Tendon Injuries by Dr John Kohnke BVSc RDA.

TENDONS

Tendon injuries can result in extended downtime from training, and only a 60-65% chance of returning to race soundly for 5 or more races.
Fortunately, tendon strains are not a common injury in racing greyhounds, because the muscles usually tear first, although the tendons carry very high loading forces between the muscles and their bone attachment points.

Structure Tendons are composed of long thin fibrils that make up bundles of fibres of a special type of collagen that provides elasticity and load strength. They extend from the end of a muscle, usually pass over a joint and insert onto a bone to transfer the muscle power to the lower limb.

The collagen fibres develop a crimped appearance when unloaded if the limb is not bearing weight. Upon contraction of the muscle and its loading forces, the crimp straightens and flattens. The tendon then stretches using its elastic properties as the load energy is absorbed. Tendons are elastic structures, that not only stretch when loaded, but release the stretch energy to give the spring in the animal's movement. If the loading forces are excessive, or the tendon suddenly bears an instant high load force, such as when the limb slips and grips on the track surface, the loaded tendon can exceed its elastic limit. This can result in partial or more widespread rupture of the fibrils or tearing away from the attachment points at the muscle, or most commonly, at the weaker anchor point to a bone.

Tendon fibrils are a living tissue, and need nutrition to maintain their strength. Their blood supply is often limited because the tendon is very thin and long and is constantly stretching. Blood and nutrient fluids are also forced out as the tendon bears a load, further reducing the nutrient supply during hard, high loading exercise.

Common Injuries
There are two tendons that are more likely to suffer strain injuries in the racing greyhound, and account for the majority of tendon failures.

Stopper Tendon:
The stopper tendon, or the tendon of the Flexor Capri Ulnaris muscle, inserts on the prominent accessory carpal bone behind the wrist, just under the stopper pad. When overloaded, the tendon fibres usually tear just above the stopper where they start to thin and spread out to attach onto the bone. In most cases, the failure of this tendon is preceded by a partial overstrain in a previous race, which weakens the insertion point or bruising of the stopper bone.
Minor injury may cause slight swelling and pain which may not be easily observed if a greyhound is raced again within a few days. In the next race, the weakened tendon begins to fail or tear off the stopper bone when loaded, usually as the greyhound leans into the rail when cornering on a loose or uneven track surface.
Greyhounds that are heavily muscled in the front end bear heavier loading forces. Those with wrist injuries or weakness also have more down flexion when galloping, and are more likely to over stretch the tendon.

Achilles Tendon
The other common site of tendon failure is the area of attachment of the hamstring or Achilles tendon onto the large calcaneus bone at the point of the hock joint. This tendon carries the majority of its fibres from the gastrocnemius or hamstring muscle, but also from the biceps femoris, semitendinosus and gracilis muscles.

Another tendon, the superficial digital flexor tendon, also runs in the Achilles bundle to continue over the hock. Because of the load carried by the hamstring muscle, the greyhound is usually lame, with swelling and a collection of blood at the site of tearing at the tendon insertion.
The toes on the injured limb in a severe hamstring tendon strain will develop a 'claw-like' appearance with the toenails off the surface when standing. The hock is also weakened and often appears more acutely bent or over flexed.

First Aid
Early recognition, applying effective first aid, support and therapy are paramount to success in tendon injuries. Prompt application of first aid to reduce internal bleeding and control swelling that disrupts the direction and healing of damaged fibres within the tendon bundles is absolutely critical in the case of tendon injuries.

If you notice a swelling in the tendon above the stopper pad, or the lower hamstring area after a race, apply an ice pack over the tendon area as soon as possible. Don't delay and apply it just in case there is a minor strain injury. With the greyhound lying on its side and not bearing weight on the limb, hold the ice pack in place for 2 minutes, remove it for 5 minutes and repeat the application at least for 3 or 4 times.
Although cold therapy will rapidly reduce the swelling and discomfort, the symptoms will only be masked in a severe tendon sprain. It does not mean that the tendon has healed, as proper repair to enable a greyhound to race again may take 6 months or more.

