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Reasons for Performing Study: Fracture of the metacarpal/tarsal condyle is usually preceded by prodromal pathology. Early recognition of injury is desirable to minimise the risk of serious breakdown; however, the clinical and diagnostic characteristics of unicortical condylar fractures have been poorly documented to date., Objectives: To describe the clinical, imaging and outcome features of racehorses in first opinion practice diagnosed with short unicortical fracture of the metacarpal/tarsal condyle., Study Design: Retrospective case series., Methods: All flat racehorses sustaining a unicortical condylar fracture while under the primary care of a single first opinion UK veterinary practice (2006-2013) were identified from imaging records and histories analysed for clinical presentation, lesion location, treatment, rehabilitation guidance and outcome., Results: Forty-five cases were identified during the period of study. Forelimb injuries predominated (35/45, 77.8%). Mean age of cases was 3.4 ± 1.3 years. Palpable clinical abnormality referable to the fetlock region was not a feature. The majority (35/45, 77.8%) of injuries were diagnosed with radiography (flexed dorsopalmar/plantar projection), with the remainder requiring magnetic resonance imaging (MRI) for diagnosis. Seven horses underwent surgery either at the time of original diagnosis or following reinjury. Twenty-eight of 30 horses (93.3%), not retired for unrelated reasons, returned to racing, with 5 (16.7%) conservatively managed horses sustaining reinjury at a median of 305 days. Misdiagnosis resulted in progression to catastrophic fracture in 2 cases., Conclusions: Clinical findings associated with unicortical condylar fractures can be mild and appropriate diagnostic imaging is necessary for injury detection. Failure to detect injury can lead to catastrophic fracture. Most cases respond to conservative management and return to racing, but risk of reinjury merits consideration of surgery in selected cases. Veterinary vigilance and timely intervention has the potential to considerably reduce the incidence of complete condylar fracture of the fetlock in the racehorse. The Summary is available in Chinese - see Supporting information., (© 2014 EVJ Ltd.)

Reasons for Performing Study: Ultrasonographic (US) abnormalities of the suspensory ligament branch (SLB) have been poorly investigated but can have considerable impact on market value and career path when encountered in athletic horses. There is a need for determination of the prevalence and relationship to clinical injury of these US abnormalities in the Thoroughbred (TB) racehorse., Objectives: To establish the prevalence of, and the repeatability of an US grading system for, subclinical US abnormalities of the forelimb SLB in a population of UK TB flat racehorses., Methods: Ultrasonographic assessment of the forelimb SLBs of 60 TB racehorses free from history and clinical indication of SLB desmopathy in a single UK training yard was performed. Images were viewed independently by 2 blinded observers and graded for US abnormality. Interobserver agreement was assessed using Cohen's kappa statistic with 95% confidence intervals (95% CI)., Results: Prevalence of horses with subclinical US abnormality of the forelimb SLB of moderate severity was 6.7%. Medial branches were overrepresented. Inter observer agreement was substantial for US grade (kappa = 0.743; 95% CI 0.652-0.834) and almost perfect for appearance of sesamoid bone at ligament insertion (kappa = 0.817; 95% CI 0.66-0.98)., Conclusions: The study reveals that a proportion of TB racehorses in flat training free from history or clinical signs of SLB injury have US abnormalities that could negatively impact on market value and career path., Potential Relevance: Clinicians should be aware that US abnormalities of the SLB may not always be related to clinical desmopathy. Further longitudinal studies are required to determine whether such findings are predictive for future injury., (© 2012 EVJ Ltd.)

