UNDERSTANDING TENDON INJURIES & REHABILITATION IN THE RACEHORSE


UNDERSTANDING TENDON INJURIES PDF FINAL
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What are they?

Tendon and ligaments injuries can occur virtually in any ligament in the body, from the horse’s foot to the ligaments at the back of the head. They go from minor inflammation to damage to their substance.


Time Window

If you suspect a tendon injury, please have it checked sooner rather than later: exercising an injured tendon or ligament can make it worse.

What should I do?

Rest, ice, bandaging, anti-inflammatories are helpful in the acute phase.


What should I NOT do?

If you suspect a tendon or ligament injury, do not continue exercising the horse as this could make things worse. Tendons and ligaments are robust in their own way but fragile at the same time, particularly in performance horses.


How frequent are tendon injuries?

It really depends on the disipline and intensity of exercise. They are like a car crash for a taxi driver: they can happen and come with the job. Most tendon and ligament injuries however have a good long term prognosis, as long as adequate healing time is allowed.


How long does it take for a tendon injury to heal?

It depends on the severity of the injury, however typical flexor tendon and suspensory injury take approximately a year to go back to optimal strength.


Which is the weakest part of an old, healed injury?

Injuries tend to reoccur at either the bottom or upper edge of the previous injury: this is the weakest part and secondary injuries are likely to propagate from these edges.



What will the vet do?

It all starts with a clinical examination, followed by diagnostic steps. In most cases palpation is sufficient to localise the site of injury, however nerve blocks can be necessary at times.

Is corrective shoeing helpful?

Yes, it is. A well-balanced foot is the starting point. Different types of shoes can shift vertical load from one structure to another one, therefore we need to aim to protect the injured one


 

Tendons and ligament injuries affect all disciplines of horses: they are quite common in racing, eventing, show jumping and dressage. Each discipline is more prone to specific injuries, at the same way as footballers get sore knees and tennis players sore elbows. To make a horse related example, collateral ligaments injuries are more frequent in show-jumpers than racehorses, who will suffer more of flexor tendon injuries.


Tendons move joints, ligaments stabilise them. Tendons and ligaments are both made of roughly the same type of connective tissue fibres (this is a simplification but makes it easier for the purpose of this paper): think of these as climbing ropes, made of thousands of little tiny filaments. When these little fibres break, you’ve got tendon damage. Same as with a climbing rope, it’s bad news when it snaps.


Tendon fibres are made of collagen, which are proteins, same as our hair. It takes us time to grow long hair, particularly if you are getting bald (like in my case), so it takes time to the horse to rebuild collagen fibres.


Healed tendons and ligaments will lose some of their elasticity: the scar tissue that develops in areas of fibre damage is not 100% identical to the original in mechanical terms.


Management, treatment and rehab is different depending on the affected structure and severity of damage. By definition, horses can suffer of more or less severe forms of “tendonitis” or “desmitis” (anything that ends in “itis” just means inflammation). More severe damage will coincide with worse prognosis.


From now onwards, in this review we will focus on superficial flexor (SDFT) and suspensory injuries. Deep flexor (DDFT) injuries are uncommon in racehorses.


The main causes of fibre damage are overstrain, either in one single extreme episode, or progressively over time. Going back to the example of the climbing rope above, it can either wear off over time, or snap all of a sudden.

Diagnosis relies on clinical exam, ultrasound scans (US) and occasionally MRI. Xrays are helpful in localising associated bone injuries, especially when dealing with ligament injuries. Ultrasound scans are generally conclusive in identifying lesions at the level of cannon bone and pastern; MRI scans can be necessary in case of fibre damage affecting the soft tissue structures in the foot. Not always, but often.


Clinical exam

There will be 1 to 4 cardinal signs of inflammation in all cases of tendon injury: these are heat, swelling (enlargement), pain to palpation, lameness. Experienced hands can pick these signs fairly quick and precisely, helping greatly both in diagnosis and rehab. None of us really want to see banana looking sets of tendons so monitoring tendons regularly (checking/handling tendons) is helpful in picking up early stages of inflammation. Typically horses are not lame in case of SDFT trouble, but generally are lame in case of DDFT and suspensory issues.


Ultrasound scan

Something you might be familiar with, my favourite piece of kit to play with. Tendon lesions have a different appearance on scans, depending on nature of injury. Size, shape and “texture” of the fibres are the main elements to assess.

  • Absence of fibre damage on scans is great news, as this indicates that the substance making tendons and ligaments is intact. Hopefully these cases indicate only an inflammatory process without significant damage.

  • Visible ultrasound changes in fibre texture indicate damage or old, healed (healing) scar tissue.


A “black hole” (core lesion) within an otherwise white, regular looking tendon structure indicates a focal area of thorn fibres. Core lesions are every trainer’s (and owner’s) nightmare. They are characterised by length and affected cross sectional area, this being the percentage of damage affecting a section (or a slice) of the tendon. In such cases, as part of naturally occurring healing process, over time the “black hole” fills up with a blood clot, which becomes scar tissue, which slowly but surely becomes fibre tissue again.


In most severe cases, almost all of the fibres in one area of the tendon are damaged: this is called a “breakdown injury”. There is a big difference between a core lesion to a broken down tendon: in case of a 25% core lesion (which is pretty much standard in jump horses), there are still 75% of fibres holding together and carrying the weight; vice versa a breakdown injury will involve much more damage to the fibres of the tendon, which is therefore unable to take any weight.


