Analysis of horse race videos to identify intra-race risk factors for fatal distal limb fracture.

The objective of this study was to identify risk factors, during racing, associated with imminent fatal distal limb fracture in Thoroughbreds. One hundred and nine cases of fatal distal limb fracture were identified from all 59 UK racecourses over a 2-year period (February 1999-January 2001). Three uninjured control horses were randomly selected from the same race as the case horse. Videos of races in which fractures occurred were viewed using a defined protocol. Fractures in flat races occurred at any time during the race, whereas 74% (45/61) of cases in national hunt type races occurred in the second half of races. More than 75% (79/103) of cases were spontaneous, i.e. there was no obvious external influence such as a fall at a fence or collision with another horse. Sixty-six percent (44/67) of horses, sustaining a forelimb fracture, fractured the forelimb they were using as lead leg at the time of fracture. When case and control horses were compared, horses that were: (a) making good progress through the race, (b) reluctant to start and (c) received encouragement in the final 10s before the time of fracture, were more likely to sustain a fracture.

Catastrophic fracture of the lateral condyle of the third metacarpus/metatarsus in UK racehorses - fracture descriptions and pre-existing pathology.

The characteristics of, and pre-existing pathology associated with 75 cases of fatal lateral condylar fracture sustained by Thoroughbreds while racing in the UK were described. Cases were identified from 220 cases of fatal distal limb fracture submitted as part of studies designed to identify risk factors for all fatal distal limb fractures. Fractures were most common in hurdle races and affected the right forelimb twice as often as the left forelimb. Fracture dimensions were similar to previous reports, however there was a much greater prevalence of articular and diaphyseal comminution and of concurrent fractures in the current report. Pre-existing pathology was particularly common in the medial and lateral parasagittal grooves of the distal articular surfaces of the third metacarpus/metatarsus. The degree of this pathology was not associated with horse age, length of career or number of career starts.

Risk factors for fatal lateral condylar fracture of the third metacarpus/metatarsus in UK racing.

REASONS FOR PERFORMING STUDY: Lateral condylar fractures of the third metacarpus/metatarsus are the most common cause of equine fatality on UK racecourses. Identification of risk factors for such injuries and the subsequent implementation of intervention strategies could significantly reduce the total number of racecourse fatalities. OBJECTIVES: To identify horse-, race- and course-level risk factors for fatal lateral condylar fracture in Thoroughbreds on UK racecourses. METHODS: Case-control study designs were used. Case horses were defined as those that were subjected to euthanasia having sustained an irreparable lateral condylar fracture while racing at any of the 59 UK racecourses. Case races were defined as those in which one or more horses sustained a fatal lateral condylar fracture. Three controls for each case horse were selected at random from the race in which the case was running. Three controls for each case race were selected at random from all races of the same type held in the same year. Ninety-eight cases were included in the study. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture. RESULTS: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have started racing as 3- or 4-year-olds. Fractures were found to be more likely in longer races with a larger number of runners, races in which professional jockeys were not permitted to ride and races in which the going was described as firm or hard. CONCLUSIONS AND POTENTIAL RELEVANCE: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal lateral condylar fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 201 m (1 furlong) and 1609 m (8 furlongs) per week. The association with age at first race requires further investigation for flat and National Hunt racing separately. A reduction in the number of races taking place on very firm going could have an impact on the number of lateral condylar fractures.

Race- and course-level risk factors for fatal distal limb fracture in racing Thoroughbreds.