Diagnosis.
Once the swelling and pain has been reduced by the ice pack procedure, then the tendon can be examined by your vet more closely to evaluate the degree and long term prognosis for a return to racing.
New imaging techniques, using ultrasound scans of the tendon structure are widely used to 'look inside' the injured flexor tendons that run down the back of the limbs of horses to determine the extent of the fibre rupture and disorientation.
A scan can be repeated at set intervals to monitor the healing process and prior to return to training. However, these techniques are not used to the same extent on tendon injuries in racing animals.
Tendons heal slowly because of their poor blood supply, and excessive scarring can weaken the tendon in the long term. Initially, a severely sprained or ruptured tendon will repair with a bridge of fibrous and weaker collagen tissue, which if given sufficient time and controlled loading, will be replaced by a much more elastic collagen tendon tissue.

It is important that the fibres realign themselves, and in the case of a complete rupture, that weaker fibrous tissue bridge or scar that forms to reunite the fibres is minimised. The scar is formed from weaker, disorientated tissue and can remain the 'weak link' in the healing process. Surgery In cases of rupture, or where the bone anchorage point is pulled off, then your vet may recommend surgery to either stitch and reunite the torn tendon, or other technique to reattach the anchorage area to the bone.

Certainly, if the tendon is severely pulled apart, the surgery will help reunite the tendon fibres more quickly and limit the extent of the weaker scar tissue in the area. Management In the case of both a simple sprain injury without partial rupture, and following surgery to reunite a torn tendon, overactivity and excessive weight bearing must be avoided to prevent further damage or tearing of the tendon as it repairs.

Studies have shown that it can take 12 weeks or more for tendons to reunite, reorganise, repair and return to minimum weight bearing capacity.

If the tendon injury is only mild, then kennel rest with ice packs applied each morning and evening for 1-2 minutes until the swelling is controlled, and an elastic conforming bandage, such as Vetwrap or Coban, can be applied to support the joint. This will help to prevent overflexion of the wrist or hock joints. In some ways, it is lucky that both major injury sites are located on joints that can be bandaged to prevent overflexion when the greyhound is standing or moving around.

Once the swelling settles down, and the pain reaction to gently squeezing the area disappears, then light massage, laser or magnetic field therapy may help stimulate the blood flow to speed up the healing process.

Gentle massage of a warming liniment, such as Iodised oil to the injury area twice daily is helpful for minor injuries, taking care to wipe off excess before reapplying the support bandage.

Controlled laser application for 1-2 minutes 3 times daily, rather than using a longer duration less often, is also helpful. A 20-minute stint in a Portamac unit twice daily is widely considered to aid blood circulation within the injured area and thereby assist healing processes.

Controlled Exercise
Obviously the greyhound should be prevented from placing excessive loading onto the injured tendon. However, walking on the lead in a quiet area with a support bandage applied to the joint will help to avoid adhesions and promote realignment of the fibres and maturity of the collagen repair processes.

Initially a 100-metre walk once daily increasing by 100 metres each week, is a useful program to strengthen the healing tendon. Where surgical repair has been carried out, ask your vet for a detailed exercise and rehabilitation program.
Once the tendon has been given sufficient time, up to 4-5 weeks for a minor strain, up to 12 weeks for a lower grade tear, and up to 20 weeks following surgical repair, then trotting exercise on the lead for 50 metres, increasing to 100 metres daily over 7-10 days is helpful in promoting strength within the tendon without risking overload. Return to full training over a 6-8 week period can begin once the tendon has had sufficient time to repair, and your vet is satisfied that it is strong enough to bear the loading.

I always handslip greyhounds in a straight line over 50 metres, increasing to 100 metres over a 14-21 day period, before allowing them to gallop around the circle on a training track.

Nutrition There are some nutritional aids to tendon repair. A supplement containing zinc, copper and manganese, Vitamin A and D such as Feramo Greyhound, will provide specific nutrients to maintain the rate of tendon healing. As collagen requires Vitamin C to form, providing 500 mg of Vitamin C daily is often recommended, and 1 mg biotin (as a health food tablet) is also regarded as being beneficial.