Equine Tendinitis:Treatment of Acute Tendon Injury in Horses
TendinitisTendon injuries in horses can usually be classified into two groupings:
The strain overload from weight bearing and exercise experienced by the flexor tendons at the caudal aspect of the distal limb can result in tendinitis or bowed tendon. For an example of severely bowed SDF tendon see these Ultrasound Scans.
Laceration trauma is the other common injury known to horses, and, depending on severity, can be devastating to soundness and athletic pursuits.
Both of these injuries are often encountered in performance and pleasure horses. This may be due to husbandry conditions or work demands and can be the reason a horse is removed from another career and relegated to pleasure use.
Tendinitis is often the result of physical weight bearing strain overload by the soft tissue support of the distal limb. In other words the digital flexor tendons and the suspensory ligament can be pushed beyond the elastic capabilities of the tissues and individual and multiple fibre tearing can result.
Tendinitis is commonly recognised in racing horses, but it is also known to occur in horses that work or compete at lesser speeds. Conformation can exacerbate an individual horse's propensity to tendinitis. Long sloping pasterns, long toes, over at the knees, and tied in knees can increase the forces at the flexor surface when extreme extension is required by the limb.
The superficial digital flexor tendon (SDFT) is most commonly affected, and the central aspect of the anatomy in the middle of the cannon bone region is the most common lesion location. Possible explanations for this are the caudal position of the SDFT, the narrow hour-glass tapering at the mid-cannon region, and the fact the this site is the furthest from the vascular supply from muscular origin and osseous insertions.
An additional factor in the origin of tendinitis is the state of physical conditioning of the horse and the tendon tissue. The tendon does not appear to respond to exercise and conditioning, and resistance to injury can be considered to increase as fitness improves.
Racehorses often experience tendinitis when transitioning from sedentary activity to conditioning work. Thus young horses and those returning to exercise from lay-off are those most expected to suffer from tendinitis. Performance and pleasure horses can experience tendinitis injury as well, and the same conditions are applicable. The difference is that horses with less severe exercise demands may be less likely to develop a primary tendinitis lesion. As with many other situations, however, racehorses with tendinitis are often retired from race careers but can very satisfactorily enter other performance or pleasure activities.
Nevertheless, it should be recalled that once a tendon has experienced tendinitis, it is easier for subsequent injury to occur. This is likely due to the manner in which the tendon heals. Disorganised and somewhat rigid fibrous scar tissue is often the result of tendon fibre tearing. This can act as a stress riser and therefore predispose to further injury when the forces are reapplied. This is also the reason investigators have sought a means to provide better, more normal tendon healing.
The diagnosis of tendinitis can often be made with a physical examination and a good history. More information, however, is usually desired as the extent of the injury and a means of more appropriately following response to treatment isneeded. This has benn well served by ultrasonography. A means of total description and a grading scale (0=normal, 4 = totally anechoic) of lesion severity has been reported and works well for diagnosis and management of affected horses. Ultrasonography can also monitor healing in a rather crude fashion. With improved resolution of ultrasound generated images, it may be possible to determine the degree of fibrous tissue healing and the ability of an injured tendon to realign more normal fibres.
The first aid rendered to a horse affected with an acute bowed tendon can reduce the subsequent severity of tendon disruption. Frequently, the tendon injury is apparent at the time of occurrence or workout. The first step in treatment is probably obvious: affected horses should be removed from any exercise, and rest becomes a hallmark of therapy.
Tendon fibre rupture results in haemorrhage and delivery of inflammatory cells and chemical mediators, which can exacerbate inflammation. Efforts to reduce the initial influx of blood and fluid appear to be beneficial in the tendon response to treatment. Local cooling can help accomplish this. Ice baths and cold hydrotherapy are very good for recently injured tendons. Intermittent application of these cooling techniques for 24 to 48 hours after injury can be very successful in limiting the entrance of potentially injurious cells and chemical mediators to the tendon lesion site. Interestingly, after this initial period it appears to be beneficial to warm the local tissues to encourage vasodilation and delivery of needed systemic components for healing. Although these approaches seem to be contradictory, they appear to result in successful treatment.
Coincident with the rest and tissue cooling it is beneficial to attempt to reduce inflammation by conventional methods.
© E M Gaughan DVM
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