue and a stable clean environment to reach in ideal conclusion. If the granulation tissue remains infected and becomes fibrous or excessive motion is present, a permanent hoof defect may remain. In some cases, improved healing can be achieved in older wounds by periodically debriding the granulation surface, which stimulates new capillary formation. If proper wound care follows, some of these older wounds will go on to heal completely. Although avulsion injuries of the coronary region, complete or incomplete, may result in deformities and/or permanent hoof wall defects, if treated properly initially the majority heal without problems. If a horny spur develops as a result of complete avulsion or from partial avulsion, it usually remains painful until surgical treatment is employed. Neither partial loss of the distal phalanx or digital cushion or collateral cartilages appears to be a serious detriment to future soundness. Involvement of the deep digital flexor tendon, although serious, can result in pasture soundness and in some cases riding soundness if treatment is not delayed. On the other hand, treatment delay often results in degenerative changes within the tendon and necrotic tendinitis may follow. Infection naturally accelerates this degeneration process and duly alters the prognosis. Other complications that may arise from these injuries include osteomyelitis, septic arthritis, and fracture of the distal phalanx. Even if these complications are not present, the horse may remain permanently lame simply due to the volume of tissue loss. Although the time required for healing depends on the size and extent of the avulsion injury and the method of treatment, generally three to five months are needed for healing of a complete avulsion, whereas incomplete avulsions that are reconstructed surgically usually heal in three to four weeks. Even when healing is complete, soundness may not be appreciated for many months and in some cases a year may be required. Because the duration to final outcome is so long, it is difficult to prognosticate on many of these cases at the onset of treatment.

2 2 Etiology Incomplete avulsion of the hoof wall of the heel can be caused by vertical tears of the hoof wall, infection and subsequent separation between the epidermal and dermal laminae, kicking or stepping on sharp objects, continued foot imbalance and improper shoe removal where nails are torn out of the heel and quarter regions. Other avulsions of the foot and pastern region are usually caused by laceration from sharp objects. The horse either steps on, kicks at, or the foot becomes entrapped, resulting in the avulsion. Clinical signs and diagnosis The degree of lameness usually varies with the duration, extent and location of the avulsion injury. Excessive contamination due to the foot's distal location may result in infection if proper treatment is not employed. Moderate lameness is usually seen with the acute superficial injury that does not involve deeper vital structures. However, palpation may cause considerable pain and render the animal nonweightbearing. More extensive avulsion injuries usually cause nonweightbearing lameness. If the injury involves the digital vessels, hemorrhage may be excessive, resulting in shock. Gentle manipulation of the foot and phalanges can provide important information regarding the status of support structures. Where laxity and instability of a joint indicate loss of collateral ligament support, a sucking noise may indicate an open joint. More discriminate palpation is performed after the region has been cleaned and antiseptically prepared. For the chronic avulsion injury, varying degrees of lameness will be seen. If the wound is healing without problems, lameness usually subsides with time. However, if lameness is persistent, look for the cause. This often requires radiographic examination and in some cases ultrasound examination may be helpful to assess soft tissue involvement. If a portion of the wound remains unhealed and drainage is present or historically drainage or pus is seen periodically, infection deep to the site is most likely the problem. Although the diagnosis of avulsion injury is straightforward, the involvement of deeper structures should be identified. Prior to a more complete examination of the injury, the hair is clipped from the surrounding wound and the wound and surrounding tissue are cleaned with an antiseptic scrub after which they are rinsed with a mild antiseptic sterile salt solution. If the avulsion extends to the sole, the sole may be trimmed and cleaned in a similar fashion. Loose pieces of dead tissue and debris are removed during this cleaning process. Once complete, the wound is palpated. Further manipulation of the foot and phalanges at this time may be helpful to identify an open synovial structure, torn support structure, or a potential fracture of the distal phalanx (Fig 1). A sterile probe can be used for palpation of a small opening. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 2 EM EQUINOS VETNIL & PÓS EQUINOS

