www.ivis.org Proceeding of the SEVC Southern European Veterinary Conference Oct. 17-19, 2008 Barcelona, Spain http://www.sevc.info Reprinted in the IVIS website with the permission of the SEVC www.ivis.org
Equine How I Treat... Puncture Wounds to the Sole of the Foot: Street Nail Procedure Etiology Dr. A. Fürst DECVS - Facultad Vetsuisse, Universidad de Zurich "Nail prick" refers to injury caused by inadvertently driving a nail through the horn and into the sensitive laminae during shoeing. Nail tread refers to puncture of the solar surface of the hoof by nails or other sharp objects such as screws or other sharp things. Nail bind occurs when a horseshoe nail is driven too deep into the horn, causing excessive pressure on the corium. All three types of injuries may result in pain, inflammation and infection. Although puncture wounds of the sole appear small (Fig. 1), they are often deep and can be disastrous when structures such as the third phalanx, navicular bone, joints, bursae, tendons or tendon sheaths are injured (Fig. 2). As well, the penetrating object is usually dirty, which may result in serious infection. The superficial wound in the sole usually heals quickly, leaving no area for drainage. The anaerobic environment created favors the growth of Clostridium tetani, the agent causing tetanus. The hoof structures affected depend on the location and depth of the puncture wound and require complicated techniques such as radiography and synoviocentesis(richardson and O'Brien, 1985; Gibson et al., 1990) for diagnosis. Deep puncture wounds are extremely serious and difficult to treat; affected horses are often referred to specialized clinics for surgical therapy. For these reasons, deep puncture wounds must be treated as an emergency to prevent the infection of bones, joints and tendon sheaths.
Fig. 1 Puncture wound Fig. 2 Schematic drawing Diagnosis Horses usually have a moderate to severe supporting-leg lameness with toe-pointing, in which the horse rests the affected limb on the toe. The hoof is warmer than normal, and there is increased pulsation of the digital arteries. The horse may have a fever. Examination with hoof testers usually elicits severe pain. In horses with severe acute lameness, the hoof must be thoroughly cleaned and
examined for a foreign body or puncture wound (Fig. 1). Treatment and Aftercare The nail or foreign body should be promptly removed. However, it is imperative that the depth and direction of the tract be noted, and the point of entry marked on the sole or recorded on paper because it will rapidly become inapparent. The point of entry is cleaned, and the entire hoof bandaged. Based on the location, direction and depth of the injury, the horse may be treated on site or referred. When there is suspicion of injury to deeper structures such as the navicular bursa, distal interphalangeal joint or the deep digital flexor tendon sheath the horse must be referred immediately for surgical treatment. Broadspectrum antibiotics are started and tetanus antitoxin/toxoid administered. Treatment in a clinic A thorough clinical examination is carried out, after which local anesthesia is performed. The shoe is removed and the entire hoof trimmed (Fig. 1). The puncture tract is carefully cleaned and disinfected. A metal probe is inserted into the puncture tract, and the hoof is radiographed in two planes (Fig. 3). The decision to pursue further treatment is based on the results of clinical examination and radiography. Synoviocentesis and radiography using a contrast medium may enhance the diagnosis. For synoviocentesis, a 20 gauge needle is placed in the distal interphalangeal joint and synovia is collected into an EDTA-tube. Approximately 10 of contrast medium are then injected into the joint. After a few minutes, the hoof is radiographed again to determine whether the contrast medium has travelled into the puncture tract (Richardson and O'Brien, 1985). The same procedure is repeated in the podotrochlear bursa and the deep digital flexor tendon sheath (Fig. 4).
