Dimensions and Characteristics

The European Standardbred (STB) is historically the result of different crosses between the classic American bloodlines and European families. The French STB is known for its stamina and aptitude for long distances. The American-derived families, however, have been selected for speed and racing at a fixed distance of 1 mile and are represented more widely in Italy and Sweden. Several countries (especially France, Italy, Germany, and the Scandinavian countries) have developed individual bloodlines and today are able to produce good-quality STB trotters. In Europe no races are available for pacers. In Table 109-1 the STB population and racing activity of different European countries are listed.

TABLE 109-1 Distribution of Standardbreds Born in Different European Countries, Summary of the Racing Activity, Earnings, and Betting

Europe has a large number of racetracks for STBs, and they are characterized by different circuit lengths, surfaces, and designs. Half-mile tracks have been replaced progressively by 1-km (-mile) tracks, and no 1-mile racetracks (with the exception of training centers) are present in Europe. The most characteristic and popular racetrack is the Plateau de Gravelle in Vincennes, Paris, where the Prix d’Amerique is held. The track surface is made of pressed charcoal powder; slopes and descents are present; and the circuit is egg-shaped, which is unique in Europe, where other racetracks have a regular design. Another famous French racetrack, Cagnes-sur-Mer in Nice, is well known for being 1200 m in length and for hosting the Criterium de Vitesse, one of the main European free-for-all races. In Sweden, Solvalla racetrack in Stockholm represents the heart of the Swedish STB racing, and in late May the multiple-heat race Elitlopp is held. In Norway, in addition to well-developed STB racing (the main racetrack being Bjerke near Oslo), races for Warmblood horses (a breed historically devoted to hard work but now genetically selected for speed) are still popular and meet the special interest of the local public.

A variety of track designs and purposes are present in Europe. For example, a large number of small country tracks are found in France, and local races are organized in a fairlike fashion, whereas the main racing activity is concentrated in Paris. In Italy, however, important races have a more even distribution among racetracks, Milan and Rome being the main places. In Table 109-2 the distribution of racing tracks in the main European countries is summarized.

TABLE 109-2 Racetrack Distribution in Different European Countries

Differences exist in availability of prize money among different countries, and this makes France and Italy the most attractive countries for trainers and owners. A number of well-known trainers started to move in the early 1980s toward France and Italy, especially from northern Europe, and this has enhanced the exchange of experiences between trainers and veterinarians.

Prize money distribution among horses of different ages has strongly influenced racing, especially in Italy, where 2- and 3-year-olds have the richest races. Higher purses for younger horses have also affected breeding programs and have stimulated an interest in many of the orthopedic problems affecting young horses, especially osteochondrosis, which has been studied widely in northern Europe.

Approaching Lameness Problems

Only STB trotters are allowed to race in Europe, and this makes the trainer’s work more challenging. Any possibility to switch gaits or to move an unnaturally fast gaited trotter to a potentially good pacer is precluded. When the fast gait is compromised by biomechanical problems and substantial interference between limbs (unlike in the pacer), corrections aimed at avoiding interference are attempted. Finding a solution for mechanical problems is not always possible, and corrective shoeing that alters the natural gait may cause compensatory lameness in different locations.

A series of mechanical limitations may be present at the beginning of training, and relatively soon they are followed by pain-related problems, usually affecting joints and less frequently digital flexor tendons and the suspensory ligament (SL). A less than 100% natural trotting athlete is more likely than a natural trotter to have its gait totally compromised, even by a mild subclinical lameness problem, and consequently gait limitations increase. However, anything that is attempted by the trainer to improve gait (corrective shoeing, special equipment that prevents turning the head and neck toward one side, or shifting the hindlimbs toward one shaft) forces the horse to a nonnatural fast gait and often results in lameness. In fact, when a nonnatural gait is forced, the end result is usually that a single limb (or a biped) is overloaded, and the uneven loading is exacerbated by the progression of training.

When young horses start training, they frequently have been subjected to basic lameness and radiological evaluations. This allows trainers the opportunity to treat conditions such as osteochondrosis or to be aware of other abnormalities. Prepurchase radiographic examinations and, when needed, preventative arthroscopic surgery (mostly for osteochondrosis of the tarsocrural joint and osteochondral fragments in the fetlock joints) are now practices that have received general acceptance. The reason to operate early is to have the horse rested before any training program is started. In yearlings eligible for autumn sales, it is important to perform surgery early to have presale radiographs without evidence of osteochondral fragments and to decrease effusion before the sale.