3 3 Fig 1 Left, incomplete avulsion injury that extends from the coronary band to the collateral sulci. Right, indicates instability of the avulsed hoof wall. Radiographic examination Since fracture of the distal and middle phalanges may accompany these injuries, radiographic examination should be performed on all cases where deep avulsion injuries are present (fig 1) or where draining tracts have developed during the healing process (Fig 2). Additionally, contrast radiographic studies of draining tracts may be helpful in identifying openings in synovial structures. Fig 2 DP radiograph of the horse in Fig 1 identifying a P3 fracture. Treatment Incomplete avulsion (coronary band not involved) Incomplete avulsion of the hoof wall at the heel and quarter without involvement of the coronary band can be managed either with the horse standing for limited involvement or in recumbency under general anesthesia for a larger avulsion. Although a sharp hoof knife and nippers can be used to excise these undermined regions, I prefer to use a hand-held electric drill to burr the hoof wall at its attachments. Using this method allows a more discrete removal of the hoof wall without tearing of healthy hoof wall from the dermal laminae. Care should be taken when using a hoof knife or nippers not to tear healthy tissues. Additionally, the burring procedure allows the surgeon to superficially debride the infected underlying tissues. The dorsal attachment of the unaffected hoof wall can be beveled flush to the wound so there is little tendency for it to be snagged resulting in further separation. All crevices within the wound are debrided including the fracture until only healthy tissue remains (fig 3). After debridement is completed, the wound is lavaged with a mild antiseptic sterile salt solution delivered under pressure to achieve at least 7 PSI. Following this, an antiseptic or antibiotic dressing is applied to the wound, which is protected by a sterile bandage. Bandages are changes at two to four day intervals at which time the wound is cleaned, re-treated and protected in a similar fashion. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 3 EM EQUINOS VETNIL & PÓS EQUINOS

4 4 Alternatively, a rubber or plastic boot can be used instead of a bandage. Sterile dressings are still applied to the wound surface. Protection from contamination and the application of antiseptics and antibiotics are continued until exposed tissues become keratinized. After this, a full support shoe (egg-bar, heart-bar shoe) is applied to provide hoof wall stability and a hoof acrylic can be used to fill the deficit until the hoof wall grows to approximate the solar margin. Fig 3 Debridement of hoof avulsion with fracture of P3 illustrated in Fig 1 & 2. Notes: Incomplete avulsion (coronary band involved) Incomplete avulsion of the coronary band alone or coronary band and hoof wall is generally best managed by suture, although in some cases loss of blood supply will require excision of the separated tissue, thus converting it to a complete avulsion. The treatment for this latter situation will be covered under complete avulsion. The acute incomplete avulsion injury of the coronary band and a small portion of the hoof wall may be treated acutely if a good blood supply exists. The hoof wall adjacent to the defect is thinned with a hoof rasp and a separated piece of hoof wall is thinned with a motorized burr to allow suturing. After debridement and cleansing, sutures of 0 or1 monofilament nylon are placed through the hoof wall into the separated horn in an interrupted vertical mattress pattern to appose them after which the coronary band and tissues in the pastern region are apposed with a #2-0 monofilament nylon using an interrupted vertical mattress suture pattern (Fig 4). If the blood supply is questionable or excessive contamination exists, delayed primary closure may be selected. Usually, granulation tissue will have to be removed before the tissues are sutured. If left untreated, these incomplete avulsion injuries of the coronary band remain elevated, eventually producing a horny spur at the distal extremity of the avulsion while the remaining underlying tissue heals by scarring and epithelialization. Invariably these avulsions protrude above the skin and hoof wall surface, making them susceptible to further trauma and generally they are quite painful to palpation. If the avulsed tissue is removed, a hoof wall defect may remain. Therefore, surgical reconstruction is recommended. After thinning the hoof wall adjacent to the defect, the horny spur is contoured and thinned with a hand-held electrical drill and burr until it will fit into the hoof wall defect. Scarred tissue is then excised (debulked) from underneath the avulsed skin flap and within the wound so the flap will lay flat. A thin (1.5 mm) piece of skin is removed from all edges of the wound before suturing. Suture apposition is as previously described. If the coronary band has been destroyed making it difficult to identify, yet proliferative hoof continues to be produced that causes pain and lameness, the proliferative hoof can be completely excised. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 4 EM EQUINOS VETNIL & PÓS EQUINOS