REASONS FOR PERFORMING STUDY: Considerable variation in the rates of equine fatality at different racecourses draws attention to probable risk factors at the level of course or race that might be partly responsible. Distal limb fractures are the most common cause of equine fatality on UK racecourses and identification of risk factors for such injuries and subsequent implementation of intervention strategies could significantly reduce the total number of racecourse fatalities. OBJECTIVES: To identify race- and course-level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses. METHODS: A case-control study design was used. Case races were defined as those in which one or more horses sustained fatal fracture of the distal limb. Controls were selected in 2 different ways. Firstly, 3 races in which no fracture occurred were selected from all races of the same type held within 5 days of the case race (Analysis 1). Secondly, 3 control races were selected for each case race from all races of the same type held in the same year (Analysis 2). One hundred and nine cases were included in the study. Information about the race and the racecourses was collected from Computer Raceform. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture in a race. RESULTS: Longer races with a larger number of runners were more likely to contain a fracture. Firmer going and fewer days since the last race on the same course were associated with an increased risk of fracture. The going at the course at the previous race meeting was also associated with the likelihood of fracture. CONCLUSIONS: Modifications to the going on the day of a race and greater emphasis on ground maintenance between race meetings may have an impact on the risk of fatal distal limb fracture during racing. POTENTIAL RELEVANCE: Modification of risk factors such as the going and number of days since the last race meeting could reduce the number of equine fatalities on UK racecourses. The condition of the racecourse may be an important risk factor and future research should focus on the identification of course maintenance techniques that produce the safest possible racing surfaces.

Horse-level risk factors for fatal distal limb fracture in racing Thoroughbreds in the UK.

REASONS FOR PERFORMING STUDY: Fractures below the level of the radius or tibia (distal limb fractures) are the most common cause of equine fatality on UK racecourses; however, little is known about their epidemiology or aetiology. Identification of risk factors could enable intervention strategies to be designed to reduce the number of fatalities. OBJECTIVES: To identify horse-level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses. METHODS: A case-control study design was used. Fractures in case horses were confirmed by post mortem examination and 3 matched uninjured controls were selected from the race in which the case horse was running. One hundred and nine cases were included and information was collected about previous racing history, horse characteristics and training schedules. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture. RESULTS: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have trained on a sand gallop, i.e. a gallop described by trainers as being primarily composed of sand. CONCLUSIONS: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal distal limb fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 805-2012 m (4-10 furlongs)/week. POTENTIAL RELEVANCE: The information from this study can be used to alter training schedules in an attempt to reduce the incidence of fatal distal limb fracture in Thoroughbred racehorses. Training should include some gallop work, and further studies, recording the exact level of work, will help to identify an optimum range of training speeds and distances which will reduce the liklihood of catastrophic fracture on the racecourse.

Risk of fatal distal limb fractures among Thoroughbreds involved in the five types of racing in the United Kingdom.

The risk of fatal distal limb fractures in thoroughbreds racing in the UK was calculated and shown to vary considerably between the different types of race. Flat turf racing was associated with the lowest risk (0.4 per 1000 starts) and national hunt flat racing was associated with the highest risk (2.2 per 1000 starts). The types of fracture were classified by detailed radiographic and postmortem examinations of all the cases recorded over two years, and the distribution of the different types of fracture in the five main types of racing was examined. Overall, lateral condylar fractures of the third metacarpus were the most common, and they were also the most common in national hunt-type races (hurdle, steeplechase and national hunt flat races). In all-weather flat racing biaxial proximal sesamoid fractures were most common, and in turf flat racing fractures of the first phalanx were most common. The risk of fractures of more than one bone was greater in national hunt-type races.

An experimental clot model in sheep; generation of a heterologous clot and its detection in vivo using venography and (125)I labelled fibrinogen.

An experimental venous clot model using the lateral saphenous vein of sheep is described. Eight experimental Suffolk crossbred sheep were used. A mixture of human fibrinogen, in some cases labelled with (125)I, bovine thrombin and homologous whole blood was placed via a catheter into a surgically isolated segment of the lateral saphenous vein. The resulting heterologous clot was imaged daily for 6 days using venography, or monitored using an external gamma ray detector. Clots were radiographically detectable for the 6 days of the study. They were totally occlusive for a mean of 4.2 days (SD 2.2) and were occlusive in the immediate 24 hour period after surgery. The fibrin component of the clot was persistent (85 per cent of the initial fibrin[ogen] present after 6 days). Radiographically the clots were seen as filling defects within partially filled vessels, or their presence was inferred from the absence of filling. A collateral blood supply was apparent immediately on vessel occlusion. No adverse effects, evidence of infection or limb oedema were seen. The model provided a reproducible blood clot within the lateral saphenous vein of the sheep. Clot imaging using venography was effective and readily achieved. It is suggested that the model is useful when a stable, intravenous deposit of heterologous (e.g. human) fibrin is required in vivo at a site suitable for venography and radionucleid monitoring.

