Texas Equine Veterinary Association

www.texasequineva.com | 12 2012). During regional limb perfusion, high concentrations and pressure gradients between the intravascular and extravascular compartments are obtained. is facilitates diffusion of the antimicrobial drug into the surrounding tissues. Specific indications for surgical exploration include presence of foreign material, synovial sepsis, some cases of osteochondral fragmentation and foci of infected osteitis/osteomyelitis. In addition, surgical exploration should be considered in cases with a greater degree of lameness than anticipated from the injuries identified, and in nonhealing and/or chronically discharging wounds. In such cases radiologically silent lesions oen are identified, such as infected and/ or devitalized so tissues and bone, or foreign material. e approach used will vary between cases. With synovial sepsis, endoscopic techniques should be employed, but oen, endoscopic evaluation is appropriate even in the absence of synovial involvement. More extensive open approaches will also be necessary in some cases, by creating a window in the sole to facilitate exploration and surgical manipulations. Debridement of infected and devitalized tissues, and removal of foreign material is indicated in many of these cases. Infected osteitis with or without fracture and sequestration of a portion of the distal phalanx are potential sequelae of deep solar penetrations (Gaughan et al. 1989; Baird et al. 1990; Linford et al. 1994; Cauvin and Munroe 1998.) History of a penetration may or may not be known, and many cases will present with a chronic subsolar abscess. Radiographic examination oen will identify an area of irregularly marginated, decreased bone density, usually at the margin of the distal phalanx (Gaughan et al. 1989). ere may also be separate, sequestrated fragments present (Baird et al. 1990; Cauvin and Munroe 1998). Effective treatment almost always requires a combination of surgical debridement and antimicrobial therapy (Gaughan et al. 1989). Surgery can be performed under general anesthesia, or standing in the sedated patient, with regional anesthesia. An Esmarch bandage and tourniquet positioned proximal to the metacarpophalangeal/metatarsophalangeal joint facilitate surgery by minimizing hemorrhage during the procedure and allowing improved visibility. A window is created in the sole centered over the draining tract to provide access to the area of osseous infection. is can be performed with either hoof knives, a trephine, an oscillating saw or a specialized drill bit (Honnas and Sustaire 2010). e solar corium is then sharply dissected to expose the distal phalanx (Honnas 1991). Diseased bone can be differentiated from normal surrounding bone by differences in color and texture (Gaughan et al. 1989). e affected area should be curetted until healthy margins are reached. At the end of the procedure the wound is lavaged and the foot dressed. Medical management is almost always unsuccessful (Gaughan et al. 1989). However, following the treatment protocol outlined above, the condition carries a favourable prognosis for both resolution of infection and return to athletic function (Gaughan et al. 1989; Baird et al. 1990; Linford et al. 1994; Cauvin and Munroe 1998). Puncture wounds to the central third region of the frog are the most likely to result in penetration of the navicular bursa (Figure 3). (Richardson et al. 1986a,b; Honnas et al. 1988, 1995; DeBowes and Yovich 1989; Steckel et al. 1989; Honnas 1991, 1992; Richardson 1999; Wright et al. 1999; Wright 2004). is invariably involves penetration through the DDFT. Less commonly, following puncture of the navicular bursa the penetrating tract then extends into the DIP joint, or through the T-ligament into the digital flexor tendon sheath or DIP joint. ere may also be concurrent traumatic damage to the palmar/plantar fibrocartilage of the navicular bone and the navicular bone itself (Wright et al. 1999). Le untreated this can progress to the development of osteomyelitis (Honnas et al. 1995). If the puncture wound is through the coronary band, there is risk of DIP joint penetration. e principle potentiating factors for the establishment of synovial infection are the number and nature of contaminating organisms (Bertone 1996), the presence of foreign material (Reginato et al. 1990) and devitalized tissue (Wright et al. 2003). Following colonization of the synovium, a combination of bacterial pathogenicity and host immune response leads to the release of a variety of enzymes and free radicals, which result in substantial inflammation and ultimately destruction of the tissues in the synovial cavity (Bertone 1996). Established infection frequently results in the production of large amounts of fibrin and pannus (McIlwraith 2002) which may cover foreign material and devitalized tissue, act as a nidus for bacterial multiplication and is rich in inflammatory cells, degradative enzymes and radicals. It also is a barrier to synovial membrane diffusion; it therefore further compromises intrasynovial nutrition and limits access for circulating antimicrobial drugs (Bertone 1996). With chronic articular infection, there is progressive Figure 3: Typical appearance and location of a penetration of the sole that also penetrated the navicular bursa. (Photo courtesy of M. Smith) Figure 4: Use of the penetration site as an instrument portal during bursoscopy to treat an infected navicular bursa. (Photo courtesy of M. Smith)

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