Breakdown injuries require generally a more prolonged period of rest and rehab. Immobilisation (using splints or casts) is generally necessary for the first 6 to 8 weeks following a breakdown injury.


Occasionally breakdown injuries require euthanasia.


Nerve Blocks

These are helpful to localise a site of pain in absence of obvious clinical findings. Nerve blocks are helpful to establish presence of pain originating from high suspensory ligament. There should be no need to nerve block a flexor tendon injury, unless suspecting an issue within the digital sheath (tendon windgalls).


What treatment options are available?

There is a large variety of treatments available claiming beneficial effects on tendon healing and reduction of recurrence of injury. The fact that there are so many different options, makes us realise that there is no single magic fix, otherwise we would all be doing it. Time is the mainstay of healing anyway; patience is equally as important, especially during the last months of rehab.


Immediate post injury care: You might have heard of the acronym of RICE: rest, ice, compression, elevation. Forget about elevation, unless you feel particularly strong, what can be done in the acute phase is bandaging, cold hosing, icing; however, depending on severity of injury, horses will need different types of care.


Anti-inflammatories:

They are helpful in the early stages of damage to reduce pain, inflammation and swelling. Typically they should be given full dose for 5-7 days, followed by half dose for another 5-7 days.

There are preliminary studies suggesting the usage of small doses of anti-inflammatories (including aspirin) for prolonged periods avoids excessive inflammatory damage during the repair phase of tendon healing.



Rehab:

There are only general guidelines to rehab, and for a simple reason - each case is a bit different. Time and patience are essential when dealing with a tendon injury.


In case of minor sprains, with absence of fibre damage, a few months of controlled exercise, guided by regular ultrasound rechecks, often are sufficient in allowing tendons to return to normality.


In case of focal areas of fibre damage (“core lesions”), the general, “not written”, consensus focuses on box rest for the acute inflammatory phase (the first 3-4 weeks), followed controlled exercise for the first 8-12 weeks. Eight to twelve weeks of walking exercise allows the tendon to kickstart healing and go through the first stages of blood clot formation and transformation into early scar tissue without having to stand excessive strain. A limited amount of walking in these stages is beneficial as it tends to gently stretch the early scar tissue, which is advantageous in the long run. Assuming all is well then, a more permissive field turnout can be introduced. These injuries take generally 12 months to heal and return to optimal strength. Nasty injuries can take a bit longer. See the table to the left: this is taken from an article focusing on tendon injuries. It is quite specific but I don’t think it is very practical.


In case of true breakdown injuries, early immobilisation is essential to optimise outcome. My approach is to immobilise the distal limb in a cast for 4-6 weeks, followed by a thick, compressive bandage for another 6 weeks. After that, gentle walking exercise can be reintroduced for 6 more weeks prior to field turnout (assuming all looks as good as it can possibly do). Breakdown injuries carry a poor prognosis for return to athletic function but as long as rehab goes well, most of these horses return to pasture, general riding soundness or breeding soundness.


Blood products (and similar):

Tendon lesions, when suitable, can be injected with blood products (mainly stem cells or platelets). The principle is fairly straightforward: we take a sample of blood (or bone marrow) off the horse, process it to separate cells that contain healing factors and other goodies, and inject them at a high concentration, directly into the lesion, generally using ultrasound guidance.

PRP (platelet rich plasma) is my treatment of choice when dealing with a core lesion in performance horses: this is driven by personal experience, practicality, consistency of procedure, technique and quality of final product. A PRP injection is obtained by centrifuging a sample of blood, separating the platelets from other blood cells, and re-injecting them into the tendon defect. It’s straightforward, financially reasonable, especially compared to stem cells, and seems to promote quality of healing.






Supplements:

Supplementing, either in the feed or injectables, with elements and molecules that take part in the healing process, is a treatment currently used by some vets and trainers. These have anecdotally a beneficial effect. With reference to oral supplements, there is a jungle of them out there. If you’d like to try an oral supplement, I’d say as long as it comes from a respectable manufacturer, give it a go: it might be worth a try.


Counter-irritation:

This involves the use of hot rods or blisters to produce an inflammatory response in the periphery of the tendon. It’s old school but still performed nowadays. Tendons are white organs, hence with little blood supply into them. By counter-irritating the tissues around the tendons, we aim at increasing the blood supply to the area and consequently bringing more healing factors (or at least that’s the idea behind it).


These procedures are anecdotally reported to be helpful (depending who you speak with) but there is no research or data supporting these claims. Vets are still allowed to perform such procedures as long as they are last resort.


Shoes, Conformation, Surface:

Each tendon (and each ligament) is loaded differently depending not only on its function but also depending on the moment of the stride. Corrective shoeing can help during convalescence and during training. The interaction between surface and shoe plays a paramount role in loading selectively specific structures.


Each case is a bit different but there are general guidelines dictated by biomechanical studies. Specific kinetherapeutic shoes can be purchased directly from manufacturers, or custom made by farriers. Collaboration between farrier and vet leads to better outcomes.


Ancillary therapies:

My approach is “sure why not” however there is little to no scientific literature suggesting a clear improvement produced by therapeutic laser, ozone, therapeutic ultrasound etc but again “sure why not trying them”.