5 5 Often this results in a granulating wound proximal to the coronary band that can be skin grafted at an appropriate time. Fig 4 Illustrates repair of an incomplete avulsion injury of the cornet band. The granulation tissue is removed before the reconstruction is begun. When the avulsion injury extends from the solar surface proximad through the coronet, the majority of the hoof wall is removed to within 1 cm of the coronary region and the coronary band and soft tissues are sutured. Accurate approximation of the coronary band is important. If the entire avulsion injury is sutured (fig 5 left & center), a semi-occlusive dressing is applied to the wound and held in place with elastic gauze. If an open wound remains, a topical antiseptic or antibiotic is applied prior to wound dressing. A foot pastern cast is then applied for two to three weeks after which bandages are maintained up to six weeks postoperatively (fig 5 right). Generally, systemic antibiotics are not required unless question exists regarding the blood supply or the cleanliness of surgery. In cases where a portion of the hoof wall was excised, a full support shoe should be applied to provide stability. This is done shortly after the cast is removed. Acrylic can be used when complete keratinization of the entire wound is complete. Fig 5 Notes: Complete avulsion Complete avulsion injury of the hoof, including some tissues in the pastern region, may be managed by bandaging alone if the injury site does not appear unstable during movement. If the wound is unstable and/or a large defect is present, a foot pastern cast is recommended as soon as you are sure that infection will not be a problem (fig 5 right). Casts are usually left in place for two to three weeks. In some cases, two to three cast changes will be required before the wound is completely healed. The more stable these wounds remain, the better the chance a complete III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 5 EM EQUINOS VETNIL & PÓS EQUINOS

6 6 reformation of the hoof wall will occur. For the acute injury involving deeper structures, the decision for cast application should be delayed until such time you are assured infection is not going to be a problem and a good blood supply exists. Debridement is important, including necrotic lacerated cartilage and of the distal phalanx if it has been involved and appears abnormal. All soft tissues and support structures should be assessed. If the injury has entered a synovial cavity, adequate drainage should be afforded and broad-spectrum antibiotics administered systemically. The injury should be protected in a sterile bandage until healthy tissue is formed. At this time, a cast can be applied. If the wound is chronic and already infected, cast application should be delayed until the infection is under control. Bandages are changed as often as necessary during this period. Additionally, periodic debridement of the wound, particularly if dense fibrogranuloma or dense scar has formed within the wound, can be helpful in restimulating the healing process. Occasionally, a chronic complete avulsion injury of the foot will develop into a keratomatous growth that extends proximad to the hoof wall. This horny spur often irritates the pastern region during movement. In these, periodic removal of the horn may render the horse pain free. However, they can be treated by surgical excision of the horny growth and reapposition of adjacent soft tissue after they have been mobilized by undermining. A cast is applied for two to three weeks, after which bandages are recommended for at least six weeks. Fig 6 A keratoma growth following an incomplete Avulsion injury Generally, incomplete superficial avulsion injuries of the hoof wall alone and/or including the coronary band if they are sutured will result in a functional and in many cases cosmetic end result. Prognosis for deeper avulsion injuries may have to be withheld until complete healing has occurred. Complications such as fracture of the distal phalanx, osteomyelitis, septic arthritis and potential DJD of a damaged pastern joint and their implications in the prognosis should be discussed with the client at the onset of treatment. Penetrating wounds Penetrating wounds of the foot are commonly seen in equine practice. The injury is often sustained by the horse stepping on (bottom of foot) or contacting (cornet band) a sharp object. Although any deep puncture wound of the foot can be potentially serious, those that penetrate the frog region or coronary band and involve vital structures (deep digital flexor tendon and/or digital sheaths, navicular bone and/or bursa, and the distal interphalangeal [coffin] joint) can be life threatening. Early identification of the involvement of a vital structure, aggressive medical treatment, and early surgical intervention have much to do with the success of the outcome. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 6 EM EQUINOS VETNIL & PÓS EQUINOS