When moderate gait anomalies are present, experienced trainers usually give the horse time and keep going with a light exercise program instead of making radical changes. This allows, in many horses, a complete maturation of the equine athlete, and when the growth is complete and the muscular function well conditioned, the gait in many horses automatically improves without injuring the immature skeleton. Shoeing is also central in early training. Light plastic shoes are ideal to allow foot growth and expansion and to minimize trauma in the early phases of fast training.

Lameness Examination

Horses with acute, severe lameness should be allowed to rest. Radiographs are frequently diagnostic, revealing the most common severe musculoskeletal injuries affecting trained STBs, such as incomplete sagittal fractures of the proximal phalanx, fractures of the proximal sesamoid bones (PSBs), splint bone fractures, fractures of the third or radial carpal bones, fractures of a palmar process of the distal phalanx, fractures of the lateral condyle of the third metacarpal bone (McIII), slab fractures of the third tarsal bone, and stress fractures of the palmar aspect of the McIII or the plantar aspect of the third metatarsal bone (MtIII). Apical fractures of the PSBs are a common injury in young STBs, and the lateral PSB in the hindlimbs is the most common location.¹

The conditions mentioned previously represent injuries of the racing STB requiring rest or surgical repair. More commonly the veterinarian is consulted for mild or obscure lameness, gait disturbances, or poor performance. In any case, a thorough history is mandatory before the lameness examination is initiated.

A basic lameness history must include the following:

Concerning conformation, the clinician should check the following:

Diagnostic Analgesia

Diagnostic analgesia can be performed in sequence from distal to proximal, or, to save time, selective analgesic techniques can be used. For example, European trotters with a positive response to forelimb lower limb flexion inconsistently respond to palmar digital analgesia; therefore analgesia of the metacarpophalangeal or DIP joints may be the first option. Perineural analgesia is preferred, however, to avoid minor risks of joint infections or to save the opportunity to provide intraarticular therapy immediately (when working in stables, trainers frequently are interested more in treatment than in diagnosis). I frequently start with low plantar analgesia in the hindlimbs because lameness of the digit is rare. In young STBs with forelimb lameness and a positive response to carpal flexion, I block the middle carpal joint first.

In horses with obscure lameness or when lameness is only apparent during fast exercise, examining the horse on the track may be useful. The horse is rigged in full harness and first examined trotting in a clockwise direction. Speed then is increased, and the horse is turned to train in a counterclockwise direction, the same as racing. Clinicians can drive the horse themselves, sit in a two-seat wagon, or observe the horse from a car or from a distance. In my opinion, watching the horse during exercise is important, especially when routine training and racing can be simulated, and I prefer the horse to be driven by its usual trainer. Having the horse fully equipped, mimicking the stress of racing, and observing the horse in turns are important advantages to this form of lameness examination.

Diagnostic analgesia is useful, but the clinician must be aware of related risks and make the trainer and owner aware as well. Diagnostic blocks should be avoided in horses suspected of having incomplete fractures. Radiographic examination should precede diagnostic analgesia in these horses. When examining a horse on the track after local analgesia, the trainer should be told to limit the speed as much as possible, avoiding any sudden stop or sharp turn. An experienced trainer normally is able to appreciate the benefits of a block quickly and without stressing the horse. Examination at speed is needed to make a diagnosis in horses with plantar process osteochondrosis fragmentation of the proximal phalanx and fragmentation of the distal border of the distal phalanx.

Diagnostic Imaging

Sophisticated equipment for diagnostic imaging is now available in most European equine clinics. Scintigraphy is available in Europe but is limited to large referral hospitals. Radiography remains the mainstay of equine diagnostic imaging, and the availability of excellent portable units has improved the radiographic examination under field conditions. Digital radiography offers advantages in terms of imaging processing, time saving, radiation protection, and easier image storage. Ultrasonographic examination is commonly performed.