Although considered relatively common in horses, there is little information on the prevalence, distribution and aetiology of peripheral caries of the equine cheek teeth (CT). The objective of this study was to investigate a possible association between this lesion and diastemata or 'gaps' between the CT which facilitate the entrapment of food material. Video recordings of oroscopic examinations of all dental cases at an equine hospital over a 3-year period were reviewed, and the location of all diastemata, peripheral caries, trapped food, and of gingival recession were recorded. A total of 108 cases met study inclusion criteria and 298 diastemata and 445 CT with peripheral caries were noted. Diastemata were found predominantly in the mandibular arcades (80%) and 75% of animals had at least one diastema. Peripheral caries was uniformly distributed between the maxillary and mandibular CT, being most prevalent on the most caudal three teeth (87%). Overall, diastemata were not associated with peripheral caries at either a tooth or individual patient level. However, a highly significant association was found between the presence of trapped food within diastemata and gingival recession., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Objective: To evaluate a technique for oral extraction of fractured cheek teeth (CT) under oral endoscopic guidance., Study Design: Case series., Animals: Horses (n = 30) with fractured CT., Methods: Medical records (April 2007-August 2010) of horses that had standing oral extraction of fractured CT under endoscopic guidance were reviewed., Results: Thirty horses (median age, 11.5 years; range, 5-23 years) had 31 fractured CT (21 maxillary, 10 mandibular) removed. Midline sagittal fractures of maxillary teeth (n = 13; 42%) were the most common type, followed by buccal or palatal (10; 32%), and transverse or multiple (5; 16%) fractures. Extraction under endoscopic guidance was successful for 27 (87%) teeth. Median age of the surgical failure group was 7 years (range, 5-8 years), significantly lower than that of the surgical success group (P = .0135, Mann-Whitney U-test)., Conclusions: Endoscopic viewing facilitates instrument use and removal of fractured CT in standing horses., (© Copyright 2011 by The American College of Veterinary Surgeons.)

Musculoskeletal injury is the most common cause of lost training days in the young Thoroughbred horse in flat race training. To date, there has been little investigation of the regional patterns of injury frequently observed by clinicians in racehorse practice. The present study was conducted to determine incidence of musculoskeletal injuries in Thoroughbreds in training in Newmarket, United Kingdom. Veterinary records for all horses resident in three large (>100 horse) training yards were assessed for occurrence of significant musculoskeletal injury. A total of 248 injuries were recorded in 217 individual horses, from a total population of 616 individual horses; fractures of the tibia (20.7%) and proximal phalanx (14.5%) were the most common. Overall injury rates were similar between yards (23-26%/year), with seasonal patterns noted for some injury types. Incidence of certain injuries (P1, metacarpal/metatarsal condylar, pelvic fractures, and superficial digital flexor tendonitis) varied between yards. The majority of carpal, P1 fracture and SDF tendonitis cases were right-sided., (Copyright © 2009 Elsevier Ltd. All rights reserved.)

Sagittal fracture of the proximal phalanx (P1) is an important musculoskeletal injury of the performance horse. Although widely considered to be monotonic in nature, there is emerging evidence that some P1 fractures may have stress-injury aetiology. Three cases are described in which imaging features found were suggestive of prodromal bone injury. All cases returned to full performance use after a period of rest. The authors conclude that it is possible that some P1 fractures in the Thoroughbred racehorse may develop through stress/fatigue injury pathways. It is proposed that intervention prior to overt fracture may be possible in some cases.