7 7 Clinical signs and diagnosis The clinical signs may vary depending on the depth (superficial vs. deep), location of the injury (sole vs. coronary band), and the chronicity of the injury. Where superficial wounds that do not penetrate the dermis may be asymptomatic for a few days until a subsolar abscess develops, deep wounds involving the dermal lamina generally result in acute localizing signs of lameness. Also, wounds in the central frog region that involve vital structures usually become rapidly symptomatic. Horses are often seen pointing the foot and when walking, selective weightbearing (landing on the toe if the heel region is involved) may be seen before inflammation and infection become widespread. Careful examination of the sole (visual, hoof tester and probing) and coronary band is important (fig 1). One study suggested that any penetrating wound of the foot deeper than 1 cm should be considered serious. The approximate depth of a perpendicular penetration before vital structures become involved is: sole, 1 cm; frog, 1.5 cm; and hoof wall, 1.2 cm. Fig 1 Notes: If a foreign body is present in the bottom of the foot, it should be left in place while a radiograph is taken, however care is taken so it is not driven deeper into tissue. A contrast study may follow (fig 2) Fig 2 Notes: If a wound is not obvious, careful application of hoof testers may be helpful in identifying focal pain which in turn may indicate a site of penetration. If the sole is thick and firm, trimming may have to precede hoof tester examination. Once a focal site of pain is found in the sole or frog, it is then pared with a hoof knife. If the injury is acute (before infection) and involves the sole, all that may be seen is a crack or small hole. Wounds that penetrate the frog can be particularly difficult to identify because the tissues being softer and more elastic than the sole tend to collapse and fill in the tract. More complete paring of the frog is required in some cases to visualize a tract. Sterile probing of the tract can be helpful to identify depth and direction of the injury. Care, however, should be taken not to push the probe deeper than the depth of the III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 7 EM EQUINOS VETNIL & PÓS EQUINOS

8 8 wound. While the probe is in place, a radiograph can be taken. If infection is present but localized, paring of the sole and frog to thin them may allow pus to drain from a puncture site. Occasionally, gentle pressure with the thumbs or hoof testers may be required to visualize the pus (fig 3). Additionally, walking the horse after the sole is pared may cause sufficient pressure that a subsolar abscess may begin to drain. This approach is generally of little benefit if the frog and/or white line are involved. In these cases gentle sterile probing of the tract may be helpful. Once the infection becomes diffuse (e.g., subsolar abscess), hoof tester examination is generally less beneficial in identifying the site of penetration. Careful paring of the sole and probing of the tract (e.g., dark spots or cracks) may be most helpful. Fig 3 Left, A small hole was seen at the apex of the frog. Right hoof tester pressure resulted in puss being exuded from the hole. Palpation of the coronary band for heat, pain and swelling may also be helpful in identifying the location of a penetrating wound to the white line and coronary band. A penetrating wound of the coronary band can be overlooked if the hair is long or if local swelling and wound drainage is not present. Heat, pain and swelling of one heel bulb and a pounding digital pulse may indicate migration of a subsolar abscess (fig 1 right). Swelling of the digital sheaths and distal interphalangeal joint may indicate a septic arthritis. If infection is suspected, a sample of synovial fluid should be taken for analysis. An elevated white blood cell count (> 30,000) with neutrophilia, a ph below 6.9 and elevated protein (> 4.0 gm/dl) are highly suggestive of a septic process. Radiographic examination can be helpful in identifying involvement of vital structures. While a radiograph with a sterile probe placed in a tract or with a foreign body in place may provide important information regarding depth and direction of the injury, this approach is limited in its ability to identify an abscess cavity or extension of the injury into a synovial structure. A fistulogram in these cases is most often definitive (fig 4). Fig 4 Left probe in place. Right contrast study indicating involment of the digital sheath. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 8 EM EQUINOS VETNIL & PÓS EQUINOS