Fig. 3 Radiographic picture with a probe Fig. 4 Radiographic picture with contrast medium Surgical debridement/treatment of puncture wounds Surgical debridement of puncture wounds is usually done with the horse under general anesthesia. This procedure entails two parts: initial debridement of the horn followed by aseptic treatment of the hoof (Fürst, 2002). With the horse sedated and standing, the hoof is cleaned and the horn around the
puncture tract is pared. The horn should be pared liberally around the puncture tract leaving a thin layer of horn that can be cut with a scalpel blade. The hair from the hoof to the fetlock joint is clipped. The prepared area is cleaned with chlorhexidene scrub (Hibiscrub ) and covered with a bandage. Sometimes it is necessary to pare away more horn with the horse under general anesthesia. The horse is then ready for the aseptic part of the procedure. The horse is positioned in lateral recumbency and a tourniquet is applied. All affected structures around the puncture tract are excised. The horn around the tract is removed in an area measuring approximately 3 by 3 cm. The corium and subcutis are then removed and the underlying structures exposed. When the foreign body has penetrated the deep digital flexor tendon, a 1.5 x 1.5 cm area of the tendon is resected. Curettage is necessary when the foreign body penetrates the third phalanx or navicular bone (Fig. 5a-e and Fig. 6). With perforation of the ligamentum impar and penetration of the distal interphalangeal joint, the ligament must be resected and the joint lavaged. The flexor tendon sheath requires lavage when it is involved, and curettage is recommended with injury to the third phalanx. The affected synovial structures are lavaged with lactated Ringer s solution to which antibiotics have been added. A pressure bandage is applied followed by a hoof bandage and a wedge under the heel. Regional intravenous perfusion with an antibiotic is recommended (Murphey et al., 1999). Wright advocated endoscopy of the navicular bursa (Fig. 7) with deep puncture wounds, to better evaluate and lavage the bursa (Wright et al., 1999). Depending on the severity of the injury, lavage may be repeated once or twice with the horse under general anesthesia. Afterwards, with the horse standing and sedated, the bandage is changed as aseptically as possible. Systemic antibiotics and antiinflammatory drugs are administered for at least 2 weeks. After a certain period of time, a shoe with a removable pad can be applied (Fig. 7). An arthroscopic technique has been developed to lavage and treat a deep puncture wound that penetrates the navicular bursa or distal interphalangeal joint (Fig. 8). This technique has good results and permits a less-invasive approach to the penetrated structures, because débridement is carried out under endoscopic guidance. Also, the area is under constant lavage during treatment, decreasing surgery time. Depending on the severity of the injury, lavage may be repeated once or twice with the horse under general anesthesia. Afterward, with the horse standing and sedated, the bandage is changed under aseptic conditions. Systemic antibiotics and anti-inflammatory drugs are administered for at least 2 weeks. After a certain period of time, a medication-plate shoe can be applied (Fig. 7).
Fig. 5a Horn around the puncture wound is removed Fig. 5b The corium and subcutis are removed
Fig. 5c 1.5 x 1.5 cm piece of the tendon is resected Fig. 5d Puncture wound in the navicular bone
Fig. 5e Curettage of the navicular bone Fig. 6 Curettage of the navicular bone
Fig. 7 Shoe with a removable pad Fig 8 Bursoscopie of the navicular bursa Prognosis The prognosis for puncture wounds of the sole is generally guarded. Horses that receive prompt surgical treatment and have few deep structures affected have the best prognosis (Fürst, 2002). Injury to the distal sesamoid bone can eventually result in adhesions between the bone and the DDF tendon, necessitating neurectomy. Bursoscopic treatment can lessen the development of these types of
morbidity. Fürst, A. (2002). Penetration wounds of the hoof. 11 th Annual Scientific Meeting, Vienna, European College of Veterinary Surgeons: 106. Gibson, K. T., C. W. McIlwraight and R. P. Park (1990). A radiographic study of the distal interphalangeal joint and navicular bursa of the horse. Veterinary Radiology 31(1): 22-25. Murphey, E. D., E. M. Santschi and M. G. Papich (1999). Regional intravenous perfusion of the distal limb of horses with amikacin sulfate. J Vet Pharmacol Ther 22(1): 68-71. Richardson, G. L. and T. R. O'Brien (1985). Puncture wounds into the navicular bursa of the horse. Veterinary Radiology &Ultrasound 26(6): 203-207. Wright, I. M., T. J. Phillips and J. P. Walmsley (1999). Endoscopy of the navicular bursa: a new technique for the treatment of contaminated and septic bursae. Equine Vet J 31(1): 5-11.