Reason for Performing Study: Fissures of the occlusal surface of the equine cheek tooth are poorly understood and their association with dental disease is unknown., Objective: To describe the prevalence and location of occlusal fissures in the cheek teeth (CT) of a group of horses referred for dental investigation/treatment, and determine association with intercurrent dental disease., Methods: Digital video recordings of oral endoscopic examinations for all horses referred to the Rossdales Equine Hospital for dental investigation from November 2006 to June 2009 were reviewed. Location of occlusal fissures in relation to both Triadan tooth position and pulpar secondary dentine was recorded; direction of fissure and concurrent involvement of enamel was also documented. The CT location considered at the time of examination to be the primary site/s of disease was correlated with presence of fissures on these teeth., Results: 91 cases meeting the inclusion criteria were identified. Occlusal fissures were documented in 58.2% (53/91) cases, with a total of 227 CT being affected. Fissures were most prevalent mid-arcade. The majority (92.1%) of fissures in maxillary CT were associated with the caudal palatal pulp horn. Fissures in mandibular CT were predominantly associated with the buccal pulp horns (95.7%). There was no significant difference in the median number of CT with fissures in relation to gender. There was no correlation between age (r(2)= 0.01) of horse and number of CT with fissures. A significantly greater number of CT with multiple occlusal fissures was found in mandibular compared to maxillary arcades. No correlation was found between presence of fissures and location of individual CT considered to be primarily responsible for presentation., Conclusions: Occlusal fissures in this group of animals were common and not correlated to primary site of dental disease., Potential Relevance: In horses subjected to dental investigation, occlusal fissures of the cheek teeth should not be considered an indicator of tooth compromise. Location and direction of fissure propagation in most cases is inconsistent with occlusal fissures being causally implicated in slab fractures of cheek teeth, although site predilection may indicate a possible association with masticatory forces.

Reason for Performing Study: The proximal metacarpal region is a common site of origin of lameness in the performance horse. A number of disease entities are recognised as causes of proximal metacarpal lameness but a definitive diagnosis is often elusive. Magnetic resonance imaging (MRI) is hypothesised to offer advantages over traditional imaging modalities in the investigation of proximal metacarpal pain., Objective: To describe clinical and imaging features of cases of lameness in racehorses arising from the proximal metacarpal region in which standing MRI identified 'bone marrow oedema-type' (BMO-type) signal patterns., Methods: Records for all horses undergoing standing MRI of the proximal metacarpus/distal carpus from September 2006 to December 2008 were reviewed. Cases underwent a standardised protocol for diagnostic analgesia, radiography and ultrasonography of the proximal metacarpus and distal carpus. Cases with proximal metacarpal lameness displaying a characteristic BMO-type signal pattern on MRI were identified and outcomes analysed., Results: Eight cases were identified with characteristic MRI findings of extensive hyperintensity on T2* gradient echo and short tau inversion fast spin echo sequences and corresponding hypointensity on T1 gradient echo images within the palmaroproximal aspect of the third metacarpal bone. Follow-up information was available for all cases; at the time of writing 7/8 had returned to full work and were free from lameness., Conclusions: The BMO-type signal patterns visible on MR images in these cases may signal the existence of a previously under-diagnosed pathological process associated with proximal metacarpal lameness in racehorses. This finding is postulated to be associated with a stress reaction and possible prodromal stress fracture of the palmaroproximal metacarpus not appreciable radiographically or ultrasonographically., Potential Relevance: MRI of the proximal metacarpal region permits detection of pathological processes, which may elude conventional imaging and, therefore, has important therapeutic and prognostic implications in these cases.

Fractures involving the fetlock region are encountered commonly in Thoroughbred racehorses. Condylar fractures of the distal metacarpus/metatarsus and mid-sagittal fractures of the proximal phalanx account for the majority of fetlock injuries during both racing and training and clinical features, management and outcome of these injuries have been well described. Transverse fractures of the distal diaphysis of the third metacarpus, however, are seldom observed and have received little attention in the literature. This paper describes clinical and radiological findings associated with 6 cases encountered in first opinion racehorse practice over a 3 year period. Transverse third metacarpal fractures vary in presentation but typically have clinical signs referable to the fetlock region and may, on occasion, be life-threatening. They are therefore an important differential diagnosis when a fracture involving the fetlock is suspected.