9 9 Although a fracture of the phalanx or navicular bone can often be identified shortly after injury, bone changes secondary to infection and inflammation are often not observed for a period of two to three weeks after injury. Radiographic changes consistent with septic osteitis of the distal phalanx include: bone lysis, irregular margins, and increased vascular channel size. Treatment Treatment of penetrating wounds that do not involve bone, tendon or synovial structures is generally uncomplicated. Effective treatment involves providing adequate drainage, removal of infected and necrotic tissues and the protection of the site from contamination. The majority of cases can be treated while the horse is standing. While small local abscesses can be debrided effectively without perineural anesthesia, more extensive infection usually requires perineural anesthesia of the digital nerves at the base of the sesamoid bones and of course, more extensive debridement. Drainage is established by removal of the undermined sole with a sharp hoof knife and/or a hoof groover. Underlying necrotic/infected tissue can be removed with the aid of a standard curette or a nail hole curette. For the superficial localized infection, antiseptic dressing and protection is usually all that is needed. Tetanus toxoid should be administered. For more extensive infections, local periodic flushing with a sterile polyionic salt antiseptic solution and foot protection may be required. Although hyperosmotic treatment with foot soaks or topical application to draw out infection are commonly used, the value of this approach is yet to be clearly identified. Therefore, the use of this treatment is by personal choice. Protection of the foot is accomplished with bandages, bandages with duct tape, bandages with an easy boot and in some cases a treatment plate. Generally, the use of broad-spectrum antimicrobial agents is relegated for those cases of extensive involvement and they are used until healthy granulation tissue develops. Nonsteroidal anti-inflammatory drugs are also often used at low doses and only as needed. Astringents such as 2% formalin, 2% phenol, or 7% or half strength tincture of iodine can be applied to the wound as a drying agent after the exudation process has subsided and mature granulation tissue fills the wound. Horses with resolving lesions may be shod with pads. Penetrating wounds that enter bone or synovial structures should be treated promptly. Broad-spectrum antibiotics, nonsteroidal anti-inflammatory drugs and tetanus prophylaxis are indicated. Immediate debridement is recommended. Unfortunately, many horses are presented after infection has become established. Superficial curettage and local flushing of a deep wound is generally unsuccessful. For proper treatment, general anesthesia is usually required and the hoof and sole should be prepared by trimming and rasping and a standard surgical preparation is performed. A tourniquet is placed at the midcannon bone region to reduce bleeding. Wounds that penetrate the distal phalanx should be opened and the distal phalanx curetted until healthy bone is visualized. If osteomyelitis is established, or a sequestrum is present, it should be surgically treated in the same fashion with the exception that a culture and sensitivity are taken. It is reported that up to 24% of the distal phalanx can be removed and function of the foot can be normal. Wounds that penetrate the navicular region should be carefully dissected to their depth. If the navicular bursa has been penetrated, a "street nail" operation is performed by creating a III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 9 EM EQUINOS VETNIL & PÓS EQUINOS

10 10 window into the deep digital flexor tendon (fig 5). Alternatively an arthroscope can be used (fig 5 right). Fig 5 Left, Street nail procedure. Center, palmar view of DDFT. Right arthroscope placement. Additionally, medullary or intravascular perfusion can be done (fig 6). The antimicrobial (usually an aminoglycoside > 1gm) is diluted in 55 ml of sterile solution and injected over a ten minute time period. This increases the antibiotic levels in the osteomyelitic bone and infected synovial cavity. In all cases, systemic broad-spectrum antimicrobials should be used until the results of culture and sensitivity are available. The choice of broad-spectrum antibiotics should be guided by Gram stain and culture and sensitivity. Penicillin and aminoglycoside combination is a good selection while awaiting culture and sensitivity analysis. Fig 6 Intravascular perfusion. A tourniquet is applied and a catheter is placed in the palmar digital vein. If a communication between the distal interphalangeal joint and navicular bursa exists, 1-2 liters sterile polyionic fluid followed with 1 liter of 10% DMSO solution should be flushed through the joint. Intrasynovial injection of a broad-spectrum antimicrobial is also appropriate. If the infection is chronic and osteomyelitis of the navicular bone is present, curettage to healthy bone is indicated. Although packing the curetted navicular bone with cancellous grafts or methyl methacrylate have been used, too few cases have been done to make strong recommendation for this approach. However, antibiotic impregnated polymethyl methacrylate (AI PMMA) beads can be packed in the wound for short-term postoperative treatment. The beads are removed and replaced at bandage changes and are used until a healthy bed of granulation tissue develops and all evidence of infection is gone. The AI PMMA allows the antibiotic to elute out providing a high concentration of antibiotic locally. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 10 EM EQUINOS VETNIL & PÓS EQUINOS

