Texas Equine Veterinary Association

www.texasequineva.com | 13 destruction of the articular cartilage and in chronic tenosynovitis, synovial adhesions develop. e features of chronic bursal infection are a similar to those of both joints and tendon sheaths. e objectives for effective treatment of synovial infection are common to joints, tendon sheaths, and bursae (Wright et al. 2003), and include removal of foreign material, debridement of contaminated/infected and devitalized tissue, elimination of microorganisms, removal of destructive enzymes and radicals, promotion of tissue healing and restoration of a normal synovial environment. e endpoint of surgical treatment should be conversion of the synovial cavity from a contaminated/infected state to a clean contaminated status, thereby enabling natural defenses and antimicrobial therapy to eliminate remaining microorganisms (Steckel et al. 1989). ese endpoints are best achieved with synovial lavage in combination with the previously noted treatments including antimicrobial drugs and wound care. e primary treatment employed is surgical exploration, debridement and lavage using the so-called 'streetnail' procedure (Richardson et al. 1986a,b; Honnas et al. 1995) or by endoscopy of the navicular bursa (Wright et al. 1999, 2003; Wright 2004), which has resulted in a significant reduction in morbidity and mortality. e streetnail procedure (Richardson et al. 1986a,b; Honnas et al. 1995) is performed under general anaesthesia with the horse in lateral recumbency and the affected limb uppermost. e central one-half to two-thirds of the frog and underlying digital cushion are removed in layers to expose the underlying DDFT. A window (approximately 2 x 3 cm) is created in the DDFT exposing the navicular bursa and navicular bone. e bursa can then be debrided, including removal of all devitalised tendon and bone, infected and foreign material, and lavage performed. e solar wound is bandaged and le to heal by secondary intention. Endoscopy of the navicular bursa for treatment of contaminated and infected bursae was first described by Wright et al. (1999), and results of an expanded number of cases were subsequently reported (Wright 2004). In the majority of cases, the puncture wound through the DDFT will be able to be visualised, and identification may be facilitated by passing an arthroscopic probe along the solar puncture wound. Once identified, the wound acts as a convenient instrument portal for endoscopic debridement etc (Figure 4). In the occasional case without a patent penetrating wound, instruments may be introduced through a portal similar to that created for arthroscopic entry on the contralateral side of the limb. Foreign material, and infected and devitalised tissues are removed. Foci of osteomyelitis are debrided with curettes. e defect in the DDFT, digital cushion and sole/ frog is also debrided at this time, with a motorised synovial resector. Once debridement is complete, high pressure lavage is performed, and the final fluids may be impregnated with antimicrobials. e endoscopic portals are sutured and the solar wound le to heal by secondary intention. e foot/ limb is bandaged routinely. In cases in which the DIP joint and/or the DFTS are also affected, these may be treated endoscopically at the same time. e arthroscope can be directed into the palmar/plantar compartment of the DIP joint and distal portion of the DFTS using the same skin portal as that created for endoscopy of the navicular bursa. e dorsal pouch of the DIP joint is then evaluated and treated using a conventional arthroscopic approach. A combination of DIP joint and navicular bursa infection carries a worse prognosis for survival and return to soundness and athletic function. When the DIP joint has been infected following a coronary band puncture, treatment should follow the same principles outlined above, and both the dorsal and palmar/plantar joint pouches should be evaluated. Injury to the DDFT is inevitable following a solar puncture and infection of the navicular bursa. e DDFT may also be damaged by a penetrating object without synovial infection. ese horses are typically more lame than would be expected following an uncomplicated penetration, and remain lame for longer. Diagnosis can be difficult, and confirmation usually requires MRI (Boado et al. 2005; Kinns and Mair 2005; Urraca et al. 2012). If infected tendonitis of the DDFT is suspected, exploration and debridement of the solar penetration is indicated. e surgical technique is similar to the aforementioned streetnail procedure, but without fenestration of the DDFT (Richardson et al. 1986a; Honnas 1991). Involvement of the DDFT dictates a prolonged convalescence, usually 6–12 months. Rest and controlled exercise are paramount in modulating tendon healing. Following a penetrating injury, if infection is successfully resolved, the degree of DDFT injury is oen the limiting factor for horses returning to soundness and athletic function. Penetrating injuries to the coronary band may traumatize the medial or lateral cartilage of the foot. is may in turn lead to infection and subsequent necrosis of the affected cartilage, resulting in a chronic discharging tract proximal to the coronary band (Honnas et al. 1988). Radiographic examination should be performed to rule out the presence of osseous involvement or radio- opaque foreign bodies. Ultrasonographic examination is useful to confirm involvement of the underlying cartilage. Medical treatment is usually unrewarding, and frequently only prolongs the decision for surgical intervention (Honnas 1991). Surgical excision of the infected portion of the collateral cartilage is usually curative, however surgery should be proceeded with caution as to not penetrate the DIP joint. e incision may be le open to heal by second intention or closed primarily if there is enough skin to perform the closure. Postoperatively, it is imperative that the veterinarian have a good relationship with an accomplished farrier. A hospital plate (Figure 5) applied to a shoe will give the horse stability in a shoe, keep the surgical wound clean, and allow for ease of post-operative treatment of the surgical wound. In closing, a full and correct diagnosis with quick and effective treatment is essential in improving the prognosis for penetrating injuries to the hoof Figure 5: Standard hospital plate for treatment of penetrating hoof injury. (Photo courtesy of C. Honnas)

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