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EQUINE VETERINARY EDUCATION / AE / MAY 2015


were collected and collated within the Veterinary Medical Information System (VMIS), a custom designed Microsoft Access database (Microsoft Corporation, 2010). A search of horses within the VMIS was conducted using


the keywords of ‘wither fracture’ or ‘wither injury’. Only horses in race training at the time of injury were included in the study. Clinical records of all the horses identified were examined and horses with other causes of wither injury apart from fracture of the DSP were excluded. Diagnosis of all cases of wither fracture were made on radiographic examination by the attending veterinarian. Lateromedial views were taken with a horizontal beam from left to right using an Agfa Computed Radiography system and Agfa CRMD4.0 general cassettes and one of several generators (Siemens Polydoros LX80, Toshiba Superlight HF9020 and Atomoscope DLC TR9030). Digital radiographs were evaluated using a dedicated radiographic viewing program (Agfa Picture Archiving and Communication Systems). The relevant clinical records relating to injury were summarised for each case and the exact spinous process and total number involved, type of fracture and displacement were noted and entered into a Microsoft Excel (Microsoft Corporation, 2010) spreadsheet. The following variables were extracted from the VMIS and


racing records: horse identification, age at the time of injury, date of import into Hong Kong, date of injury, number of starts (including distances and placings) of races pre- and post injury, performance rating (preinjury, post injury and at retirement) and reason for retirement. The term ‘placing’ was used to describe any horse that had finished fifth or better out of 12 or 14 horses or fourth or better out of 10 horses. The horse’s rating provides an objective indicator of its


racing ability. Every racehorse in Hong Kong is allocated an individual rating on arrival. If the horse has raced elsewhere prior to import into Hong Kong, the rating is based on past race performance and international rating, if applicable, in the exporting country. All unraced horses under the age of 5 years are allocated a rating of 52. This is subsequently adjusted on the basis of performance during races, taking into account finishing position and distance behind winner. Each horse’s rating is also adjusted at the end of each racing season depending on its race performance that season, with a drop in rating if the horse did not start that season. The time to return to training after wither fracture, in days,


was recorded for the activities of swimming, ridden work at a trot or slow canter, galloping, first barrier trial and first race. The total number of days in training in Hong Kong (up to date of retirement, if applicable, otherwise total time up to 31 December 2013) were noted.


Statistical analysis Median and interquartile range (IQR) were used to describe continuous data that were non-normally distributed and counts and percentages were used to describe categorical data. Analyses were conducted in Stata 111.


Results


In total, 5263 horses entered race training at the Hong Kong Jockey Club over the 10 year study period. Eight horses sustained a wither fracture, representing a prevalence of 1.52 horses per 1000. Cases had been imported to Hong Kong a median of 321 (IQR 105–887) days and a minimum of 43 days prior to


© 2015 EVJ Ltd


Fig 1: Fracture of the dorsal aspect of the sixth to ninth spinous processes with cranioventral displacement (Case 1). Cranial is to the left of the radiographs.


sustaining the fracture. The median age of horses at the time of injury was 3.5 (IQR 3–5) years. The median rating at the time of import was 52 (IQR 52–55) and prior to injury, ratings had increased to a median of 59.5 (IQR 52–68.5). Two horses had not started in a race prior to injury. The 6 horses that had raced had started a median of 12.5 times (IQR 1–35) at varying distances between 1000m and 2000 m, with a median of 13 (IQR 1–14) placings. Six of the 8 cases were in full race training. The remaining 2 horses were in light work whilst undergoing rehabilitation from unrelated musculoskeletal injuries.


Clinical findings In all cases diagnosis was confirmed by radiographic evidence of fracture of one or more DSP (Figs 1 and 2). Swelling over the dorsal withers and sensitivity to palpation were identified in 7 cases, of which 6 had swelling immediately after the initial trauma (Fig 3). Crepitus was palpable in 4 of these cases, with concurrent visible deformation (deviation and flattening) of the withers in one case. Bilateral forelimb lameness, manifested as a stiff gait, was described in 3 cases but there was no report of concurrent lameness in the other cases. Two horses sustained wounds of the poll and withers at the same traumatic incident that caused fracture. Neurological signs were not reported as a feature in any of the cases. The median number of clinical signs per horse was 3 (IQR 2.5–4). All but one of the 8 cases involved DSP fracture of multiple


vertebrae, with a median of 4 (IQR 3.75–5.25) seen. The maximum number of DSP involved in any one horse was 6 vertebrae. The sixth thoracic vertebra (T6) was involved in all cases, while T7 and T5 were involved in 6 and 5 cases, respectively (Fig 4). Horses with a greater number of fractured DSP did not have a greater number of clinical signs of fracture.


Treatment and management All horses were treated with nonsteroidal anti-inflammatory drugs, either phenylbutazone (Equipalazone2;n=7)or flunixin meglumine (Flunixil3; n = 1), for 3–12 days in total. Additionally, one case was administered dexamethasone (Dexadreson4) immediately post injury and 2 cases were prescribed adjunctive antibiotic therapy for wounds sustained at the time of the injury. In all cases, advice was given to apply ice to the withers twice daily for one week. The veterinary recommendation for short-term management was strict box


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