Reasons for Performing Study: There are few published data to support the ages of emergence of permanent dentition widely reported in horses., Objectives: To clarify the chronology and sequence of permanent premolar (PM) tooth emergence in Thoroughbred racehorses., Methods: A prospective study was undertaken in which records were kept of deciduous PM 'cap' extractions performed during routine dental examinations in Thoroughbred racehorses. Mixed effects multiple regression analysis was used to relate the observed ages, measured in days, for PM 'cap' extractions simultaneously with different predictive variables. Care was taken to account for clustering of multiple observed outcomes within individual horses., Results: A total of 508 deciduous premolar 'caps' were removed from 207 horses, mean ages at removal from PM2, PM3 and PM4 were 35.1, 37.7 and 45.1 months, respectively. Age at which deciduous 'cap' removal occurred was associated significantly with tooth row, upper or lower jaw and gender of the horse concerned. There was a significant trend for later 'cap' extraction age with more caudal teeth, teeth in the upper jaw and female gender., Conclusions: Age at removal of deciduous premolar 'caps' in this population differed considerably from the ages of emergence of permanent dentition reported widely in equine publications. The results provide the first evidence of sexual dimorphism in the eruption of the permanent premolar dentition in horses. These findings strongly support a model of cheek tooth eruption in the horse in which chronology and sequence of emergence are more complex than previously thought, but which is consistent with understanding of tooth eruption in species that have been studied in greater detail., Potential Relevance: Abnormalities of cheek tooth eruption are thought to be a factor in the pathogenesis of a variety of dental conditions, and a thorough understanding of the process of eruption is fundamental to the development of rational strategies for prevention and treatment.

Reasons for Performing Study: Removal of cheek teeth in all but the aged horse or pony is a serious undertaking with potentially deleterious sequellae. Rigid endoscopy permits detailed examination of the oral cavity and erupted dental tissues and has the potential to assist in the correct identification of the diseased tooth., Objectives: To document oral endoscopic findings associated with infected equine cheek teeth in cases without gross oral pathological changes and thereby determine the usefulness of rigid oral endoscopy as an aid to diagnosis of such infections., Methods: Records of all cases of equine cheek tooth removal attempted under standing sedation over a 38 month period were examined. Cases were excluded from the study if apical infection was associated with gross dental fracture, malalignment, diastema/periodontal pocketing or supernumerary teeth. Endoscopic and radiographic findings were analysed and correlated to diseased tooth location., Results: Seventeen cases of apical dental infection fitting the inclusion criteria (nonresponsive to antibiotics and with no gross oral abnormality of the affected arcade) were identified in which oral endoscopy was used as an aid to diagnosis. In 15 (88%) of the 17 cases, oral endoscopy revealed abnormalities specific to the infected tooth. Focal gingival recession (10/17 cases) was the most common visible abnormality associated with infected teeth., Conclusions: In the majority of cases of apical infection of equine cheek teeth there is visible intraoral evidence implicating the affected tooth., Potential Relevance: Oral endoscopy facilitates detailed examination of the mouth and should be considered along with radiography as an important aid to diagnosis in cases of equine dental infection.

A novel radiographic projection is described for assessing part of the temporomandibular articulation of horses. It minimises the superimposition of osseous structures of the cranium that limit the usefulness of conventional projections and permits improved imaging in cases of suspected disease.

Reason for Performing Study: There has been much research directed at potential causative agents and the epidemiology of lower respiratory tract disease (LRTD), but few reports of the clinical progression and outcome., Objectives: To define clinical features of LRTD in racehorses, including association with age and average duration of disease, through the analysis of endoscopic data., Methods: A retrospective analysis of records from a single training yard of endoscopic examinations undertaken over a 2-year period was performed. Horses were subjected to regular endoscopic examination for a variety of reasons, and all horses placed on antibiotic therapy for lower respiratory tract disease were rescoped following treatment. Data analysed included a 0-8 tracheal mucus score based on visible endoscopic mucus and gross tracheal lavage turbidity, as well as age and treatment duration and type., Results: A total of 522 endoscopic examinations undertaken on 123 horses and tracking 169 episodes of lower respiratory tract disease were recorded. Mean duration of disease episode was 15.5 days (median = 11 days, range = 4-61 days). Horses age 2 years were significantly more likely than those age > or=3 years to have at least one episode of respiratory disease (P<0.001). There was a direct association between initial tracheal mucus score and rescope score after treatment., Conclusions: Lower respiratory tract disease was more common in 2-year-olds than in older horses. Affected horses had endoscopic evidence of increased tracheal mucus accumulation for an average of 15.5 days per episode, a considerably shorter period than that suggested by previous studies., Potential Relevance: Endoscopic examinations permit longitudinal tracking of lower respiratory tract disease in Thoroughbred racehorses. A prolonged duration of disease, sometimes extending for months, can be expected in a small proportion of cases, some of which appear to be refractory to treatment. There is a clear need for evidence-based analysis of treatment regimes to assist clinicians in decision making when managing disease in both individual and group situations.