Common pathological findings in the distal limb of European trotters include osteophyte formation on the distal aspect of the middle phalanx, sometimes associated with modeling of the extensor process of the distal phalanx, as seen on a lateromedial image of the foot (Figure 109-1). This radiological pattern often is associated with heel growth proceeding faster than toe growth (club foot). When associated with a positive lower limb flexion test and lameness abolished using analgesia of the DIP joint, this radiological finding is important and indicates the presence of OA. Fragmentation of the extensor process of the distal phalanx has controversial clinical significance, but in my experience these fragments cause synovitis of the DIP joint and should be removed using arthroscopy.

Fig. 109-1 Lateromedial radiographic image of the distal interphalangeal joint of a Standardbred trotter. Osteophyte formation on the distal border of the middle phalanx associated with moderate remodeling of the extensor process of the distal phalanx (arrows) is a common pathological finding in European trotters.

The dorsoproximal-palmarodistal oblique radiographic image of the distal phalanx, unlike scintigraphy, rarely helps in diagnosing pain arising from stress remodeling of the distal phalanx; thus the diagnosis of pedal osteitis is limited to horses with chronic lameness characterized by substantial radiolucency.⁴ Fragmentation of the lateral and medial palmar processes of the distal phalanx, although controversial as a cause of acute lameness, may be an important source of pain best managed by shoeing.

The flexed lateromedial image of the metacarpophalangeal or metatarsophalangeal joints is useful in evaluating lesions of the distal aspect of the McIII or the MtIII. In the hindlimb, the oblique images must be acquired in a proximal to distal direction (down-angled) to see better the area between the proximal phalanx and the base of the PSBs. Fragmentation of the proximal plantar aspect of the proximal phalanx represents a major cause of subtle hindlimb lameness (Figure 109-2).

Fig. 109-2 Dorsoproximal 45-degrees medial-plantarodistolateral oblique radiographic image of a hind fetlock of a 2-year-old Standardbred. There is plantar fragmentation (arrow) of the proximal medial aspect of the proximal phalanx.

A dorsopalmar image of the carpus helps to evaluate the proximal suspensory origin from the McIII, and focal or diffuse increased radiopacity of the McIII may be found (Figure 109-3). In yearlings and young horses, this image allows examination of the distal radius, and pathological modifications of the growth plate on the medial side (physitis) are a frequent cause of early lameness. The most common lesions of the carpus are seen with the dorsolateral-palmaromedial oblique image and the dorsal 35° proximal-dorsal distal oblique (skyline) image of the flexed carpus to highlight the distal row of carpal bones. The radiographs must be of excellent quality, and the appropriate projection must be obtained because false-negative radiographic images are frequent. Abnormal findings include areas of radiolucency in the dorsoproximal articular border of the radial fossa of the third carpal bone, radiolucent lines suggestive of fractures, and increased radiopacity of the third carpal bone.⁵ A moderate degree of increased radiopacity in the radial fossa of the third carpal bone is considered normal in racing horses, but more severe increased radiopacity associated with radiolucent areas represents a pathological finding.^6,7

Fig. 109-3 Dorsopalmar radiographic image of the proximal metacarpal region of a Standardbred trotter (lateral is to the left). Increased radiopacity of the palmar cortex of the proximal aspect of the third metacarpal bone (arrows) is a common finding in trotters with chronic proximal suspensory desmitis.

In the hindlimb the centrodistal and tarsometatarsal joints frequently appear normal radiologically even when distal hock joint pain is diagnosed clinically as the source of pain. Scintigraphy is an excellent tool for diagnosing OA of these joints.⁸ The tarsocrural joint is a predilection site for OC in STBs, and the presence of fragments associated with effusion may represent an indication for arthroscopic surgery. Lesions affecting the lateral trochlear ridge of the talus and medial malleolus of the tibia more frequently cause lameness and effusion than do those of the cranial aspect of the intermediate ridge of the tibia. In horses with effusion but without obvious fragmentation, a specific dorsal 10° to 15° lateral-plantaromedial oblique image is required to evaluate the axial aspect of the medial malleolus. Subtle osteochondral fragmentation or radiolucency easily can be overlooked (Figure 109-4).

Fig. 109-4 Dorsal 15° lateral-plantaromedial oblique radiographic image of the hock of a 2-year-old Standardbred colt. There is axial fragmentation of the medial malleolus of the tibia (arrows), which is difficult to detect unless oblique images are obtained. The condition can cause effusion of the tarsocrural joint and lameness.

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