In vivo penetration of experimentally produced clots by monoclonal antibodies.

Antifibrin monoclonal antibodies show potential as clot targeting agents for diagnosis and possibly therapy in thrombotic disease. To be effective the antibody must bind to the fibrin component of the clot. The ability of two antifibrin mabs (NIB 1H10 and NIB 12B3) to penetrate occlusive clots in vivo was investigated. Both mabs react with human fibrin but not with human fibrinogen nor with the fibrin or fibrinogen from the species used in this study. Two heterologous animal (sheep and rabbit) thrombus models were used. Clots in both cases were made within isolated vein segments using a mixture of human and native fibrinogen. The clots in sheep veins were observed radiographically and found to be occlusive for a mean of 4.2 +/- 2.2 days and thereafter appeared only partially occlusive. When targeted in their occlusive phase (131)I labelled mab accumulated in the clot reaching a maximum ratio of 1.82 +/- 0.42 when compared to counts in homologous sheep clots in the contralateral limb. It was confirmed in the rabbit jugular vein model that total occlusivity did not prevent antibody accumulation in the heterologous clot by injecting the fibrin specific mab 1H10 and examining the clot excised after 1, 6 and 24 h using immunofluorescence. In a further series of similar experiments (125)I labelled mab 1H10 was used and detected using autoradiography. Both sets of experiments indicated that penetration of occlusive clots by the antibody occurred and that considerable accumulation was present at 6 and 24 h. The results indicate that a circulating antibody can readily gain access to experimentally produced clots in occluded veins.

The distribution of cartilage oligomeric matrix protein (COMP) in tendon and its variation with tendon site, age and load.

A protein prominent in guanidine hydrochloride extracts of adult bovine and equine digital flexor tendons was confirmed to be Cartilage Oligomeric Matrix Protein (COMP) by non-reducing and reducing SDS-PAGE, reaction with rabbit anti-COMP polyclonal antiserum on Western blots, trypsin digestion followed by HPLC on a C2/C18 column, and identification of COMP mRNA from tendon on Northern blots. Immunohistochemistry and Western blots of extracts showed COMP to be present in all regions of digital flexor tendons. Equine tendon COMP was purified by ion exchange chromatography and gel filtration and used in a heterologous inhibition ELISA to quantify COMP in equine digital flexor tendons at different ages, and in other tendons and ligaments. Mean COMP levels in digital flexor tendon were approximately 2-5mg/g wet weight, but they showed a large variation. Levels were low in neonatal tendon but rose rapidly during growth, with the metacarpal (tensional) superficial digital flexor tendon having the highest levels (approximately 10mg/g wet weight). Levels subsequently declined in this region, while in areas which experience a variable amount of compression, levels increased less but then remained constant. Extensor tendons and collateral ligaments, which experience less loading in vivo, had levels similar to those in neonatal tendon. COMP was identified in scarred skin and granulation tissue but not in normal skin, chronic fibrosis, or a fibrosarcomatous skin growth. A unilateral non-weight-bearing growing animal contained three to six times more COMP in the weight-bearing digital flexor tendons compared to the paralyzed limb, while the extensor tendons had similar amounts in both limbs. With the recent discovery of a COMP gene mutation causing pseudoachondroplasia (Hecht et al., 1995), in which lax tendons and ligaments are a feature, the present data suggest that COMP is synthesized in response to, and is necessary for tendon to resist, load.

Detection of fibrin in canine neoplasia.

A murine monoclonal antibody, designated 1H10, produced using a human fibrin-related immunogen, was shown to bind avidly to dog fibrin, but not to dog fibrinogen. Using immunofluorescence, fibrin was detected in canine gastric adenocarcinoma and in mixed tissue from a mammary tumour. No fibrin could be detected in bronchogenic carcinoma tissue.

