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EQUINE VETERINARY EDUCATION / AE / JANUARY 2017


Original Article


Wounds to the dorsal carpus (coronation injury) in horses: Treatment, complications and survival N. Butz†, A. Dreyfus‡,A.E.F€


urst† and A. S. Bischofberger*† †Equine Hospital, Equine Department; and ‡Epidemiology Section, Vetsuisse Faculty, University of Z€


Switzerland. *Corresponding author email: abischofberger@vetclinics.uzh.ch


Keywords: horse; dorsal carpus; wounds


Summary Studies evaluating complications, treatment and survival following wounds to the dorsal carpus (coronation injuries), despite being frequent injuries in equine practice, are lacking. The aim was to describe clinical features and identify risk factors associated with short- and long-term outcomes following coronation injury in horses. Clinical data were obtained for horses undergoing treatment of unilateral or bilateral coronation injuries in a single hospital population. Descriptive data were generated for the clinical variables. Multivariable linear or logistic regression analyses was used to generate six models with short-term outcomes defined as hospitalisation time and hospital survival; and long-term outcomes (>6 months) defined as coronation specific mortality, sound and return to intended use, increased post- injury stumbling and recurrence of coronation injury. One hundred and thirty-eight horses were included. In 15.9% an extensor tendon and in 17.4% a carpal joint was involved. The prognosis for hospital survival was 97.8% and the long- term coronation specific mortality risk was 4.3%. 87.5% were sound and returned to intended use. Risk factors for prolonged hospitalisation time were extensor tendon involvement (4.2 days), carpal joint involvement (3.8 days) and complications (skin necrosis [9.5 days] and local infection [3.2 days]. Coronation injuries reccurred in 8.8% and 20% had evidence of increased post-injury stumbling. Administration of intra-articular antimicrobials (7.8 times) (likely reflecting injury severity grade) and bilateral coronation injury (6.7 times) increased the odds for increased post-injury stumbling. This study has identified risk factors for increased hospitalisation time and post-injury stumbling, which clinicians managing coronation injuries should be aware of.


Introduction


In the German and French literature, an injury to the dorsal aspect of the carpus that typically occurs after a horse stumbling and falling on hard ground is anecdotally called ‘courronement’. In the English literature this term has been referred to as ‘coronation’ (Ruggles 2012) or ‘broken knees’. This type of injury can occur unilaterally or bilaterally and the injury may vary in degree of severity (Fig 1). Coronation injuries are potentially serious. Although most coronation injuries are superficial and respond well to symptomatic treatment, deeper coronation injuries can lead to potentially life-threatening and/or performance-limiting complications.


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Deeper injury can result in damage to the extensor tendons (extensor carpi radialis tendon and common digital extensor tendon), their synovial tendon sheaths or any of the carpal joints (Ruggles 2012). To avoid these potentially life- threatening complications, careful physical examination (wound exploration, recognition of involved synovial structures and underlying vital structures) and radiographic examination (recognition of debris and bone damage) to decide the best course of management are essential. Treatment of coronation injuries generally consists of wound management (wound debridement, repair, implantation of drains and immobilisation), management of any of the involved synovial structures (needle or arthroscopic lavage) and supportive therapy (systemic anti-inflammatory medication and systemic and local antimicrobial medication). These cases often need intensive management and hospitalisation costs can become high. This is especially true when joints are involved requiring repeated lavage, when there is a large area of skin loss over the carpus precluding primary wound closure or when primary wound closure or ruptured extensor tendons need protection by external stabilisation for good quality healing (Mespoulhes- Riviere et al. 2008). Several studies have emphasised the importance of


prompt recognition and treatment in cases of synovial infection (Fraser and Bladon 2004; Wereszka et al. 2007). Survival rates of 45–90% have been reported following the treatment of synovial infection (Schneider et al. 1992; Wright et al. 2003; Smith et al. 2006; Wereszka et al. 2007; Walmsley et al. 2011). Thus if the synovial structures respond appropriately, wounds characterised by significant loss of tissue over the dorsum of the carpus can also heal and result in a satisfactory outcome (Ruggles 2012). In the current literature there are no studies evaluating the specific complications, treatment and survival following coronation injuries, despite this being a frequently diagnosed injury in equine practice. Identification of positive and negative prognostic indicators could aid the ability of clinicians to use an evidence-based approach when managing coronation injuries and when informing owners about treatment, complications, financial expenditure and prognosis. The aims of this study were to describe the clinical


features of horses with coronation injuries, their treatment and complications, and, to determine survival to discharge, hospitalisation time, long-term coronation specific mortality, soundness and return to intended use, evidence of increased post-injury stumbling and coronation injury recurrence and associated risk factors for these outcomes. It was


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