Reasons for Performing Study: Dantrolene sodium (Dantrium) has been used extensively for the treatment of myopathies in man and anecdotal evidence suggests it is of clinical benefit in the control of exercise-induced rhabdomyolysis (ER) in racehorses, although data to support this are currently lacking., Objectives: To investigate the efficacy of oral dantrolene sodium in controlling ER in a randomised, double-blind, placebo-controlled crossover trial involving 77 Thoroughbred racehorses in Newmarket, UK., Methods: Horses were treated on 2 occasions 1 week apart, with treatment days coinciding with a return to exercise following 2 days box rest on each occasion. For the first treatment, each horse was randomly selected to receive either 800 mg dantrolene sodium or a colour-matched placebo administered orally 1 h before exercise. This was followed by crossover to the other treatment on the second occasion, with each horse thereby acting as its own control. Degree of ER was assessed using rising serum creatine kinase (CK) levels, by subtracting pre-exercise blood CK levels from those measured in 6 h post exercise blood samples. For each horse, the difference in change between pre- and post exercise CK values between placebo and dantrolene treatments was calculated, with positive values indicating a greater rise with placebo than with dantrolene sodium treatment., Results: The overall mean difference for all horses was +104.8 iu/l and the null hypothesis, that there was no true difference in non-normally distributed post exercise rises in CK values between placebo and dantrolene treatments, was rejected (P = 0.0013) using the nonparametric Wilcoxon signed rank test. Additionally, no horses given dantrolene sodium showed clinical signs of ER, whereas 3 horses given the placebo developed ER following exercise. The incidence of ER in the study was 4% (3/77)., Conclusions: The results confirmed that oral administration of dantrolene sodium, 1 h before exercise, had a statistically significant effect on reducing the difference between pre- and post exercise plasma CK levels compared with a placebo in the same animals, and preventing clinical ER in susceptible individuals., Potential Relevance: This study suggested that dantrolene sodium is of use in controlling ER in the Thoroughbred racehorse. Further investigation into pre- and post exercise myoplasmic calcium levels and the repeat of the study late in the season when horses receive a much higher energy ration and more strenuous exercise would appear to be warranted.

Reasons for Performing Study: Tibial stress fractures are an important cause of lameness in the Thoroughbred racehorse. While it is recognised that these injuries can vary in clinical presentation and radiographic or scintigraphic appearance, little has been done to quantify lesion severity. By contrast the scintigraphic grading of tibial stress fractures in human athletes is widely reported and assists in the selection of appropriate management regimes., Objectives: To determine the relationship between scintigraphic grade, clinical severity and radiographic appearance of tibial stress fractures., Methods: The current study involved the retrospective analysis of records from 42 Thoroughbreds with abnormal tibial scintigraphic activity., Results: There was a significant association between lesion site and scintigraphic grade and good correlation of scintigraphic scoring between investigators. No significant association was found between scintigraphic grade and either radiographic grade or degree of lameness., Conclusions: The study confirmed that radiographic appearance is an unreliable measure of clinical severity or stage of progression of lesions. The scintigraphic grading system used in the study was not of use in defining stress fracture severity in the equine tibia., Potential Relevance: Despite this finding, there is clearly a need for prospective investigations to explore the potential for targeted management regimes for tibial injuries based on lesion site or clinical criteria.