The cross-sectional areas of normal equine digital flexor tendons determined ultrasonographically.

Fifty-two animals, comprising 22 Irish Draught crosses (Group A), 15 Thoroughbreds (Group B) and 15 ponies (Group C) were examined ultrasonographically using a 7.5 mHz linear array probe and stand-off pad. All animals were free of tendon disease as determined from clinical and ultrasonographical examination. The superficial (SDFT) and deep (DDFT) digital flexor tendons were scanned at 7 transverse (axial) levels between the carpus and metacarpophalangeal joint. Each transverse image was digitised using a commercially available frame grabber and the cross-sectional areas of each tendon at each level measured using a dedicated software application. Excellent accuracy (averaging less than 5%) was demonstrated between the ultrasound generated areas and those measured from the tendons post mortem in 12 limbs. The mean, s.d. and tolerance intervals of both SDFT and DDFT cross-sectional areas at each level were determined for each group of horses. There was no statistically significant difference between Groups A and B and these 2 groups were, therefore, combined for further analysis. The cross-sectional areas of both tendons were statistically smaller for Group C when compared to Groups A and B. The ratio of SDFT to DDFT cross-sectional areas was calculated for each level and this demonstrated less variation between groups. The difference in measurements between limbs of the same horse was analysed. The mean differences for all groups were 9.13 mm2 for the SDFT and 11.64 mm2 for the DDFT. Upper limits (95% of the population) were 22.67 mm2 (SDFT) and 29.22 mm2 (DDFT).(ABSTRACT TRUNCATED AT 250 WORDS)

Normal venographic appearance of the pelvic limb in the dog.

The normal venographic appearance of the pelvic limb of the dog was determined by using a technique adapted from that used in man. A water soluble iodine contrast medium (1.5 ml/kg) was infused slowly through a catheter placed in one of the dorsal interdigital veins. For three minutes before, and during the infusion, the dog was maintained at 60 degrees to the horizontal and radiographs were taken at the end of the infusion. The technique produced good images of the venous system in the pelvic limb.

Imaging of human thrombi in the rabbit jugular vein: I: Comparison of two fibrin-specific monoclonal antibodies.

The development of monoclonal antibodies with a specificity for cross-linked fibrin may have a potential role in the detection and of thrombi and thrombolytic therapy. In this study, two monoclonal antibodies with a specificity for fibrin have been examined. In vitro studies have shown NIBn 123 (which has a high affinity for X-oligomer) and DD-3B6 to bind to immobilised fibrin on PVC plates as well as plasma clots which were incubated in the presence of plasma. The Km values for NIBn 123 and DD-3B6 wre 1.0 x 10(10)/7.7 x 10(8) M and 2.6 x 10(8) M respectively. No significant binding to fibrinogen either immobilised or in solution was found. The binding of these antibodies to a human thrombus in the jugular vein of the rabbit was monitored over a 24 hour period. Preferential binding of each antibody reached a ratio of approximately 1.0 (jugular/heart) at 24 hours and an image was detected.

The use of radionuclide bone scanning in the diagnosis of tibial 'stress' fractures in the horse: a review of five cases.

Five horses, all two year old Thoroughbreds, presented with acute onset hindlimb lameness following moderate to fast exercise. The use of a hand-held scintillation detector after Tc99 MDP injection greatly aided the diagnosis of tibial stress fractures in these horses. Radiological findings were subtle, involving only periosteal new bone and callus at the fracture site. In two cases this took several weeks to develop but in three others was present at the onset of lameness, indicating insidious pre-fracture bone pathology. The site of the most obvious radiological signs was constant in all five cases, being the proximal lateral tibia some 8 to 9 cm from the femoro-tibial joint surface. The diagnosis of five cases of tibial fracture in one racing season suggests that this condition has been underdiagnosed in the past in this clinic, prior to the availability of bone scanning.