11 11 Penetrating wounds of the coronary band can be managed in a similar fashion as just described. There is often a separation in the coronary band at the puncture site. Curved hemostats or a probe can be used to explore and palpate the wound. Since these wounds are commonly caused by a stob of wood that penetrates the cornet and breaks off, it may be removed with hemostats. Following the removal of the object the wound is debrided and flushed with a dilute antiseptic. The wound is then packed with an antiseptic soaked gauze or an antimicrobial dressing (fig 7). Importantly, penetration of a synovial structure (coffin joint most commonly) must be ruled out. This is done by placing a needle in a site in the synovial structure remote to the injury (a synovial fluid sample can be obtained for cytology and culture), after which sterile fluid is injected with pressure. Fluid coming from the wound indicates the synovial cavity was entered. Radiographs should be taken and, in some cases, a contrast study is done. Fig 7 Right forceps are being used to remove A piece of wood. Left the wound is being packed with gauze. Generally, a good prognosis can be expected for deep puncture wounds that do not involve vital structures and a poor prognosis is expected for those that involve vital structures that have not been treated early and aggressively. In a retrospective study of 50 cases with deep puncture wounds of the foot, 95% (21/22 cases) with deep puncture wounds outside the frog or frog sulci regained full athletic soundness. In the same study, only 50% (14/28 cases) of horses receiving deep puncture wounds in the frog region fully recovered from the injury. However, of the horses that were operated within a few days after injury to the frog region, 80% (4/5 cases) returned to full function. In another study on horses with puncture wounds into the navicular bursa, 32% (12/38 cases) were able to return satisfactorily to function. The most common reason for failure is osteomyelitis of the navicular bone, rupture of the deep digital flexor tendon and septic arthritis of the distal interphalangeal joint. An improved outcome is seen in horses sustaining puncture wounds of the navicular region if they are operated within a few days after injury. Follow-up on 9 cases with septic osteitis revealed that 7/9 horses returned to intended use within 12 weeks after surgery. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 11 EM EQUINOS VETNIL & PÓS EQUINOS

12 12 Selected references 1. DeBowes RM, Yovich JV: Penetrating wounds, abscesses, gravel, and bruising of the equine foot. Vet Clin North Am: Equine Pract, 1989, 5: Gaughan EM, Rendano VT, Ducharme NG: Surgical treatment of septic pedal osteitis in horses: Nine cases ( ). J Am Vet Med Assoc, 1989, 195: Honnas CM, et al: Surgical management of difficult foot problems in the horse: Current concepts. Proc AAEP, 1988, 34: Markel MD, Richardson GL, Peterson PR, Meagher DM: Surgical reconstruction of chronic coronary band avulsion in three horses. J Am Vet Med Assoc, 1987, 190: Pascoe JR: Difficult foot wounds. Proc, Bain Fallon Memorial Lecture, 1990, 12: Richardson GL, O Brien TR: Puncture wounds into the navicular bursa of the horse: Role of radiographic evaluation. Vet Radiol, 1985, 26: Richardson GL, O Brien TR, Pascoe JR, et al: Puncture wounds of the navicular bursa in 38 horses: A retrospective study. Vet Surg, 1986, 15: Richardson GL, Pascoe JR, Meagher D: Puncture wounds of the foot in horses: Diagnosis and treatment. Compend Contin Educ: Pract Vet, 1986, 8:S Stashak TS: Management of lacerations and avulsion injuries of the foot and pastern region and hoof wall cracks. Vet Clin North Am: Equine Pract, 1989, 5: Steckel RR, Fessler JF, Huston LC: Deep puncture wounds of the equine hoof: A review of 50 cases. Proc 35 th Annual Meeting AAEP, 1989, in press. 11. Young J: Hoof wall avulsion: Three case reports. J Equine Vet Sci, 1988, 8:420. III SIMPÓSIO INTERNACIONAL DE ATUALIZAÇÃO 12 EM EQUINOS VETNIL & PÓS EQUINOS